21 -CYSTS,TUMORS,TUMORLIKE LESIONS OF SPINAL CORD and SPINE .

Cephalad flow of contrast is blocked by the compressive lesion, and the CSF distal to the obstruction shown in white is un Common incidental finding at MR round "white spot" on T1WI, C

Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal

Cysts and Tumorlike Masses

Spinal cord tumors and tumorlike masses are traditionally

classified by location into three categories,1,2 (see box, p

877, top left) as follows:

1 Extradural lesions (lesions of the osseous spine,

epidural space, and paraspinous soft tissues)

2 Intradural extramedullary lesions (lesions that

are inside the dura but outside the spinal cord)

3 Intramedullary lesions (spinal cord cysts and

complete block, is used) occurs with large lesions and is

seen as a displaced thecal sac with obliterated noid space and compressed spinal cord The border between the lesion and the head of the contrast column has

subarach-a poorly delinesubarach-ated "fesubarach-athered" subarach-appesubarach-arsubarach-ance (Fig 21-1, B

and C).2 MR scans clearly show the dura draped over the mass (Fig 21-1, D) In some cases a crescent of displaced

epidural fat can be seen capping the lesion (see Fig 21-16,

Location: outside thecal sac

Tissues: osseous spine, epidural space, paraspinous soft

tissues

Examples: herniated disk, spondylitic spurs, fractures,

metastases

Classic myelogram appearance: thecal sac extrinsically

compressed; if block, interface between lesion and

contrast column is poorly defined with "feathered"

appearance at level of obstruction

Intradural extramedullary masses

Location: inside thecal sac but outside cord

Tissues: nerve roots, leptomeninges, CSF spaces

Examples: nerve sheath tumors, meningiomas

Classic myelogram appearance: intradural filling defect

outlined by sharp meniscus of contrast; spinal cord

deviated away from mass; ipsilateral subarachnoid

space enlarged up to mass

Intramedullary masses

Location: inside spinal cord

Tissues: cord parenchyma, pia

Examples: astrocytorna, hydrosyringomyelia

Classic myelogram appearance: diffuse, multisegmental

smoothly enlarged cord with gradual subarachnoid

space effacement

The most common neoplastic extradural mass is

me-tastasis In this section, we consider neoplasms, cysts,

and tumorlike masses of the osseous spine and

paraspinal soft tissues

Benign Tumors

Hemangioma

Pathology Vertebral hemangiomas (VHs) are

slow-growing benign primary neoplasms of capillary,

cavernous, or venous origin The most common

his-tologic type is cavernous hemangioma These lesions are

composed of mature thin-walled vessels and large

blood-filled endothelial-lined spaces.3,4 The dilated

vessels are interspersed among longitudinally oriented

trabeculae that appear reduced in number but are thicker

in diameter.5 VHs vary from predominantly fatty lesions

(Fig 21-2, A) to hemangiomas comprised largely of

vascular stroma with little or no adipose tissue (see box,

right).4

Incidence, age, and gender Hemangiomas are found

in 10% to 12% of all autopsies, making VH the most

common benign spinal neoplasm.3 The peak incidence is

in the fourth to the sixth decades Asymptomatic

hemangiomas occur equally in men and

Fig 21-1 Imaging features of an extradural mass A,

An-atomic diagram, lateral view, depicts a pathologic compression fracture with spinal cord compression The

dura (small arrows) and spinal cord (large arrows) are

displaced The subarachnoid space is filled with

intrathecal contrast (gray area: open arrows) Gradual

tapering of the contrast column with a "feathered"

appearance (double arrows) is present Cephalad flow of

contrast is blocked by the compressive lesion, and the

CSF distal to the obstruction (shown in white) is un

Common incidental finding at MR (round "white spot"

on T1WI), CT ("polka dot" vertebral body) Most are asymptomatic; can expand, cause pathologic fracture, epidural mass with cord compression Differential diagnosis: fatty marrow replacement

women but there is a female predominance withsymptomatic lesions

Location Nearly 75% of all osseous hemangiomas

occur in the spine.3 The lower thoracic and lumbar regions are the most common sites.5 Multiple lesions are seen in 25% to 30% of cases.6,7

Most hemangiomas are located in the vertebral body Lesion extent is variable (Fig 21-2) Some le-sions involve only part of the vertebral body, whereas others affect the entire medullary space Hemangi-

878 PART FIVE Spine and Spinal Cord

Fig 21-1, cont’d B and C, Myelographic findings of extradural mass are shown

Lat-eral view (B) shows an extradural mass effect (small arrows) with block of contrast flow (large arrow) AP view (C) in another case shows the ill-defined "feathered"

appearance at the head of the contrast column (arrows), caused by an extradural mass

with block D, Sagittal T2-weighted MR scan in a patient with metastatic breast

carcinoma and a high signal intensity pathologic compression fracture (large arrow) shows the dural displacement (open arrows) that is characteristic of an extradural mass

effect

oma isolated to the neural arch is uncommon, but 10%

to 15% of vertebral body VHs have concomitant

involvement of the posterior elements (Fig 21-3).3 Most

epidural hemangiomas occur secondarily as extensions

of expanding intraosseous lesions.8 Completely

extraosseous hemangioma is rare, accounting for only

1% to 2% of all VHs

Clinical presentation and natural history

Ap-proximately 60% of VHs are asymptomatic lesions that

are discovered incidentally on imaging studies.6 Pain is

the presenting complaint in 20%.6 In most patients with

VHs, back pain is related to other etiologies, not the

hemangioma.4 Approximately 20% of VHs present with

progressive neurologic deficits or symptoms of acute

spinal cord compression Progression of an

asymptomatic or painful lesion to a neurologically

symptomatic one is rare, occurring in less than 5% of

cases.6

VHs usually become symptomatic when pathologic

compression fracture or epidural extension occurs

Symptom onset is often, although not invariably, acute

and is probably secondary to hemorrhage with sudden

increase in mass effect.8 Pregnancy may

exacerbate some lesions.8a Some authors report fatty VHs are usually clinically inactive, whereas those with imaging findings suggesting a more vascular stroma have the potential to cause spinal cord compression.4

Imaging findings Plain film radiographs show lytic

foci with honeycomb trabeculation or thick vertical striations.5 NECT scans show a lucent lesion with typical

