Localization in the Neuraxis

The Approach to a Patient with Neurologic Disease zThe H&P accurately localizes most lesion zDivisions of the neuraxis have specialized functions zDamage to various divisions produce unique clinical deficits zLocalization is important yinvestigation modalities differ widely depending upon the level affected

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Neurologic Examination zHigher Cortical Function zCranial Nerves zCerebellar Function zMotor zSensory zDeep Tendon Reflexes zPathologic Reflexes

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Cortical Brain zDepends upon hemispheric dominance zNon-neurologists generalize: yright: visual/spatial, perception and memory yleft: language and language dependent memory zThrough detailed examination, neurologists should lateralize and localize within a lobe

Cortical Brain zFrontal Lobe: yL: xBroca’s Aphasia yR: ? yB: xprecentral gyrus: motor homunculous xsupplementary motor cortex: eye and head turn xprefrontal cortex: personality, initiative xparacentral lobule: cortical inhibition of voiding B/B

Cortical Brain zParietal Lobe: yR: xanosognosia: left hemineglect xdressing and constructional apraxia xgeographic agnosia yL: xGerstman’s Tetrad (not triad): L/R confusion, finger agnosia, acalculia, agraphia without alexia xWerneke’s Aphasia

Cortical Brain zParietal Lobe: yB: xabnormal posture and passive movement xlocalization of touch x2-point discrimination xastereognosis xperceptual rivalry

Cortical Brain zTemporal: yR: xhearing language yL: xhearing sounds, rhythm, rhythm, music yB: xlearning and memory: mid/inferior gyri xolfaction: limbic xAuditory cortex: Heschel’s gyrus

Cortical Brain zOccipital Lobe: yR: xmicropsia xmacropsia yB: xvisual hallucinations: elemental and unformed xprosopagnosia: familiar faces xcortical blindness: striate cortices, normal pupil rx xAnton’s: (para)striate, denial of obvious blindness xBalint’s: inability to direct voluntary gaze with visual agnosia

Neurologic Examination when Cortical Brain is Lesioned zHigher Cortical Function yaphasia, apraxia, agnosia zCranial Nerves: normal, unless forced eye deviation zCerebellar Function: normal zMotor: yweakness of face/arm>leg (or vice versa) if motor homunculous is hit yhypertonia if corticospinal tracts are hit zSensory: ysensory abn of face/arm>leg (or vice versa) zDeep Tendon Reflexes: yhyper-reflexia zPathologic Reflexes: yBabinski’s reflex if corticospinal tracts are hit yFrontal release signs (nonspecific), possibly Kernig and/or Brudzinski

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Subcortical Brain zDeep white radiating fibers produce equal involvement of face/arm/leg yweakness ysensory abnormalities zVisual radiating fibers: (know how visual abnormalities morph with lesions from anterior to posterior brain) ydeep parietal: bilateral homonomous quad on the floor ydeep temporal (Meyer’s loop): bilateral homonomous quad in the sky

Neurologic Examination when Subcortical Brain is Lesioned zHigher Cortical Function: normal zCranial Nerves: yvisual field cuts zCerebellar Function: usually normal zMotor: yweakness in face=arm=leg yhypertonia zSensory: ysensory abnormalities in face=arm=leg zDeep Tendon Reflexes: yhemi-hyper-reflexia zPathologic Reflexes: yBabinski’s reflex if corticospinal tracts are lesioned yfrontal release signs (nonspecific)

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Brainstem zCN symptoms characterize BS disease zThe Brainstem is basically spinal cord with embedded cranial nerves ycause symptoms of spinal cord disease, also yLong Tract signs: (bilateral and crossed) xcorticospinal (pyramidal): motor xspinothalamic: pain/temp to the thalamus xdorsal 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 zHigher Cortical Function: normal zCranial Nerves: xIII, IV, VI: diplopia xV: decreased facial sensation xVII: drooping xVIII: deaf and dizzy xIX, X, XII: dysarthria and dysphagia xXI: decreased strength in neck and shoulders zCerebellar Function: usually normal zMotor: hemi-paresis (may be crossed), hemi-hypertonia, spasticity zSensory: hemi-dysesthesias (may be crossed) zDeep Tendon Reflexes: hemi-hyper-reflexia, brisk jaw jerk zPathologic Reflexes: Babinski’s reflex

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Cerebellar Function zSome people believe that one can not test specifically for cerebellar abnormalities yno one test on examination reliably evaluates the cerebellum zH: hypotonia zA: assynergy of (ant)agonist muscles zN: nystagmus zD: dysmetria, dysarthria zS: stance and gait zT: tremor

Neurologic Examination when the Cerebellum is Lesioned zHigher Cortical Function: normal zCranial Nerves: usually normal zCerebellar Function: ynystagmus yflaccid dysarthria zMotor: ynormal bulk and strength with ipsilateral hemi-hypotonia yintention worse than positional ipsilateral tremor yaxial instability with dysmetria zSensory: normal zDeep Tendon Reflexes: normal zPathologic Reflexes: normal y(plantar flexing to plantar stimulation)

