Differential Diagnosis in Neurology and Neurosurgery - part 9 docx

Random missteps mar the evenness of thestrides, as the choreiform twitches superveneSpastic – athetoid gait A combination of athetosis and moderate spastic diplegia or double hemiplegia

Spastic diplegic gait Patients affected by diplegic cerebral palsy have small

and short legs in contrast to normally developedchest, shoulders, and arms In spastic diplegia, there issevere spasticity in the legs, minimal spasticity in thearms, and little or no deficit in speaking or swallowing;whereas in double hemiplegia, there is pseudobulbarpalsy and more arm weakness than leg weaknessSpastic – ataxic gait If, in addition to spasticity, the disease impairs the

dorsal columns or cerebellum, as in spinocerebellardegeneration or multiple sclerosis, patients have awider-based, unsteady gait and take irregular steps

Basal ganglia gaits

Marche à petits pas

(gait with little steps) Elderly patients with small vessel disease due to arte-riosclerosis, appearing as multiple lacunar infarcts in

the basal ganglia, develop a characteristic gait withshuffling, short steps, and are unable to lift the feetfrom the ground Progress in walking ceases if thepatient tries to speak (they are unable to walk and talk

or chew gum at the same time)Parkinsonian gait Patients with degeneration of the substantia nigra or

neuroleptic medication toxicity rise and walk slowlywith short steps, lack any arm swing, turn en bloc like

a statue rotating on a pedestal, and have a tremorwhen at rest, which disappears during intentionalmovement

Festinating gait When patients are pushed after prior warning, they

move forward or backward with tiny steps of ing speed and decreasing length, as if chasing thecenter of gravity, and they may fall over

increas-Choreiform gait When patients with Huntington’s or Sydenham’s

chorea walk, the play of finger and arm movementsincreases, or may even appear clearly for the firsttime Random missteps mar the evenness of thestrides, as the choreiform twitches superveneSpastic – athetoid gait A combination of athetosis and moderate spastic

diplegia or double hemiplegia secondary to perinatalhypoxic damage of the basal ganglia and thalamus hasthe characteristics of spastic gait, associated withslow, writhing movements of fingers and arms, whichtend to increase during walking

Equinovarus dystonic

gait Dystonia may initially manifest in a child as an inter-mittent inturning of the foot that impedes walking,

while in later stages dystonic truncal contortions andtortipelvis may cause the trunk to incline strongly for-ward

Types of Stance and Gait

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Dromedary gait Patients with dystonia musculorum deformans may

take giant, uneven strides, exhibiting flexions or risingand falling of the trunk, like the ungainly gait of adromedary camel

secondary to Alzheimer’s disease, multi-infarctdementia, or senility have difficulty in initiating thesequence of movements for rising, standing, andwalking When starting to walk, patients makesseveral efforts to move the feet, appearing somewhatpuzzled—as if searching for lost motor engrams, or theright buttons to press in order to set off

Dancing bear gait The effort to progress may only result in stepping on

the spot, as if trying to free the feet from thick, stickymud

Apraxic gait When patients do manage to make progress, the feet

cling to the floor as if magnetized

Psychiatric gaits

Astasia – abasia The patient tilts, gyrates, and undulates all over the

place, proving unwittingly—by not falling during thismarvelous demonstration of agility—that strength,balance, coordination, and sensation must still be in-tact

Sexual behavior and

biological orientation

gaits

The gait is characteristic of and diagnostic of the logical and behavioral state of a person’s brainHeterosexual male –

bio-female gait

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269 Neurotrauma

Glasgow Coma Scale*

The Unconscious Patient

! Venous occlusion– Trauma (closed head

– Infection ! Meningitis

! Encephalitis

! Abscess– Primary neuronal or

glial disorders ! Progressive multifocal leukoencephalopathy (PML)

