AP07 Upper and Lower Motor Neurone Disorders

Question 1

What UMN signs of the arm might you expect on inspection?

Answer 1

no fasciculation or significant wasting (some disuse atrophy)

Question 2

What LMN signs of the arms might you expect on inspection?

Answer 2

wasting and fasciculation of muscles

Question 3

Would you expect pronator drift in an UMN pathology?

Answer 3

maybe

Question 4

Would you expect pronator drift in a LMN pathology?

Answer 4

there may be some drift/movement of the arms if weak or deafferented, but not pronator drift

Question 5

How would arm tone change with UMN pathology?

Answer 5

increased

sapsticity/rigidity

Question 6

How would arm tone change with LMN pathology?

Answer 6

decreased / normal

hypotonia

Question 7

How would arm power change with UMN pathology?

Answer 7

‘pyramidal’ weakness

extensors weaker than flexors in arms, vice versa in legs

Question 8

How would arm power change in LMN pathology?

Answer 8

different patterns of weakness depending on cause

Question 9

How would arm reflexes change in UMN pathology?

Answer 9

exaggerated or brisk

hyperreflexia

Question 10

How would arm reflexes change in LMN pathology?

Answer 10

reduced / adsent

hyporeflexia / areflexia

Question 11

What innervates extrafusal muscle fibres of skeletal muscle?

Answer 11

alpha-motoneurones

Question 12

What innervates intrafusal fibres of muscle spindles?

Answer 12

gamma motoneurones

Question 13

What would be the consequence of a pure lesion of the cell body of the alpha motoneurones acutely?

Answer 13

loss of involuntary control of muscles, then flaccid paresis

Question 14

What would be the consequence of a pure lesion of the cell body of the alpha motoneurones chronically?

Answer 14

Weakness and atrophy
loses most bulk
fasciculations disappera as muscle replaced by fat and CT
permanent contracture of joint

Question 15

What explains changes between acute and chronic LMN denervation of muscles

Answer 15

upregulated nAChR +sensitivity

produce uncoordinated and random minute contractions of individual fascicles (fasciulations)

muscle loses bulk

Question 16

Name 4 types of paralysis

Answer 16

monoplegia
hemiplegia
paraplegia
quadriplegia

Question 17

What is a clonus?

Answer 17

seen when deep tendon reflexes are tested in a patient with UMN lesion
tapping a tendon to elicit a single tendon reflex contraction results in ongoing contractures of the joint or limn being tested

Question 18

What structures are damaged to give chorea?

Answer 18

usual defect is due to a lesion in the sub-thalamus which leads to a disinhibition of the thalamus and high activity in the cortex leading to the abnormal movement