Lesions to Subcortical Structures

• Basal Ganglia
• Bradykinesia, rest tremor (course, large amplitude, cogwheel), chorea/ballismus, athetosis/dystonia, stooped posture with festinating gait, normal strength and reflexes
• Thalamus
• can get thalamic pain syndrome (Dejerine-Roussy) due to infarction of VPm or VPl (PCA, thalamoperforators)
• Pyramidal Tract
• Spasticity, weakness (upper extremity extensors and lower extremity flexors are more affected), slowing of RAM’s, hyperreflexia, Babinski
• Perisellar
• Endocrine dysfunction, visual loss (typically bitemporal hemianopsia), hypothalmic signs (alterations of sleep patterns, eating habits, temperature regulation), increased ICP (secondary to hydrocephalus)
• Mamillary bodies
• Korsakoff’s syndrome (amnestic confabulatory syndrome) – severe impairment of memory without clouding of consciousness, confusion and confabulation
• Posterior Fossa
• “Crossed paralysis” (LMN sensory/motor signs involving one or more cranial nerves ipsilateral to lesion and UMN sensory/motor signs involving contralateral body), cranial nerve palsies, cerebellar dysfunction, brainstem dysfunction, frequent hydrocephalus
• Cerebellum
• Dysmetria, intention tremor, wide-based staggering gait, nystagmus, scanning speech, hypotonia
• Midline cerebellar lesions
• Rostral – stance and gait affected
• Caudal – Axial and tuncal posture and equilibrium
• Lateral lesions – impair limb movement
• Floculonodular lobe – ataxic gait, wide-based gait, nystagmus
• Spinocerebellum – tremor, hypotonia (pendular reflexes, flaccid posture)
• Vermis – disturbances in axial and truncal control
• Titubation or tremor in trunk
• Dysarthria, scanning speech
• Interposed nuclei – limb ataxia, action tremor, hypotonia
• Cerebrocerebellum
• Delay in initiating and terminating movements
• Terminal tremor at the end of a movement
• Disorders in temporal coordination involving multiple joints
• Disorders in spatial coordination
• Terminal tremor
• Brainstem
• Midbrain: paralysis of upward gaze, convergence nystagmus, miosis, abulia, disorientation, 3rd nerve palsy
• Ponto-medullary junction: contralateral hemiplegia, 6th and 7th nerve palsies, contralateral loss of pain sense on body, ipsilateral loss of facial pain sensation
• Lateral medulla:  Vertigo, nystagmus, ipsilateral ataxia, ipsilateral loss of facial pain sensation, miosis, ptosis, anhidrosis, contralateral loss of pain sense on body
• Localization of Brainstem Dysfunction
• Subcortical lesion – cheyne-stokes breathing, pupils small and reactive
• Midbrain lesion – central hyperventilation, pupils midposition to large and fixed
• Pontine lesion – apneustic then cluster, pupils pinpoint
• Medullary lesion – ataxic breathing, midposition fixed pupils, often irregular
• Top of the Basilar Syndome – occlusion of rostral basilar artery – infarct in midbrain, thalamus, portions of temporal and occipital lobes
• Impaired ocular movements – gaze palsies, skew deviation, convergence spasms, convergence-retraction nystagmus
• Abnormalities of pupils – small minimally reactive (diencephalic dysfunction), large or mid-position and fixed (midbrain), ectopic or oval pupils
• Alterations of consciousness and behavior – stupor, apathy, somnolence, memory deficits
• Deficits in vision – homonymous hemianopsia, cortical blindness, Balint’s syndrome (impaired visual form discrimination and color dysnomia), abnormal color vision
• Motor weakness, sensory deficits, reflex abnormalities – subtle and variable
• “One-and-a-half Syndrome” – lesion of PPRF or CN VI nucleus involving MLF fibers crossing to that side from contralateral CN VI
• Horizontal gaze palsy when looking to side of lesion (“one”)
• INO when looking away from side of lesion (“half”)
• Ipsilateral eye has no horizontal movement and contralateral eye has only abduction and nystagmus
• Convergence usually unimpaired
• Medial Brainstem Syndromes
• Due to obstruction of paramedian branches of basilar artery\
• All involve disruption of long tracts
• Corticospinal – contralateral hemiparesis
• Medial Lemniscus – contralateral loss of vibration and joint position sensation
• Weber’s syndrome (midbrain)
• Long tracts above + ipsilateral IIIrd palsy
• Benedikt’s syndrome (midbrain)

§ Long tracts above + ipsilateral IIIrd palsy and ataxia

o Foville’s syndrome (pons)

§ Long tracts above + ipsilateral gaze palsy and nystagmus

o Dejerine’s syndrome (medulla)

• Long tracts above + ipsilateral XIIth
• Lateral Brainstem Syndromes
• All involve disruption of the following long tracts
• Spinothalamic – contralateral loss of pain and temperature sensation
• Autonomics – ipsilateral Horner’s
• Trigeminal tract – ipsilateral facial anesthesia
• Vestibular nucleus – nausea, nystagmus
• Cerebellar connections – ataxia
• Midbrain (obstruction of SCA)
• Long tracts above + red nucleus (ataxia)
• Pons (obstruction of AICA)
• Long tracts above + ipsilateral VIIth and VIIIth (facial palsy, tinnitus, deafness)
• Wallenberg’s syndrome (medulla, obstruction of PICA)
• Long tracts above + ipsilateral IXth, Xth, XIth (dysphagia, hoarseness, loss of taste, decreased gag)
• Dorsal Midbrain Syndromes
• Parinaud’s syndrome
• Compression of superior colliculi causes paralysis of upward gaze and ocular convergence
• Seen with hydrocephalus, pineal region lesions
• Upper Motor Neuron Signs
• Spasticity, weakness, increased tone, hyperreflexia, slowing of RAM’s, Babinski
• Lower Motor Neuron Signs
• Weakness, muscular atrophy, decreased reflexes, fasciculations, decreased tone
• Spinal Cord
• Upper or lower motor neuron weakness, atrophy from disuse, cutaneous sensory level or suspended sensory level, hyperactive reflexes, Babinski, external sphincters frequently impaired, cutaneous reflexes lost below level of lesion
• Muscle Disease
• Flaccid weakness tending to involve trunk and proximal limb segments earliest, no sensory involvement, normal DTRs early which become progressively hypoactive, sparing of cutaneous reflexes, no sphincter disturbances
• Peripheral Nerves
• Lower motor neuron (flaccid) weakness predominantly in the extremities (distal > proximal), early atrophy, sensory loss (typically beginning distally), hypo- or areflexia
• Autonomic System
• Alterations of vasomotor activity, sweating, respiration, orthostatic hypotension, Horner’s syndrome (miosis, ptosis, and anhidrosis), sexual dysfunction