Cortical motor function, basal ganglia and cerebellum

Question 1

What is the location of the primary motor cortex

Answer 1

Precentral gyrus

Anterior to the central sulcus

Question 2

What is the function of the primary motor cortex

Answer 2

Controls fine, discrete, precise, voluntary movement (input from cerebellum)
Provides descending signals to execute movement
Penfield’s motor homunculus

Question 3

Describe the corticobulbar pathway (hypoglossal example)

Answer 3

1. Originates from head region of motor cortex
2. Passes through the internal capsule of basal ganglia
3. Synapse in the medulla at the hypoglossal nucleus
4. Hypoglossal nerve fibres pass out

Question 4

Where is the premotor cortex found

Answer 4

Frontal lobe, anterior to primary motor cortex

Question 5

What is the function of the premotor cortex

Answer 5

Planning of movements

Regulates externally cued movements

Question 6

Where is the supplementary motor area

Answer 6

Frontal lobe, anterior to primary motor cortex, medially

Question 7

What is the function of the supplementary motor area

Answer 7

Planning complex movements
Programming sequencing of movements
Regulates internally driven movements e.g. speech
Becomes active when thinking about a movement before executing it

Question 8

What are the association cortexes

Answer 8

Brain areas whose activity does not correlate with motor output/act
Posterior parietal cortex - ensures movements are targeted accurately to objects in external space
Prefrontal cortex - involved in selection of appropriate movements for a particular course of action

Question 9

Define lower motor neurone and upper motor neuron

Answer 9

Spinal cord, Brainstem

Corticospinal, corticobulbar

Question 10

Define pyramidal and extrapyramidal

Answer 10

Lateral corticospinal tract

Basal ganglia, cerebellum

Question 11

What is the consequence of an upper motor neuron lesion

Answer 11

Loss of function

• Paresis: graded weakness of movements
• Paralysis (plegia): complete loss of muscle activity

Increased abnormal motor function due to loss of inhibitory descending inputs

• spasticity: increased muscle tone
• Hyper-reflexia: exaggerated reflexes
• Clonus: abnormal oscillatory muscle contraction

Babinski’s sign

Question 12

What is apraxia

Answer 12

Disorder of skilled movement. Patients are not paretic but have lost information about how to perform skilled movements
Stroke and dementia most common causes

Question 13

Which areas of the brain does apraxia involve

Answer 13

Lesion of the inferior parietal lobe, the frontal lobe (premotor cortex, supplementary motor area)

Question 14

What are the clinical features of a lower motor neurone lesion

Answer 14

Weakness
Hypotonia 
Hyporeflexia 
Muscle atrophy 
Fasciculations
Fibrillations

Question 15

What are fasciculations

Answer 15

Damaged motor units produce spontaneous action potentials, resulting in a visible twitch

Question 16

What are fibrillations

Answer 16

Spontaneous twitching of individual muscle fibres

Recorded during needle electromyography examination

Question 17

What is motor neurone disease

Answer 17

Progressive neurodegenerative disorder of the motor system
Spectrum of disorders
Amyotrophic laurel sclerosis (ALS)

Question 18

What are the upper motor neuron signs of MND

Answer 18

Increased muscle tone (spasticity of limbs and tongue)
Brisk limbs and jaw reflexes 
Babinski’s sign
Loss of dexterity
Dysarthria
Dysphagia

Question 19

What are the lower motor neurone signs of MND

Answer 19

Weakness
Muscle wasting
Tongue fasciculations and wasting
Nasal speech
Dysphagia

Question 20

What makes up the basal ganglia

Answer 20

Caudate nucleus
Lentiform nucleus (putamen + external globus pallidus)
Subthalamic nucleus
Substantia nigra
Ventral pallidum, claustrum, nucleus accumbens, nucleus basalis of Meynert

Question 21

What are the functions of the basal ganglia

Answer 21

Elaborating associated movements (e.g. swinging arms when walking; changing facial expression to match emotions)

Moderating and coordinating movement (suppressing unwanted movements)

