Ebook Decision making in neurovascular disease: Part 2

Part 2 book “Decision making in neurovascular disease” has contents: Superior cerebellar artery aneurysms, posterior inferior cerebellar artery aneurysm, mycotic intracranial aneurysms, pediatric intracranial aneurysms, spinal aneurysms, brainstem arteriovenous malformations,… and other contents.

Leonardo B.C Brasiliense, Pedro Aguilar-Salinas, Douglas Gonsales, Andrey Lima, Eric Sauvageau, and Ricardo A Hanel

Abstract The estimated prevalence of intracranial aneurysms (IA) in

the general population ranges between 2 and 4% Although fusiform

aneurysms are more commonly found in the vertebrobasilar circulation,

these challenging lesions can occur in the anterior circulation with a

prevalence ranging from 0.1 to 0.3% Fusiform aneurysms are complex

lesions that involve more than 50% of the arterial circumference and are

typically characterized by a lack of discernible neck In general, this

sub-set of lesions is associated with worse outcomes, higher rates of

compli-cations, and death In this chapter, we discuss their anatomical features

and explore pathophysiological mechanisms as well as current evidence

in surgical and endovascular options Microsurgery remains an adequate

treatment option and some of the vascular reconstructions include

trapping, wrapping, bypass, and excision and induction of aneurysm

thrombosis by proximal clipping Endovascular options for fusiform

an-eurysms are typically associated with the use of stents or flow diverters

with or without the use of adjuvant coiling Overall, these procedures

have demonstrated a safe and effective profile favoring this option over

microsurgery However, in some instances, a combined approach can

be done Although there is no consensus for the optimal management

of fusiform aneurysms in the anterior circulation, the decision is made

on a case-by-case basis assessing the patient’s hemorrhagic risk over an

estimated life span in contrast to neurosurgeon’s perceptions of

poten-tial complications, particularly major neurological morbidity and loss of

functional independence

Keywords: intracranial aneurysm, fusiform aneurysm, surgery,

endo-vascular

Introduction

Intracranial aneurysms are estimated to occur in approximately 2.8% of

the general population and giant aneurysms (≥25 mm in largest

diame-ter) represent an infrequent subset of lesions representing only 3 to 5%

of intracranial aneurysms These lesions are often also categorized into

saccular and fusiform based on their morphology and appearance on

imaging studies Saccular aneurysm implies that a discernible neck is

present, which typically occurs following a localized defect in the

arte-rial wall

In contrast, fusiform aneurysms are complex lesions involving more

than 50% of the arterial circumference and typically characterized by no

discernible neck, which has important treatment implications Although

fusiform aneurysms are more commonly found in the vertebrobasilar

circulation, these challenging lesions also occur in the anterior

circu-lation with an estimated prevalence ranging from 0.1 to 0.3% Within

the anterior circulation, the majority of fusiform aneurysms occur in the

internal carotid artery (ICA) Fusiform aneurysms involving the anterior

cerebral arteries (ACAs) and middle cerebral arteries (MCAs) are rarely

seen Fusiform aneurysms in the supraclinoid segment of the ICA have

a higher rate of rupture (~40–50% over 5 years) compared to aneurysms

located in the cavernous segment (10% over the same period) The

for-mer lesions are also associated with worse outcomes, higher rates of

complications, recanalization, and death

In the past, some authors have suggested that fusiform aneurysms

may have an atherosclerotic component in their etiology However,

other pathogenic factors unrelated to atherosclerosis have been

pre-viously demonstrated to increase the risk of aneurysm enlargement

over time and bleeding Age of the patient is a very good indicator of

lesion pathogenesis Young patients often develop these aneurysms in

the context of vessel dissection or underlying vasculopathy, while older

patients (older than 45 years) are more likely to develop these lesions in

association with vessel atherosclerosis

Major controversies in decision making addressed in this chapter include:

1 Imaging surveillance versus treatment.

2 Microsurgical treatment versus endovascular techniques.

3 Long-term durability of current treatment strategies.

4 State-of-the-art endovascular devices.

Whether to Treat

Compared to saccular aneurysms, the natural history and risk of ture for fusiform aneurysms in the anterior circulation remains a topic only marginally understood and an area that would benefit greatly from further studies As with other intracranial aneurysms, factors to aid in the treatment algorithm include (1) aneurysm size, (2) recent growth

rup-on imaging studies, (3) previous subarachnoid hemorrhage (SAH), and (4) patient preference Smaller asymptomatic lesions can be safely mon-

itored with serial imaging and rarely demonstrate further growth (1 in

algorithm) The decision to treat should always take in consideration the

estimated risks associated with treatment weighted against the natural history

Anatomical Considerations

Intracranial aneurysms are more likely to occur in certain segments of the artery, which has generally been based on regional differences in blood flow Similarly, fusiform aneurysms tend to occur between areas

of vessel bifurcation in both proximal and distal segments of major intracranial arteries The majority of fusiform aneurysms in the ante-rior circulation are found in the cavernous segment of the ICA (~42%), followed by the remaining ICA (23–39%), MCA bifurcation (32–41%), and rarely ACA (0.2–1.0%) Fusiform aneurysms involving the ACA are usually restricted to the A1 segment and similarly, these lesions are more likely

to occur at the M1 segment when the MCA is involved

Pathophysiology

The events leading to the development of fusiform aneurysms are often unknown; atherosclerosis has been postulated as a potential mechanism due to disruption of the internal elastic lamina (IEL) It has also been hypothesized that these lesions may arise from arterial microdissections with intramural hemorrhage between the intima and the media lead-ing to progressive dilatation and tortuosity As previously mentioned, dissection or nonatherosclerotic vasculopathy is more likely to occur

in younger patients, and atherosclerosis occurs more often in older patients In addition, turbulent flow within the aneurysm lumen has been shown to create nonphysiological transmural pressures and shear stress on the vessel wall, which may induce changes in smooth muscle cell homeostasis and loss of endothelial integrity Fusiform aneurysms often have unique underlying pathological features on autopsy including calcified walls, onion skin pattern in the vessel wall, partial aneurysm thrombosis, and absence of aneurysm neck Although uncommon, infec-tion involving the vessel has been found to predispose the arterial wall

to fusiform dilation, which has been correlated with medial fibrosis, loss

of smooth muscle layer, destruction of the IEL, and intimal hyperplasia Tumor cell infiltration of intracranial vessels via the vasa vasorum has also been associated with pseudoaneurysm formation and fusiform dil-atations with partial destruction of the vessel wall, microvascular occlu-sion by the tumor, and direct invasion of the arterial wall Rare cases

of fusiform aneurysm formation have been reported in patients with X-linked lymphoproliferative (XLP) syndrome in which the immune system is unable to mount an adequate response to viral infections,

32 Fusiform Aneurysms of the Anterior Circulation

213Algorithm 32.1 Decision-making algorithm for fusiform aneurysms in the anterior circulation SAH, subarachnoid hemorrhage; TIA, transient ischemic attack

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

Aneurysms—Anterior Circulation

214

particularly by the Epstein–Barr virus, which may result in diffuse

nec-rotizing vasculitis affecting major intracranial arteries Fibromuscular

dysplasia may also facilitate aneurysm formation by causing various

degrees of collagen hyperplasia, IEL rupture, and disorganization of the

medial layer, which can result in dilatation of the artery

Classification

From an angiographic and pathological standpoint, these lesions can be

classified into the following:

• Type 1: classic dissecting aneurysms Angiographic features of a

fusiform aneurysm with irregular wall and irregular stenotic

por-tion near the proximal or distal end Pathological features include

widespread disruption of the IEL without intimal thickening, and the

presence of a pseudolumen, which is filled with thrombus

• Type 2: segmental ectasia Angiographic features of a fusiform

aneurysm with a smooth contour and typically associated with other

cerebrovascular diseases Pathological features such as stretched or

fragmented IEL, moderately thickened intima, and no evidence of

thrombi

• Type 3: dolichoectatic dissecting aneurysm Angiographic features of

tortuous fusiform appearance with irregular contrast opacification

caused by intraluminal thrombus Pathological features include

frag-mentation of IEL combined with multiple dissections of thickened

intima, and organized laminar thrombi

• Type 4: saccular aneurysm arising from arterial trunk Angiographic

features of saccular aneurysms unrelated to the branching zones

Pathological features of a mixed type such as IEL pattern resembling

a type 1 lesion without a discernible pseudolumen or organized

thrombus as well as absence of IEL at the dome of the aneurysm with

distended fragile adventitia

Workup

Clinical Evaluation

Fusiform aneurysms arising in the anterior circulation often

pres-ent with symptoms of mass effect such as headaches, cranial

neu-ropathy (especially visual symptoms) as well as transient ischemic

attacks (TIAs) or stroke SAH occurs less often and similar to saccular

aneurysms; the majority of fusiform aneurysms (nearly 60%) are found

incidentally Visual deficits due to optic nerve compression are more

frequently associated with fusiform aneurysm located in the ACA (2 in

algorithm) Skull base erosion with massive epistaxis has been reported

with these lesions although the true incidence is unknown

Imaging

Imaging of fusiform aneurysms is similar to its saccular counterpart and

should evaluate the aneurysm wall, lumen, and flow Magnetic resonance

imaging (MRI) based techniques are clearly the best modality for wall

imaging since these provide important information about wall thickness,

the presence of intramural thrombus, and the extent of mass effect Lumen

imaging can be assessed with multislice helical computed tomography

angiogram (CTA) and has become the primary modality for noninvasive

imaging Time-of-flight (TOF) magnetic resonance angiography (MRA) is a

reasonable alternative in patients with severe renal disease or in patients

requiring repeated imaging, with the caveat that MRA TOF can provide

misleading information such as apparent vessel stenosis or occlusion

However, the “gold standard” modality remains digital subtraction

angi-ography (DSA) because it provides real-time imaging of blood flow inside

the parent vessel and aneurysm as well as accurate vessel measurements,

which are essential for endovascular strategies Catheter-based imaging

also allows us to perform better assessment of collateral flow, very often

useful for treatment of these lesions Balloon test occlusion for the carotid

artery or superselective into the MCA and ACA (with newer low-profile

balloons) often provides valuable therapeutic guidance

Differential Diagnosis

The differential diagnosis of fusiform aneurysms in the anterior lation is broad and includes nonvascular processes such as intracranial tumors, demyelinating diseases, intracranial infections, and other vas-cular events such as acute ischemic stroke, vasculitis, and sinus throm-bosis

circu-Treatment

In general terms, treatment of fusiform aneurysms remains an ualized assessment of patient’s hemorrhage risk over an estimated life span in contrast to the neurosurgeon’s perceptions of potential compli-cations, particularly major neurological morbidity and loss of functional independence As with other intracranial aneurysms, the patient’s age, pretreatment functional status, aneurysm size, location, and relationship

individ-to arterial branches and perforaindivid-tors are important aspects individ-to be uated Management of fusiform aneurysms in the anterior circulation remains a formidable challenge and is frequently incompatible with conventional surgical and/or endovascular techniques For instance, fusi-form cavernous aneurysms with intramural thrombus, highly calcified aneurysms, dissecting aneurysms, and aneurysms with major branches originating in the dome are often not amenable to conventional micro-surgical techniques Treatment of fusiform ICA aneurysms frequently requires cerebral revascularization of the distal territory with aneurys-mal and/or parent artery occlusion through direct surgical or endovas-cular approaches Goals of treatment include preservation of emerging perforator arteries and the parent vessel Partial occlusion may result in complete thrombosis of the aneurysm, but recanalization is not a rare event

eval-Endovascular options for fusiform aneurysms are typically associated with the use of stents or flow diverters with or without use of adjuvant coiling Unless therapeutic sacrifice is the goal, simple coiling of fusiform aneurysms is usually unfeasible or unsafe and may place the parent ves-sel at unnecessary risks Stent-assisted coiling as a primary treatment for fusiform aneurysms has been reported to have high rates of recanal-ization, ranging from 19 to 50% Constructs overlapping multiple stents have also been used with variable success rates

Flow diverters represent a landmark in the management of fusiform aneurysms because these stentlike devices are the first stand-alone option to reconstruct the disease segment of the parent vessel by redi-

recting blood flow away from the aneurysm (4 in algorithm) Increased

experience with these devices has expanded their use to include plex anterior circulation aneurysms such as fusiform lesions in the ICA and MCA It has been demonstrated that aneurysm thrombosis following placement of flow diverters is a dynamic process that can be manipulated with different techniques of device placement including telescoping or deployment of loose coils inside the aneurysm prior to device placement Overall, flow diverters could be considered the first-line endovascular treatment for fusiform aneurysms following several studies that demon-

com-strated their safety, effectiveness, and durability (4 in algorithm).

Microsurgery remains an adequate treatment option for fusiform aneurysms involving the ICA or its branches with the caveat that it requires complex techniques for vascular reconstruction Some of the goals of the vascular reconstruction are trapping, excision, and induction

of aneurysm thrombosis by proximal clipping Aneurysm trapping and resection are usually unfeasible in the distal anterior circulation due to perforators originating from the aneurysmal segment Aneurysm wrap-ping has fallen out of favor, especially with refinements in microsurgical techniques and endovascular devices Bypass surgery either in situ or with extracranial anastomosis continues to be an important surgical option in the neurosurgeon’s armamentarium Depending on flow patterns in the donor vessel, these reconstructive procedures may be divided into low-flow and high-flow bypasses High-flow bypass is usually performed for fusiform aneurysms in the ICA where a saphenous vein or radial artery must be harvested to provide approximately 50 mL/min of blood flow for adequate distal perfusion In situ bypass is an elegant solution that

32 Fusiform Aneurysms of the Anterior Circulation

may be performed for MCA or ACA aneurysms after careful assessment

for size match and length between vessels Interposition grafts may also

be employed in these lesions prior to parent vessel occlusion or surgical

trapping Although recent innovations in aneurysm treatment have

lim-ited the indications for bypass surgery, it remains an essential skill for

cerebrovascular neurosurgeons who intend to treat these lesions

Conservative Management

When a decision is made for aneurysm observation, aspirin therapy is

generally recommended, although it lacks the support of clinical

stud-ies The anti-inflammatory properties of aspirin can potentially decrease

the risk of progression and hemorrhage It is prudent to maintain close

surveillance of these lesions with the first repeat imaging at 6 months

to document aneurysm stability (3 in algorithm) As previously

men-tioned, other aspects to consider prior to treatment include age, baseline

functional status, severity of symptoms, and comorbid conditions

Cerebrovascular Management—Operative

Nuances

In preparation for open reconstructive procedures, patients typically

undergo ICA balloon test occlusion to assess collateral flow and tolerance

to proximal occlusion

Hunterian ligation remains a viable option for giant fusiform

aneu-rysms with a relatively simple surgical technique that has been used to

divert flow away from the aneurysm and induce aneurysm

thrombo-sis Of note, fusiform aneurysm proximal to the anterior clinoid may be

amenable to proximal occlusion alone, whereas supraclinoid aneurysms

are generally better managed with trapping techniques, especially to

alleviate symptoms of mass effect

When considering microanastomotic techniques, the superficial

tem-poral artery (STA) is a very versatile donor for these lesions, allowing for

simple or double barrel, or in association with a high-flow graft For in

situ grafts, the internal maxillary artery (IMA) is also a useful alternative

For ICA lesions, high-flow revascularization with the radial artery or

saphenous vein (~18–20 cm of graft) is necessary The cervical ICA is

exposed using a standard anterior approach and a pterional or

orbitozy-gomatic craniotomy for intracranial exposure Exposure of the external

carotid artery for an extracranial–intracranial (EC–IC) bypass,

end-to-end, or end-to-side anastomosis is performed between the graft and the

ECA distal to the lingual artery Clip application is performed parallel to

the branch vessels to avoid narrowing of the parent artery Perforating

or branch arteries emerging from the fusiform aneurysm of the

ante-rior circulation are important determinants of the timing and degree

of occlusion after revascularization as hemodynamic alteration by flow

diversion and acute thrombosis may result in serious adverse effects

Postoperatively, the pulsations of the graft in the subcutaneous tunnel

are monitored with palpation and Doppler for the first 24 hours Graft

occlusion within the first 24 hours should prompt immediate bypass

surgery with a new graft Heparin (5.000 units) is administered every

8 hours for 3 days in addition to 81 mg of aspirin daily for approximately

1 year MR perfusion and CTA are performed on postoperative day 1 to

confirm revascularization and graft patency Follow-up MRA or CTA are

recommended at 3 months and then annually ►Figs 32.1 and ►32.2

illustrate the management of complex fusiform aneurysms

Endovascular Management—Operative

Nuances

Patients are preloaded with dual-antiplatelet therapy, aspirin (325 mg

daily), and clopidogrel (75 mg daily) or ticagrelor (90 mg twice a day)

1 week prior to the intervention Steroids (dexamethasone 10 mg

bolus or 4 mg every 6 hours) are used for giant fusiform aneurysms

and patients with symptoms of mass effect and continued for

microca-A number of intracranial stents are currently available, for example, Neuroform or Atlas Neuroform (Stryker Neurovascular, Fremont, CA), LVIS

or LVIS Jr (Microvention, Tustin, CA) Multiple flow diverters are currently available or under development, but we typically prefer to use the pipe-line embolization device (PED) or PED FLEX (PED; ev3-Covidien, Irvine, CA) due to increased experience and positive evidence in the literature

In general, flow diverters are considered excellent treatment options for fusiform aneurysms, especially in the anterior circulation where their use appears to be associated with fewer number of thromboembolic events

In brief, arterial access is obtained (more often femoral, occasionally radial/brachial/axillary) with a 6F- or 8F-long sheath and the interme-diate catheter (058 Navien; ev3) is navigated selectively in the distal ICA under road-map guidance A Marksman (ev3), Phenom 27 (Phenom), or

an XT-27 (Stryker Neurovascular) microcatheter is advanced distal to the landing zone and the device is deployed across the neck of the aneurysm Expansion of the PED is closely monitored with fluoroscopy and Xpert CT angiography after final deployment (►Fig 32.3) When the device seems

inadequately opposed to the vessel wall, it can be manipulated with a wire and catheter or balloon angioplasty (Hyperglide or Hyperform; ev3 Neurovascular, Irvine, CA) can be performed

Complication Avoidance

Complications of open revascularization include occlusion of the graft, which can best be prevented by meticulous surgical techniques and adequate sizing prior to implantation Stroke may occur after inadver-tent placement of the aneurysm clip over adjacent perforators, which has been greatly reduced with routine use of intraoperative indocyanine green (ICG) angiography Other complications include intraoperative aneurysm rupture and SAH, injury to cranial nerves, and chemical men-ingitis from intradural drilling of the anterior clinoid and sphenoid bone.Ischemic events are one of the most frequent complications with end-ovascular procedures With flow diverters, the rate of ischemic events ranges from 4 to 8%, most likely because these devices have a higher metal density compared to intracranial stents and the procedures require more extensive catheter manipulation Other uncommon complications include acute device thrombosis, vessel dissection, vasospasm, and delayed aneu-rysm rupture Long-term complications include device stenosis, sponta-neous bleeding from dual-antiplatelet therapy, and stent migration

Outcome

As mentioned in the earlier sections, the choice of treatment should be made on a case-by-case basis The available data on outcomes are lacking and have been obtained mostly from retrospective case series partially due to the low prevalence of anterior fusiform aneurysms, which makes

it difficult to compare outcomes between microsurgical and lar techniques In general, microsurgical strategies have estimated rates of clinical improvement between 58 and 84% (modified Rankin Scale [mRS] score 0–3) but rates of mortality ranging from 14 to 22% In contrast, endo-vascular strategies such as flow diverters have shown excellent outcomes with rates of clinical improvement in up to 90% (mRS 0–2) of patients and

endovascu-acceptable rates of aneurysm occlusion ranging from 60 to 78% (supports algorithm step 4).