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Spinal Cord zSensory level zSpasticity/hypertonia zWeakness: yextensors worse than flexors ydistal > proximal zBowel and Bladder involvement: yretention comes first, then detrusor hyperactivity (both produce incontinence)

Neurologic Examination when the Spinal Cord is Lesioned zHigher Cortical Function: normal zCranial Nerves: normal zCerebellar Function: normal zMotor: yweakness (extensors worse than flexors) below the lesion ypara-hypertonia below the lesion with spasticity zSensory: yhorizontal level usually lower than the lesion, poorly localizing ymay be somewhat assymetric zDeep Tendon Reflexes: ypara-hyper-reflexia below the level, possibly clonus zPathologic Reflexes: yloss of superficial reflexes (Beavor’s sign, cremasteric, anal wink, etc) yBabinski’s reflex

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Root/Radiculopathy zPain is the hallmark of a radiculopathy ySensory abnormalities in a dermatome yprovocative maneuvres exacerbate ysharp, stabbing, hot, electric, radiating zWeakness in a myotome (assymetric) yproximal (C5C6) ydistal (L5S1)

Neurologic Examination when a Root is Lesioned zHigher Cortical Function: normal zCranial Nerves: normal zCerebellar Function: normal zMotor: yassymetric weakness, atrophy, and fasiculations in a myotome ytone should be normal, unless multiple roots are severed zSensory: yassymetric dysesthesias confined to a dermatome yanesthesia requires >1 root transection zDeep Tendon Reflexes: yhypo- to a-reflexia if the root carries a reflex zPathologic Reflexes: ySpurling’s sign ydural tension signs may be present (straight leg, crossed straight leg, reverse straight leg, etc)

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Peripheral Nerve (presuming nonfocality) zWeakness: distal predominant, (a)symetric zSensory Dysesthesias: distal predominant zAutonomic involvement may occur zTrophic changes: smooth shiny skin, vasomotor abnormalities (edema, temperature dysregulation, vascular flushing), hair loss, nail changes

Neurologic Examination with Diffuse PN Lesioning zHigher Cortical Function: normal zCranial Nerves: ymay be abnormal (know which peripheral CN’s associate with specific diseases) zCerebellar Function: normal zMotor: weakness is distal predominant if the PN is diffuse yatrophy, fasiculations, (hypotonia) zSensory: ydysesthesias, anesthesias, hyperpathia, allodynia, etc zDeep Tendon Reflexes: ydistal predominant hypo- to a-reflexia zPathologic Reflexes: ymute responses to plantar stimulation

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Neuromuscular Junction zFatiguability is the hallmark zWeakness: proximal and symmetric yexacerbated with use, recovers with rest yoften affects facial muscles (ptosis, dysconjugate gaze, slack jaw) ymuscles have normal bulk and tone zSensation: preserved

Neurologic Examination in Disorders of the NMJ zHigher Cortical Function: normal zCranial Nerves: yfatiguability in ptosis, dysconjugate gaze, slack jaw zCerebellar Function: normal zMotor: yfatiguable proximal weakness in both UE’s and LE’s yno atrophy or fasiculations ytone may be slightly decreased zSensory: ynormal, though may complain of lowback pain zDeep Tendon Reflexes: ymay be hypo- to a-reflexic in LEMS ymay be normal in MG zPathologic Reflexes: none

Divisions of the Neuraxis zCortical Brain zSubcortical Brain zBrainstem zCerebellum zSpinal Cord zRoot zPeripheral Nerve zNeuromuscular Junction zMuscle

Muscle zWeakness of proximal arm and leg muscles ysymmetric zSensation is normal ythough patients complain of cramping, aching, and atrophy

Neurologic Examination in Disorders of Muscle zHigher Cortical Function: normal zCranial Nerves: yptosis, dysconjugate gaze, slack jaw, bow-string lip, myopathic facies, dysphagia, dysphonia, (dysarthria) zCerebellar Function: normal zMotor: yusually proximal weakness in both UE’s and LE’s yatrophy and fasiculations ydiffuse hypotonia yaccentuated primary and secondary curvature, scoliosis zSensory: ynormal, though may complain of lowback pain zDeep Tendon Reflexes: preserved until late in the disease zPathologic Reflexes: ? Myotonia or cramping

Just a Few Things to Remember zNot all aphasias and apraxias are cortically based ythalamus zThe absence of Babinski’s reflex does not imply a lesion distal to the cord ybasal ganglia ythalamus ycerebellum zCompromised attention span results from lesioning: ybrain stem and RAS ydiencephalon: both sides ybilateral cerebral hemispheres

Just a Few Things to Remember zSome neurologic diseases hit more than one level in the neuraxis zThe tempo of progression allows one to narrow a differential diagnosis remarkably well... Always always always clarify this issue with the patient zParsimony rules zNever fabricate part of the exam for sake of being “thorough”

Just a Few Things to Remember zIf you do not think of a complete differential diagnosis, you can not expect to catch the interesting diagnoses. zYou must think of the possibile accademic diagnoses at this point in your career. zPatients pay you to rule out the worst first zWhen you are unsure of a diagnosis, it is important to communicate this to patients and other physicians.