Disorders Of The Motor System Flashcards
What makes up the lentiform nucleus?
Putamen
Globus pallidus
What makes up the striatum?
Caudate nucleus
Putamen
Function of the cerebellar peduncles
What do each section connect to?
Connection between brainstem + cerebellum
- superior cerebellar peduncle to midbrain
- middle cerebellar peduncle to pons
- inferior cerebellar peduncle to medulla
How does the basal ganglia communicate with the motor cortex?
Via thalamus
Describe the communication between the cortex and basal ganglia
How does that affect basal ganglia signs?
- Cortex communicates with ipsilateral basal ganglia
- contralateral signs to damage
Describe communication between cortex + cerebellar hemisphere
How does that affect cerebellar signs?
- Cortex communicates with contralateral cerebellar hemispheres
- ipsilateral sign to damage
Role of the direct pathway
- reinforces appropriate movement
- excitatory on cortex
Role of the indirect pathway
- inhibits inappropriate movements
- inhibitory on cortex
Describe the effect of dopamine release from the substantia nigra
- SN releases dopamine
- excites direct pathway > excites cortex
- inhibits indirect pathway > inhibition of inhibition > excites cortex
Role of sub-thalamic nucleus
How does the indirect pathway affect this?
- Inhibits movement
- indirect pathway inhibits the inhibtion of by globus pallidus externa STN > inhibition of inhibition > stimulation
Signs + symptoms of cerebellar lesions in vermis
DANISH
- dysdiadochokinesia
- ataxia
- nystagmus
- intention tremor
- slurred speech
- hypotonia
What can cerebellar lesion present with?
Vomiting
Vertigo
Difficulty walking
What is the inheritance of Huntington’s disease?
Autosomal dominant
What is Huntington’s due to?
- Loss of inhibitory projections from striatum to globus pallidus externa > hyperkinetic features
- CAG repeat expansions
Presentation of Huntington’s chorea
- choreiform movements (looks like fidgeting)
- dystonia
- uncoordination
- psychiatric features + cognitive decline
What is Parkinson’s disease due to?
Degeneration of substantia nigra dopamine neurones > hypokinetic/decreaed movement
Triad of Parkinson’s disease presentation
Tremor
Lead pipe rigidity
Bradykinesia
How can Parkinson’s disease tremor improve?
Can improve if you ask them to do something
Describe Parkinsonian gait
- Struggle to initiate + stop movement
- Shuffling
- no arm swing
Presentation for Parkinson’s disease
- tremor
- rigidity
- bradykinesia
- hypophonia (quiet speech)
- micrographica (small hand writing)
- decreased facial movement
- dementia
- depression
What is hemiballismus?
Unilateral explosive movements
What is hemiballismus due to?
damage to sub thalamic nucleus > loss of inhibition of thalamus via globus pallidus interna
Anatomy of cerebellum + how this relates to function
- Midline vermis - trunk
- Two laterally placed hemisphere - ipsilateral body
What is dysdiadochokinesia?
Difficulty with rapidly alternating movements
(Issue with rapid pronation + supination)
Function of cerebellum
Sequencing + co-ordination of movements
What is ataxia?
Unsteady gait due to difficulty sequencing lower limb muscle contractions + loss of unconscious proprioception from lower limbs
What is an intention tremor?
Tremor that worsens as a target is approached
What effect would stimulation of globus pallidus interna have on movement?
Increased inhibition of thalamus > decreased movement
What effect would stimuation of subthalamic nucleus have on movement?
Increased activity in GPi > increased inhibtion of thalamus > decreased movement
Why can upper motor neurones lead to spasticity?
Loss of descending inhibition to lower motor neurones
What structure in the midbrain is important for motor control?
Red nucleus
What could destruction of the subthalamic nucleus cause?
Hemiballismus
Unilateral involuntary explosive movements
Why might a stroke affecting the lateral aspect of the motor cortex compromise swallowing?
Denervation of cranial nerves which distribute lower motor neurones in vagus nerve
How is a patient with Parkinson’s disease at an increased risk of DVT?
- flat foot shuffling gait > diminished calf pump activity
- this normally helps to pump blood up the legs in veins
- predisposing to DVT
- also more likely to have reduced mobility