A recently published series of 323 intracranial dissecting and/or form aneurysms were classified based on a modified imaging classifi-cation in dissecting (type I), segmental ectasia (type II), dolichoectatic dissecting aneurysm (type III), and large bleeding mural ectasia (type IV)

fusi-A logistic regression was done to find predictors of outcome Of the 323, 66.8% was treated with stent-assisted coiling, 14.5% with internal trap-ping, and 18.6% with sole stenting Clinical follow-up was available for

309 patients with a mean of 10.4 months (range 3–60 months) Imaging

Aneurysms—Anterior Circulation

216

Fig 32.1 Case illustration 1 A 48-year-old female patient with previous subarachnoid hemorrhage presenting with enlarging complex fusiform dilatation of the left middle

cerebral artery (MCA) aneurysm demonstrated on computed tomography angiography (CTA; a,b) Cerebral angiogram showed a complex fusiform aneurysm extending from M1 to superior M2 division (c,d) Note areas of stenosis at the origin of the inferior division on three-dimensional (3D) reconstruction (e) Our initial plan consisted

in performing a superficial temporal artery–middle cerebral artery (STA–MCA) bypass to the superior division with clipping of the M1-inferior division lesion Prior to treatment, the stenotic segment of the M1–M2 inferior division was stented (f,g) The STA–MCA bypass was performed 30 days later (h) A remnant M1-inferior division aneurysm could not be clipped (i) The patient was later treated with coiling of the remaining aneurysm sac (j) and persistent aneurysm occlusion at 5-year follow-up

32 Fusiform Aneurysms of the Anterior Circulation

217

follow-up was available for 262 patients only; there was a recurrence

rate of 9.16% The only independent predictor factor was aneurysm type;

types III and IV had a significant unfavorable outcome Reconstructive

endovascular treatment using conventional stents did not resolve the

mass effect and had a higher recurrence rate compared to the cases that

had reconstruction using flow diverter stents (supports algorithm step 4).

Clinical and Radiographic Follow-Up

Following treatment of fusiform aneurysms, patients are best managed

with clinical evaluation at 1 month to identify early signs of open or

endovascular complications such as TIAs and worsening cranial

neurop-athy Vascular imaging is usually obtained at 3 months using noninvasive

tests and at 6 months with DSA, followed by yearly thereafter following

endovascular procedures A DSA-based scale is used to determine

aneu-rysm occlusion (Raymond–Roy)

Expert Commentary

Fusiform aneurysms of the anterior circulation are some of the most challenging lesions we face in cerebrovascular surgery The natural history for these lesions remains less defined compared to saccular ones A thorough risk-versus-benefit analysis should be made prior

to making a decision to treat Careful analysis with MRI-based images and catheter-based angiography, including balloon test occlusion, and collateral flow assessment are paramount The advent of improved stent technology, especially flow diverters, has provided a significant upgrade to endovascular tools The decision for endovascular versus microsurgical or combined approaches should be done on a case-by-case basis

Ricardo A Hanel, MD Baptist Neurological Institute, Jacksonville, FL

Fig 32.2 Case illustration 2 A 34-year-old male patient presented with seizures Brain magnetic resonance imaging (MRI; a,b) demonstrated a giant thrombosed

aneu-rysm of the anterior cerebral artery (ACA) Cerebral angiogram with anteroposterior (c–e) and lateral (f–h) views showed a giant serpentine aneuaneu-rysm on the left ACA with delayed transit time compared to middle cerebral artery (MCA) territory Balloon test occlusion performed under local anesthesia with balloon placed at distal left A2 (i) demonstrated adequate A3–A4 collaterals from posterior circulation branches (j) The patient underwent a craniotomy for clip trapping of the lesion and a possible A3–A3 bypass Intraoperative angiography posttrapping confirmed presence of collaterals (k) and a decision was made for trapping only with evacuation of the aneurysm content The patient was seizure free with persisted aneurysm occlusion at 6-month follow-up (l,m)

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

Aneurysms—Anterior Circulation

218

Editor Commentary

Fusiform aneurysms come in many varieties, and each demands its own

solution These lesions are almost certainly the result of earlier

dissec-tion and can be found incidentally or can become symptomatic from

thrombus formation, mass effect, or SAH

Asymptomatic lesions may best be treated with continued

observa-tion, while those that present symptomatically may require the entire

endovascular and surgical armamentarium Flow diverters, vessel

occlu-sion, bypass, clip reconstruction, and circumferential wrapping are all

options depending on the specific lesion

Peter Nakaji, MD and Robert F Spetzler, MD Barrow Neurological Institute, Phoenix, AZ

Suggested Reading

Anson JA, Lawton MT, Spetzler RF Characteristics and surgical treatment of choectatic and fusiform aneurysms J Neurosurg 1996;84(2):185–193 Darsaut TE, Darsaut NM, Chang SD, et al Predictors of clinical and angiographic out-come after surgical or endovascular therapy of very large and giant intracra-nial aneurysms Neurosurgery 2011;68(4):903–915, discussion 915 Drake CG, Peerless SJ, Ferguson GG Hunterian proximal arterial occlusion for giant aneurysms of the carotid circulation J Neurosurg 1994;81(5):656–665

doli-Fig 32.3 Case illustration 3 A 55-year-old female patient with previous history of subarachnoid hemorrhage and clipped right middle cerebral artery aneurysm She

presented with headaches and workup demonstrated a fusiform aneurysm in the right M1 trunk (a,b) We decided to treat it with a flow diverter A single pipeline lization device (PED; 5 × 35 mm) was used, oversized to decrease mesh density over the M1 perforators covered with the PED (c) Contrast stasis in the aneurysm was noticed after device placement (d) Intraoperative cone beam computed tomography (CT) demonstrates device in adequate position (e) A 6-month follow-up angiogram demonstrates complete aneurysm occlusion and preservation of perforators (f,g)

embo-32 Fusiform Aneurysms of the Anterior Circulation

219

Kashimura H, Mase T, Ogasawara K, Ogawa A, Endo H Trapping and vascular

recon-struction for ruptured fusiform aneurysm in the proximal A1 segment of the

anterior cerebral artery Neurol Med Chir (Tokyo) 2006;46(7):340–343

Mizutani T, Miki Y, Kojima H, Suzuki H Proposed classification of

nonatheroscle-rotic cerebral fusiform and dissecting aneurysms Neurosurgery 1999;45(2):

253–259, discussion 259–260

Monteith SJ, Tsimpas A, Dumont AS, et al Endovascular treatment of fusiform

cerebral aneurysms with the pipeline embolization device J Neurosurg

2014;120(4):945–954

Nurminen V, Lehecka M, Chakrabarty A, et al Anatomy and morphology of giant

aneurysms—angiographic study of 125 consecutive cases Acta

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

Circulation

Stephen R Lowe, Jan Vargas, Alejandro Spiotta, and Raymond D Turner, IV

Abstract Dissecting intracranial aneurysms are anatomically unique

and thus are not easy to classify in the same way that saccular aneurysms

have been in the neurosurgical literature These lesions are dynamic and

may present with both hemorrhagic (i.e., subarachnoid hemorrhage)

and ischemic symptoms These are complex anatomical lesions and

gen-erally require some form of neurosurgical intervention Neurosurgical

intervention may be both an open surgical procedure or endovascular

vessel reconstruction, or vessel sacrifice In cases where endovascular

reconstruction is feasible, it is generally preferred However, given the

variability in location and morphology of these lesions, treatment must

be individualized as much as possible In this chapter, we present the

relevant natural history, prognosis, anatomy, pathophysiology, workup,

and management of dissecting intracranial aneurysms of the anterior

circulation We will also discuss blister-type aneurysms, a special subset

of dissecting aneurysms with a unique physiology, natural history, and

treatment algorithm

Keywords: dissecting intracranial aneurysm, dissecting

pseudoaneu-rysm, blister-type aneupseudoaneu-rysm, subarachnoid hemorrhage, clip

recon-struction, flow diversion

Introduction

Dissecting intracranial aneurysms (DIAs) represent a unique challenge

to the cerebrovascular surgeon These rare lesions must be addressed

carefully and thoughtfully to ensure a safe and durable treatment for

the patient Their friable anatomy makes them technically complex

lesions to treat, either by open or by endovascular techniques More

significantly, these are lesions that do not conform to the typical

sac-cular morphology seen with aneurysms described in the large

Interna-tional Subarachnoid Aneurysm Trial (ISAT) and InternaInterna-tional Study of

Unruptured Intracranial Aneurysms (ISUA) series Due to this lack of

high-quality randomized and observational data, and due to the

rela-tive paucity of reports in the literature regarding the natural history,

prognosis, and treatment of these lesions, developing a well-validated

treatment algorithm for these lesions is challenging We aim to describe

the classification, natural history, pathogenesis, and treatment

consider-ations for DIA of the anterior circulation

For the purposes of this chapter, we will consider dissecting

pseudoaneu-rysms (i.e., those that arise either spontaneously or secondary to trauma or

iatrogenic causes), which we will term DPA, separately from a unique group

of dissecting aneurysms, which we will term blister-type aneurysms (BTAs)

The abbreviation “DIA” will refer to DPAs and BTAs collectively

Major controversies in decision making addressed in this chapter

include:

1 Whether or not treatment is indicated.

2 Open versus endovascular management for DIAs.

3 Advanced strategies for open reconstruction of DIAs.

4 Advanced strategies for endovascular reconstruction of DIAs.

Whether to Treat

DIAs are uncommon lesions with an ill-defined incidence in the

litera-ture While BTAs are reported to represent 0.3 to 2% of all intracranial

aneurysms, DPAs of the anterior circulation are even more unusual, with

less than 100 reports of spontaneous DPAs in the literature and less than

50 reports of DIA secondary to trauma reported in the literature Unlike

the more common saccular or “berry” aneurysm, where long-term rates

of rupture are well defined, the natural history of DIAs is not well defined

due to their infrequent presentation and lack of observational studies The large majority of these lesions in the literature are described in the setting of subarachnoid hemorrhage (SAH), suggesting a malignant nat-

ural history (1, 2, 3 in algorithm) Additionally, many retrospective

stud-ies have shown these lesions to be dynamic in nature (particularly for BTAs), demonstrating rapid growth and rapid change in the conforma-tion of the aneurysm, even in short intervals of follow-up Rapid growth and change in these lesions is even observed after attempted treatment, particularly with BTAs In the setting of SAH, patients with DIAs tend

to have worse outcomes than those with a ruptured saccular aneurysm

history (2 in algorithm).

As noted earlier, the natural history of these lesions is not well mented BTAs are almost always described in the ruptured setting, and short-interval follow-up vascular imaging suggests that these lesions are dynamic, demonstrating rapid conformational change suggestive of instability and a malignant natural history DPAs were historically impli-cated as a rare cause of ischemic symptoms in young patients; however, recent reports suggest that they are more commonly associated with SAH When presenting with SAH, DIAs have been reported to have a higher rate of rebleeding (44%) compared to saccular aneurysms (14%), and as such the prognosis is worse in these patients As such, when a DIA

docu-is diagnosed in the setting of SAH, it should be treated aggressively and

promptly (1, 2, 3 in algorithm).

DPAs with ischemic symptoms, on the other hand, can have a more benign course Compared to dissecting aneurysms of the vertebral artery, DPAs of the internal carotid artery (ICA) tend to persist longer, but carry little risk of recurrent ischemic events Patients with recur-rent ischemic symptoms may warrant definitive treatment, but in the light of the good prognosis of these lesions, medical management to prevent thromboemboli is usually first-line treatment before subject-

ing a patient to invasive treatments (4, 12 in algorithm) Despite the

associated higher risk of treatment, the aggressive course of DIA seen in the literature suggests that these lesions should be treated aggressively when presenting with SAH Treatment should be offered to all patients with evidence of a ruptured DIA

In patients with an incidentally discovered DPA with ischemic toms, conservative management is appropriate, unless the patient suf-fers recurrent ischemic events DIA secondary to trauma should be given strong consideration for treatment in the unruptured setting given they likely have an aggressive natural history The natural history of inciden-tally discovered BTAs is not well documented, but the malignant natural history of these lesions suggests that conservative management is not appropriate and these lesions must be treated aggressively despite clear risks of treatment

symp-Anatomical Considerations

Dissecting Pseudoaneurysms

The majority of dissections occur in the extracranial ICA, and most taneous DPA arise in the same location DPAs that originate at the skull base, however, are more challenging to access and treat, both with open microsurgery and endovascular techniques These lesions tend to have large, irregular domes with irregular and variable neck segments, and generally arise from nonbranching segments of their parent vessel.DPAs secondary to trauma are generally seen arising from distal branches of the anterior cerebral artery However, traumatic dissections can be seen in any location involved with a penetrating trauma or iat-rogenic injury, including in association with malpositioned ventricu-lostomy catheters or intracranial pressure monitors Traumatic DPA can

33 Dissecting Intracranial Aneurysms of the Anterior Circulation

Algorithm 33.1 Decision-making algorithm for dissecting intracranial aneurysms of the anterior circulation

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

Aneurysms—Anterior Circulation

also be seen in the ICA along the skull base secondary to blunt trauma

and often in association with fractures of the skull base Iatrogenic DPAs

tend to be unique to each individual circumstance Both of these types

tend to demonstrate large, irregular aneurysms with ill-defined neck

segments arising at nonbranching segments of their parent vessel

Blister-Type Aneurysms

While occasionally described at other sites, such as the anterior or

mid-dle cerebral arteries, the BTA classically originates from a nonbranching

segment of the supraclinoid ICA They are typically “hemispheric” in

appearance, with a thin-walled protruding dome generally seen arising

from the dorsal or anteromedial wall of the supraclinoid ICA, although

other morphologies can be seen (see section Pathophysiology and

Clas-sification) Unlike saccular aneurysms, these lesions do not typically

have a well-defined neck

Pathophysiology and Classification

Due to the paucity of literature regarding anterior circulation DIA, much

of the proposed pathophysiology has been adapted from

histopatholog-ical studies of vertebrobasilar DIA

Dissecting Pseudoaneurysms

Primary DPAs arise from a dissection of the parent vessel, and as such the

natural history of these lesions is linked to that of cerebral artery

dissec-tions (►Fig 33.1) Most dissections of the anterior circulation present

spontaneously Connective tissue disorders, dissections of multiple

ves-sels and redundancies of vesves-sels, and a history of migraines and tobacco

use have been identified as risk factors for the formation of DPAs after

an intracranial dissection A subset of these lesions will be secondary to

trauma or to iatrogenic causes Aneurysms secondary to trauma can be

either penetrating or blunt, but those arising secondary to blunt trauma

are extremely rate, accounting for approximately 0.5% of all intracranial

aneurysms The pathophysiological mechanism of the classic type of

traumatic DIA arising from the anterior cerebral artery (ACA) is felt to be

related to injury to the vessel arising from contact with the falx cerebri

Iatrogenic causes are generally a result of complications from surgical or

endovascular manipulation of the intracranial vasculature

In cases of DPA that present with SAH, a dissection plane is

gener-ally seen confined to the subadventitia, whereas ischemic strokes

are generally associated with dissection planes seen in subintimal layer Hirao et al classified DPA of the ACA into types I, II, and III Type

