Motor Disorders Flashcards

1
Q

Through what structures does the cerebellum communicate with the brain

A
  • Communicates with the brainstem and cortex
  • Communicates with the brainstem via the cerebellar peduncles
    • Superior cerebellar peduncles attaches cerebellum to midbrain
    • Middle cerebellar peduncle attaches cerebellum to pons
    • Inferior cerebellar peduncle attaches cerebellum to medulla
  • Communicates with the cortex via the thalamus
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2
Q

Describe the structure of the cerebellum and the role of each

A
  • Consists of the vermis and two lateral hemispheres
  • Vermis regulates trunk musculature
  • Lateral cerebellar hemispheres regulate distal structures (limbs)
  • Tracts are ipsilateral in the cerebellum
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3
Q

Describe how lesions of the vermis and cerebellar hemispheres cause different symptoms

A
  • Lesions in the midline (vermis) can cause truncal ataxia and abnormal gait
    • Extensions of midline lesions can also cause compression of the fourth ventricle and lead to hydrocephalus
  • Cerebellar hemispheres lesions cause ipsilateral symptoms in the limbs
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4
Q

State the significance of the fourth ventricle to the cerebellum

A
  • Fourth ventricle located between cerebellum and pons

- Extensions of midline lesions can also cause compression of the fourth ventricle and lead to hydrocephalus

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5
Q

Describe the symptoms of cerebellar disease

A
  • DANISH
  • Dysdiadochokinesis - repetitive movement problem
  • Ataxia - lack of voluntary coordination of muscle movements, eg. Abnormal gait, balance problem
  • Nystagmus - quick lateral movement of eyes, uncoordinated eye movement
  • Intention tremor
  • Slurred speech
  • Hypotonia - floppy movement of limbs
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6
Q

Describe the structure that make up the basal ganglia

A
  • Caudate nucleus - C-shaped nucleus which wraps around lentiform nucleus
  • Lentiform nucleus consists of the putamen + globus pallidus externa + globus pallidus interna
  • Striatum consists of the putamen + caudate nucleus
  • Substantia nigra made up of pigmented neurones called the pars compacta dorsally, and a ventral strip called the pars reticularis
    • Dopaminergic neurones found in substantia nigra pars compacta
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7
Q

Describe the direct pathway of the basal ganglia

A
  • Substantia nigra sends excitatory dopaminergic connections to the putamen, stimulating it and inhibiting globus pallidus interna
  • Normally globuls pallidus interna inhibits thalamus activity, thus inhibition of it increases thalamus activity
  • Direct pathway is overall excitatory to thalamus and cortex without dopamine
    - Dopamine acts as an ‘on’ switch to increase stimulation of cortex
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8
Q

Describe the indirect pathway of the basal ganglia

A
  • Substantia nigra sends inhibitory dopaminergic connections to the putamen, which leads to decreased inhibition of globus pallidus externa
  • Enhanced globus pallidus externa stimulation increases inhibitory input to subthalamic nucleus
  • Thus decreased stimulation of subthalamic nucleus decreases stimulation of globus pallidus interna, which decreases inhibition to thalamus
  • Indirect pathway is overall inhibitory to thalamus and cortex without dopamine
    • Dopamine acts as an ‘off’ switch, turning off the inhibition and thus promoting stimulation of cortex
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9
Q

What is the overall net effect of dopamine on the basal ganglia

A

The overall net effect of dopamine in the direct and indirect pathways is motor cortex stimulation via the thalamus

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10
Q

State the symptoms of basal ganglia disorders

A
  • Abnormal motor control
  • Altered posture
  • Affects muscle tone
  • Dyskinesia - abnormal movement
  • Contralateral symptoms
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11
Q

Describe Parkinson’s disease and its pathophysiology

A
  • Chronic, progressive movement disorder characterised by a triad of bradykinesia, tremor, and rigidity
  • Degeneration of substantia nigra pars compacta causes deficiency of dopamine
    • Direct pathway - has overall stimulatory effect on thalamus without dopamine
      • Pathway stimulation will decrease in Parkinson’s - bradykinesia
    • Indirect pathway - has overall inhibitory effect on thalamus without dopamine
      - No stimulations from the indirect pathway - bradykinesia
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12
Q

Describe the symptoms of Parkinson’s disease

A
  • Parkinson’s disease symptoms are unilateral
  • Cardinal symptoms
    • Bradykinesia - slow movement
    • Tremor - resting tremor (disappears on movement)
    • Rigidity - increased muscle tone
  • Other associated features
    • Hypophonia - quieter phonation/tone
    • Reduced facial expression
    • Micrographia - handwriting small overtime
    • Dementia
      • Depression
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13
Q

Describe the mechanism behind Huntington’s disease

A
  • Autosomal dominant, progressive neurodegenerative disorder
  • Onset of disease around 30-50 years
  • Associated with cell loss with the striatum (putamen + caudate nucleus)
    • Decreased inhibition to GPe due to less cells in putamen
    • Causes increased stimulation from the thalamus causing increased cortex stimulation
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14
Q

Describe the symptoms of Huntington’s disease

A
  • Chorea - involuntary jerk movements
  • Dystonia - sustained or repetitive movements causing twisting of trunk/limbs
  • Incoordination
  • Cognitive decline
  • Behavioural difficulties
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15
Q

Describe the different symptoms at each stage of Huntington’s

A
  • Early stage - chorea within the limbs, severe behavioural symptoms (depression, irritability)
  • Middle stage - severe chorea, cognitive problems, behavioural symptoms
  • Late stage - trouble walking, chorea stopped, cognitive symptoms
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16
Q

What are hemiballismus

A
  • Rare movement disorders
  • Associated with dysfunctional contralateral subthalamic nuclei damage
  • Results in unilateral abnormal movement
  • Often secondary to sub-cortical stroke