Localization in the Neuraxis. The Approach to a Patient with Neurologic Disease zThe H&P accurately...

Localization in the Neuraxis

The Approach to a Patient with Neurologic Disease

The H&P accurately localizes most lesionDivisions of the neuraxis have

specialized functionsDamage to various divisions produce

unique clinical deficitsLocalization is important

investigation modalities differ widely depending upon the level affected

Divisions of the Neuraxis

Cortical BrainSubcortical

BrainBrainstemCerebellumSpinal CordRootPeripheral

Nerve

Neuromuscular Junction

Muscle

Neurologic Examination

Higher Cortical FunctionCranial NervesCerebellar FunctionMotor SensoryDeep Tendon ReflexesPathologic Reflexes




Nerve


Muscle

Cortical Brain

Depends upon hemispheric dominanceNon-neurologists generalize:

right: visual/spatial, perception and memory

left: language and language dependent memory

Through detailed examination, neurologists should lateralize and localize within a lobe

Cortical Brain

Frontal Lobe: L:

Broca’s Aphasia

R: ? B:

precentral gyrus: motor homunculoussupplementary motor cortex: eye and head

turnprefrontal cortex: personality, initiativeparacentral lobule: cortical inhibition of

voiding B/B

Cortical Brain

Parietal Lobe: R:

anosognosia: left hemineglectdressing and constructional apraxiageographic agnosia

L:Gerstman’s Tetrad (not triad): L/R confusion,

finger agnosia, acalculia, agraphia without alexia

Werneke’s Aphasia

Cortical Brain

Parietal Lobe: B:

abnormal posture and passive movementlocalization of touch2-point discriminationastereognosisperceptual rivalry

Cortical Brain

Temporal: R:

hearing language

L:hearing sounds, rhythm, rhythm, music

B:learning and memory: mid/inferior gyriolfaction: limbicAuditory cortex: Heschel’s gyrus

Cortical Brain

Occipital Lobe: R:

micropsiamacropsia

B:visual hallucinations: elemental and unformedprosopagnosia: familiar facescortical blindness: striate cortices, normal pupil rxAnton’s: (para)striate, denial of obvious blindnessBalint’s: inability to direct voluntary gaze with

visual agnosia

Neurologic Examination when Cortical Brain is

Lesioned

Higher Cortical Function aphasia, apraxia, agnosia

Cranial Nerves: normal, unless forced eye deviation Cerebellar Function: normal Motor:

weakness of face/arm>leg (or vice versa) if motor homunculous is hit hypertonia if corticospinal tracts are hit

Sensory: sensory abn of face/arm>leg (or vice versa)

Deep Tendon Reflexes: hyper-reflexia

Pathologic Reflexes: Babinski’s reflex if corticospinal tracts are hit Frontal release signs (nonspecific), possibly Kernig and/or Brudzinski




Nerve


Muscle

Subcortical Brain

Deep white radiating fibers produce equal involvement of face/arm/leg weakness sensory abnormalities

Visual radiating fibers: (know how visual abnormalities morph with lesions from anterior to posterior brain)

deep parietal: bilateral homonomous quad on the floor

deep temporal (Meyer’s loop): bilateral homonomous quad in the sky

Neurologic Examination when Subcortical Brain is

Lesioned

Higher Cortical Function: normal Cranial Nerves:

visual field cuts Cerebellar Function: usually normal Motor:

weakness in face=arm=leg hypertonia

Sensory: sensory abnormalities in face=arm=leg

Deep Tendon Reflexes: hemi-hyper-reflexia

Pathologic Reflexes: Babinski’s reflex if corticospinal tracts are lesioned frontal release signs (nonspecific)




Nerve


Muscle

Brainstem

CN symptoms characterize BS diseaseThe Brainstem is basically spinal cord

with embedded cranial nerves cause symptoms of spinal cord disease, also Long Tract signs: (bilateral and crossed)

corticospinal (pyramidal): motorspinothalamic: pain/temp to the thalamusdorsal columns: prioprioception/vibration to thal.(due to decusation of long tracts, BS lesions do not produce

horizontal motor/sensory levels as in the cord, but rather vertical levels of hemiparesis/hemidysesthesias)

Neurologic Examination when Brainstem is Lesioned


III, IV, VI: diplopia V: decreased facial sensation VII: drooping VIII: deaf and dizzy IX, X, XII: dysarthria and dysphagia XI: decreased strength in neck and shoulders

Cerebellar Function: usually normal Motor: hemi-paresis (may be crossed), hemi-hypertonia,

spasticity Sensory: hemi-dysesthesias (may be crossed) Deep Tendon Reflexes: hemi-hyper-reflexia, brisk jaw jerk Pathologic Reflexes: Babinski’s reflex




Nerve


Muscle

Cerebellar Function

Some people believe that one can not test specifically for cerebellar abnormalities no one test on examination reliably evaluates the cerebellum

H: hypotoniaA: assynergy of (ant)agonist musclesN: nystagmusD: dysmetria, dysarthriaS: stance and gaitT: tremor

