Basal ganglia & cerebellar pathology

Vivian Phan

Cerebellum

MAJOR TRACTS THAT GO THROUGH CEREBELLUM:- Spinocerebellar (sensory/ascending): unconscious proprioception- Vestibulospinal (motor/ extrapyramidal): balance, posture (+ extensors)- Olivocerebellar

Cerebellar lesionsLesion Causes Symptoms

Posterior lobe= Neocerebellar lesions

- Vascular e.g. stroke- Tumours- Neurodegenerative

Dysmetria, DysdiadochokinesiaAtaxiaNystagmusIntention tremorSlurred speechHypotonia

Anterior lobe= Gait/limbic ataxia

- Alcohol- Malnutrition-> improve symptoms if stop drinking

- Drunken gait, can’t walk straight- Head tremor

Midline= Truncal ataxia

Medulloblastoma in 4th ventricle – young children-> Affect Vestibular n.

- Fall towards most affected side- May involve eye movements

Basal ganglia

Basal ganglia consists of 4 subcortical nuclei:1. Striatum (caudate nucleus, putamen, nucleus accumbens)2. Globus pallidus (Gp)3. Subthalamic nucleus4. Substantia nigra

BG movement disorders

• Bradykinesia / hypokinesia• Rigidity• Dystonia• Athetosis• Chorea• Ballismus• Tics• Myoclonus• Tremor (fast or slow depending on type)

FAST

SLOW

HYPERKINETICUnwanted or excessive

movements

BG movement disorders

Striatum Huntington’s chorea

GP Choreoathetosis e.g. Wilson’s

Subthalamic nucleus (Hemi)Ballismus

Substantia nigra Parkinson’s

BG disorder treatmentsDisorder Pathology Drugs

Huntington’s (AD)

- Degeneration of cholinergic neurons in striatum- Extended CAG repeat- Movements + dementia

- Dopamine depleting drugs (release = involuntary mvmts): Tetrabenazine- Antipsychotics (chorea, hallucinations, violence): Risperidone, Quetiapine- Benzodiazepines - relax- Treat moods: SSRIs, TCAs

Wilson’s (AR)

- copper metabolism -> deposits in liver & BG- Choreathetosis, dementia- Liver cirrhosis- Kayser-Fleischer ring

Copper chelators (pick up excess copper): Penicillamine, Trientine

Ballismus - Degeneration of subthalamic nucleus

- Unilat, involuntary flinging mvmts of prox limbs

- Dopamine antagonists- Dopamine depleting drugs- GABAergics e.g. antiepileptic,

gabapentin, benzodiazepine

BG disorder treatmentDisorder Pathology Treatment

Parkinson’s - Loss of dopamine in SN and striatum- Degeneration of SN (and other basal ganglia nuclei)- Lewy bodies (plaques)

- Levodopa = Dopamine precursor- Drugs to dopamine breakdown: DDC inhibitor, COMT inhibitor, MAO-B inhibitor- Anticholinergics

Essential tremor

- Progressive, intention tremor (not at rest)- Start in arms -> other parts of body

Beta blockers - Propanolol

General rule:- Hypokinesia (e.g. Parkinson’s): Dopamine levels – precursor, prevent breakdown- Hyperkinesia (the rest!): Dopamine levels – antagonists, depletors, then relaxants

(to calm them down)

Motor controlMotor System Normal role Dysfunction

Descending tracts Purposeful, rapid, skilled, intricate movements;

influence over motor tone & reflexes

Loss of skilled voluntary movements; characteristic changes in tone &

reflexes

Basal ganglia Fine control/adjustment of movement by facilitation

&/or suppression

Movement disorders - affecting the speed of movement &/or unwanted

movements

Cerebellum Coordination of movements, posture,

balance, eye movement, planning of movement,

procedural memory

Ataxia = Unsteady & jerky movements = loss of coordination & accuracy of limb/trunk movement