"polka dot" densities in the medullary space that represent the coarsened vertical trabeculae characteristic of VHs VHs range in size from small, localized lesions (Fig 21-2, C) to hemangiomas that involve the entire vertebral body (Fig 21-2, B) Myelography or CT-myelography in cases with extraosseous extension show an extradural mass (Fig 21-4, B) Angiographic findings vary from normal to intense hypervascular stain on selective segmental spinal angiograms.4

MR imaging findings vary Most VHs are seen as round, relatively well-delineated vertebral body lesions that are high signal intensity on both T1- and T2-weighted sequences (Fig 21-4, A) The hyperintense stroma surrounds foci of very low signal inten-

Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord

879

Fig 21-2 Pathology and imaging findings of typical vertebral, body hemangiomas A,

Gross pathology specimen shows a classic hemangioma Note marrow replacement by

fatty stroma (large arrows) and fewer but strikingly thickened trabeculae (small

arrows) B and C, Axial CT scans show typical hemangiomas This hemangioma (B)

(large arrows) occupies nearly the entire vertebral body Note "polka-dot" appearance

caused by the thickened trabeculae seen in axial section (open arrows) Post-myelogram

CT scan (C) in another patient shows a very small incidental focal hemangioma

(arrows) (A, From archives of the Armed Forces Institute of Pathology.)

sity, representing the thickened vertical trabeculae (Fig

21-3, B)

Some VHs are predominately low signal on T1WI

These lesions often enhance following contrast

ad-ministration and may be associated with an extradural soft

tissue mass Histologically, these VHs contain

predominately vascular rather than fatty stroma.4

Differential diagnosis The major differential

diag-nostic consideration on MR scans is focal fatty marrow

replacement or hemangioma VHs typically have high

signal intensity on both T1- and T2WI, whereas fatty

lesions become hypointense on standard T2-weighted spin

echo images VHs that are mostly fatty can be

indistinguishable from fatty marrow replacement; both are

clinically indolent lesions that are common causes of

vertebral body "white spots" seen incidentally on MR

scans Fat suppression sequences are helpful in

distinguishing fatty marrow replacement from VHs that

are primarily vascular

Osteoid osteoma (Table 21-1)

Pathology Osteoid osteoma is a benign skeletal

neoplasm that has a central nidus of interlacing osteoid

and woven bone mixed with loose fibrovas-

Fig 21-3 Hemangioma that involves the vertebral

body, pedicle, and articular pillar of C5 A, Axial NECT

scan shows the lesion (arrows) (Courtesy M Fruin.)

Continued

880 PART FIVE Spine and Spinal Cord

Fig 21-3, cont'd B, Axial T2-weighted MR scans show the high signal stroma

(arrows) (Courtesy M Fruin.)

Fig 21-4 This 42-year-old man had a 48-hour history of back pain and leg

weakness followed by sudden onset of paraplegia and incontinence A, Sagittal

postcontrast T1-weighted MR scan shows a high signal lesion in the vertebral

body (curved arrow) and an extradural soft tissue mass with enhancing rim

(straight arrows) that is compressing the conus medullaris B, Post-myelogram

CT scan with reformatted sagittal image shows the extradural mass (arrows)

Surgery disclosed extradural hemangioma with acute hemorrhage

cular stroma.9,10 Osteoid osteomas are sharply demarcated

from surrounding bone and are surrounded by varying

degrees of osteosclerosis.9 Associated paraosseous soft

tissue masses occasionally occur with extremity lesions but

have not been reported in the spine.11

The nidus of an osteoid osteoma rarely exceeds 1.5 to

2.0 cm in diameter9; larger lesions are typically categorized

as osteoblastoma, although the distinction between these

two entities is not always clear.10

Incidence, age, and gender Osteoid osteoma is a

relatively common lesion that accounts for

approxi-mately 12% of benign skeletal neoplasms.9 Osteoid osteomas represent approximately 6% of benign spine tumors.5

Patients with osteoid osteoma are usually young Osteoid osteomas are rarely seen beyond 30 years of age.5 Approximately half of all cases present between the ages

of 10 and 20 years.9,10 The male:female ratio is 2-4:1.5,9,10

Location Osteoid osteoma may occur in virtually any

location; the lower extremity is the site for more than half

of all lesions Approximately 10% of osteoid osteomas are found in the spine The most commonly

Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 881

Table 21-1 Benign osseous tumors and tumorlike lesions of the spine

L>C) MR: "hot spot" on

T1WI

spine) nidus, lesion <2 cm

sacrum) spine) matrix mineraliza-

tion

rum >>vertebrae) structive, highly vas-

cular

processes (10% to spine) lesion; periosteum, 12% multiple) cortex, marrow in

continuity with host bone; cartilaginous cap ± Ca+ +

T most common) sile; eggshell-like

rims; blood products with fluid-fluid lev- els; highly vascular

affected region is the lumbar spine, and the usual site is

the neural arch Vertebral body lesions are unusual.9

Clinical presentation and natural history Pain is the

presenting symptom in over 95% of cases10; 75% of

patients report pain relief following salicylate

ad-ministration.9 Symptom duration ranges from 1 month to

several years, with an average length of 15 to 16 months.10

Scoliosis is common in patients with spinal osteoid

osteomas.5

Imaging findings Bone scintigraphy reveals focal

activity on both immediate and delayed images.9 Spinal

osteoid osteomas may be difficult to identify on plain film

radiographs because these are often normal or may

demonstrate only subtle osteosclerosis.9 NECT scans

typically show dense sclerosis of the facet, pedicle, or

lamina surrounding a lytic lesion that may have a central

calcific nidus (Fig 21-5).5,9

MR imaging of osteoid osteoma has been reported in

only a few cases Spinal lesions have variable signal The

nidus is typically low to intermediate in signal intensity

on both T1- and T2-weighted MR scans.9,11 Some osteoid

osteomas enhance following contrast administration.11

Osteoblastoma (Table 21-1)

Pathology Osteoblastoma, also known as giant osteoid

osteoma, occupies a histologic continuum

Fig 21-5 Axial NECT scan in this 15-year-old girl

with neck pain shows a typical osteoid osteoma in the T1- lamina Note thickened, sclerotic bone

surrounding a lucent nidus (black arrows) Some central calcifications (open arrow) are present