Neurologic Examination when the Cerebellum is

Lesioned

Higher Cortical Function: normal Cranial Nerves: usually normal Cerebellar Function:

nystagmus flaccid dysarthria

Motor: normal bulk and strength with ipsilateral hemi-hypotonia intention worse than positional ipsilateral tremor axial instability with dysmetria

Sensory: normal Deep Tendon Reflexes: normal Pathologic Reflexes: normal

(plantar flexing to plantar stimulation)




Nerve


Muscle

Spinal Cord

Sensory levelSpasticity/hypertoniaWeakness:

extensors worse than flexors distal > proximal

Bowel and Bladder involvement: retention comes first, then detrusor

hyperactivity(both produce incontinence)

Neurologic Examination when the Spinal Cord is

Lesioned

Higher Cortical Function: normal Cranial Nerves: normal Cerebellar Function: normal Motor:

weakness (extensors worse than flexors) below the lesion para-hypertonia below the lesion with spasticity

Sensory: horizontal level usually lower than the lesion, poorly localizing may be somewhat assymetric

Deep Tendon Reflexes: para-hyper-reflexia below the level, possibly clonus

Pathologic Reflexes: loss of superficial reflexes (Beavor’s sign, cremasteric, anal

wink, etc) Babinski’s reflex




Nerve


Muscle

Root/Radiculopathy

Pain is the hallmark of a radiculopathy Sensory abnormalities in a dermatome provocative maneuvres exacerbate sharp, stabbing, hot, electric, radiating

Weakness in a myotome (assymetric) proximal (C5C6) distal (L5S1)

Neurologic Examination when a Root is Lesioned

Higher Cortical Function: normal Cranial Nerves: normal Cerebellar Function: normal Motor:

assymetric weakness, atrophy, and fasiculations in a myotome tone should be normal, unless multiple roots are severed

Sensory: assymetric dysesthesias confined to a dermatome anesthesia requires >1 root transection

Deep Tendon Reflexes: hypo- to a-reflexia if the root carries a reflex

Pathologic Reflexes: Spurling’s sign dural tension signs may be present (straight leg, crossed

straight leg, reverse straight leg, etc)




Nerve


Muscle

Peripheral Nerve(presuming nonfocality)

Weakness: distal predominant, (a)symetric

Sensory Dysesthesias: distal predominant

Autonomic involvement may occurTrophic changes: smooth shiny skin,

vasomotor abnormalities (edema, temperature dysregulation, vascular flushing), hair loss, nail changes

Neurologic Examination with Diffuse PN Lesioning


may be abnormal (know which peripheral CN’s associate with specific diseases)

Cerebellar Function: normal Motor: weakness is distal predominant if the PN is diffuse

atrophy, fasiculations, (hypotonia) Sensory:

dysesthesias, anesthesias, hyperpathia, allodynia, etc Deep Tendon Reflexes:

distal predominant hypo- to a-reflexia Pathologic Reflexes:

mute responses to plantar stimulation




Nerve


Muscle


Fatiguability is the hallmarkWeakness: proximal and symmetric

exacerbated with use, recovers with rest

often affects facial muscles (ptosis, dysconjugate gaze, slack jaw)

muscles have normal bulk and toneSensation: preserved

Neurologic Examination in Disorders of the NMJ


fatiguability in ptosis, dysconjugate gaze, slack jaw Cerebellar Function: normal Motor:

fatiguable proximal weakness in both UE’s and LE’s no atrophy or fasiculations tone may be slightly decreased

Sensory: normal, though may complain of lowback pain

Deep Tendon Reflexes: may be hypo- to a-reflexic in LEMS may be normal in MG

Pathologic Reflexes: none




Nerve


Muscle

Muscle

Weakness of proximal arm and leg muscles symmetric

Sensation is normal though patients complain of cramping,

aching, and atrophy

Neurologic Examination in Disorders of Muscle


ptosis, dysconjugate gaze, slack jaw, bow-string lip, myopathic facies, dysphagia, dysphonia, (dysarthria)

Cerebellar Function: normal Motor:

usually proximal weakness in both UE’s and LE’s atrophy and fasiculations diffuse hypotonia accentuated primary and secondary curvature, scoliosis

Sensory: normal, though may complain of lowback pain

Deep Tendon Reflexes: preserved until late in the disease Pathologic Reflexes: ? Myotonia or cramping

Just a Few Things to Remember

Not all aphasias and apraxias are cortically based thalamus

The absence of Babinski’s reflex does not imply a lesion distal to the cord basal ganglia thalamus cerebellum

Compromised attention span results from lesioning: brain stem and RAS diencephalon: both sides bilateral cerebral hemispheres


Some neurologic diseases hit more than one level in the neuraxis

The tempo of progression allows one to narrow a differential diagnosis remarkably well . . . Always always always clarify this issue with the patient

Parsimony rulesNever fabricate part of the exam for

sake of being “thorough”


If you do not think of a complete differential diagnosis, you can not expect to catch the interesting diagnoses.

You must think of the possibile accademic diagnoses at this point in your career.

Patients pay you to rule out the worst firstWhen you are unsure of a diagnosis, it is

important to communicate this to patients and other physicians.

Localization in the Neuraxis. The Approach to a Patient with Neurologic Disease zThe H&P accurately...

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