! Paraldehyde– Other ! Organic phosphates

! Cyanide

! Heavy metals

! Cardiac glycosides

! Steroids (insulin)Endogenous

– Hyperglycemia ! Ketotic coma

! Nonketotic coma– Hypoglycemia Endogenous insulin, liver disease, etc

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– Uremic coma Kidney failure

– Hepatic coma Liver failure

– CO2narcosis Pulmonary failure

! Adrenal (Addison’s disease, Cushing’s disease,pheochromocytoma)

! Thyroid (myxedema, thyrotoxicosis)

! Pancreas (diabetes, hypoglycemia)– Systemic illness ! Cancer

Decreased cardiac

out-put Congestive heart failure

vessel occlusions ! Subacute bacterial endocarditis

! Disseminated intravascular coagulation (DIC)

! CNS arteritis (systemic lupus erythematosus)

! Fat embolism

The Unconscious Patient

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Metabolic and Psychogenic Coma

In unresponsive patients, metabolic disease can be distinguished frompsychiatric disease on the basis of differences between the mental state,the motor signs, the breathing pattern, the electroencephalogram (EEG),and the oculovestibular or caloric reflexes

Comatose patients with metabolic disease

– Confusion, stupor and coma precede motor signs

– The motor signs are usually symmetrical

– The EEG is generally very slow

– Caloric stimulation elicits either tonic deviation of the eyes or, if the patient

is deeply comatose, no response

– Seizures are common

Psychologically unresponsive patients

– The EEG is normal

– Caloric stimulation: there is a normal response to caloric irrigation, withnystagmus having a quick phase away from the side of ice-water irrigation;there is little or no tonic deviation of the eyes Nystagmus is present

– Lids close actively

– No pathological reflexes are present

– Pupils are reactive or dilated (cycloplegics)

– Muscle tone is normal or inconsistent

EEG: electroencephalogram

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Metabolic and Structural Coma

Metabolic and structural diseases are distinguished from each other bycombinations of motor signs and their evolution, and electroencephalo-gram (EEG) changes

Comatose Patients with Metabolic Disease

Patients are usually suffering from partial dysfunction affecting manylevels of the neuraxis simultaneously, while at the same time the integ-rity of other functions originating at the same level is retained Ingeneral, a suspicion of metabolic disease should be raised if the follow-ing findings are present

Cognitive and behavioral

Diffusely abnormal motor

Tremor

Myoclonus

Bilateral asterixis

EEG Diffusely, but not focally, slow

Acid – base abnormalities Frequent, with hyperventilation and hypoventilationPupillary reactions Usually preserved even if the patient is comatoseEEG: electroencephalogram

Metabolic and Structural Coma

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Comatose Patients with Gross Structural Disease

Patients generally have a rostrocaudal deterioration that is characteristic

of supratentorial mass lesions, which does not occur in metabolic braindisease, and the anatomical defect is not regionally restricted as it iswith subtentorial damage The clinical signs are certainly helpful, butthere is too much overlap to allow the diagnosis to be established by theclinical findings alone It is not uncommon, for example, for patientswith hepatic encephalopathy or hypoglycemia to develop focal motorsigns such as hemiparesis or visual field defects, which are characteristic

of a structural lesion, whereas patients with multiple brain metastasesmay develop nothing other than a global alteration of cognitive function.The laboratory screening listed below are therefore essential for ex-cluding structural disease

CT/MRI with enhancement E.g., metastases, infection

Lumbar puncture E.g., infection, meningeal carcinomatosis

EEG

Hematological work-up

– Blood cultures E.g., sepsis, septic emboli

– Full blood count

– Coagulation tests E.g., PT, PTT, FDP

– Blood gases

Biochemical work-up

– Electrolytes E.g., Na, K, Ca, Mg, PO4

– BUN, creatinine, glucose,

lactate

– Endocrine tests E.g., FSH, T3, T4, cortisol

– Thiamine, folic acid,

vita-min B12

Drug levels E.g., digoxin, anticonvulsants, theophylline, etc.BUN: blood urea nitrogen; CT: computed tomography; EEG: electroencephalogram; FDP:fibrin degradation product; FSH: follicle-stimulating hormone; MRI: magnetic resonanceimaging; PT: prothrombin time; PTT: partial thromboplastin time; T3: triiodothyronine; T4:thyroxine;