I originates at the ICA and extends into the ACA and middle cerebral artery (MCA) Type II often occurs at the A1 segment of the ACA, and type III generally involves the distal ACA branches There are no classification schemes described for DPA secondary to trauma or iatrogenic causes and the exact pathophysiology is not well delineated owing to the paucity of reports and lack of anatomical studies Indeed, these aneurysms tend to

be unique to the process that created them, and as such each aneurysm

is slightly different

Blister-Type Aneurysms

BTAs of the anterior circulation are manifested by a disruption of the normal internal elastic lamina and media with normal adventitia cover-ing the defect Sim et al noted an interesting corollary between the BTAs seen classically on the supraclinoid ICA and Mizutani type IV dissections

of the vertebral artery, suggesting a focal dissecting process is ble for the unique morphology of this lesion While generally the caus-ative factor is thought to be shear stress on the arterial wall caused by the unique flow dynamics of the supraclinoid ICA, other rare causes of BTA, such as Ehlers–Danlos syndrome and invasive Aspergillosis have also been described, generally in conjunction with BTAs in locations out-side of the supraclinoid ICA

responsi-There are no widely accepted classification schemes for BTAs of the supraclinoid ICA Bojanowksi et al proposed a four-tiered classification scheme, with type I dissections representing a small bulge in the arte-rial wall without an appreciable neck segment (►Figs 33.1, ►33.2, and

►33.3) Type II BTAs are larger, with a defined neck that is not greater

in size than the diameter of the ICA Type III has a neck segment that

is longer in the longitudinal plane than the diameter of the ICA Type

IV represents circumferential disease of the carotid at the diseased ment, with or without a focal outpouching The authors recommend simple clip reconstruction for types I and II, a multiclip reconstruction for type III lesions owing to their large size, and a clip-over-wrapping technique for type IV lesions They note that these lesions may not be separate, but may in fact represent different stages of the same disease process This survey included only 10 patients, which underscores the paucity of literature on the topic

seg-Workup

Clinical Evaluation

Generally, patients present with signs and symptoms of aneurysmal SAH Many of the patients without SAH may also present with head-ache (►Figs 33.2 and ►33.3) Clinical evaluation and management

should proceed according to the standard of care for patients with this life-threatening condition

Patients can also present with a wide range of ischemic symptoms such as massive cerebral infarction, transient hemiparesis, loss of vision,

or headaches These symptoms are almost exclusively seen in patients with DPA and never in patients with BTA

Imaging

In patients presenting with clinical suspicion of SAH, a computed raphy (CT) and CT angiography (CTA) should be obtained For patients with ischemic symptoms, CTA has been used to definitively diagnose an intimal flap and subsequent aneurysm, and in patients in which radi-ation or contrast loads prohibit CTA, magnetic resonance angiogra-phy (MRA) has been equally helpful in diagnosing DIAs Addition-ally, for unruptured DPAs, diffusion-weighted magnetic resonance imaging (MRI) is critical for the diagnosis of ischemia Formal digital subtraction angiography (DSA) is usually undertaken next for definitive diagnosis and to prepare for treatment (►Figs 33.2 and ►33.3) If cath-

tomog-eter angiography including three-dimensional (3D) reconstructions

Fig 33.1 Artist’s illustration demonstrating the pathophysiology of a dissecting

aneurysm

33 Dissecting Intracranial Aneurysms of the Anterior Circulation

is unrevealing, a short-interval follow-up DSA is warranted as a

rap-idly evolving lesion such as a DIA can be identified in this setting It

is important to ensure a complete and adequate image of the lesion is

obtained as angiographic appearance will guide treatment

Treatment

Conservative Management

In the setting of a DPA presenting with ischemic symptoms,

conserva-tive management and clinical follow-up is warranted Patients should

be placed on antiplatelet therapy; however, due to the rarity of these

lesions, there are currently no recommendations for duration of

anti-platelet therapy Conservative management should never be attempted

in the setting of SAH for any DIA, nor should it be attempted for an

inci-dentally discovered BTA

Cerebrovascular Management—Operative Nuances

Open cerebrovascular management options are well documented in the literature, and include parent vessel sacrifice, trapping with or without bypass, clip occlusion of the lesion by any number of techniques, or wrapping techniques with or without clip application Open cerebrovas-cular management can be challenging due to friability of the aneurysm dome, adhesion of the dome to the surrounding parenchyma, difficulty

in reconstruction of the diseased vessel via clip application techniques, and potential rerupture due to incomplete occlusion of the diseased vessel segment

Definitive management of DIAs involves sacrifice of the parent sel with complete removal of the lesion from circulation (►Fig 33.3; 7

ves-in algorithm) However, ves-in many cases parent vessel sacrifice is not a

feasible option due to a high resultant neurological morbidity for the

Fig 33.2 Internal carotid artery (ICA) dissecting

aneu-rysm (a) A 65-year-old female patient presented with acute subarachnoid hemorrhage (Hunt and Hess 2 and Fisher 2) (b,c) Digital subtraction angiography revealed dissecting aneurysms of the right ICA Notice the

blister (arrow) component of the dissection (e,f) The

dissecting ICA aneurysm was successfully treated with a flow-diverting stent The patient did not require any fur-ther interventions and recovered successfully (Images provided courtesy of Leonardo Rangel-Castilla, MD, Mayo Clinic, Rochester, MN.)

Fig 33.3 Anterior cerebral artery (ACA) dissecting aneurysm (a) A 49-year-old female patient presented with acute subarachnoid hemorrhage (Hunt and Hess 4 and

Fisher 3) (b,c) Digital subtraction angiography revealed a dissecting aneurysm of the left ACA Notice the blister (arrow) component of the dissection Patient underwent

a microsurgical exploration with the intention of primary clipping During the procedure, the parent vessel (ACA) was found to be very fragile and had to be sacrificed

(d,e) Intraoperative images of the left ACA blister aneurysm (arrow heads) treated with complete parent vessel occlusion (e) (f,g) Postparent vessel occlusion angiography

demonstrating complete occlusion of the dissected left ACA with preservation of both ACAs (A1 and A2) and left Heubner artery The patient recovered successfully Her modified Rankin Scale (mRS) score at the last visit was 0 (Images provided courtesy of Leonardo Rangel-Castilla, MD, Mayo Clinic, Rochester, MN.)

Aneurysms—Anterior Circulation

patient Additionally, DPAs that originate at the skull base are difficult to

access and occlude Trapping the diseased segment between clips with

or without bypass represents an alternative option for definitive

treat-ment of the diseased segtreat-ment, and can achieve a permanent occlusion

from the circulation similar to vessel sacrifice Bypass is not ideal in the

setting of acute SAH for a variety of reasons; it could be technically

chal-lenging due to cerebral edema and cisternal blood inherent to the

post-SAH state Also, even “high-flow” bypass techniques ultimately provide

lower flow than the carotid itself, which can be deleterious in a patient

who may develop vasospasm as a sequela of SAH Despite these

obvi-ous drawbacks, these techniques represent the only definitive way of

permanently occluding the aneurysm itself and thus obviating the risk

of rerupture, and should be considered if felt to be technically safe and

with low risk of neurological morbidity in all patients Indeed, Kamijo

and Matsui reported a 100% occlusion and long-term patency rate in four

patients treated with trapping and extracranial–intracranial (EC–IC) bypass

in the setting of acute SAH However, given success of other, lower risk

strategies, the above options should only be considered in the hands

of an experienced and high-volume surgeon who has a high

preoper-ative certainty of success with minimal neurological morbidity for the

patient (9 in algorithm).

If parent vessel sacrifice and/or trapping are not possibilities, then

more traditional methods of clip reconstruction remain a viable option

An open clipping procedure in a patient with DIA is fraught with risk and

should be undertaken only with the most meticulous of preoperative

preparation and care As these patients have a high risk of intraoperative

rupture, the surgeon should make all preparations to manage

intraoper-ative rupture or avulsion of the aneurysm dome during clip application

One particular clip application technique specific to the clipping of BTAs

worth highlighting involves a parallel clipping of the aneurysm along the

length of the vessel (almost always the supraclinoid ICA), incorporating

a portion of the healthy vessel wall into the clip tines in order to provide

a better stability for the clip and minimize risk of recurrence This does

result in some degree of stenosis of the ICA, so careful assessment of the

patient’s preoperative angiography is important in determining what

degree (if any) of iatrogenic stenosis the ICA is able to tolerate prior to

this type of clipping

If the above are not options, clipping-and-wrapping techniques or

wrapping techniques alone remain fallback options These are associated

with high rates of recurrence and should never be first-line therapies;

rather, they should be reserved for lesions that either fail a first-line

clipping (or endovascular) procedure or are not deemed suitable for

such an approach due to complicated morphology (9 in algorithm).

Endovascular Management—Operative

Nuances

Endovascular treatment of DIA with traditional coil embolization

tech-niques have been associated with high recurrence rates Introduction

of a coil mass into dissecting aneurysms can lead to rupture given the

fragility of the aneurysm walls; similarly, manipulation with a

micro-catheter may also result in intraprocedural rupture In cases where the

aneurysm is broad based, care must be taken to prevent coil loop

hernia-tion into the parent vessel In many cases, this would require balloon- or

stent-assisted coiling The use of such adjuvant techniques may lead to a

more satisfactory initial result but ultimately still have an unacceptably

high recurrence and rebleed rate Another strategy that was developed

and has proven to be more effective and durable is the use of multiple

overlapping stents to preferentially shunt flow down the parent artery

and disrupt the inflow at the neck of the aneurysm (8 in algorithm)

Such early “flow-diverting” techniques promoted aneurysm

thrombo-sis over time and, as they did not involve manipulation of the fragile

aneurysm itself, were associated with lower rates of intraprocedural

rehemorrhage The downside of this strategy is that it requires dual-

antiplatelet therapy As the next-generation strategy to the use of

mul-tiple overlapping stents, the development of novel, flow-diverting stents

has allowed for the treatment of dissecting aneurysms without vessel sacrifice or coil packing into a friable aneurysm (►Fig 33.2) When asso-

ciated with a dissection, flow diverters can be used to treat the

underly-ing injury and remodel the vessel (8 in algorithm).

Some limitations to flow diversion include the need for platelet therapy for 3 to 6 months to minimize the risk of thromboem-bolic complications This requirement can be a large deterrent in the setting of SAH Conversely, patients with ischemic symptoms from a DIA may benefit from antiplatelet therapy to prevent recurrent ischemic symptoms Additionally, while these devices immediately divert blood flow away from the aneurysm lumen, it can take several weeks for endothelial and neointimal tissue to form along the scaffolding provided

dual-anti-by the flow diverter

al showed a higher rate of morbidity and mortality in surgical patients

as compared to endovascular patients and recommended an ualized approach to treatment depending on institutional expertise

(supports algorithm step 8).

Endovascular management is not without peril Aggressive catheter practice and/or coiling of aneurysm increase risk of intrap-rocedural rupture Use of a multiple-overlapping stent technique or a flow-diverting stent brings with it the risk of early or delayed in-stent thrombosis, with potential resultant ischemic complications The use

micro-of antiplatelet agents after stent placement can also present an issue, particularly if patients may later warrant further surgical intervention While there are no guidelines on use of antiplatelet agents after SAH specifically in conjunction with a treatment procedure such as intrac-ranial stent placement, rates of hemorrhage with ventriculoperitoneal shunting in patients on antiplatelet agents range from 32 to 74%

Outcome Dissecting Pseudoaneurysms

There have been reports of unruptured DPAs resolving on angiographic follow-up In cases where patients present with ischemic symptoms, the outcome is good once patients are started on antiplatelet therapy,

and most do not exhibit recurrent ischemic events (4 in algorithm) In

contrast, patients presenting with SAH from a ruptured DPA tend to have

a poor prognosis, with a mortality of up to 50%, which given the ity of these lesions is not unsurprising In untreated cases, rebleeding has been reported to occur in 50% of patients within 14 days, highlighting the

complex-need for early intervention (supports algorithm steps 2, 4, 5, 6)

Unfortu-nately, due to the rarity of these lesions, outcome data are available only through case reports and case series

Blister-Type Aneurysms

Outcomes for BTAs are invariably poor Morbidity and mortality rates range from 20 to 40% in most studies for all patients with BTAs In patients with rerupture, mortality rates are high and many survivors are left permanently disabled Operative outcomes are similarly worse

33 Dissecting Intracranial Aneurysms of the Anterior Circulation

225

for BTAs as well, with up to 25% of patients undergoing any type (i.e.,

open or endovascular) of intervention experiencing an intraprocedural

rupture, as compared with a 2.5% rate of intraprocedural rupture for

sac-cular aneurysms treated via endovassac-cular means and a 6% risk of

intra-operative rupture for that same group Similar to DPAs, outcome data are

limited to small case series and small reviews, and much of the outcome

data are dated and dependent on the type of treatment utilized (which,

in retrospect, may have been suboptimal)

Durability and Rate of Recurrence

Dissecting Pseudoaneurysms

Due to the lack of outcome data, the durability and recurrence rates of

anterior circulation DPAs are limited No cases of DPA that were treated

with open surgery showed evidence of rerupture or recurrence There

are also reports of ICA and MCA lesions that were successfully treated

with flow diverters, with no evidence of recurrence or endoleak at

fol-low-up Thus, newer endovascular techniques represent an attractive

alternative to open surgery Given paucity of data, we cannot

recom-mend endovascular techniques over open microsurgical reconstruction

(or vice versa) if vessel sacrifice is not an option, although endovascular

therapies with flow diversion appear promising and may in fact

rep-resent best practice, depending on the optimal skill set of the treating

physician (5, 6 in algorithm).

Blister-Type Aneurysms

There are few reports that directly compare outcomes of open

neuro-surgical clipping to endovascular management Two meta-analyses

pub-lished in 2013 attempted to draw parallels between the two, albeit with

fundamentally different review and paper inclusion criteria Szumuda et

al found that all combined types of endovascular therapy had a higher

rate of aneurysm regrowth and rerupture as compared to surgical

inter-vention Additionally, Gonzalez et al showed a higher rate of

retreat-ment (46–21%) in patients undergoing endovascular reconstruction as

opposed to open clip reconstruction (supports algorithm steps 7 and 9)

Szumuda et al were able to show a very significant increase in rate of

regrowth and recurrence in patients treated with a stent-assisted

coil-ing technique, makcoil-ing this a last-line option in our algorithm Indeed,

in many of the older series looking at endovascular therapies for BTA,

retreatment rates approached 50% Efficacy of flow-diversion and

over-lapping stent techniques appears to be much higher, though because

reports of these techniques are few in number, accurate assessment of

recurrence and retreatment rates are difficult Yoon et al report a 63%

complete occlusion rate and a 27% complication rate in their series of 11

patients treated via the Pipeline device Chalouhi et al showed complete

occlusion in five of six patients treated with the Pipeline device who

were available for long-term follow-up They did not report any

proce-dural complications (supports algorithm step 8) Similar to DPAs, we

can-not recommend open microsurgical intervention over flow diversion (or

vice versa) as second-line treatment for BTAs if vessel sacrifice is not an

option Again, flow diversion may in fact represent best practice as the

overall morbidity is likely lower than with open surgery, but there is no

high-level evidence to support this The technique that is felt to be safest

in the hands of the treating physician taking into account each unique

clinical scenario should be utilized (supports algorithm steps 5–9).

Clinical and Radiographic Follow-Up

In patients with ruptured DIAs, angiographic follow-up is

criti-cal to ensure no signs of recurrence or, in the cases of flow diversion,

endoleaks Serial angiography and clinic visits help establish a baseline

to which treatments can be compared There are no consensus

guide-lines on number and frequency of follow-up imaging studies; however,

given the tendency for early and rapid regrowth of suboptimally treated

DIAs, we would recommend early and aggressive follow-up, preferably

with posttreatment diagnostic angiography prior to hospital discharge

Expert Commentary

Dissecting or blister-type pseudoaneurysms are a rare and highly lenging subset of intracranial aneurysms Most frequently identified in the setting of SAH, these aneurysms have a more sinister clinical course with higher rates of rerupture and growth, which justifies aggressive and definitive treatment Due to the fragility of the aneurysm wall, tra-ditional methods of aneurysm treatment including conventional micro-surgical clipping and coil embolization have unacceptably high rates of intraprocedural rerupture, so treatment modalities have been adjusted

chal-to address these high-risk aneurysms Surgical treatment has evolved chal-to include trapping and bypass or intentional “over clipping” and stenosing

of the parent artery Endovascular methods include flow diversion with either multiple overlapping stents or newer generation flow-diverting stents, with the caveat that dual antiplatelet therapy will be required However, if the dual antiplatelet therapy can be managed safely, flow diversion has proven to be effective in reducing the likelihood of immediate rerupture and delayed growth These complex, technically challenging aneurysms are best addressed at centers with high-volume surgical and endovascular expertise

Raymond D Turner, IV, MD, and Alejandro Spiotta, MD Medical University of South Carolina, Charleston, SC

Editor Commentary

The malignant natural history of atherosclerotic dissecting aneurysms that present with SAH both justifies an aggressive approach to treat-ment and should give the microsurgeon pause about the same These aneurysms tend to have fairly extensive SAHs at presentation and high risk for rebleeding At the same time, they are at higher risk for bleeding

or thrombosing during surgery Where possible, trapping and bypass or primary occlusion should be the first choice Where this is not possible, clip wrapping is an option Endovascular deconstruction is an option if

it appears that distal ischemia is not an issue However, stenting must

be approached with caution as the risk of rehemorrhage is high, and the use of antiplatelet agents in this setting can therefore pose a problem Aggressive isolation of the aneurysm is the best treatment

Peter Nakaji, MD Barrow Neurological Institute, Phoenix, AZ

Suggested Reading

Barrow DL, Spetzler RF Cotton-clipping technique to repair intraoperative rysm neck tear: a technical note Neurosurgery 2011;68(2, Suppl Opera-tive):294–299, discussion 299

aneu-Bojanowski MW, Weil AG, McLaughlin N, Chaalala C, Magro E, Fournier JY phological aspects of blister aneurysms and nuances for surgical treatment J Neurosurg 2015;123(5):1156–1165