Osteoid osteoma

882 PART FIVE Spine and Spinal Cord

with osteoid osteoma Osteoblastomas are typically 2 cm

or greater in size; smaller lesions are usually classified as

osteoid osteomas.5

Incidence, age, and gender Osteoblastomas are

un-common neoplasms, accounting for approximately 1% of

primary bone tumors The reported age range is from 5 to

50 years, with an average age at presentation of 19.5

years More than 80% of all patients are symptomatic by

age 30.12 The male:female predominance is approximately

2.5-1.12

Location Whereas only 10% of osteoid osteomas occur

in the spine, approximately 40% of all osteoblastomas are

located here Nearly 40% are found in the cervical spine,

23% in the lumbar spine, 21% in the thoracic spine and

17% in the sacrum Two thirds are confined to the

posterior elements; one third extend anteriorly to involve

the vertebral body Osteoblastomas are nearly always

solitary lesions.12

Clinical presentation and natural history Pain is the

most common presenting symptom, seen in 80% of

cases.12 Neurologic deficit and scoliosis are sometimes

observed Although osteoid osteomas are biologically

nonprogressive lesions, osteoblastomas often enlarge.13

Occasionally, these lesions have atypical histologic

features and may behave aggressively About 10% recur

following surgical excision.14

Imaging findings Plain films and NECT scans typ-

ically show a well-defined scalloped or lobulated lytic expansile mass arising from the neural arch Approximately one half of spinal osteoblastomas are predominantly lucent; the remainder display varying degrees of matrix

mineralization.12 A thin bony or sclerotic rim with soft tissue extension is a common appearance (Fig 21-6, A).5

Intermediate signal intensity on T1WI with mixed high signal foci on T2WI and a wide band of reactive sclerosis have been reported on MR scans (Fig 21-6, B).14

Differential diagnosis The differential diagnosis of

spinal osteoblastoma is osteoid osteoma, aneurysmal bone cyst, and giant cell tumor Aggressive tumors can resemble

osteosarcoma

Giant cell tumor (see Table 21-1)

Pathology Grossly, giant cell tumors are lytic, expansile,

locally aggressive primary benign bone tumors that extend to the cortex but rarely transgress the periosteum.5

Histologically, giant cell tumors contain sinusoidal vessels with hypervascular stroma Hemorrhage is common; matrix mineralization is rare.5,15 Monocyte-macrophages and multinucleated giant cells are common

Incidence, age, and gender Giant cell tumors comprise

approximately 5% of primary bone tumors Most patients are

in the second through the fifth de-

Fig 21-6 Two cases of osteoblastoma A, AP plain film radiography in this 23-year-old

woman shows an expansile lesion of the left L2 pedicle and transverse process Note thin

bony rim (arrows) B, Sagittal T2-weighted MR scan in a 29-year-old woman shows a

mixed signal mass (curved arrows) in the C2 spinous process Osteoblastoma was found

at surgery in both cases (A, Courtesy B.J Manaster.)

Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 883

cades; the peak incidence is in the third decade There is

a female predominance in giant cell tumors involving

vertebrae other than the sacrum.5

Location Most giant cell tumors occur at the ends of

long bones, characteristically around the knee Giant cell

tumors of the spine are uncommon, accounting for only

3% to 7% of these tumors Most occur in the sacrum;

other vertebral segments are rarely involved.5

Clinical presentation and natural history Pain and

neurologic deficits are common presenting symptoms.16

Local recurrence following incomplete resection is

common, and some giant cell tumors are biologically

aggressive lesions Malignant transformation occurs in

approximately 10% of cases.17

Imaging findings Plain film radiographs and NECT

scans typically disclose a lytic, expansile, destructive

sacral or vertebral mass (Fig 21-7) Angiography often

demonstrates hypervascularity MR scans show a

mixed-signal, multicompartmented cystic mass that

frequently contains blood degradation products.15

Differential diagnosis The differential diagnosis of

giant cell tumor in the spine is osteoblastoma and

aneurysmal bone cyst

Osteochondroma (see Table 21-1)

Etiology and pathology Osteochondroma, also known

as osteocartilaginous exostosis, arises through lateral

displacement of epiphyseal growth cartilage

This results in formation of a bony excrescence with cartilaginous-covered cortex and a medullary cavity contiguous with that of the parent bone.18 Osteo-chondromas grow from their tips as the cartilage un-dergoes ossification.18 Histologically, the cartilaginous cap and underlying bone in an osteochondroma are identical to normal bone

Incidence, age, and gender Osteochondromas are

common lesions, comprising 8% to 9% of all primary bone tumors and slightly more than one third of benign tumors.18 The mean age of patients with multiple spinal osteochondromas is 21 years, whereas solitary osteochondromas have a mean age at presentation of 30 years.18 The male: female predominance is 1 5-2.5: 1.18

Location Osteochondromas affect mostly long bones;

only 1% to 4% of solitary osteochondromas arise in the spine The spinous or transverse processes are the most common location.17 Approximately half occur in the cervical spine; C2 is the most commonly affected segment The thoracic region is the next most common location Multiple osteochondromas account for 12% of all cases Approximately 10% of patients with hereditary multiple osteochondromas have spinal lesions.18

Clinical presentation and natural history

Osteo-chondromas rarely cause neurologic symptoms lignant transformation occurs in about 1% of solitary and 10% of multiple osteochondromas.18

Ma-Imaging findings Plain film radiographs may show a

sessile or pedunculated bonelike projection On NECT scans the cortex of the parent bone flares into the cortex

of the osteochondroma, with which it is contiguous The cartilaginous cap often contains calcific foci (Fig 21-8).18 MR scans show mixed signal intensity on both T1- and T2WI.17

Fig 21-7 Axial NECT scan in this 62-year-old man

with midback pain shows a lytic, destructive lesion

that involves the T11 vertebral body, pedicle, and

neural arch (arrows) No other lesions were present

Giant cell tumor was found at surgery

Fig 21-8 Axial NECT scan shows a cauliflower-like

calcified lesion with a mineralized cap (small arrow) and a densely ossified base (large arrow) that is

continuous with the underlying cortical lamina Osteochondroma (osteocartilagenous exostosis) (Courtesy B.J Manaster.)