The patient should be suspected of suffering from structural brain ease, either alone or in combination with metabolic brain disease, if thefollowing findings are present

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Coma-Like States

The basic brain structure that is responsible for arousal is the ascendingreticular activating system (ARAS) This system originates in the brainstem reticular formation, and extends to the cortex via the diffuse ornonspecific thalamofrontal projection system Reticular activation bymeans of an external stimulus alerts widespread areas of the cortex andsubcortex, enabling the patient to be alert and to think clearly, learn ef-fectively, and relate meaningfully to the environment

If there is damage to the extension of the brain stem reticular system

in the thalamus or hypothalamus, the full picture of coma will not occur.Since the brain stem portion of the ARAS is intact, reticular activity in-nervates the nuclei of the extraocular nerves, and patients can opentheir eyes and look about The cortex, however, is not sufficiently stimu-lated to produce voluntary movement or speech These patients are in acoma-like state The characteristics of the coma-like states are presented

in the following tables:

Coma-Like States

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Trauma Score

The trauma score is a numerical grading system for estimating the ity of injury The score consists of the Glasgow Coma Scale (reduced toapproximately one-third of its total value) and measurements of car-diopulmonary function Each parameter is given a number (high for nor-mal and low for impaired function) The severity of the injury is esti-mated by adding up the numbers; the lowest score is 1, and the highestscore is 16

sever-– Abnormal focal motor signs (including focal seizures) occur, which progressrostrally to caudally, and are asymmetrical

– Neurological signs point to one anatomical area (mesencephalon, pons,

medulla)

– Specific cognitive function disorders, such as aphasia, acalculia, or agnosia,appear out of proportion to a general overall decrease in mental state

– The EEG may be slow, but in addition there is a focal abnormality

– The patient is at particular risk of developing one of the complications ofcancer that may mimic metabolic brain disease, particularly DIC or meningi-tis

EEG: electroencephalogram

Trauma Score

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Trauma score Survival (%)

Respiratory Patterns in Comatose Patients

Anatomical level of pathological lesion Respiratory patterns

Forebrain damage

Bilateral widespread cortical lesions

Bilateral thalamic dysfunction Eupneic, with sighs or yawns

Lesions in the descending pathways

any-where from the cerebral hemispheres to

the level of the upper pons

Cheyne–Stokes

Hypothalamic-midbrain damage

Patients with dysfunction involving the

rostral brain stem tegmentum Lesions

have been found between the low

mid-brain and the middle third of the pons,

destroying the paramedian reticular

for-mation just ventral to the aqueduct and

fourth ventricle

Sustained regular hyperventilation(despite the prolonged and rapid hy-perpnea, patients are hypocapnic andrelatively hypoxic, and have pulmo-nary congestion, leading rapidly topulmonary edema This type ofbreathing can therefore not betermed “primary hyperventilation”)

Lower pontine damage

Patients have lesions or dysfunction of

the lateral tegmentum of the lower half

of the pons adjacent to the trigeminal

motor nucleus More prolonged

apneu-sis has developed when the lesions

ex-tend caudally to involve the dorsolateral

pontine nuclei

Apneustic breathing

Pontomedullary junction damage

Patients have lesions at the lower

pon-tine or high medullary level Cluster breathing

Medullary damage or dysfunction

Follows lesions of the respiratory

cen-ters located in the reticular formation of

the dorsomedial part of the medulla and

extending down to or just below the

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Pupillary Changes in Comatose Patients