Mor-Chalouhi N, Zanaty M, Tjoumakaris S, et al Treatment of blister-like aneurysms with the pipeline embolization device Neurosurgery 2014;74(5):527–532, discussion 532

Chan RS, Mak CH, Wong AK, Chan KY, Leung KM Use of the pipeline embolization device to treat recently ruptured dissecting cerebral aneurysms Interv Neu-roradiol 2014;20(4):436–441

Kamijo K, Matsui T Acute extracranial-intracranial bypass using a radial artery graft along with trapping of a ruptured blood blister–like aneurysm of the internal carotid artery Clinical article J Neurosurg 2010;113(4):781–785

Kurino M, Yoshioka S, Ushio Y Spontaneous dissecting aneurysms of anterior and middle cerebral artery associated with brain infarction: a case report and review of the literature Surg Neurol 2002;57(6):428–436, discussion 436–438 McLaughlin N, Laroche M, Bojanowski MW Surgical management of blood blis-ter-like aneurysms of the internal carotid artery World Neurosurg 2010; 74(4-5):483–493

Ohkuma H, Suzuki S, Ogane K; Study Group of the Association of Cerebrovascular Disease in Tohoku, Japan Dissecting aneurysms of intracranial carotid circula-tion Stroke 2002;33(4):941–947

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

Aneurysms—Anterior Circulation

226

Sikkema T, Uyttenboogaart M, Eshghi O, et al Intracranial artery dissection Eur J

Neurol 2014;21(6):820–826

Szmuda T, Sloniewski P, Waszak PM, Springer J, Szmuda M Towards a new treatment

paradigm for ruptured blood blister-like aneurysms of the internal carotid

artery? A rapid systematic review J Neurointerv Surg 2016;8(5):488–494

Walsh KM, Moskowitz SI, Hui FK, Spiotta AM Multiple overlapping stents as

mono-therapy in the treatment of “blister” pseudoaneurysms arising from the

supraclinoid internal carotid artery: a single institution series and review of the literature J Neurointerv Surg 2014;6(3):184–194

Yoon JW, Siddiqui AH, Dumont TM, et al; Endovascular Neurosurgery Research Group Feasibility and safety of pipeline embolization device in patients with ruptured carotid blister aneurysms Neurosurgery 2014;75(4):419–429, discussion 429

34 Traumatic Intracranial Aneurysms of the Anterior

Circulation

Ben A Strickland, Joshua Bakhsheshian, and Jonathan J Russin

Abstract Traumatic intracranial aneurysms (TICAs) are rare lesions that

present diagnostic and operative challenges TICAs are often present

in delayed fashion following blunt head trauma, most commonly in

the anterior circulation in locations immediately adjacent to the falx

cerebri TICAs have been noted to have a higher rate of rerupture and

aneurysmal growth as compared to their saccular counterparts Due

to the high morbidity profile, endovascular or operative intervention

is recommended Any patient experiencing a traumatic injury with

delayed hemorrhage suspicious for a TICA should have urgent imaging

Computed tomography angiography (CTA) remains a viable useful initial

screening test; however, in some cases cerebral angiogram is necessary

There are reports of successful management utilizing a multitude of

strategies including endovascular intervention or microsurgical

tech-niques When approaching TICAs with an open surgical treatment, it is

important to decide whether parent vessel sacrifice or preservation is

the goal In cases where the parent vessel requires preservation,

multi-ple strategies should be prepared Primary clip ligation is the treatment

of choice; however, bypass donors, grafts, and instruments should be

readily available if clip ligation is not possible Follow-up imaging is

indi-cated in most cases at least up to a year to rule out aneurysmal regrowth

or recurrence To date, there is no clear consensus on the optimal

treat-ment strategy, and cases should be approached on an individual basis

Keywords: traumatic intracranial aneurysm, revascularization, EC–IC

bypass, vascular neurosurgery, trauma

Introduction

Traumatic intracranial aneurysms (TICAs) can present with both

diag-nostic and management challenges Intracranial aneurysms related

to trauma comprise ≤1% of all cerebral aneurysms and are associated

with morbidity and mortality rates as high as 50% TICAs are most

com-monly associated with blunt head trauma and less comcom-monly a result

of penetrating trauma TICAs are more commonly reported in the

pediatric population rather than adults The delayed presentation and

difficult diagnosis of TICAs can contribute to the high mortality rates

(1, 2, 3 in algorithm) A male predominance has been described, likely

attributable to the greater frequency of head trauma in young males

Traumatic aneurysms typically involve vessels in the anterior

circula-tion, likely explained by the arteries’ relationship to the falx cerebri and

skull base, which can result in shearing forces during trauma leading to

arterial wall destruction and aneurysm formation Traumatic aneurysms

tend to form distal on the anterior cerebral artery (ACA) and are at risk of

being missed on diagnostic testing This potential for delayed diagnosis

can also help explain the high morbidity and mortality rates observed

in these patients

Major controversies in decision making addressed in this chapter

include:

1 Which traumatic brain injury patients have a high risk of TICA

and when should they undergo vascular neuroimaging?

2 Open versus endovascular treatment for TICAs.

3 Ideal timing for TICA treatment.

Whether to Treat

Most authors agree that surgical treatment of traumatic aneurysms

is indicated because of their very poor natural history The

morbid-ity and mortalmorbid-ity of untreated ruptured TICAs can be as high as 50 to

70%, whereas the morbidity and mortality with surgical treatment

is 15 to 30% The common occurrence of these lesions on the ous and paraclinoid internal carotid artery (ICA; ►Fig 34.1) and dis-

cavern-tal ACAs allows for acceptable surgical exposure through a pterional

or interhemispheric fissure Distal aneurysms can be challenging for endovascular access

Conservative Management

Conservative management of TICAs is associated with high morbidity and mortality, and is typically not recommended However, one study estimated that 20% of all TICAs will spontaneously resolve and pro-posed that repeat angiography be performed for observation and rec-ommended surgical intervention only in cases with aneurysm enlarge-ment or neurological deterioration The majority of studies, however, have consistently demonstrated that spontaneous resolution of TICAs

is improbable with an estimated 40% of TICAs hemorrhaging and 21% enlarging on follow-up imaging Ultimately, the large majority of the published literature supports early and aggressive management of trau-

matic aneurysms (7 in algorithm).

Anatomical Considerations

Traumatic aneurysms are classically located in regions were noid arteries are in transition from or in contact with a rigid structure The most common locations for TICAs include distal branches of ACA, pericallosal, callosomarginal, and the proximal ICA The proximal ICA is

subarach-at risk due to it being fixed subarach-at the distal dural ring and transitioning subarach-at that point into the subarachnoid space (►Fig 34.1).

Histologically, traumatic aneurysms can be categorized as true, false (or pseudoaneurysms), dissecting, or mixed True TICAs are a dila-tion of the arterial wall in which only the adventitia is intact, as opposed

to saccular aneurysms that involve both the adventitia and intima A rupture of all arterial layers with associated perivascular hematoma formation describes false TICAs, considered the most common his-tological subtype Dissecting TICAs form following a traumatic event splitting the arterial wall layers with false lumen forming between the intima and elastica as blood enters through intimal tears Mixed TICAs form following the posttraumatic rupture of true aneurysms with false lumen development and hematoma formation The histological type is not clinically relevant as the high risk of hemorrhage warrants inter-vention regardless, and angiography cannot always reliably differentiate between subtypes

Classification/Pathophysiology

In 1988, Buckingham et al reported that TICAs secondary to blunt injury can be classified as skull base or peripheral Skull base TICAs are clas-sically associated with shearing forces resulting in arterial injury at transition points from being fixed in the skull base to being free in the subarachnoid space (►Fig 34.1) Shearing forces can also damage dis-

tal ACAs when they impact the falx cerebri More distal, cortical ies can suffer TICAs when local trauma results in linear skull fractures that can traumatize underlying arteries Location of the aneurysm is strongly indicative to the mechanism of injury The anterior circulation

arter-is the most frequent location for TICA formation Up to 90% of reported TICA following blunt trauma are associated with underlying skull frac-tures (►Fig 34.1).

Traumatic aneurysms have been described following iatrogenic injury and penetrating trauma Several case reports have detailed

Aneurysms—Anterior Circulation

228

Algorithm 34.1 Decision-making algorithm for traumatic intracranial aneurysms of the anterior circulation

34 Traumatic Intracranial Aneurysms of the Anterior Circulation

TICA formation following endoscopic surgery, paranasal sinus

sur-gery (►Fig 34.2), skull base surgery, and ventriculostomy Aneurysms

following these procedures are generally the result of injury to the

internal carotid, but less commonly secondary to insult of the ACA,

mid-dle cerebral artery (MCA), or basilar artery The majority of TICAs are

reported following blunt injuries Of the TICAs following penetrating

injury, it is has been observed that low-velocity injuries are more likely

to lead to TICA formation as compared to high-velocity injuries

Workup

Clinical Evaluation

The most common presentation of traumatic aneurysms is delayed

hemorrhage This is typically associated with an acute deterioration

and/or new neurological deficits Different locations and subtypes of

TICAs can give rise to variable clinical presentations Infraclinoid TICAs

can present with epistaxis, cranial nerve palsy, diabetes insipidus, or

headaches Supraclinoid TICAs can present with cranial nerve palsies,

severe headaches, and/or neurological deterioration resulting from

subarachnoid hemorrhage (SAH) The timeline for TICA presentation is

variable; however, the majority of patients will be diagnosed within 2

to 3 weeks of injury The risk of SAH is significant with morbidity and mortality estimated as high as 70%, but is lowered to 30% with treat-ment Fewer than 20% of TICAs are detected while still asymptomatic; however, early identification and intervention can significantly reduce morbidity and mortality

Imaging

Computed tomography angiography (CTA) is the screening modality of choice for the initial workup of suspected cerebrovascular injury after head trauma However, CTA is sometimes limited by the field of view and can be further compromised by the initial superimposed brain injury at time of presentation Although TICAs are rare, they are associated with a high morbidity and mortality Early diagnosis and intervention are cru-cial in order to provide the patient with the best chance for a functional recovery As such, clinical decision makers should hold a high index of suspicion for patients presenting with traumatic brain injury, particularly when SAH is present within the interhemispheric or basal cisterns A neg-ative CTA is generally acceptable to rule out a TICA However, when there is

a high clinical suspicion, and the patient’s overall status allows, a digital

subtraction angiogram (DSA) can be performed (1, 3, 12 in algorithm)

In most cases, a DSA is an option but is not a recommendation

Fig 34.1 Traumatic internal carotid artery (ICA) aneurysm This is a 23-year-old male patient who was involved in an autopedestrian accident (a) Computed

tomogra-phy (CT) with diffuse traumatic subarachnoid hemorrhage (SAH) (b) Initial CT angiogratomogra-phy (CTA) demonstrated a left ICA traumatic aneurysm that enlarged

signifi-cantly on a repeat CTA 4 days later (c) The patient was not a candidate for endovascular stenting due to the need of dual antiplatelet therapy and multiple systemic

injuries requiring multiple procedures, ICA sacrifice, and high-flow bypass (using radial artery [RA]) was then performed (d) Intraoperative view of the intracranial

anastomosis (radial artery–middle cerebral artery [RA–MCA]) (e) Intraoperative view of the extracranial anastomosis (ICA–RA) (f) Intraoperative indocyanine green

angiography demonstrating bypass patency

Fig 34.2 Traumatic iatrogenic anterior cerebral

artery (ACA) This is a 33-year-old female patient who developed acute arterial hemorrhage while undergoing sinus surgery because of which surgery was aborted

(a) Computed tomography (CT) head demonstrated intraparenchymal and subarachnoid hemorrhage

(b) Digital subtraction angiography demonstrated a

distal ACA aneurysm (arrow) successfully treated with primary coiling (c; arrow).

Aneurysms—Anterior Circulation

However, when a patient suffers a delayed SAH after head trauma and a

CTA is negative, a DSA is recommended due to the improved sensitivity

Additionally, in cases when foreign body or bone artifact interferes with

CTA imaging, a DSA is recommended to allow for adequate visualization

of the intracranial vasculature

Timing of CTA can be complicated by patients requiring multiple

inter-ventions from different services In general, when evaluating for TICAs

imaging should be obtained as soon as the patient is stable for transport to

radiology Patients being evaluated in a delayed fashion who present with a

history of brain trauma associated with recurrent epistaxis, blurred vision,

or progressive cranial nerve palsy should undergo a CTA as soon as possible

Differential Diagnosis

In some cases, history alone cannot determine whether an aneurysm

is traumatic or not Typical angiographic features of a traumatic

aneu-rysm include its lack of an associated branch point, peripheral location,

delayed filling and/or emptying, and irregular contour It is important to

differentiate between traumatic aneurysms and preexisting aneurysms

when possible When an accurate history is unobtainable and a likely

preexisting aneurysm is identified, treatment consideration is

war-ranted, particularly when radiographic evidence raises a concern for a

possible rupture of the preexisting aneurysm that could have preceded

the traumatic event Traumatic aneurysms of the ICA at the skull base

can obscure the parasellar region Formal angiography can be helpful to

rule out a carotid-cavernous fistula

Treatment

Initial treatment of TICAs is dependent on the clinical status of the

patient at the time of diagnosis There have been reports of both open

surgical and endovascular modalities employed in the management of

these lesions When associated with intracranial hemorrhage resulting

in elevated intracranial pressure (ICP) that is refractory to medical

ther-apy, emergent open surgical treatment with evacuation of the

hemor-rhage is recommended (2, 5, 6 in algorithm) However, in less emergent

cases, the consideration of endovascular aneurysm management,

fol-lowed by surgical decompression is reasonable When ICP is controlled,

the presence of an intracerebral hematoma is not as critical of a

consid-eration and both open surgical and endovascular management can be

considered (5, 6, 7–11 in algorithm).

Open surgical approaches should be considered when there is an

opportunity to preserve the parent vessel, particularly when eloquent

territory is at risk Primary clip ligation is the treatment of choice;

how-ever, secondary to relatively large aneurysm size when compared to

peripheral vessels and the frequency of pseudoaneurysm formation, it is

not always feasible In cases when parent vessel preservation is favored,

a backup strategy of aneurysm excision with re-anastomosis or bypass

and trapping of the aneurysm should be prepared When parent

ves-sel occlusion is an option, endovascular techniques tend to be favored

in this population Exceptions would be cases when branching arteries

are in close approximation to the segment requiring occlusion In these

cases, it may be beneficial to perform open trapping of the aneurysm

with direct visualization of the branching arteries Due to the multiple

comorbidities in polytrauma patients, there is an associated morbidity

and mortality of up to 30% regardless of treatment

Several authors have begun to report their experience with

endovas-cular treatment for TICAs A few recent reports have advocated for the

use of liquid embolic polymers, such as Onyx, in the treatment of TICAs

Unfortunately, the same anatomical nuances that complicate open

surgi-cal management also affect endovascular techniques TICAs are common

in distal vasculature, making the accessibility for endovascular

tech-niques difficult Coiling of the aneurysm sac without parent vessel

sac-rifice is associated with a high risk of recurrence and hemorrhage since

pseudoaneurysm formation is common Coiling can be further

compli-cated by the dome-to-neck ratio As TICAs do not necessarily form at

bifurcations, the placement of a catheter can prove difficult

Ultimately the treatment modality employed is determined on a by-case basis Both open and endovascular strategies are complicated

case-by the frequency of pseudoaneurysm formation, the peripheral location, and the often poorly defined aneurysm neck To date, there is yet to be

a method demonstrating superiority as a dominant treatment strategy

Complication Avoidance

The first step for complication avoidance in TICAs is early diagnosis and treatment Any patient experiencing a traumatic injury with delayed hemorrhage suspicious for a TICA should have urgent imaging When CTA is negative, a formal diagnostic angiogram should be obtained A delay in diagnosis can have disastrous consequences in this popula-

tion (1, 2, 3, 4 in algorithm) Delaying treatment is another pitfall to be

avoided when dealing with TICAs A treatment plan should be lished and implemented as soon as possible Using a wait-and-see pol-icy for these lesions is inviting complications When approaching TICAs with an open surgical treatment, it is important to decide whether par-ent vessel sacrifice or preservation is the goal In cases where the parent vessel requires preservation, multiple strategies should be prepared Primary clip ligation is the treatment of choice; however, bypass donors, grafts, and instruments should be readily available if clip ligation is not possible (►Fig 34.1) Preparation allows the surgeon flexibility when

estab-dealing with unpredictable pathology and is paramount for tion avoidance when managing TICAs

is difficult to draw conclusions from the existing literature with regard

to long-term outcomes Of the reported cases, regardless of treatment modality, there are only a few instances of recurrence Most recurrences are associated with initial endovascular management, and such recur-rences are subsequently treated with the open surgical technique.Moon et al presented their results of a small series of patients with traumatic cerebral pseudoaneurysms They included eight patients with

a mean age of 25 years Six of the pseudoaneurysms were located at the cavernous/ophthalmic segments of the ICA and two located at the MCA (M2 segment) The causes of the trauma were car accidents in six patients, penetrating injury thought the orbit in one patient, and slip down injury in one patient Massive epistaxis occurred in all patients with ICA pseudoaneurysms Treatment included trapping of the ICA

in one patient, balloon ICA occlusion in five patients, and clipping of both MCA pseudoaneurysms All patients with ICA pseudoaneurysms underwent balloon test occlusion and passed Clinical outcome was excellent (modified Rankin Scale [mRS]: 0–1) for ICA pseudoaneurysm patient group and good/fair (mRS: 2–3) for the two patients with MCA

pseudoaneurysms (supports algorithm steps 8–11).