884 PART FIVE Spine and Spinal Cord

Miscellaneous benign tumors Other primary bone

neoplasms rarely involve the spine Occasionally,

chondromyxoid fibromas, malignant

heman-gioenclotheliomas, and hemangiopericytomas occur in the

axial skeleton

Cysts and Other Benign Tumorlike Masses

Several benign nonneoplastic tumorlike masses can

cause an extradural mass These include the following:

1 Aneurysmal bone cyst

Aneurysmal bone cyst (see Table 21-1)

Etiology and pathology Aneurysmal bone cyst (ABC)

is a benign, nonneoplastic lesion of unknown etiology.19

Between 30% and 50% of ABCs are associated with a

preexisting osseous lesion such as chondroblastoma, giant

cell tumor, osteoblastoma, nonossifying fibroma, or

fibrous dysplasia.20 Some ABCs may represent a vascular

anomaly induced by trauma or hemorrhagic infarction of

the precursor lesion Rapid expansion may obliterate the

underlying abnormality, leaving behind the blood-filled

cavities that are characteristic of ABCs.20

Grossly, ABCs are multiloculated, expansile,

highly vascular osteolytic lesions that often contain blood degradation products Histologically, ABCs consist of thin-walled, blood-filled cavities that lack normal endothelium and elastic lamina.21 Solid portions of the lesion contain benign spindle cells in a collagenous stroma Multinucleated giant cells are commonly observed.19

Incidence, age, and gender ABCs are uncommon and

represent less than 1% of primary bone tumors Nearly 80% occur in patients less than 20 years of age, whereas 85% of patients with giant cell tumors are 20 years or

older 5 There is a slight female predominance

Location ABCs occur in all parts of the skeleton The

metaphyses of long bones are the most common sites.20 Approximately 20% are found in the spine; the cervical and thoracic regions are the most common locations.5 ABCs typically occur in the posterior elements but often expand secondarily into the pedicles and vertebral body Neural canal encroachment is common.21 Involvement of contiguous vertebrae may occur.17

Clinical presentation and natural history Pain and

swelling are the most common overall presenting symptoms.19 Spinal ABCs may cause cord compression and pathological fractures.21 Recurrence following surgical resection is common.,

Imaging Plain films and NECT scans show an

os-teolytic lesion surrounded by expanded, thinned, eggshell-like cortical bone (Fig 21-9, A) A soft tis-

Fig 21-9 Two cases of aneurysmal bone cyst A, Axial NECT scan in a

6-year-old girl shows a lytic, scalloped, expansile mass in the C2 neural arch

(arrows) B, Axial T1-weighted scan in an 11-year-old girl shows an expansile

mass in the articular pillars and neural arch Note bone expansion (large arrows) and multiseptated cysts with fluid-fluid levels (open arrows) Aneurysmal bone

cysts with hemorrhage were found in both cases (B, Courtesy R.J Facco.)

Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 885

sue mass is often present (Fig 21-10, B).5 Matrix

cal-cification is absent.21 Myelography shows an extradural

mass effect; large lesions can cause a contrast block (Fig

21-10, A) Most ABCs are very hypervascular at

angiography (Fig 21-10, C).19 MR scans typically

demonstrate a lobulated, multiseptated lesion with

fluid-fluid levels and blood degradation products (Fig

21-9, B) 21

Differential diagnosis The major differential diagnosis

of a cystic expansile posterior element mass is ABC

versus osteoblastoma The presence of fluidfluid levels is

suggestive of ABC but also occasionally occurs with

other lesions such as giant cell tumor, telangiectatic

osteosarcoma, chondroblastoma, and nonneoplastic cyst

with fracture.19-21

Eosinophilic granuloma (see Table 21-1)

Eosino-philic granuloma (EG) is a benign, nonneoplastic disorder

of which Langerhans cell histiocytosis is one

manifestation (see Chapter 15) EG in the spine is seen as

a lytic lesion without surrounding sclerosis EG is a

classic cause of a single collapsed vertebral body,

so-called vertebra plana (Fig 21-11) Spine EGs most commonly occur between the ages of 5 and 10 years; EG

is very rare over age 30 years.17 EG is typically hyperintense on T2-weighted MR scans, although signal

on T1WI is variable Strong enhancement following contrast administration is seen.21a

Epidural lipomatosis

Etiology and pathology Epidural lipomatosis (EL) is

excessive deposition of unencapsulated fat in the epidural space EL occurs as part of the central or truncal lipomatosis associated with both exogenous and endogenous hypercortisolemia.22 The majority of symptomatic cases are associated with chronic steroid use; occasionally, ELs occur in morbidly obese patients, and a few cases have no definable etiology.23,24 Asymptomatic EL is not uncommon in classic pituitary dependent Cushing disease and is even more common in the ectopic adrenocorticotropic hormone (ACTH) syndrome.22

Incidence, age, and gender EL is rare Most reported

cases have occurred in males.23,24

Location Approximately 60% of EL cases occur in

the thoracic spine and 40% in the lumbar spine; bined thoracolumbar involvement also occurs and is

com-Fig 21-10 A 17-year-old woman with back pain had these imaging studies A,

Coronal reformatted post-myelogram CT scan shows typical findings of an

extradural mass The contrast-filled thecal sac (small arrows) and spinal cord

(open arrows) are displaced Cephalad flow of contrast is blocked (large arrow)

Note destructive, expansile mass in the pedicle at this level (curved arrows) B,

Scout view for spinal angiography shows the T11 vertebral body is compressed,

the pedicle is destroyed, and an adjacent focal soft tissue mass (large arrows) is present Retained contrast (open arrows) from previous Pantopaque myelogram

is present C, Selective angiogram of the right T11 segmental artery shows a

vascular stain (arrows) Aneurysmal bone cyst was found at surgery

886 PART FIVE Spine and Spinal Cord

Fig 21-11 Typical imaging findings in spinal eosinophilic granuloma illustrated

in two cases A, Lateral plain film shows "pancaked" L1 vertebral body B,

Sagittal T1-weighted MR scan in 10-year-old boy with torticollis shows the C4

vertebral body marrow is replaced by low signal soft tissue (arrows) (compare

with the high signal seen in the adjacent normal vertebral bodies) Some loss of height of the vertebral body is present, i.e., there is mild vertebra plana

