Basal Ganglia and Movement Disorders Flashcards
Functions of basal ganglia
Refinement of motor plan
Regulation of action selection
Facilitation of Habit Seeking
Reward Seeking
Inputs to basal ganglia
Cortex (glutamate)
Thalamus
Midbrain (VTA and SN)
Raphe + LC in pons
SNPc
SNPr
Compacta- dopamine
Reticulata- gaba
Dorsal striatum
Ventral Striatum
Caudate and putamen
NAcc
Both have medium spiny neurons (gabaergic with D1 and D2 receptors)
Why is basal ganglia a loop?
Because there are projections in from cortex, and back out to cortex
Direct Pathway
Cortex + SNPc + Striatum - GPi/SNPr - VA/VL + Cortex
Indirect Pathway
CTX + SNPc - Striatum - GPe- STN + GPi - VA/VL +CTX
Hyperdirect Pathway
Fast inhibitory, activates STN directly
PD
Degeneration of SNPc –> reduced activation of striatum, no inhibition of GPi so tonic inhibition. Usually asymmetric, rest tremor present.
Huntingtons
Degeneration of striatal MSNs. Leads to activation of GPe, causing inhibition of STN, causing inhibition of GPi, causing movement.
Lewy Bodies composed of?
Alpha synuclein
Dementia with Lewy Bodies
Like parkinson’s but includes psychosis (hallucinations) and personality
MSA-C
Pancerebellar dysfunction – wide based gait, ataxia, nystagmus, cerebellar atrophy
MSA-A
Dysfunction in autonomics, get orthostatic hypotension, urinary dysfunction, severe constipation, erectile dysfunction, excessive sweating.
MSA-P
Like parkinson’s but more symmetrical and with less control of postural reflexes so more falls. These falls also happen earlier in disease course.
Progressive Supranuclear Palsy
Called toppling disease, most axial and symmetric of the parkinsonisms. Minimal response to levodopa, extension of the neck. Square wave visual jerks
Corticobasal Syndrome/Degeneration
Alien limb syndrome, dystonia of the arm. Hyperphosphorylated tau protein.
What improves essential tremor (f=6hz)
Alcohol
What causes essential tremor?
Loss of purkinje cells in the cerebellum
Dystonia
Involuntary movement. Agonist and antagonist muscles contract together.
Tardive dystonia
Arises after medications that are Dopamine antagonists
Myoclonus
Lightning fast jerky movements
Sydenham chorea
Chorea after a streptococcal infection that resolves on its own.
How to treat HTT
Tetrabenzine, deletes dopa by inhibiting VMAT.
Ballism
Throwing movements of the limb
Wilson’s Disease
Great imitator of movement disorders. Generally presents with parkinsonism, gait disturbance, and dysarthria. Kayser-fleischer rings around the eyes. Copper accumulation.