Rangel-Castilla et al reported their experience of a group of patients with iatrogenic skull base ICA injury It included eight patients in whom the injury was related to endoscopic transsphenoidal surgery, endo-scopic transfacial–transmaxillary surgery, myringotomy, cavernous sinus meningioma resection, posterior communicating artery aneurysm clipping, and cavernous ICA aneurysm coiling Endovascular manage-ment was considered first-line treatment but was not successful All the patients underwent high-flow extracranial–intracranial (EC–IC) bypass with radial artery graft and parent vessel (ICA) sacrifice At a mean clinical/radiographic follow-up of 19 months (3–36 months), all the patients had an mRS score of 0–1 All bypasses remained patent

(supports algorithm steps 8–11).

A single center experience of patients with TICAs from blunt injuries included 15 patients Etiology of trauma included motor vehicle acci-dent and falls The most common clinical presentation was epistaxis

34 Traumatic Intracranial Aneurysms of the Anterior Circulation

231

and ophthalmologic symptoms The anatomical locations were

infracli-noid (nine patients), supracliinfracli-noid (five patients), and parafalcine (one

patient) Majority of them (11 patients) were treated endovascularly,

bypass surgery and trapping (2 patients), and balloon-assisted transnasal

endoscopic repair (2 patients) At discharge, two (13.3%) patients had poor

clinical outcome, five (33.3%) had fair, and eight (53.3%) had good outcome

Durability and Rate of Recurrence

TICA have significantly higher rates of rupture when compared to

saccular or nontraumatic aneurysms Although it is difficult to assess

the true incidence of TICAs, it is estimated that 40% will hemorrhage and

21% will grow in size after initial diagnosis Most will rupture in the first

2 to 3 weeks after formation with mortality as high as 50%

Once treated, rarely do TICAs reoccur; however, there has been an

association with initial endovascular management Coiling of the

aneu-rysm sac without parent vessel sacrifice is associated with a higher risk

of recurrence as pseudoaneurysms are frequent There are no reported

cases of TICAs reoccurring following open surgical management

Clinical and Radiographic Follow-Up

There is no clearly defined algorithm for the timing of follow-up

imag-ing Lack of TICA diagnosis on initial screening does not exclude eventual

TICA formation Although most institutions will include CTA as part of

the initial trauma screening, it is possible for the TICA to be missed on

initial imaging Patients that develop new intracranial hemorrhage

post-trauma that is not explained by evolving injuries should undergo CTA

and subsequent DSA in the cases in which CTA is negative and there is a

high suspicion Those patients with both a negative CTA and DSA

suspi-cious of harboring a TICA should have a repeat CTA at 2 weeks Patients

that undergo treatment for their TICA are typically reimaged at 1 year

to rule out any recurrence In the case that 1-year follow-up is negative,

typically no further imaging is obtained These imaging

recommenda-tions are made based on the senior author’s experience, given that there

are insufficient data to support a rigid protocol Individual cases may

require more frequent imaging, or no follow-up imaging based on

clini-cal course and treatment employed

Editor Commentary

One needs a high index of suspicion and a positive CT scan to diagnose a

TICA Blunt trauma with a normal CT is likely low yield unless the patient

has neurological findings suspicious of posttraumatic ischemic events In

nonpenetrating trauma cases, the direct vascular injury source is either a

dural fold or bone The most common sources include injury to ACA at the

falx or posterior cerebral artery at the tentorium or the M1 segment from

the sphenoid wing or supraclinoid ICA at the clinoidal segment

In ruptured cases, the safest means for treatment is parent vessel

occlusion, which can usually be performed endovascularly following a

balloon test occlusion If the patient fails a balloon test occlusion and

vessel deconstruction is going to result in major neurological deficit,

then one can consider clip reconstruction usually using a clip-wrap

approach or possible clip occlusion with bypass In unruptured cases,

one can consider flow diversion or coiling with stents My strong

prefer-ence in sidewall situations is flow diversion alone without coils

Cases of penetrating injury with associated subarachnoid or

intracer-ebral hemorrhage absolutely need adequate vascular imaging including

CTA and possibly diagnostic angiogram The penetrating object should

be removed only under direct vision out of the brain For example,

I recommend performing craniotomy leaving the penetrating object in

situ and then exposing brain area including potentially opening deep cerebrospinal fluid (CSF) spaces to gain proximal control of closest major vessel prior to direct extraction of penetrating object from the brain Once the object is removed, one should inspect cavity to make sure there

is no concern for residual injury and delayed hemorrhage

Adnan H Siddiqui, MD, PhD University at Buffalo, Buffalo, NY

Editor Commentary

Traumatic ICAs are unusual aneurysms that are true pseudoaneurysms and have a high risk of rerupture They vary considerably in their loca-tion and morphology, so general rules in their management are hard to define For larger ones, bypass and trapping is likely the best strategy When multiple branches are involved, strategies can quickly turn com-plicated Iatrogenic trauma is often more straightforward, with simple repair or isolation of the segment and bypass Those associated with skull base trauma are less likely to be repairable, and salvage more often consists of bypass and endovascular or open sacrifice Furthermore, these patients are often sicker due to polytrauma or associated brain injury Timing of repair therefore needs to be adjusted to the clinical cir-cumstance

Peter Nakaji, MD Barrow Neurological Institute, Phoenix, AZ

Suggested Reading

Buckingham MJ, Crone KR, Ball WS, Tomsick TA, Berger TS, Tew JM Jr Traumatic intracranial aneurysms in childhood: two cases and a review of the literature Neurosurgery 1988;22(2):398–408

Cohen JE, Gomori JM, Segal R, et al Results of endovascular treatment of traumatic intracranial aneurysms Neurosurgery 2008;63(3):476–485, discussion 485–486

Fleischer AS, Patton JM, Tindall GT Cerebral aneurysms of traumatic origin Surg Neurol 1975;4(2):233–239

International Study of Unruptured Intracranial Aneurysms Investigators Unruptured intracranial aneurysms—risk of rupture and risks of surgical intervention

N Engl J Med 1998;339(24):1725–1733 Larson PS, Reisner A, Morassutti DJ, Abdulhadi B, Harpring JE Traumatic intracranial aneurysms Neurosurg Focus 2000;8(1):e4

Lath R, Vaniprasad A, Kat E, Brophy BP Traumatic aneurysm of the callosomarginal artery J Clin Neurosci 2002;9(4):466–468

Mao Z, Wang N, Hussain M, et al Traumatic intracranial aneurysms due to blunt brain injury—a single center experience Acta Neurochir (Wien) 2012;154(12): 2187–2193, discussion 2193

Medel R, Crowley RW, Hamilton DK, Dumont AS Endovascular obliteration of

an intracranial pseudoaneurysm: the utility of Onyx J Neurosurg Pediatr 2009;4(5):445–448

Miley JT, Rodriguez GJ, Qureshi AI Traumatic intracranial aneurysm formation lowing closed head injury J Vasc Interv Neurol 2008;1(3):79–82

fol-Moon TH, Kim SH, Lee JW, Huh SK Clinical analysis of traumatic cerebral eurysms Korean J Neurotrauma 2015;11(2):124–130

pseudoan-Parkinson D, West M Traumatic intracranial aneurysms J Neurosurg 1980;52(1): 11–20

Rangel-Castilla L, McDougall CG, Spetzler RF, Nakaji P Urgent cerebral ization bypass surgery for iatrogenic skull base internal carotid artery injury Neurosurgery 2014;10(Suppl 4):640–647, discussion 647–648

revascular-Wiebers DO, Whisnant JP, Huston J III, et al; International Study of Unruptured cranial Aneurysms Investigators Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment Lancet 2003;362(9378):103–110

Intra-Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

35 Previously Coiled Recurrent Aneurysms of the Anterior

Circulation

Ethan A Winkler, Brian P Walcott, and Michael T Lawton

Abstract Multiple large randomized clinical trials have led to the

wide-spread adoption of endovascular treatment of cerebral aneurysms

Cerebrovascular neurosurgeons are therefore increasingly confronted

with recurrent or residual aneurysms that have been previously treated

with endovascular coiling Previously treated aneurysms present unique

anatomical and decision-making challenges to open microsurgical or

endovascular retreatment In this chapter, we discuss several major

controversies complicating clinical decision making when treating

pre-viously coiled cerebral aneurysms Topics addressed include whether

treatment is indicated, selection of treatment modality (microsurgical

vs endovascular), anatomical considerations that should guide

selec-tion of the optimal microsurgical technique (clipping vs bypass), and

complication avoidance

Keywords: recurrent aneurysm, residual aneurysm, endovascular

coil-ing, microsurgical clippcoil-ing, cerebral bypass, prior treatment

Introduction

Multiple large randomized clinical trials—the International

Subarach-noid Aneurysm Trial (ISAT) and Barrow Ruptured Aneurysm Trial

(BRAT)—have led to the widespread adoption of endovascular treatment

of cerebral aneurysms However, many of these techniques are

associ-ated with lower rates of complete aneurysm occlusion than

microsurgi-cal clipping Incomplete obliteration and/or compaction of the coil mass

may lead to aneurysm recurrence over time In the reported literature,

rates of residual and recurrent aneurysms range from 39 to 61% and 13

to 21%, respectively

Cerebrovascular neurosurgeons are increasingly confronted with

recurrent or residual aneurysms previously treated with endovascular

coiling At the University of California San Francisco, there was in excess

of a threefold increase in the number of incompletely coiled and

recur-rent aneurysms requiring microsurgical treatment from 1997 to 2007

More recent publication has suggested that the incidence of retreatment

has stabilized Still, retreatment following endovascular coiling

repre-sents approximately 2% of all microsurgically treated aneurysms and is

most commonly encountered for aneurysms in the anterior circulation

Major controversies in decision making addressed in this chapter

include:

1 Whether or not treatment is indicated.

2 Microsurgical versus endovascular treatment of previously coiled

anterior circulation aneurysms.

3 Anatomical guidance of proper selection of microsurgical technique.

Whether to Treat

There is an absence of unequivocal clinical evidence to guide decision

making for retreatment of recurrent aneurysms after endovascular

coiling This leads to substantial variability among experienced

clini-cians on whether to re-treat The decision to re-treat and selection of

appropriate technique requires careful clinical judgment on a

case-by-case basis (►Fig 35.1) Risk of rehemorrhage from residual and/or

recurrent aneurysms following endovascular coiling is not trivial

Pub-lished studies—including ISAT, BRAT, and Cerebral Aneurysm Rerupture

Treatment (CARAT)—have suggested that the annual risk for rebleeding

after coiling ranges from 0 to 1.3%, but varies with the timing from initial

intervention For example, in CARAT and ISAT, rates of rerupture in the

first year following treatment occur in 1.7 and 1.8%, respectively, across

treatment modalities, but may be as high as 3.4% in those treated with

endovascular coiling After the first year, the annual risk declines, but

remains higher in those treated with endovascular coiling lar: 1.56 per 1,000 patient-years; microsurgical clipping: 0.49 per 1,000 patient-years) Despite this relative infrequency, rerupture of previously treated aneurysms is frequently neurologically devastating with a mor-

(endovascu-tality rate up to 58% (1, 2 in algorithm).

The identification of clues of looming rupture in the context of viously coiled aneurysms is less well established Similar to the initial treatment of cerebral aneurysms, factors to consider are size, location, and morphology of the recurrent aneurysm and whether it previously ruptured Additional factors unique to recurrence should also be con-sidered, including time since initial treatment and degree of aneurysmal occlusion In the CARAT study, the risk of rerupture of recurrent aneu-rysms varied as a function of initial aneurysm occlusion (overall risk: 1.1% for complete occlusion, 2.9% for 91–99% occlusion, 5.9% for 70–90%, and 17.6% for <70% occlusion) Given the consequences of rerupture, we favor retreatment when postcoiling residual or recurrence is detected in our center However, desires to treat should be tempered by the patient’s perioperative risk including age and comorbid conditions, patient pref-erence, surgeon or interventionist experience, and likelihood of success-ful intervention, and clinicians should engage in detailed risk versus benefit discussions with the patient and/or family to carefully design the most appropriate treatment plan

pre-Anatomical Considerations

Recurrence following endovascular coiling presents challenging omy not present in an untreated aneurysm The normal soft, compress-ible sac is no longer empty, but now filled with a hard coil mass that prevents collapse or softening of the aneurysmal dome with application

anat-of temporary clips Coil-induced separation between the aneurysm’s walls similarly converts the soft, easily closeable neck into a more rigid wedge Clip blades are more prone to splaying or sliding down the less compressible neck and risk occluding the parent vessel, nearby branches,

or adjacent perforating arteries Protrusion of coils into the aneurysm neck confounds this issue, and may further interfere with permanent clip placement and/or oppose closure In up to 55% of cases, coils extrude from the aneurysm dome into the subarachnoid space, but coil extru-sions are rarely detected on preoperative angiogram (►Figs 35.2, 35.3).

Fig 35.1 Factors influencing clinical decision making of microsurgical versus

endovascular management of previously coiled anterior circulation aneurysms

35 Previously Coiled Recurrent Aneurysms of the Anterior Circulation

233Algorithm 35.1 Decision-making algorithm for previously coiled recurrent aneurysms of the anterior circulation

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

Aneurysms—Anterior Circulation

234

Several morphological parameters may be measured on preoperative

angiography to facilitate operative planning—including neck width (N),

compaction height (H, which is the distance beneath the compacted

coils to the neck of the aneurysm), and the coil width (C), which is the

widest diameter of the coil mass parallel to the neck but perpendicular

to the direction of anticipated clip application Prior works have shown

that the ratio of coil width to compaction height (C:H), but not the ratio

of neck width to compaction height (N:H), is predictive of successful

Fig 35.2 Tandem clipping of a recurrent left posterior communicating artery aneurysm after stent-assisted coiling in a 49-year-old woman Surveillance digital subtraction

angiography with internal carotid artery injection and lateral (a) and anteroposterior (b) views showing recurrent aneurysm (c) Intraoperative photograph showing coil sion into the subarachnoid space Note the Neuroform stent is visible through the wall of the internal carotid artery (d) The aneurysm was clipped with a fenestrated clip on the proximal neck with a straight clip closing the fenestration distally (e) Extruded coils were seen to extend into the temporal lobe and were surrounded by hemosiderin from ante-cedent subarachnoid hemorrhage (f) Intraoperative indocyanine green angiography showing complete aneurysm occlusion and preservation of the anterior choroidal artery

extru-35 Previously Coiled Recurrent Aneurysms of the Anterior Circulation

235

Imaging

Four-vessel digital subtraction angiography is the preferred modality of

choice and permits detailed analysis of aneurysm and parent vessel

mor-phology A computed tomography angiography may also provide

addi-tional information regarding partially thrombosed and/or calcified vessels

However, the sensitivity and utility of these techniques may be limited by

artifact from the radiopaque coil mass A noncontrast computed

tomog-raphy scan of the head should evaluate for potential subarachnoid

hem-orrhage in any patient presenting with sudden or severe headache with

known aneurysm previously treated with endovascular coiling

Differential Diagnosis

The differential diagnosis for a recurrent aneurysm following initial

coiling is limited, but comparison with prior angiograms may help

deduce the etiology—including incomplete initial treatment, regrowth,

and/or compaction of the coil mass—as this may influence selection

of treatment modality Coil compaction results from a decrease in the interspaces between adjacent coils, whereas regrowth is an increase in aneurysm volume without decrease in coil volume

tech-If the recurrence is small and can be packed densely, coiling may be preferred However, a second recurrence may occur in 50% of cases

Fig 35.3 Clipping of a residual anterior communicating artery (ACoA) aneurysm requiring coil extraction in a 34-year-old man with subarachnoid hemorrhage

compli-cated by aneurysm perforation and hemorrhage during attempted coiling Lateral view of digital subtraction angiography with left internal carotid injection (a) and three- dimensional reconstruction (b) showing residual aneurysm (c) Intraoperative photograph showing perforation of the aneurysm dome with coil extrusion and intrasaccular coils filling the neck (d) The ACoA aneurysm was trapped with temporary clips (gold) The aneurysm was then transected and the coil mass was gently removed (e,f) The aneurysm neck was clipped with a straight clip, and the untreated anterior lobe of the residual aneurysm was clipped with four stacked clips Anteroposterior view of post-operative digital subtraction angiography with left internal carotid injection (g) and three-dimensional reconstruction (h) confirming complete occlusion of the aneurysm

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

Aneurysms—Anterior Circulation

with repeated coiling More sophisticated endovascular techniques—

such as stent-assisted coiling and flow diversion with pipeline

embo-lization devices—have shown initial promise, and further work is

ongo-ing to refine their application in previously coiled aneurysms (11 in

algorithm) Microsurgical clipping is favored under the following

condi-tions: when the recurrence is larger in size with sufficient tissue in the

neck for clip placement; when the predominant mechanism of

recur-rence is regrowth rather than coil compaction as this excludes the

dys-plastic tissue; or when there is evidence of coil extrusion (►Figs 35.2,

35.3) Microsurgical clipping offers a more durable solution to

avail-able endovascular options (5, 8 in algorithm) A large associated

intra-cerebral hematoma would favor microsurgical treatment—as with

untreated ruptured aneurysms—as this would facilitate securing the

ruptured aneurysm and enable subsequent evacuation of the clot

(5 in algorithm).

