5.1 - Lesions of the Motor System

Question 1

Define a positive and negative sign of a neurological lesion?

Answer 1

Negative sign - Loss of function or capacity

Positive sign - Emergence of a feature e.g. tremor

Question 2

Label the cerebellar functional divisions

Answer 2

Question 3

What is the general function of each functional zone of the cerebellum?

Answer 3

vestibulocerebellum - Balance and ocular reflexes

spinocerebellum - Involved in Error correction

Cerebrocerebellum - Movement planning and motor learning, esp visually guided movements and coordination of muscle activation

Question 4

Label the arteries that supply the cerebellum. From which arteries are these derived?

Answer 4

Question 5

Which veins drain the cerebellum and where do these veins then drain into?

Answer 5

Superior and inferior cerebellar veins

drain into transverse and sigmoid sinuses

Question 6

Give 3 common causes of cerebellar dysfunction

Answer 6

Tumours

Cerebrovascular disease

Genetic e.g. Friedrichs ataxia

Question 7

Give 4 possible signs of damage to the cerebrocerebellum and spinocerebellum

Answer 7

ataxia, dysarthria and scanning speech, hypotonia, dysdiadochokinesia, inability to learn new movements

Question 8

Give 2 signs of damage to the vestibulocerebellum

Answer 8

abnormal gait with a wide stance, and loss of balance

Question 9

Label the anatomical divisions of the cerebellum

Answer 9

Question 10

describe the embryonic development which leads to the cerebellum

Answer 10

Neural tube forms prosencephalon, mesencephalon, and rhombencephalon

Rhombencephalon splits into metencephalon (superior) and myelencephalon (inferior) - Metencephalon forms cerebellum

Question 11

Give 6 signs of a UMN lesion

Answer 11

Hyperreflexia, hypertonia, spastic paralysis, babinski sign, myoclonus, choreas

Question 12

What is a positive and negative sign of babinski?

Answer 12

Positive - abduction of toes and dorsiflexion of big toe

Negative - flexion of toes

Question 13

What does a positive babinski mean?

Answer 13

UMN lesion in the corticospinal tract

Question 14

Give 4 signs of LMN lesions

Answer 14

flaccid paralysis, denervation atrophy, areflexia / atonia, fasciculations

Question 15

Explain why fasciculations occur in LMN lesions

Answer 15

deinnervation of muscles means nACHRs have become hypersensitive to any neurotransmitter substances or molecules even vaguely similar to ACh such as those found in the blood. Results in slight muscle contractions

Question 16

In the case of LMN lesions, when is the damage irreversible?

Answer 16

If the cell body is damaged, no regeneration can take place.

Question 17

How is micturition affected by a LMN lesion in S2-S4?

Answer 17

Overflow incontinence - autonomous bladder

Question 18

Describe what spinal shock is. Why does it occur?

Answer 18

When descending tracts damaged, there is a recovery period of 4 - 6 weeks where there is flaccid paralysis and areflexia in the affected limbs. This is then replaced with spasticity and hyperactive deep reflexes.

It occurs because the loss of reflexes is due to loss of motor influences exerted by descending fibres. As these fibres degenerate the intact connections in the reflex circuits become dominant and show themselves as upper motor neurone signs