Brain stem areas controlling consciousness are anatomically adjacent tothose controlling the pupils Pupillary changes, therefore, are a valuableguide to the presence and location of brain stem diseases producingcoma Pupillary shape, size, symmetry, and response to light reflectpatency or nonpatency of the brain stem and third nerve function Thepupillary light reflex is very sensitive to mechanical distortion, but veryresistant to metabolic dysfunction Abnormalities of this reflex, particu-larly when unilateral, are the single most important physical sign poten-tially distinguishing between structural and metabolic coma

Location of the coma producing

structural lesions

Pupils

Sleep or diencephalic dysfunction

(metabolic coma) Small, reacting well to light(“diencephalic pupils”)

Unilateral hypothalamic damage or

dysfunction

Miosis and anhidrosis (ipsilateral to the sion)

le-Midbrain tectal or pretectal damage Medium-sized (5 – 6 mm) or slightly large,

“fixed” hippus (spontaneous oscillations

in size), becoming larger when the neck ispinched (ciliospinal reflex)

Midbrain tegmental damage (third

cranial nerve nucleus involvement)

Medium-sized (4 – 5 mm), often unequal,usually slightly irregular (irregular con-striction of the sphincter of the iris results

in a pear-shaped pupil), midbrain topia (displacement of the pupil to oneside), fixed to light and lack of ciliospinalresponse

corec-Pontine tegmental damage Pinpoint, constricting to light (due to a

combination of sympathetic damage andparasympathetic irritation)

Pontine lateral, lateral medullary,

and ventrolateral cervical cord

dam-age or dysfunction

Ipsilateral Horner’s syndrome

Peripheral lesions The light reflex is sluggish or absent, and

the pupil becomes widely dilated(7 – 8 mm) due to sparing of the sympa-thetic pathways (Hutchinson’s pupil).Oval-shaped pupils due to nonuniformparesis of the pupil sphincter, causing aneccentric antagonistic effect of pupil di-lators

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Spontaneous eye movements

Bilateral cerebral damage (bilateral

cerebral ischemia), with intact brain

stem Rarely seen in posterior fossa

hemorrhage

Periodic alternating gaze (ping-ponggaze) Roving of the eyes over the fullswing of the horizontal plane in oscillatingcycles of 2 – 5 seconds

Mid- or lower pontine damage Nystagmoid jerking of a single eye, in a

horizontal, vertical or rotatory fashion andoccasionally bilateral disconjugate verticaland rotatory eye movements (one eyemay rise and intort as the other falls andextorts)

Intrinsic pontine lesions

(hemor-rhage, tumor, infarction etc.),

extra-axial posterior fossa masses

(hemor-rhage or infarction), diffuse

enceph-alitis, and toxic metabolic

en-cephalopathies

Ocular bobbing (intermittent, often jugate, brisk, bilateral downward move-ment of the eyes, with slow return to themid-position) When associated with pres-ervation of horizontal eye movements,this becomes a specific finding, but is notpathognomonic of acute pontineinjury

con-Diffuse brain dysfunction and

en-cephalopathy (anoxic coma, or after

prolonged status epilepticus) No

definite brain stem lesion

Ocular dipping (slow downward eyemovement, with fast return to mid-posi-tion) Brain stem horizontal gaze reflexesare usually intact

Pontine hemorrhage, viral

encepha-litis, and metabolic encephalopathy Reverse ocular bobbing (fast-upward eyemovement with a slow return to

mid-posi-tion)Pretectal area (acute hydro-

cephalus) Pretectal pseudobobbing (arrhythmic, re-petitive downward and inward,

“V-pat-tern”, eye movements at a rate rangingfrom one per three seconds to two persecond, with an amplitude of one-fifth tohalf of the full voluntary range) Often as-sociated with abnormal pupillary light re-actions, intact horizontal eye movements,open and often retracted eyelids, a blinkfrequently preceding each eye move-ment, and a mute or stuporous patient.This situation requires immediate surgicaldecompression of hydrocephalusSpontaneous Eye Movements in Comatose Patients

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