Fig 21-12 Sagittal (A) and axial (B) T1-weighted MR scans show severe

lumbosacral epidural lipomatosis, seen as widespread high signal surrounding

the thecal sac Note thecal sac compression (small arrows)

Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 887

seen in 16% of cases Cervical EL has not been

re-ported.24

Clinical presentation and natural history

Weak-ness and back pain are the most frequent presenting

complaints, seen in two thirds of all patients with EL

Radicular pain, numbness, and dysesthesias occur in

half the cases.24 EL may resolve after cessation of

ex-ogenous corticosteroid administration, suppressive

therapy, or bilateral adrenalectomy.22 Seventy-eight

percent of patients undergoing multilevel

laminec-tomy improve after surgery, but reported mortality in

operated patients is 22%.24

Imaging findings Myelographic findings range

from normal to block.23,24 CT and MR scans show in

creased extradural fat and diminished subarachnoid

space (Fig 21-12).23

Spinal angiolipoma

Pathology Spinal angiolipomas (SAS) are benign

neoplastic-like lesions composed of mature

adipo-cytes and abnormal blood vessels that vary from

capillary to sinusoidal, venular, or arterial in size.25

SAS are considered a separate entity from the more

cornmon lipoma.26

Incidence, age, and gender SAS are very rare,

ac-counting for 0.14% to 1.2% of spinal axis tumors.25,26

Symptom onset is typically in the fifth decade There

is a slight female predominance.25

Location SAS are almost always epidural,

al-though a few intramedullary lesions have been

re-ported.25 The thoracic spine is the most common site

Most SAS are dorsal or dorsolateral to the cord.26

Clinical presentation Back pain, lower extremity

numbness or paresthesias, and leg weakness are

common Bowel or bladder dysfunction is present in

half of all cases Some patients experience Symptom

onset during pregnancy.25

Imaging findings Myelograms typically show a

thoracic extradural mass or block CT scans

demon-strate a low- or intermediate-density epidural soft

tis-sue mass that enhances following contrast

adminis-tration.27 SAS are typically iso- or hyperintense on

T1WI and hyperintense on T2WI Diffuse

homogeneous enhancement is typical.26 A few

angiolipomas extensively infiltrate the adjacent

vertebral body.26

Cysts Several different types of spinal cysts can

cause an extradural mass effect Synovial

(juxta-articular) cysts are rare causes of extradural mass

ef-fects These cysts are nearly always associated with

facet degeneration and are discussed in Chapter 20

Congenital and acquired arachnoid cysts are

uncommon but important nonneoplastic causes of

extra and intrad6ral mass effects

Extradural arachnoid cysts Extradural arachnoid cysts

(EACs) are CSF-filled outpouchings of arachnoid that protrude through a dural defect.28,29 EACs can be congenital

or acquired Two thirds occur in the mid to low thoracic spine; 20% are found in the lumbosacral region and 9% at the thoracolumbar junction Cervical EACs are uncommon.29

EACs cause a spectrum of symptoms Painless progression of either flaccid or spastic para- or quad-riparesis with initial relative sparing of sphincter tone is typical Kyphosis with localized or radicular pain may develop.29 Imaging studies typically show a long-segment CSF-equivalent thoracic extradural mass that causes spinal cord compression or myelographic block Secondary bony changes include widened interpedicular distance, scalloping of vertebral bodies, or pedicle thinning and erosion (Fig 21-13).28

The differential diagnosis of EAC includes traumatic meningocele and lateral thoracic meningocele Traumatic meningoceles typically have a large extraspinal component that extends through the neural foramina Lateral thoracic meningoceles are usually associated with neurofibromatosis type 1 (NF-1) and widespread dural ectasia.29

Malignant Tumors

By far the most common extradural malignant neoplasm

is metastasis Primary extradural malignant neoplasms are uncommon Chordoma, Hodgkin and non-Hodgkin lymphoma, and sarcomas such as Ewing sarcoma, chondrosarcoma, and osteogenic sarcoma are examples of

primary extradural malignant spine tumors

Chordoma

Etiology and pathology Chordomas originate from

intraosseous notochordal remnants (see box) Grossly, chordomas are locally invasive, lobulated,

Chordoma

Arise from intraosseous notochordal remnants Two types: typical and chondroid chordoma Any age; peak incidence is 50 to 60 years Preferential location for both ends of axial skeleton 50% sacrum/coccyx

35% skull base 15% vertebral bodies NECT scans show lytic, destructive lesion; Ca+ + in 30%

to 70%; soft tissue mass often associated Inhomogeneous signal on MR; typical chordomas are often very hyperintense on PD/T2WI

888 PART FIVE Spine and Spinal Cord

Fig 21-13 Extradural arachnoid cyst A, AP plain film radiograph shows

expansion of the lower thoracic canal, seen as widened interpediculate distance

and thinned pedicles (arrows) B, Lumbar myelogram, lateral view, shows the

widened canal with posterior vertebral body scalloping (large arrows) The

contrast column is displaced anteriorly, and cephalad contrast flow is blocked

(curved arrow) The "feathered" appearance (open arrows) is characteristic of an

extradural mass C, Sagittal T1-weighted MR scan shows the lobulated mass

(arrows) is isointense with CSF Note anterior displacement and thinning of the

thoracic cord D, Post-myelogram CT scan at the L1-L2 level shows the thecal

sac is displaced anteriorly and compressed (small arrows) by a low density

intraspinal mass (large arrows) E, Bone window shows the enlarged canal and

markedly thinned pedicles (arrows) (Courtesy W.R.K Smoker.)

Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 889

Fig 21-14 Skull base chordoma A, Sagittal gross pathology (left) and specimen

radiograph (right) show the inhomogeneous-appearing, destructive

cartilaginous-like clivus mass Pre- (B) and postcontrast (C) sagittal

T1-weighted MR scans show a large mixed signal, destructive, strongly

enhancing mass (arrows) (A, From Okazaki H, Scheithauer B: Slide Atlas of

Neuropathology, Gower Medical Publishing, 1988 B and C, Courtesy N Yue.)

