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 lesions Lesion Causes Symptoms Posterior lobe = Neocerebellar lesions Vascular e.g. stroke Tumours Neurodegenerative Dysmetria, Dysdiadochokinesia Ataxia Nystagmus Intention tremor Slurred speech Hypotonia 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 If you want to learn any more about cerebellum, learn some key points on Freidrich’s ataxia (recessive, most common inherited cerebellar disorder)

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

Unwanted or excessive movements BG movement disorders Bradykinesia / hypokinesia Rigidity Dystonia Athetosis Chorea Ballismus Tics Myoclonus Tremor (fast or slow depending on type) SLOW HYPERKINETIC Unwanted or excessive movements FAST

BG movement disorders Striatum  Huntington’s chorea GP  Choreoathetosis e.g. Wilson’s Subthalamic nucleus  (Hemi)Ballismus Substantia nigra  Parkinson’s

BG disorder treatments 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 Treatment for ballismus, chorea, athetosis is the same.

BG disorder treatment Disorder 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)

Fine control/adjustment of movement by facilitation &/or suppression Motor control Motor 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