The preferred microvascular technique for retreatment of

previ-ously coiled residual and/or recurrent aneurysms is direct surgical

clipping Clips should be placed below or against the coil mass to

facili-tate complete mechanical closure This configuration prevents refilling,

excludes dysplastic tissue, and places the healthy arterial wall tissues in

direct apposition to facilitate repair and re-endothelialization (5, 8 in

algorithm; ►Figs 35.2, 35.3) In our clinical series, ≥80% of previously

coiled aneurysms were successfully treated with microsurgical clipping

alone To predict successful clipping, preoperative determination of the

coil width and compaction height (C:H, or compaction ratio) is

informa-tive A compaction ratio ≤2.5 correlates with the likelihood of successful

clipping (8 in algorithm) A noncompressible coil mass with a wider coil

width and shorter coil height (compaction ratio >2.5) creates a wedge

to which the clip is applied An angle greater than 90 degrees opposes

clip closure and increases risk of the downward displacement of the clip

to occlude the parent vessel and/or branches Roughly 70% of all

aneu-rysms with a C:H ratio greater than 2.5 require complex clip

reconstruc-tion after thrombectomy or coil mobilizareconstruc-tion, bypass, and/or wrapping

(9 in algorithm) Aneurysms with little coil compaction—a compaction

height greater than 2 mm—may not leave enough room to accommodate

placement of a clip across its neck, and delay in surgical treatment may

allow for further compaction and easier operation at a later date

Cerebrovascular Management—Operative

Nuances

Previously coiled aneurysms of the anterior circulation are surgically

accessed through a standard pterional or modified orbitozygomatic

cra-niotomy—like their untreated counterparts Subarachnoid dissection,

acquisition of proximal and distal control, adequate visualization and

preparation, and contingency planning (e.g., temporary clip strategy, in

case of intraoperative rupture) are of paramount importance To date,

the risk of intraoperative rupture appears lower with a previously coiled

aneurysm—none in our experience

Clipping of a recurrent aneurysm with favorable anatomy is relatively

straightforward However, less favorable anatomy requires contingency

plans If the coil mass interferes with aneurysm mobilization and/or clip

placement, opening the aneurysm dome to mobilize and/or extract coils

may convert an unclippable aneurysm into a clippable one The

aneu-rysm should first be successfully trapped with temporary clips The

aneurysm dome should be opened by transecting the aneurysm at its

equator to access the coil mass Coils accessed early after deployment in

the acute period are easily mobilized With greater time elapsed,

intra-luminal fibrosis makes the coils more adherent to the aneurysm wall

Careful dissection at the points of adhesion will release the coils

Exces-sive and more diffuse force applied to coils runs the risk of tearing the

aneurysm further complicating repair After mobilization, gentle

trac-tion may be applied to extract the coil mass from the opening Removal

of coils through a small opening is unpredictable Complete extraction

of coils is rarely required, and should be avoided The goal of coil

extrac-tion is to soften the neck and make room for the clip, and usually only

a portion of the coils need to be removed This maneuver may be

com-plicated by a multitude of factors, including bleeding from incomplete proximal and distal control, backbleeding from perforators or branches, insufficient tissue for reconstruction of the aneurysm neck, extensive scarring of the coil mass, or distal embolization from the thrombosed coil mass These complications may prolong ischemia times

Bypass is another viable surgical option for recurrent aneurysms that cannot be clipped (►Fig 35.4) With bypass, the vascular territory distal

to the aneurysm is first revascularized through a variety of techniques—including extracranial–intracranial bypasses, in situ bypasses, and radial artery, or saphenous vein grafts—which are tailored to the anatomy, loca-tion, and desired blood flow The aneurysm is then trapped or proximally occluded, eliminating or altering blood flow to promote thrombus forma-tion within the aneurysm Bypass has a number of potential advantages when confronting a previously coiled aneurysm—most notably avoidance

of direct aneurysm manipulation and predictable ischemia times erative decision making is important because selection of technique influ-ences patient positioning, draping, and preservation of structures, like the superficial temporal artery, with initial dissection We routinely prepare a bypass contingency plan and prepare the forearm or leg for potential har-vest of the radial artery or saphenous vein, should microsurgical clipping not be possible Finally, aneurysms not able to be clipped or bypassed may

Preop-be wrapped with muslin or cotton to induce scarring of the aneurysm wall

This should be treatment of last resort (10 in algorithm) With experience,

ingenuity, and technical skill, one can design a strategy to permit more definitive clipping and/or bypass in the vast majority of clinical scenarios

In our published clinical series, 81% of previously coiled residual and recurrent aneurysms were treated with microsurgical clipping—including 72% in which the clip was placed below the coil mass and 6%

in which clips were placed across coils present in the neck of the rysm Aneurysm transection with mobilization and/or removal of coils was required in 12% of cases Bypass was required in 11% of cases No aneurysm has required wrapping in the past 10 years

aneu-Endovascular Management—Operative Nuances

Endovascular options for treatment are either recoiling or flow sion Additional adjuvants, such as balloon-assisted coil delivery, double microcatheter coil delivery, and stent-assisted coiling can be considered

diver-in specific situations

Balloon-Assisted Coiling

Stand-alone coiling can be challenging with recurrent aneurysms that have neck-based recurrences, bifurcation aneurysms, and aneurysms with a branch vessel originating near the neck of the aneurysm Using inflatable balloon techniques can remodel the neck and/or protect a par-ent vessel/side branch It can also reduce “kickback” during coil deploy-ment, allowing for the maximum number of coils to be deployed.For patients with subarachnoid hemorrhage, heparinization is initially held Once one or two coils are deployed into the aneurysm, systemic heparin can be administered The balloon catheter is introduced into the proximal end of the guide catheter, along with the microcatheter (through the side port) When the coil is nearing the aneurysm, the balloon is filled with 100% contrast Subsequent coils can then be delivered, mindful of distal ischemia time while the balloon is inflated Somatosensory evoked potentials and motor evoked potentials can be useful monitoring tech-niques, particularly in anesthetized patients, and if changes occur, the balloon can be temporarily deflated to restore distal blood flow Once the coil mass is delivered, the balloon is deflated If the coil mass does not herniate out of the aneurysm, then the microcatheter is removed If the coil mass appears unstable, then deployment of a stent may be required

Double-Microcatheter Technique

Stent- or balloon-assisted coiling for wide-necked recurrences have specific risks for thromboembolic complications Stent-assisted coiling

35 Previously Coiled Recurrent Aneurysms of the Anterior Circulation

237

requires long-term antiplatelet therapy, which can be problematic

during the initial management of a ruptured aneurysm The double-

microcatheter technique is a useful alternative in these situations to help

achieve a denser coil delivery without the need for antiplatelet therapy

Two microcatheters are advanced through the guide catheter and into

the aneurysm sac Sequential or concurrent coil deployment leads the

coils to “lock” onto or “weave” into each other, respectively, decreasing

the likelihood of coil herniation and may obviate the need for a stent

One of the coils is then detached For all subsequent coil deployments,

one of the catheters retains a deployed coil that is not detached, thereby

acting as a brace Embolization is continued through the available

cath-eter until aneurysm obliteration is complete The greater the aneurysm

recurrence, along with its shape (mushroom vs box), the more it can

help predict the success of this technique

Stent-Assisted Coiling

Stents to support coil placement in recurrent aneurysms are necessary

at times By “jailing” the coil mass in the aneurysm, the stent prevents prolapse of the coils Elective procedures are typically preceded by sev-eral days of pretreatment with dual-antiplatelet medications because stents are prone to thromboembolic complications Dual-antiplatelet therapy is continued for a period of several months, with some form of antiplatelet therapy continuing indefinitely

Flow Diversion

Flow-diverting stents are a new paradigm treatment for brain rysms, where intraluminal flow is redirected to the distal parent vessel, rather than into the aneurysm This is accomplished by using a stent

aneu-Fig 35.4 Trapping and bypass of a recurrent

postero-inferior cerebellar artery aneurysm in a 69-year-old woman with coil compaction Surveillance digital sub-traction angiography with left vertebral artery injection and lateral (a) and anteroposterior (b) views showing residual aneurysm (c) Intraoperative photograph show-ing anatomy not favorable for direct clipping—including

an atherosclerotic neck and inflow and outflow vessels

at roughly a 90-degree angle (d) The inflow and outflow arteries were transected and re-anastomosed end to end (e) The coiled aneurysm was intentionally left in situ to avoid manipulation of the lower cranial nerves The anastomoses flowed well as seen intraoperatively (f) and confirmed on postoperative angiogram (left vertebral artery injection, lateral view; g)

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

Aneurysms—Anterior Circulation

238

with a low-porosity mesh weave Adjunctive coils are sometimes placed

into the aneurysm to provide immediate aneurysm closure Some of the

best preliminary results for flow-diverting stents have been reported for

cavernous and paraclinoid segment carotid aneurysms Recurrences in

these segments are also readily treated with this modality

Complication Avoidance and

Outcome

With open microsurgical retreatment of previously coiled aneurysms,

our mortality rate in the perioperative period was 4% and largely the

result of antecedent subarachnoid hemorrhage With a mean follow-up

period of 6 years, 89% of patients had a good outcome (Glasgow Outcome

Scale (GOS) score of 4 or 5) The overwhelming majority of patients

neu-rologically improved or remained unchanged after treatment, with only

4% of patients showing worsening neurological status after retreatment

Higher complication rates up to 15% have been reported at other centers,

largely the result of inadvertent clip placement, vessel injury, and/or

pro-longed ischemia time Therefore, efforts to facilitate clipping and confirm

proper clip placement, as well as check patency of a bypass graft

intraop-eratively with indocyanine green video angiography, are required

No significant differences in morbidity or outcome have been found

between microsurgical and endovascular retreatment of recurrent

aneu-rysms Favorable outcomes have also been reported with endovascular

retreatment modalities Complication rates range from roughly 1 to 3%

and are largely thromboembolic or the sequela of anticoagulation

How-ever, periprocedural complication rates up to 11% have been reported in

other studies, including the CARAT study Rates of death or permanent

disability range from 1.29 to 2.19% in large clinical series Risk may

accu-mulate when multiple interventions are required to achieve complete

occlusion Stent-assisted coiling for residual or recurrent aneurysms had

a favorable outcome in 91% of patients (GOS of 4 or 5), but was

associ-ated with a rate of mortality of 2% and a comparatively higher

periproce-dural complication rate of 11% With the pipeline embolization device,

major procedural complications owing to intracranial hemorrhage occur

in 3 to 7% of patients Further studies are needed to better delineate the

safety profile and indications for adjuvant endovascular therapies

Durability and Rate of Recurrence

In our clinical series, complete angiographic occlusion with open

micro-surgical management was achieved in 89% of previously coiled residual or

recurrent aneurysms With exclusion of wrapped aneurysms, microsurgical

clipping or bypass led to complete angiographic occlusion in 95% of cases

The small minority of aneurysms that were wrapped and followed showed

no evidence of radiographic enlargement No rebleeding or subsequent

recurrence has been observed (supports algorithm steps 5, 8, 9, and 10).

Rates of complete or near-complete occlusion with endovascular

retreatment are comparatively lower and vary with selected treatment

modality Rates of complete or near-complete occlusion with detachable

coils range from 46.9 to 76% With long-term angiographic follow-up,

radiographic recurrence was observed in up to 50% of recoiled

aneu-rysms Others have reported the need for additional coiling in nearly 20%

of cases, suggesting that multiple attempts of recoiling are often required

In one larger series, rate of complete occlusion with stent-assisted coil

embolization was 59%, with 32% of re-treated aneurysms showing a

small neck remnant Studies with flow diversion embolization devices

have shown higher rates of occlusion in previously coiled aneurysms as

evidenced by a range of 83 to 93% of complete or near-complete

occlu-sion in reported studies (supports algorithm step 11) Further long-term

follow-up is needed with newer endovascular technologies to determine

whether these higher rates of occlusion lead to lower rates of recurrence

Clinical and Radiographic Follow-Up

Risk for future recurrence warrants long-term clinical and

radio-graphic surveillance in all aneurysm patients Following endovascular

retreatment, angiograms should be performed at 6 months and 2 years posttreatment For microsurgical clipping, interval angiograms should

be performed in the immediate postoperative period and 5 years treatment If a recurrence or remnant is detected, additional follow-up is indicated with an interval decided on case-by-case basis

post-Expert Commentary

One of the reasons why patients select endovascular therapy over surgical therapy for their aneurysm is to avoid an open, invasive proce-dure They make this choice knowing not only that the overall risks may be lower with coiling, but also that the efficacy and durability are also lower than with clipping When it becomes clear that their aneurysm has not been obliterated completely, difficult decisions must be made We gener-ally prefer an aggressive response to recurrences, particularly in patients who presented initially with subarachnoid hemorrhage Some recurrences are minor imperfections that seem to be safe to simply observe Other recurrences are clearly problematic, but amenable to simple “revision” with additional coils A small number of recurrences represent endovas-cular failures that require a complete shift in treatment strategy These latter patients are the ones that should be considered for microsurgical therapy, which might require a shift in their thinking and preferences.Our experience with recurrent coiled aneurysms demonstrates several important lessons First, the number of patients requiring sur-gery is small, and markedly smaller than we anticipated based on the increasing market share of endovascular therapy and the high incidence

micro-of aneurysm degradation and coil extrusion after coiling Second, the complexity of clipping recurrent aneurysms is relatively low in carefully selected patients Coil compaction can create adequate room for clip placement beneath the coil mass while protecting the aneurysm from intraoperative rupture The compaction ratio is a useful tool to help select clippable aneurysms for surgery Third, even carefully selected aneurysms that appear to be clippable may not be, and unclippable aneurysms often require advanced clipping techniques or bypasses Coil mobilization or extraction is reserved for acutely coiled aneurysms or those that need just a small amount of extra space for the clip, whereas bypass and trapping is reserved for delayed recurrences or those with complex morphology that would be difficult to clip anyway (e.g., giant aneurysms, thrombotic aneurysms, dolichoectatic aneurysms, or ather-osclerotic aneurysms with calcified walls) Fourth, surgical results with recurrent aneurysms are generally excellent, which should lower the threshold for treatment in these refractory patients

Perhaps the best way to deal with residual and recurrent aneurysms

is to prevent them by initially selecting the better aneurysm treatment Wide necks, low aspect ratios, large and giant size, intraluminal throm-bosis, and certain locations like the middle cerebral artery (MCA) bifur-cation make coiled aneurysms recanalize and recur, whereas clipping more definitively closes these aneurysm The initial choice of aneurysm treatment is best made by a collaborative team of aneurysm specialists with expertise in both endovascular and microsurgical therapies Consid-eration must be given not just to treatment risks, but also to efficacy and durability It is reasonable to select endovascular therapy preferentially for those aneurysms with favorable anatomy that optimizes treatment risks, efficacy, and durability It is also reasonable to select microsurgery for those aneurysms with unfavorable endovascular anatomy that could

be coiled safely, but may not be obliterated completely and may have

an increased recurrence risk Careful treatment selection will avoid the complexities of retreating a coil recurrence later

Michael T Lawton, MD University of California San Francisco, San Francisco, CA

Editor Commentary

Endovascular coil embolization of intracranial aneurysms has increased over the last two decades Aneurysm recurrence following coiling has

35 Previously Coiled Recurrent Aneurysms of the Anterior Circulation

239

been estimated at approximately 20% There are a number of

endovas-cular and surgical options for these difficult aneurysms Our own

expe-rience at Mount Sinai has been that, when treating recurrent aneurysms,

some form of permanent parent vessel support, either a traditional stent

or flow-diverting stent, can often be helpful in achieve long-term success

Placement of a traditional stent or flow-diverting stent in a previously

coiled aneurysm is straightforward The use of Pipeline for recurrent

pre-viously coiled aneurysms has been shown to result in a complete and

near-complete aneurysm occlusion rate of 87% with a 3% complication

rate Placement of a flow-diverting stent for an aneurysm that has

previ-ously undergone stent-assisted coiling is more complicated and has been

shown to be less effective When attempting flow diversion for aneurysms

that were previously coiled with stent assistance, we recommend using

a 5MAX Distal Delivery Catheter (DDC) intermediate catheter

(Penum-bra, Alameda, CA) and traversing the entire stent before Pipeline

deploy-ment to assure the microwire has traversed the central axis of the entire

stent and has not gone “in-out-in.” This maneuver will assure complete

Pipeline opening and help avoid intraoperative mechanical and

thrombo-embolic complications It is also crucial to remember that microvascular

clipping remains an important option for these difficult aneurysms and

the risks and benefits must be weighed for every patient

J Mocco, MD, MS

Icahn School of Medicine at Mount Sinai, New York, NY

Suggested Reading

Daou B, Starke RM, Chalouhi N, et al The use of the pipeline embolization device

in the management of recurrent previously coiled cerebral aneurysms

Neurosurgery 2015;77(5):692–697, 697

Dorfer C, Gruber A, Standhardt H, Bavinzski G, Knosp E Management of residual and recurrent aneurysms after initial endovascular treatment Neurosurgery 2012;70(3):537–553, discussion 553–554

Henkes H, Fischer S, Liebig T, et al Repeated endovascular coil occlusion in 350 of

2759 intracranial aneurysms: safety and effectiveness aspects Neurosurgery 2008;62(6, Suppl 3):1532–1537

Johnston SC, Dowd CF, Higashida RT, Lawton MT, Duckwiler GR, Gress DR; CARAT Investigators Predictors of rehemorrhage after treatment of ruptured intra-cranial aneurysms: the Cerebral Aneurysm Rerupture Treatment (CARAT) study Stroke 2008;39(1):120–125

Lawton MT Seven Aneurysms:Tenets and Techniques for Clipping Stuttgart: Thieme Medical Publishers Inc; 2011

Molyneux AJ, Kerr RS, Yu LM, et al; International Subarachnoid Aneurysm Trial (ISAT) Collaborative Group International subarachnoid aneurysm trial (ISAT) of neu-rosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion Lancet 2005;366(9488):809–817

Owen CM, Montemurro N, Lawton MT Microsurgical management of residual and recurrent aneurysms after coiling and clipping: an experience with 97 patients Neurosurgery 2015;62(Suppl 1):92–102

Raymond J, Darsaut TE An approach to recurrent aneurysms following endovascular coiling J Neurointerv Surg 2011;3(4):314–318

Raymond J, Guilbert F, Weill A, et al Long-term angiographic recurrences after selective endovascular treatment of aneurysms with detachable coils Stroke 2003;34(6):1398–1403

Spetzler RF, McDougall CG, Zabramski JM, et al The Barrow Ruptured Aneurysm Trial: 6-year results J Neurosurg 2015;123(3):609–617

Waldron JS, Halbach VV, Lawton MT Microsurgical management of incompletely coiled and recurrent aneurysms: trends, techniques, and observations on coil extrusion Neurosurgery 2009;64(5, Suppl 2):301–315, discussion 315–317

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

36 Previously Clipped Recurrent Aneurysms of the Anterior Circulation

Naif M Alotaibi, David Hasan, and R Loch Macdonald

Abstract Neurosurgical clipping of intracranial aneurysms is more

like-ly to result in complete aneurysm obliteration compared to

endovas-cular treatment, although the repair method to use depends on other

factors such as the clinical outcome of the patient so that endovascular

treatment often is recommended over clipping Despite the high clipping

repair efficacy, aneurysm remnants may be found immediately after

an-eurysm clipping in about 5% of patients They may remain

asymptom-atic or lead to growth, hemorrhage, or symptoms such as mass effect In

addition, there rarely may be regrowth, hemorrhage, or symptoms due

to regrowth of a previously completely clipped aneurysm or from a de

novo aneurysm at another site Management options for

residual/recur-rent aneurysms after clipping include no treatment, ongoing

radiologi-cal surveillance, clipping or endovascular repair Management decisions

depend on patient and aneurysm factors as well as the estimated risks

of repair

Keywords: intracranial aneurysm, subarachnoid hemorrhage,

endovas-cular coiling, neurosurgical clipping

Introduction

Randomized clinical trials found that endovascular repair of ruptured

intracranial aneurysms gives better outcomes than neurosurgical

clip-ping for aneurysms that can be treated by either method As a result,

the majority of aneurysms are now repaired by endovascular methods

and there are fewer and fewer patients living with previously ruptured,

clipped aneurysms Another reason for the decline in these cases is that

neurosurgical clipping is associated with lower rates of recurrence and

retreatment compared to endovascular options Unlike for acute repair

of ruptured aneurysms, the evidence upon which to base decisions

about whether to repair an unruptured aneurysm, if at all, are based on

anecdotal evidence and, if a decision is made to treat, how to repair it

also is not based on science

Endovascular and open neurosurgical options provided by

experi-enced physicians are recommended for the management of aneurysms

that recur after clipping as they are rare, and repeat endovascular or

intracranial surgery by themselves probably have an increased risk of

2 Timing for intervention.

3 Open neurosurgical versus endovascular treatment for recurrent

aneurysms previously clipped.