Fig 21-15 Sacrococcygeal chordoma A, Sagittal gross pathology (left) and

specimen radiograph (right) show the typical bulky, destructive inhomogeneous

soft tissue mass that is characteristic of chordoma B, Sagittal T2-weighted MR

scan in another case shows the lobulated lesion (arrows) is extremely

hyperintense (A, From Okazaki H, Scheithauer B: Slide Atlas of

Neuropathology, Gower Medical Publishing, 1988 B, Courtesy B.J Manaster.)

Continued

890 PART FIVE Spine and Spinal Cord

lytic, destructive skull base or sacral lesion (Fig 21-15, C) Mixed solid and cystic components are frequent Calcification occurs in 30% to 70% of cases.5 An associated anterior or lateral soft tissue mass is often present

Typical chordomas have inhomogeneous, dominately low signal intensity on T1-weighted MR scans

pre-(see Fig 21-16; Fig 21-14, B) and equal or exceed CSF

signal intensity on proton density- and T2-weighted sequences (Figs 21-15, C; and 21-16, C).17 Chondroid chordomas typically have shorter T1 and T2 relaxation times than typical chordomas.30,31 Enhancement following contrast administration varies from little to striking (Fig 21-14, C)

Differential diagnosis The major differential

diag-nosis of sacral chordoma is giant cell tumor and metastasis from occult primary neoplasms such as renal cell or thyroid carcinomas Other tumors that can enlarge and erode sacral segments are ependymoma and schwannoma.32 Clivus chordomas must be distinguished from other central skull

base destructive masses (see Chapter 12)

Lymphomas Lymphoma can involve the spine and

epidural soft tissues (Fig 21-17) Non-Hodgkin lymphoma accounts for over 85% of cases; Hodgkin lymphoma is much less common Most spinal lymphomas occur between

40 and 60 years of age.17 Mean age at diagnosis is 58 years; there is a strong male predominance.34 The biologic behavior of spinal NHL is similar to extranodal lymphomas

at other sites.34 Median survival is 22 months, although nearly half the patients survive more than 3 years with appropriate radiation and chemotherapy.34,35

Imaging findings in spinal extradural lymphoma are nonspecific NHL can cause bone destruction and hyperostosis.17 Spinal cord compression occurs in up to 6%

of patients with NHL during their disease course.34 Epidural extension is best delineated on MR scans Spinal lymphoma

is typically low signal on T1- and inhomogeneously hyperintense on T2-weighted MR scans.17

Sarcomas Primary spinal sarcomas are rare Ewing

sarcoma, osteogenic sarcoma, chondrosarcoma, and fibrosarcoma occasionally involve the spine

Ewing sarcoma Ewing sarcoma (ES) accounts for 7%

to 15% of all primary bone malignancies.5 The peak incidence is in the second decade; there is a definite male predominance The spine is a rare site for primary ES; most

spinal ESs represent metastatic tumor from another site of

origin.5 The vertebral bodies and epidural space are the most common locations

Imaging findings of ES are nonspecific An erode vertebral body associated with a large paraspinal soft

gelatinous-appearing masses (Figs 14, A; and

21-15, A) Chordomas are separated into two pathologic

subsets: typical chordomas and chondroid

chordo-mas.30 In typical chordomas, vacuolated

physalipho-rous cells with variable amounts of intracytoplasmic

mucin are embedded in pools of extracellular mucin

In chondroid chordomas, this watery, gelatinous

ma-trix is replaced by cartilaginous foci.31 Mitotic

activ-ity and cellular pleomorphism are typically absent in

both subtypes.30

Incidence, age, and gender Chordomas are rare

tumors They account for only 1 % to 2 % of primary

malignant bone tumors, although chordoma is the

most common primary sacral neoplasm.32 Chordomas

can occur at almost any age, but the peak incidence is

in the sixth decade.30 There is a 2:1 male

predomi-nance.17

Location Chordomas typically- although not

in-variably- arise in the midline of the spinal column at

any location from the clivus to the coccyx.33 Over

85% are found in the skull base or sacrum

Approxi-mately half of all chordomas originate in the sacrum

or coccyx Another 35% arise within the skull base,

typically in the clivus near the sphenooccipital

syn-chondrosis.30 Less than 15% of chordomas occur in

the vertebral bodies More than one vertebral segment

is often involved Completely extradural,

ex-traosseous vertebral chordomas have been reported

but are very rare.30

Clinical presentation and natural history

Chor-domas are typically slow-growing neoplasms;

symp-toms vary with location

Imaging findings NECT scans commonly show a

Fig 21-15, cont'd C, Axial NECT scan shows a low

density lytic destructive sacral mass (large arrows)

with some residual bone or calcification within the

lesion (Courtesy B.J Manaster.)

Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 891

Fig 21-16 Two cases of vertebral body chordoma illustrate MR findings of this

tumor A, Axial T1-weighted MR scan in this 35-year-old man with low back

pain and suspected lumbar disk herniation show a destructive vertebral body

mass (large arrows) with epidural extension (small arrows) B and C, Sagittal

T1- (B) and T2-weighted (C) MR scans in another case show a lobulated neural

foraminal mass (large arrows) in the upper thoracic spine The mass becomes

very hyperintense on the long TR/long TE scan Note the displaced epidural fat

(small arrows) capping the tumor and indicating its location in the extradural

compartment Chordoma was found in both cases

tissue mass is typical ES is usually hypo-to isointense

with muscle on T1- and hyperintense on T2weighted

MR scans (Fig 21-18).17

Osteosarcoma Osteosarcomas account for ap-

proximately 20% of all sarcomas but rarely affect the

spine.5 The peak age is 10 to 25 years and there is a

slight male predominance.17 Osteosarcomas occur with

increased frequency in previously irradiated bone or in

patients with Paget disease Imaging studies show

mixed osteolytic and sclerotic changes with matrix

calcification (Fig 21-19).5

Chondrosarcoma Chondrosarcomas are half as

frequent as osteosarcoma Most patients are aged or older adults and there is a 2:1 male predom-inance Chondrosarcomas may arise from malignant degeneration of solitary osteochondromas (1%) or hereditary multiple exostoses (20%).5 Lytic lesions with sclerotic margins and variable matrix calcification

middle-occur in rings and arcs (see Chapter 12) Associated

soft tissue masses are common and local extension to

an adjacent vertebra may occur.17

Fibrosarcoma Fibrosarcomas are rare primary

892 PART FIVE Spine and Spinal Cord

Fig 21-17 Spinal lymphoma A, Gross pathology specimen shows extensive

osseous and epidural tumor Non-Hodgkin lymphoma B, Axial T1-weighted

MR scan in another case shows epidural non-Hodgkin lymphoma (large arrows)

with thecal sac compression (small arrows) (A, Courtesy Rubinstein Collection,

University of Virginia.)