Performing movements in order

Question 22

Describe the circuitry of the basal ganglia

Answer 22

cortex -> globus pallidus, striatum, substantia nigra

Globus pallidus -> subthalamic nucleus -> globus pallidus -> thalamus -> SMA -> substantia nigra (C) -> substantia nigra (r)

Question 23

What is the neuropathology of parkinson’s

Answer 23

neurodegeneration of the dopaminergic neurons that originate in the substantia nigra and project to the striatum

Question 24

What are some clinical features of Parkinson’s

Answer 24

Shaking palsy (paralysis agitans)
Involuntary motion, with lessened muscular power 
Propensity to bend the trunk forward  and to pass from a walking to a running pace

Question 25

What are the main motor signs of Parkinson's

Answer 25

Bradykinesia (slowness of small movements) Hypomimic face (expressionless) Akinesia (difficulty in initiation of movements) Rigidity (increased muscle tone) Tremor at rest (4-7Hz, in one hand then other body parts)

Question 26

Describe the nigro-striatal pathway

Answer 26

-

Question 27

Describe Huntington's disease

Answer 27

Genetic neurodegenerative disorder Chromosome 4, autosomal dominant CAG repeat (>35) Degeneration of GABAergic neurons in the striatum, caudate and then putamen

Question 28

What are the motor signs of Hungtington's disease

Answer 28

``` Choreic movements (chorea) Speech impairment Difficulty swallowing Unsteady gait Later - cognitive decline and dementia ```

Question 29

What are choleric movements

Answer 29

Rapid jerky involuntary movements of the body; hands and face affected first; then legs and rest of body

Question 30

How are purkinje cells connected to other cells in the cerebllum

Answer 30

Inferior olive projects to purkinje cells via climbing fibres All other inputs to fragile cells are via mossy fibres and then parallel fibres onwards All output from purkinje cells are via deep nuclei

Question 31

What are the divisions of the cerebellum

Answer 31

Vestibulocerebellum Spinocerebellum Cerebrocerebellum

Question 32

Describe the vestibulocerebellum

Answer 32

Regulation of gait, posture and equilibrium | Coordination of head movements with eye movements

Question 33

Describe the spinocerebellum

Answer 33

Coordination of speech Adjustment of muscle tone Coordination of limb movements

Question 34

Describe the cerebrocerebellum

Answer 34

Coordination of skilled movements Cognitive function, attention, processing of language Emotional control

Question 35

Describe Vestibulocerebellar Syndrome

Answer 35

Damage (tumour) causes syndrome similar to vestibular disease leading to gait ataxia and tendency to fall (even when patient sitting and eyes open)

Question 36

Describe Spinocerebellar syndrome

Answer 36

Damage (degeneration and atrophy associated with chronic alcoholism) affects mainly legs, causes abnormal gait and stance (wide-based)

Question 37

Describe Cerebrocerebellar or Lateral Cerebellar Syndrome

Answer 37

Damage affects mainly arms/skilled coordinated movements (tremor) and speech

Question 38

What are the main signs of cerebellar dysfunction

Answer 38

Ataxia - general impairments in coordination and accuray Dysmetria - inappropriate force and distance Intention tremor - increasingly oscillatory trajectory of a limb Dysdiadochokinesia - inability to perform rapidly alternating movements Scanning speech - staccato, due to impaired coordination of speech muscles

Question 39

Describe the motor system hierarchy

Answer 39

-

Question 40

Describe the motor homunculus

Answer 40

From centre in - Leg, arm, face, tongue

Question 41

Describe the lateral corticospinal pathway

Answer 41

1. Primary motor cortex 2. Fibres pass down pass through the internal capsule of the basal ganglia 3. Descent down through the midbrain and pons 4. In the Medullary pyramids the fibres cross over (decussation, no synapse) 5. Descent through the spinal cord in the lateral corticospinal tract 6. Projection to the ventral root in the relevant spinal level

Question 42

Describe the anterior corticospinal pathway

Answer 42

1. Primary motor cortex 2. Fibres pass down pass through the internal capsule of the basal ganglia 3. Descent down through the midbrain and pons 4. Through the medulla 5. Descent through the spinal cord in the anterior corticospinal tract 6. Decussation at the level of the spinal cord