Whether to Treat

Treatment of recurrent aneurysms after clipping may be considered in several scenarios including (►Table 36.1):

1 Aneurysm remnants that are found immediately after aneurysm

clipping in about 5% of patients (1 in algorithm).

2 Regrowth, hemorrhage, or symptoms such as mass effect from a

previously completely clipped aneurysm (2 in algorithm).

3 Growth, hemorrhage, or symptoms from an aneurysm remnant

known after clipping (2 in algorithm).

4 New de novo aneurysms at site(s) distinct from the previously

clip-ped aneurysm (3 in algorithm).

This decision is based on assessment of the risks of treatment anced against the risk of the natural history of the identified aneurysm, the natural history risk being basically the risk of recurrent hemorrhage Some patients recover well after recurrent hemorrhage but for decision making, it is reasonable to assume that bleeding or rebleeding after aneurysm repair will lead to an unfavorable outcome Surgeons have published retrospective reviews of their cases of craniotomy to clip pre-viously clipped aneurysms Morbidity and mortality is about 10%, but this is likely an underestimate and must vary with all of the usual fac-tors that affect morbidity and mortality after aneurysm surgery These factors include patient- (age, medical comorbidities, intracranial ather-osclerosis) and aneurysm-related features (ruptured or not, presence

bal-of space-occupying intracerebral hemorrhage, aneurysm size, location, presence of calcifications and thrombus, presence of daughter loculi, and growth) Older age and associated medical illnesses increase the risk

of complications Ruptured aneurysms have worse outcome than tured aneurysms Larger aneurysms and those with calcification and/

unrup-or thrombus are munrup-ore complicated to repair by any method Increased size, presence of daughter sac, growth of the aneurysm, and posterior circulation location increase the risk of hemorrhage When an aneurysm remnant is found after surgery, knowledge of why the remnant was left, either purposely or not, is important in deciding whether and how to

is 0.26 to 0.52% De novo aneurysms form in patients with intracranial aneurysms at 0.84 to 2.2% per year and this must be higher than the risk

Table 36.1 Clinical scenarios of aneurysms detected after clipping

Type of aneurysm Reasons for detection, scenarios for follow-up or treatment

Aneurysm or remnant detected

immediately after surgery

Expected and intentionally left Unexpected

Aneurysm remnant followed up at

the site of initial surgery Unchanged during follow-up Asymptomatic growth during follow-up Symptomatic (mass effect or hemorrhage) during follow-upAneurysm recurrence after complete

clipping at the site of initial surgery No recurrence during follow-up Asymptomatic recurrence during follow-up Symptomatic recurrence (mass effect or hemorrhage) during follow-up

De novo aneurysm Asymptomatic development during

follow-up

Symptomatic development (mass effect or hemorrhage) during follow-up

36 Previously Clipped Recurrent Aneurysms of the Anterior Circulation

241Algorithm 36.1 Decision-making algorithm for previously clipped recurrent aneurysms of the anterior circulation

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

Aneurysms—Anterior Circulation

of recurrent subarachnoid hemorrhage (SAH), although the rates (0.79–

1.9% per year) overlap with overall recurrence rates

Most recurrent aneurysms, like aneurysms in general, are in the

anterior circulation A reasonable assumption would be that the risk

of hemorrhage from recurrent aneurysms after complete clipping and

from de novo aneurysms approximates that of an unruptured aneurysm

This risk is higher with increased aneurysm size, posterior location, and

history of SAH; so, these factors need to be taken into account when

determining management (2, 3 in algorithm).

The time from initial treatment to retreatment in most studies is about

10 years for recurrent and de novo aneurysms Remnants after initial

surgery for aneurysm repair should be detected by intraoperative means

such as indocyanine green (ICG) or intra-arterial contrast angiography

and in these cases, such remnants of the aneurysm can be left alone or

treated right away by endovascular means If intraoperative imaging is

not done, then various other unexpected findings can arise that may be

treated with reoperation, endovascular methods, or observation

Aneurysm Detected Immediately after

Surgery

If the surgeon does the best clipping they can and document a

resid-ual aneurysm by intraoperative means, then they need to decide after

the surgery whether to observe the remnant or to endovascularly coil

it If intraoperative imaging is not done, then unexpected findings can

occur such as filling of the aneurysm distal to the clip blades, presence

of a residual proximal part of the aneurysm, or finding a completely

unclipped aneurysm (1 in algorithm) Aneurysm filling distal to the

clip blades carries a high risk of rebleeding for ruptured aneurysms and

alters the hemodynamics of unruptured aneurysms, potentially leading

to catastrophic hemorrhage (1, 5, 8 in algorithm) Therefore, in general,

distal filling should be treated immediately by surgical exploration or

endovascular means with the decision based on the usual factors such

as the clinical condition of the patient, the surgeon’s impression as to

the cause of the remnant, and the potential efficacy of repeat clipping or

endovascular repair (►Fig 36.1) The same considerations apply to

unex-pected proximal remnants, although their risk of rupture is probably low

whether or not the initial indication for treatment was hemorrhage or not

and approximates that of unruptured aneurysms (2, 6, 7, 9 in algorithm).

No Change, Growth, Mass Effect, or

Hemorrhage from Previously Clipped

Aneurysm or De Novo Aneurysm

A known residual aneurysm that was not treated right after the first

repair procedure means that a decision was made not to intervene

Sometimes, it may be appropriate to discharge the patient and not

fol-low up, for example, if they are extremely elderly, frail, or medically unwell (unfavorable risk:benefit ratio) In other cases, ongoing surveil-

lance with neuroimaging would be recommended (9, 10 in algorithm)

Follow-up imaging also has been recommended for patients with tured aneurysms who have some combination of young age, female sex, smoking, and multiple aneurysms, even if completely clipped because of the higher risk of recurrence, de novo aneurysm formation, and hemor-rhage Recommendations for imaging follow-up of clipped unruptured aneurysms may be considered on a case-by-case basis There are no data upon which to make accurate recommendations

rup-For those patients with recurrence of a completely clipped aneurysm, growth of a remnant, and symptoms or hemorrhage from such a case, treatment indications differ Asymptomatic, unruptured, and nongrow-ing recurrences could be considered to have a natural history similar

to unruptured aneurysms, where the risk of rupture is related to prior history of hemorrhage, size, location, and daughter sac These risks are generally low and a nonurgent evaluation of the repair method, if any, and the risks and benefits can be done If there is growth of a remnant,

or symptoms or hemorrhage from any aneurysm, then repair is mended soon for growth and generally immediately for symptoms or hemorrhage The method of repair can be guided by the usual indica-tions for clipping or coiling, taking into account the nuances discussed

recom-later (4, 5, 6, 7 in algorithm).

The natural history and risk of treatment of de novo aneurysms can be approximated roughly from the International Study of Unruptured Intracra-nial Aneurysms and combined analysis of similar studies and management

based on this (3 in algorithm) The risk of rupture increases with aneurysm

size, posterior circulation location, and if the patient has a history of SAH

Anatomical Considerations

The physician treating aneurysm recurrence in the anterior circulation after previous clipping should recognize that preoperative imaging, scar tissue, and normal anatomy can be altered and obscured, increasing the difficulty of the surgery Repeat surgery requires clear understanding and optimal preoperative visualization of the anatomy of perforating and neighboring branches at the site of clip as well as the location of the recurrence (►Fig 36.2) Examination of the prior imaging and operative

and discharge reports from the previous clipping are useful to stand where the recurrence is, why any residual aneurysm was pres-ent, if any, and any other unexpected findings or events that occurred

under-at the initial surgery Clip artifacts on computed tomographic phy (CTA) may obscure visualization of the relationship of the aneurysm

angiogra-to bony structures (e.g., anterior clinoid process when treating recurrent internal carotid artery aneurysms) and adjacent blood vessels Catheter angiography with rotational views and three-dimensional (3D) recon-structions are highly recommended Similar considerations apply when endovascular repair is contemplated

Pathophysiology

Formation and growth of previously clipped or de novo aneurysms after SAH is more likely in smokers, patients with hypertension, multiple aneu-rysms, and possibly female sex These factors are similar to those associ-ated with recurrent SAH, but the latter includes increased aneurysm size, location, and daughter sac Several studies postulated factors that could lead to aneurysm recurrence after clipping These include clip-related factors (slippage over time, which is exceptionally rare), biomechanical factors related to aneurysm morphology, and hemodynamic or biologi-cal factors that could lead to arterial wall weakness These factors are all theoretical explanations and none of them are verified to be responsible for the etiology of recurrence in a dedicated prospective investigation

Classification

At least three types of recurrence are recognized (►Table 36.1)

There may be regrowth of a known postoperative residual aneurysm,

Table 36.2 Risk of rupture of previously clipped aneurysms

Initial

indication for

treatment

Type of recurrence Risk of hemorrhageUnruptured

intracranial

aneurysm

Remnant Natural history probably similar to

unruptured aneurysms where the risk

of rupture is related to prior history

of hemorrhage, size, location, and daughter loculi

Recurrent

De novoRuptured

intracranial

aneurysm

RemnantRecurrent Risk of rupture among completely

clipped aneurysms very low, was 0% (95% confidence interval:

0–0.14%) in the CARAT studyKnown

untreated or de novo

Most likely rupture rates similar to Group 2 (with prior hemorrhage) in the International Study of Unruptured Intracranial Aneurysms

36 Previously Clipped Recurrent Aneurysms of the Anterior Circulation

recurrence of a new aneurysm at the same site, or de novo development

of an aneurysm at a different site than the initial aneurysm (1, 2, 3 in

algorithm) The relative numbers of these cases in the literature vary

among studies and are roughly equally uncommon The most frequent

sites of recurrence of completely clipped aneurysms are distal to the clip

blades or lateral to the clip blades The least common site is proximal to

the blades It is unclear whether this classification has a role in

retreat-ment decision planning

Workup

Clinical Evaluation

A history and physical and neurological examination should be the

standard If an open surgical intervention is considered, examination of

the old surgical incision is important in planning the craniotomy and

to ensure excellent closure and cosmetic results The diagnosis of SAH

is the same as for patients who have never had an SAH and involves

CT scanning and CTA and/or lumbar puncture Most growing

rem-nants, regrowths, and de novo aneurysms that have not ruptured are

asymptomatic

Imaging

Cranial CT and CTA with 3D reconstructed images are generally obtained

to evaluate aneurysms after prior clipping They also are useful for

imag-ing surveillance over time in patients with clipped aneurysms who are

judged to require imaging follow-up The advantages are that CT

imag-ing usually shows the recurrent aneurysm, the relationship with the

old clip, patency of adjacent arteries, and the presence of de novo

aneu-rysms Clip artifact can always obscure the vascular anatomy; so,

cath-eter angiography with rotational views and 3D reconstructions remain

the gold standard for evaluation of previously clipped aneurysms and essentially always should be obtained in such cases Magnetic resonance imaging (MRI) and MR angiography (MRA) can be performed only after the type of clip can be verified either by medical records or radiography since some old clips are ferromagnetic and could move in the MRI mag-netic field with potentially catastrophic consequences This is rare now

as most aneurysm clips used in the past few decades have been MRI compatible up to 3 Tesla MRI/A will provide information on the brain and vasculature that is more than a few centimeters from the clip, which may be important but information about the brain and arteries near the clip are usually completely obscured by artifact

Differential Diagnosis

If the patient presents with SAH, then angiography should show an aneurysm that is consistent with the pattern of SAH on CT If angiogra-phy shows multiple aneurysms, determination of the rupture site fol-lows the same algorithm as in the case of a first SAH The location of the SAH, focal neurological symptoms, and larger aneurysm size are key fac-tors The main differential diagnosis for recurrent aneurysms is de novo aneurysms located close to the clip site (►Figs 36.2 and ►36.4) Careful

examination of imaging is needed to recognize whether the aneurysm arises from the old site or from a new point on the parent or branch arteries

Treatment

Conservative Management

Aneurysm remnants or recurrences following clipping do not necessarily require repair Any patient with an aneurysm should be advised to stop smoking and have hypertension treated They should be educated on

Fig 36.1 A 46-year-old man presented with subarachnoid hemorrhage and was World Federation of Neurological Surgeons grade 2 (a) Catheter angiography

(anteropos-terior right [b] and left [d] and lateral right [c] and left [e] internal carotid artery injections) showed aneurysms at the an(anteropos-terior communicating artery complex, left internal carotid artery bifurcation, and left proximal middle cerebral artery All of these aneurysms were clipped through a left pterional craniotomy Postoperative angiography

several days later showed an aneurysm at the anterior communicating artery that appeared to be distinct from the aneurysm that was already clipped at that

loca-tion (right [f] and left anteroposterior [g] and lateral [h] internal carotid artery injecloca-tions) The craniotomy was reopened about a week after the first surgery and a second anterior communicating artery aneurysm was found and was clipped Twenty years later, the patient presented with syncope He had a Montreal cognitive assessment

score of 29 and was doing well Computed tomography angiography showed no residual or recurrent aneurysms (axial [i] and coronal [j] views) After a second syncopal episode, a pacemaker was inserted and the syncope did not recur during 2 years of follow-up

Aneurysms—Anterior Circulation

244

the risks and benefits of treatment and reassured that the risk of

hem-orrhage is low in the short term and if no treatment is recommended,

then it must be very low No lifestyle restrictions should be imposed

specifically due to the aneurysm If repair would never be reasonable,

for example, in the very elderly or those with short life expectancy, then

no follow-up may be the best option In most other cases, however, serial

radiological imaging follow-up is indicated (10 in algorithm).