Fig 21-18 Two cases of Ewing sarcoma A, Coronal T1-weighted MR scan in a

12-yearold girl with Ewing sarcoma shows an extensive paravertebral soft tissue mass

(arrows) that extends through the neural foramina into the spinal canal, displacing and

compressing the thecal sac B, The mass is hyperintense on the sagittal T2WI (large

arrows) Note dural displacement (small arrows) caused by the epidural mass effect

Sagittal pre- (C) and postcontrast (D) T1WIs in another case show the vertebral body

and epidural lesion (arrows) enhances strongly Note cord compression

Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 893

malignant bone tumors Fibrosarcomas occur in wide age

range; there is no gender predilection.5 Imaging studies

typically show a lytic, destructive somewhat expansile

mass without matrix calcification.5 Primary spinal

fibrosarcomas are extremely rare

(myelomatosis) Plasmacytoma is a solitary lesion,

whereas myelomatosis has multiple lesions (Fig 21-20)

Multiple myeloma (MM) is a monoclonal ation of malignant plasma cells that usually affects the bone marrow.36 The peak incidence is during the sixth decade The spine is the most common location, and epidural involvement is frequent.37 The vertebral bodies are the most common site

prolifer-Both focal and diffuse lesions occur in MM Plain film radiographs and NECT scans show focal or dif-fuse lytic defects MR signal varies Most lesions are hypointense to adjacent marrow and iso- or slightly hyperintense compared to muscle on T1WI (Fig 21-

20, B).37,38 MM is typically hyperintense on T2WI Fat-suppressed and T2-weighted sequences are helpful studies in delineating lesion extent.37

Metastatic disease

Pathology In adults, approximately half of all

spine metastases with epidural spinal cord sion arise from breast, lung, or prostate cancer (Fig 21-21, A) Other frequent primary tumors include lymphoma, melanoma, renal cancer, sarcoma, and multiple myeloma Spine metastases in children are most often caused by Ewing sarcoma and neuroblas-toma, followed by osteogenic sarcoma, rhabdomyo-sarcoma, Hodgkin disease, soft tissue sarcoma, and germ cell tumors

compres-Fig 21-19 AP plain film radiograph shows

osteogenic sarcoma of L3 with large "sunburst"

tumor matrix calcification and large soft tissue mass

(arrows) (Courtesy B.J Manaster.)

Fig 21-20 A, Axial NECT scan in this 55-year-old man with back pain shows a

large paravertebral soft tissue mass (large arrows) with associated bone destruction (small arrows) No other lesions were present Biopsy disclosed

plasmacytoma (B), Sagittal T1-weighted MR scan in a 78-year-old woman with

multiple myeloma shows extensive multifocal replacement of fatty marrow by

894 PART FIVE Spine and Spinal Cord

Fig 21-21 A, Gross pathology specimen shows spine metastases from lung

carcinoma Note marrow replacement and pathologic compression fractures Sagittal

T1- (B) and T2-weighted (C) MR scans in a 42-year-old woman with treated breast

carcinoma show typical findings of sclerotic vertebral body metastases Note

pathologic compression fracture (arrows) and complete replacement of fatty marrow

by low signal tumor (arrows) Compare to the other vertebral bodies with diffusely

fatty marrow (secondary to radiation therapy) (A, Courtesy B Horten.)

Incidence, age, and gender Metastatic disease is

the most common extradural malignant spine tumor in

adults Autopsy studies disclose epidural (vertebral)

metastases in 15% to 40% of patients dying of

disseminated cancer.41 Middle-aged and elderly adults

are most often affected Approximately 5% of

children with solid malignant tumors develop spinal

epidural metastasis with cord compression.40 There is

no overall gender predilection.17

Location Pediatric metastatic tumors typically

in-vade the spinal canal via the neural foramen, causing

circumferential cord compression (see Fig 21-18,

A).40 In adults, the initial site is in the vertebral body,

typically the posterior aspect; epidural space and

pedicle lesions are usually secondary to vertebral

in-volvement.42 The paraspinous soft tissues are also

frequently affected

Spine metastases in adults are distributed

accord-ing to the location of red bone marrow 42,43 All

ver-tebral levels can be involved, although the lower

tho-racic and lumbar spine are the most frequently

affected sites.42,43

Clinical presentation Pain and progressive

neuro-logic deficits are common Cord compression is

among the most dreaded complications If left untreated, metastatic epidural compression inexorably progresses, causing paralysis, sensory loss, and sphincter incontinence.39

Imaging findings Most metastases are osteolytic,

although breast and prostate cancer can cause blastic or sclerotic lesions Pedicle destruction is the most common plain film finding.42 Other frequent abnormalities include multifocal lytic vertebral body lesions, pathologic compression fracture, and paraspinous soft tissue mass A subtle but useful plain film clue to epidural metastatic disease is an indistinct posterior vertebral body margin.44

osteo-Myelography typically discloses extradural mass effect

or block (see Fig 21-1, B and C) Lumbar puncture

below the level of a high-grade stenosis or block can cause rapid neurologic deterioration from "coning" of the spinal cord at the level of the block.41

Bone scintigraphy is very sensitive in detecting altered local metabolism in areas of skeletal remodeling associated with metastatic deposits Only a 5% to 10% change in lesion to normal bone area is needed.43 This compares favorably with the 40% to 50% destruction typically required for lesion detec-

Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 895

tion on plain film radiographs However, bone scans are

nonspecific and can be abnormal in cases of trauma,

infection, and degenerative disease.41 Very aggressive

metastatic disease can also have a false-negative scan.43

Single photon emission computed tomographic

(SPECT) images are sometimes helpful in differentiating

between benign and malignant lesions, Lesions with focal

or diffuse uptake in the body are usually benign; lesions

with both body and pedicle uptake are usually metastatic

Lesions in the apophyseal joints and lesions with an

intervening normal pedicle between body and posterior

element uptake are typically benign.45

NECT scans readily define osteolytic or osteoblastic

lesions, although intrathecal contrast is required to

delineate the precise extent of epidural disease.5

MR imaging is even more sensitive than bone

scintigraphy in detecting vertebral metastases.43 MR also

exquisitely and noninvasively delineates epidural and

paraspinous soft tissue involvement Cord compression is

The most common pattern is multifocal lytic lesions that

are characterized by low signal intensity on T1- and high

signal intensity on T2-weighted sequences (see Fig 21-1,

D).41 Sclerotic lesions are hypointense on both T1- and

T2WI (see Fig 21-21, B and Q Both diffuse

inhomogeneous and homogeneous lesions show low

signal intensity on T1WI and high signal intensity on

T2-weighted sequences.43

Contrast-enhanced MR is not routinely required in the

evaluation of suspected spinal metastatic dis-

Benign Versus Pathologic Compression

Fracture Benign (osteoporotic) compression fracture

Signal similar to other vertebral bodies (in elderly,

marrow is usually high signal on T1WI, low on

T2WI)

Signal is relatively uniform

Fat-suppression scans helpful

Pathologic compression fracture

Lesions often multiple

Signal usually different from other vertebral bodies

Often hypointense on T1WI, hyperintense on T2WI

Signal usually heterogeneous

Pedicle involvement common

ease.41 The degree and pattern of enhancement lowing contrast administration varies Some lesions may enhance avidly, whereas others may not enhance at all Lesions in the same patient may also behave differently.41 Some enhance to isointensity and therefore are difficult to detect unless precontrast studies or fat-suppressed sequences are used.41

fol-Distinguishing between benign (i.e., osteoporotic) and pathologic (i.e., metastatic) vertebral body com-

pression fractures is usually possible on MR scans (see

box) Chronic benign fractures typically have marrow signal intensity that is isointense with normal vertebrae

on all sequences Pathologic fractures -show paratively low signal intensity on T1- and high signal intensity on T2-weighted sequences.46

com-INTRADURAL EXTRAMEDULLARY TUMORS, CYSTS, AND TUMORLIKE MASSES

Benign Tumors

Intradural extramedullary masses arise inside the dura but outside the spinal cord By convention, nerve root tumors are grouped with the intradural ex-tramedullary masses Nerve sheath tumors and men-ingiomas account for 80% to 90% of all intradural extramedullary neoplasms.47 Other benign tumors are uncommon The general imaging features of intradural

extramedullary masses are illustrated in Fig 21-22

Nerve sheath tumors

Pathology Two main types of nerve sheath tumors

are found in the spine: schwannoma (also known as neurinoma or neurilemoma) and neurofibroma The Schwann cell is the proliferating neoplastic element in both lesions A third type of neurogenic spinal tumor,

ganglioneuroma, is relatively rare (see box, p 897)

Schwannomas are lobulated, grossly encapsulated, well-circumscribed round or oval tumors that often show cystic degeneration, hemorrhage, and

xanthomatous changes (see Chapter 15) Schwannomas

arise eccentrically from their parent nerve (Fig 21-23) Nerve fibers do not course through the tumor but are confined to the capsule.48 Microscopically, schwannomas are composed of densely packed, highly ordered spindle cells (the so-called Antoni type A) or more loosely textured myxoid stroma (Antoni type B).49 Primary malignant peripheral nerve sheath tumors occur but are very rare

Neurofibromas are unencapsulated, fusiform, less well-delineated lesions Plexiform-type neurofibromas occur in patients with neurofibromatosis type 1 (NF-1) Necrosis and cystic degeneration are rare in neurofibromas Neurofibromas usually cannot be dis-sected from the parent nerve because it typically runs

896 PART FIVE Spine and Spinal Cord

Fig 21-22 Classic pathologic and imaging findings of an extramedullary intradural mass (in

this case, a meningioma) A, Anatomic drawing shows the mass (large arrows) displaces the

spinal cord (small arrows) and enlarges the ipsilateral subarachnoid space (arrowheads) A

sharp, crescentic interface is formed between the contrast column and undersurface of the mass

(open arrow) The subarachnoid space is blocked (curved arrow), and CSF above the block

remains unopacified B, Gross pathology of a typical spinal meningioma illustrates these

findings The mass (large arrow) is intradural The spinal cord (small arrow) is displaced away from the mass, and the ipsilateral subarachnoid space (arrowhead) is enlarged The interface between CSF and the undersurface of the mass forms a sharply delineated border (open arrow)

The curved arrow indicates the theoretical level of a myelographic block C, Lumbosacral

myelogram, AP view, in a 59-yearold woman with a 3-year history of spastic paraparesis Note

block (curved arrow), sharp interface (open arrows) formed by contrast meniscus abutting the mass (large arrows) The ipsilateral subarachnoid space is enlarged (arrowheads), and the

spinal cord (small arrows) is displaced away from the mass Compare with Fig 21-22, A (B,

From Okazaki H, Scheithauer B: Slide Atlas of Neuropathology, Gower Medical Publishing,

1988.)

through the lesion and nerve fibers are dispersed

throughout the tumor.48,50

Microscopically, neurofibromas are composed of

Schwann cells and fibroblasts The bulk of the tumor

volume consists of intercellular collagen fibrils in a

nonorganized mucoid or myxomatous matrix.49,50

Ganglioneuromas are uncommon, benign spinal tumors

that can occur in either the spinal cord or peripheral nerve

roots Grossly, ganglioneuromas are well-delineated

masses that have a distinct whorled appearance

Microscopically, ganglion cells, Schwann cells, and nerve

fibers are identified.51

Incidence, age, and gender Nerve sheath tumors

the most common intradural extramedullary spinal neoplasm, accounting for 25% to 30% of all cases.5,47 Schwannomas are slightly more common than neu-rofibromas.49

Both schwannomas and neurofibromas usually come symptomatic in the middle decades In general, both sexes are equally affected, although there is a slight female predominance with schwannomas.5,52 Between 35% and 45% of patients with nerve root tumors have neurofibromatosis.49

be-Location Most nerve sheath tumors arise from dorsal

sensory roots.17 Depending on their origin along the root, nerve sheath tumors can be intradural