Cerebrovascular Management—Operative

Nuances

The standard approach for reoperation would be through the prior

cra-niotomy, which for anterior circulation aneurysms is usually a pterional

or orbitozygomatic Another option would be the anterior

interhemi-spheric approach for reoperation in the anterior communicating region,

which would have the advantage of avoiding some of the scar tissue and

adhesions for the last operation

The patient is anesthetized, positioned, and preparations for

intraop-erative angiography are made Special attention is paid to the

superfi-cial temporal artery in cases where bypass is needed or contemplated,

although it will generally be unusable due to injury during the first

craniotomy The bone flap is almost always fused in these cases and

requires a new craniotomy to re-gain access Opening of the dura usually

is easiest inferior or caudal to the previous dural incision as the brain

tends to be most adherent to the dura at the suture line Opening

infe-rior to this negates the need to dissect the brain off the dura After the

dura opening, microsurgical dissection under the operating microscope

is used to follow the adhesions and the track of the first operation to reach the old clipped aneurysm Most of pia-arachnoid adhesions are easily broken down, but if the dura is involved or there is any resistance

to blunt dissection, sharp dissection with an arachnoid knife or scissors is the best method Too much manipulation of the arteries and brain is always undesirable and risks injury to the arteries, contusion of the brain, and premature aneurysm rupture

micro-It is optimal to obtain proximal control of the feeding artery before dissecting around the old clip site After exposure of arteries for prox-imal control, of the old clip and the almost universally present two branch arteries, the recurrent aneurysm can be identified proximal, lateral, or distal to the old clip Sharp dissection by cutting the scar tis-sue with a knife or scissors is recommended This can be done along the outside edges of the clip where there generally cannot be recurrent aneurysm, although one has to watch for adherent cerebral arteries and lateral regrowth of the aneurysm This dissection may free up the clip for removal if necessary or for safe application of the new clip Next, one needs to determine whether the old clip can be left in place and the new sac clipped independently or if the old clip has to be removed It is best

to avoid removing the old clip Removing the old clip presupposes the appropriate clip applier is available, which may not be the case for some very old clips Removal also risks intraoperative rupture either from the freshly unclipped aneurysm remnant or from tearing of the sac during clip removal Clipping without removal of the old clip or adequate dis-section to mobilize the old clip and aneurysm dome risks rupture and

Fig 36.2 A 69-year-old man presented with subarachnoid hemorrhage and was World Federation of Neurological Surgeons grade 2 (plain axial computed tomography

[a,b]) He had a history of clipping of a ruptured left middle cerebral artery (MCA) aneurysm 10 years earlier, after which he recovered, returned home, and was able to live independently Catheter angiography showed the prior left MCA aneurysm clip and an aneurysm arising proximal and lateral to the clip (left internal carotid artery anter-oposterior [c] and lateral [d] injections) The aneurysm was clipped a day after the hemorrhage through the previous left pterional craniotomy Intraoperative angiography performed by retrograde injection of the superficial temporal artery showed complete clipping of the aneurysm (unsubtracted [e] and subtracted [f] oblique left internal carotid artery views) Postoperative computed tomography showed no new hypodensities and the patient was able to return home with some daily assistance with his activities [g, h]

36 Previously Clipped Recurrent Aneurysms of the Anterior Circulation

tearing the recurrent aneurysm by causing undue tension on the

recur-rent sac This is the same issue as that occurring when clipping

aneu-rysms that have been coiled or aneuaneu-rysms that are adherent to the dura

After placing the new clip, it is highly recommended that some method

be used to document patency of the adjacent arteries and lack of filling

of the aneurysm (►Fig 36.3) Intraoperative ICG angiography is fast and

easy but prone to difficulties visualizing the anatomy in repeat clipping

operations Intraoperative angiography is usually the best method;

angi-ography can be done by retrograde injection of the superficial temporal

artery if it is still patent

Endovascular Management—Operative Nuances

The two factors to consider when contemplating endovascular niques in treatment of a recurrent, previously clipped aneurysm are aneurysm location and morphology of the recurrence

tech-The location of the recurrence can be categorized from an cular perspective into side-wall and bifurcation aneurysms Side-wall aneurysms may include ophthalmic, dorsal, and ventral supraclinoid ICA segment, posterior communicating artery, anterior choroidal artery,

endovas-Fig 36.3 A 59-year-old man presented with intracerebral, subarachnoid, and intraventricular hemorrhage and was World Federation of Neurological Surgeons grade 2

He had a history of lymphoma diagnosed 3 years earlier, which had recurred after chemotherapy Axial cranial computed tomography (CT) showed an intracerebral orrhage (a) and computed tomographic angiography (b) showed the source was a distal anterior cerebral artery aneurysm The aneurysm was clipped through a frontal parasagittal craniotomy Intraoperative angiography was not done and postoperative CT angiography suggested the aneurysm was obliterated (c–f) The patient deterio-rated 6 days later and CT showed more hemorrhage at the site of the aneurysm (g) Catheter angiography showed aneurysm filling inferior to the clip blades, probably due

hem-to incomplete clipping (anteroposterior [h] and lateral [i] right internal carotid artery injections and 3D reconstruction [j]) The aneurysm was repaired endovascularly (k) The patient underwent placement of a ventriculoperitoneal shunt (l) to treat hydrocephalus

Aneurysms—Anterior Circulation

and first segments of the middle and anterior cerebral arteries These

aneurysms usually require treatment with flow diverters However,

one can use stent-assisted coiling (SAC) if placement of a flow diverter

is technically challenging or one wants to avoid dual-antiplatelet

ther-apy (DAPT) Bifurcation aneurysms may include internal carotid artery

terminus, middle cerebral artery, anterior communicating artery, and

distal anterior cerebral artery locations These aneurysms are best

man-aged with simple coiling or SAC (►Fig 36.4).

With respect to morphology of the recurrence, the neck size of the

recur-rent aneurysm is the most important The width of the aneurysm neck can

be divided into narrow neck (< 2 mm) and wide neck (> 2 mm) This is

different from the traditional cutoff (4 mm) used to classify the neck of

aneurysm This is because most recurrences from previously clipped

aneu-rysms have a shallow height and are shaped like a funnel The flat surface

is the one facing the clip and the pointed end is the neck of the aneurysm

These two factors often require using smaller coil sizes Accordingly, if the

neck of the aneurysm is wider than 2 mm and the height of the recurrence

is shallow, then the funnel shape of the recurrence becomes closer to the

shape of rectangular or square In this case, a regular stent or flow diverter is

usually required One must be very careful in this situation especially when

using SAC The small sized coils may herniate through the holes of the stent

causing unwanted complications (►Fig 36.4) If the neck of the recurrence

is less than 2 mm and the height of the recurrence is longer than 4 mm, then

the funnel could be triangular in shape and in this case one could attempt to

use coils only to obliterate the recurrence Tiny remnants or recurrences like

this may also not warrant repair

Complication Avoidance

Microneurosurgery

Reoperation can be technically more difficult with the presence of

fibrosis and adhesions from the previous surgical dissection The same

principles of aneurysm surgery apply, however, including definitive

identification of the parent and all of the branch arteries and of the

aneurysm neck and adjacent perforating arteries The old clip can also

obscure the anatomy, but removing it may cause intraoperative rupture

and injury to parent vessel Fenestrated clips and complex clip

configu-rations are more often needed for recurrent aneurysms and they offer

the advantage of not removing the old clip

Endovascular

Recurrent aneurysms are usually treated with SAC or flow diverters,

which require the use of DAPT The operator must ensure that the patient

is not resistant to these medications Occasionally, patients who have

a stent placed require life-long DAPT and cannot be weaned off due to ischemic complications This could present a challenge for these patients

if they require elective and/or emergent surgeries for other reasons Also, trauma or falls in these often elderly patients make them vulner-able to potentially devastating intracranial hemorrhagic complications

Outcomes Microneurosurgery

Clinical outcomes for retreatment of previously clipped aneurysms have improved over the past decades Surgical morbidity rates during the 1980s and 1990s were between 7 and 15%, respectively Recent surgical series report morbidity and mortality figures of less than 10%, probably still higher than for a first repair procedure, and higher in patients with SAH

than in patients with unruptured aneurysms (supports algorithm steps 4, 8, and 9) Data are limited, however, and are mostly self-reported, single-cen-

ter, retrospective case series There is also probably a higher likelihood that patients will require a planned or unplanned additional endovascular pro-cedure because of intentional or unexpected residual aneurysm

Endovascular

Despite differences in and rapidly changing endovascular methods, these in general are associated with outcomes similar to those reported after first repair Morbidity and mortality would be in the vicinity of 5

to 10%, probably lower than for repeat craniotomy, although data are limited and mostly self-reported, single-center, retrospective case series

(supports algorithm steps 4, 8, and 9).

Durability and Rate of Recurrence

It is well documented that, overall, clipping is superior to lar repair in terms of obtaining complete aneurysm closure and lack of recurrence over time The clinical outcomes, however, are probably the opposite and better with endovascular repair based on somewhat limited long-term follow-up of relatively few patients Nevertheless, this calls into question the importance of completely eliminating the aneurysm due to rarity of rupture with recurrence However, these studies were done on newly discovered aneurysms and not on residual or recurrent aneurysms Long-term outcomes are lacking for retreatment either by microsurgery or endovascular means It is reasonable to assume that the risks of aneurysm remnant growth, recurrence, and de novo formation are the same as the figures mentioned earlier, or perhaps even higher as these patients are already a group that has demonstrated a propensity

endovascu-to recurrence

Clinical and Radiographic Follow-up

Patients are seen about 6 weeks after repeat repair and further cal follow-up is generally at the time of their ongoing neuroimaging surveillance studies A baseline angiography (CTA, catheter, or MRA) is obtained, based on the nature of the procedure A preferably intraopera-tive or otherwise postoperative angiogram is good to have as a baseline

clini-in reclipped patients Clip artifacts clini-in all of these cases mean that CTA or catheter angiograms are usually needed One imaging follow-up sched-ule is 6 months (to check for stability early on) and then 2, 5, and every 2

to 5 years CTA or, less commonly, catheter angiography is used and the frequency of imaging has to be balanced against the risks of radiation and of invasive catheter angiography

Expert Commentary

There is a high degree of variation among surgeons in retreatment ommendations for recurrent aneurysms following clipping This condi-tion is rare and the natural history of hemorrhage after clipping and risk

rec-of treatment are poorly defined Therefore, the optimum decision relies

Fig 36.4 Catheter angiography images demonstrating a successful stent-

assisted coiling for a previously clipped middle cerebral artery bifurcation

aneu-rysm (a–c) Coil herniation during stent-assisted coiling in a recurrent aneuaneu-rysm

with a “rectangular” configuration (wide neck and shallow height) (d–f)

36 Previously Clipped Recurrent Aneurysms of the Anterior Circulation

247

on the expertise of the treating doctors in evaluating the factors

dis-cussed earlier and consideration of the wishes of the patient It is easier

for the surgeon to recommend more procedures for residual, recurrent,

and de novo aneurysms The risks tend to be underestimated and the

risk of hemorrhage from these aneurysms is pretty low Remember the

decision to treat is a balance between risks and benefits and it is how

the patient is likely to be clinically not what their angiogram looks like

that is the most important consideration

R Loch Macdonald, MD, PhD

St Michael's Hospital, University of Toronto, Ontario, Canada

Editor Commentary

Recurrent aneurysms can be treated either surgically or endovascularly

Although reoperations are generally more challenging because of

adhe-sions, making endovascular options more attractive as a first choice, those

recurrent aneurysms not appropriate for stents, or coils can still benefit

from reclipping Clip-wrapping can also be a useful adjunct in this setting,

which does not require as much microdissection of scarred-in anatomy

Hokari M, Kazumara K, Nakayama N, et al Treatment of recurrent intracranial rysms after clipping: a report of 23 cases and a review of the literature World Neurosurg 2016;92:434–444

aneu-Johnston SC, Dowd CF, Higashida RT, Lawton MT, Duckwiler GR, Gress DR; CARAT Investigators Predictors of rehemorrhage after treatment of ruptured intracra-nial aneurysms: the Cerebral Aneurysm Rerupture After Treatment (CARAT) study Stroke 2008;39(1):120–125

Kivelev J, Tanikawa R, Noda K, et al Open surgery for recurrent intracranial rysms: techniques and long-term outcomes World Neurosurg 2016;96:1–9 Spiotta AM, Hui F, Schuette A, Moskowitz SI Patterns of aneurysm recurrence after microsurgical clip obliteration Neurosurgery 2013;72(1):65–69, discussion 69 Tsutsumi K, Ueki K, Morita A, Usui M, Kirino T Risk of aneurysm recurrence in patients with clipped cerebral aneurysms: results of long-term follow-up angiography Stroke 2001;32(5):1191–1194

aneu-Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

37 Vertebral Artery Aneurysms 251

38 Midbasilar Artery Aneurysms 257

39 Basilar Artery Apex Aneurysms 263

40 Posterior Cerebral Artery Aneurysms 270

41 Superior Cerebellar Artery Aneurysms 277

42 Anterior Inferior Cerebellar Artery

46 Dissecting Intracranial Aneurysms of

47 Traumatic Intracranial Aneurysms of

48 Previously Coiled/Clipped Recurrent Aneurysms of the Posterior Circulation 326

Section III

Aneurysms—Posterior

Circulation

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),

copyright © 2018 Thieme Medical Publishers All rights reserved Usage subject to terms and conditions of license.

Jian Guan, Phil Taussky, and Min S Park

Abstract Vertebral artery aneurysms are generally rare aneurysms of

the posterior circulation that deserve special consideration As with all

posterior circulation aneurysms, they may present a higher rupture risk

when compared to anterior circulation aneurysms A careful workup,

including high-quality vascular imaging, is a necessity when

determin-ing the best treatment options for the patient Treatment options include

both open microsurgical and endovascular techniques However, given

the confines of the operative corridor and the emergence of flow

diver-sion, endovascular techniques may offer a specific treatment advantage

Long-term results with these newer endovascular therapies are

general-ly lacking and a thorough discussion within a robust, multidisciplinary

cerebrovascular service and the patient is beneficial in optimizing

treat-ment results

Keywords: vertebral artery, cerebral aneurysms, flow diversion,

micro-surgery

Introduction

Aneurysms of the vertebral artery (VA) are relatively rare, comprising 20

to 30% of aneurysms of the posterior circulation This rarity, combined

with their often unusual morphological characteristics, makes these

lesions particularly challenging to treat Patients with VA aneurysms

frequently present with complaints such as ataxia, lower cranial nerve

palsies, and decreased level of consciousness

Major controversies in decision making addressed in this chapter

include:

1 Whether or not treatment is indicated.

2 Open versus endovascular treatment for ruptured and

unrup-tured VA aneurysms.

3 Management of VA aneurysms that present with intracerebral

hematoma (ICH).

4 The role of flow diversion.

5 When should an advanced surgical technique (bypass) be

consid-ered?

Whether to Treat

Risk of rupture for VA aneurysms varies and is affected by both

aneu-rysm size and a history of previous aneuaneu-rysmal subarachnoid

hemor-rhage (SAH) Based on the International Study of Unruptured

Intracra-nial Aneurysms (ISUIA) 1 and 2, the 5-year cumulative risk for rupture in

aneurysms of the posterior circulation in patients without previous SAH

is 2.5% for aneurysms less than 7 mm, 14.5% for those between 7 and 12

mm, 18.4% for those between 13 and 24 mm, and 50% for those greater

than 24 mm (1, 2 in algorithm) While posterior circulation aneurysms

in general were in a higher rupture risk category than anterior

circula-tion aneurysms in the ISUIA study, other studies such as that performed

by the Japanese Unruptured Aneurysm Investigator Group (UCAS)

sug-gest that only a subset of these aneurysms (i.e., posterior

communicat-ing artery lesions) were actually more prone to rupture Patients who

have suffered previous SAH are also at significantly higher risk of

aneu-rysm rupture than those who have not, with the ISUIA group finding an

11-fold higher risk of rupture for aneurysms less than 10 mm in size

Other risk factors, including morphological characteristics of the

aneu-rysm (e.g., presence of a daughter sac) and the patient’s demographic

characteristics (e.g., history of tobacco use, hypertension), also likely

play a significant role in a specific patient’s risks of SAH

Weighed against the risk of rupture in these lesions is the risk of

treatment itself Overall treatment morbidity and mortality at 1 year

for patients in the clipping arm of ISUIA was 12.6% in those patients

without previous SAH and 10.1% in those with previous SAH ity and mortality at 1 year for patients in the endovascular treatment arm was 9.8% in those patients without previous SAH and 7.1% in those with previous SAH Patients with aneurysms of the posterior circulation, such as VA aneurysms, were at higher risk of postoperative morbidity/mortality than those with aneurysms of comparable size of the anterior circulation The risks of surgical intervention, such as the risk of rupture, vary from patient to patient Larger aneurysms, older age (particularly intervention in those older than 60 years), prerupture aneurysm-related symptomatology, and a history of ischemic stroke all placed patients at higher risk following intervention Regardless of these risks, interven-tion is clearly indicated for almost all cases of ruptured VA aneurysms

Morbid-Conservative Management

With the increasing ubiquity of advanced neuroimaging, the ment of incidentally identified VA aneurysms becomes increasingly important Patients must be carefully counseled regarding the risks of both intervention and watchful waiting, and these recommendations must be tailored based on the aneurysm’s size, its morphology, and the patient’s specific risk profile In patients who are treated nonoperatively, the need for follow-up and subsequent imaging to assess for aneurysm growth must be carefully considered

manage-Anatomical Considerations

The VA is composed of four segments From its origin, most commonly from the subclavian artery, V1 extends to the transverse foramen of the sixth cervical vertebra V2 is composed of the segment from this transverse foramen to the transverse foramen of the axis The portion

of the artery from the transverse foramen of the axis to the point at which the artery pierces the dura comprises the V3 segment V4, the only intradural portion, ends at the confluence of the left and right ver-tebral arteries where they become the basilar artery Variations may be present and must be considered prior to any open surgical or endovas-cular interventions These include the dominance of one artery over the other (approximately 40–50% of the population is left dominant)

or codominance (approximately 25% of the population), duplication of

a portion of the artery (fenestration), or duplication of an entire vessel segment

The precise location of the VA aneurysm also has implications on management Attention must be paid to the relationship of the aneu-rysm to the posterior inferior cerebellar artery (PICA), and the location of the aneurysm on the proximal versus distal artery can have implications

on which approach will offer the optimal exposure

Classification

Two specific subtypes of VA aneurysms warrant discussion: giant

aneu-rysms and dissecting aneuaneu-rysms Giant aneuaneu-rysms, classically defined as

lesions greater than 25 mm in diameter, often present a unique challenge

in the posterior circulation The mass effect exerted by these lesions in the posterior circulation can result in significant neurological deficits, sometimes necessitating aneurysmectomy for optimal symptomatic relief A large proportion of these aneurysms also demonstrate intralu-minal thrombosis, further contributing to mass effect and making pre-cise determination of aneurysm morphology more challenging on vessel imaging The need for vessel bypass in some cases also necessitates pre-cise knowledge of local vascular anatomy and collateral blood flow

Dissecting VA aneurysms are a rare entity that can present in the form

of SAH or brainstem ischemia The precise cause of these lesions is not

Rangel-Castilla et al Decision Making in Neurovascular Disease (ISBN 978-1-68420-057-3),