L26 - muscle weakness

Question 1

UMN origin

Answer 1

primary motor cortex

Question 2

LMN origin

Answer 2

ventral horn of spinal cord

Question 3

how to examine weakness

Answer 3

look for positive signs such as muscle volume, strength, tone, reflexes and involuntary movements
(observation, sensory, tone, power, reflexes)

Question 4

muscle tone of UMN causes of muscle weakness

Answer 4

increased

Question 5

reflexes in UMN causes of muscle weakness

Answer 5

increased

Question 6

plantars in UMN muscle weakness

Answer 6

increased

Question 7

muscle tone of LMN causes of muscle weakness

Answer 7

decreased

Question 8

reflexes in LMN causes of muscle weakness

Answer 8

decreased

Question 9

plantars in LMN muscle weakness

Answer 9

decreased

Question 10

causes of UMN muscle weakness

Answer 10

stroke
infection
tumour
degeneration

Question 11

clinical findings in UMN muscle weakness

Answer 11

weakness
mild atrophy
brisk reflexes
upping plantars

Question 12

clinical findings in LMN muscle weakness

Answer 12

weakness
mild atrophy
depressed or absent reflexes
down going plantars

Question 13

common LMN pathologies in muscle weakness

Answer 13

muscle
neuromuscular junction
nerve
root pathology
anterior horn

Question 14

natures of LMN muscle weakness

Answer 14

• axonal loss pathology

- demyelination pathology

Question 15

myopathy clinical features

Answer 15

• Progressive weakness (rapid or slow), usually proximal
• Normal reflexes
• Normal tone
• Moderate wasting

Question 16

causative agent of myopathy

Answer 16

genetic
inflammatory
metabolic

Question 17

clinical features of myasthenia gravis

Answer 17

weakness
fatigability
worse as the day goes by
normal sensation
normal reflexes
repetitive nerve stimulation

Question 18

muscle disease

Answer 18

myopathy

Question 19

example of neuromuscular junction disorder

Answer 19

myasthenia gravis

Question 20

causative agent of myasthenia gravis

Answer 20

any problem affecting receptors on muscles

Question 21

example of focal nerve pathology causing muscle weakness

Answer 21

carpal tunnel syndrome

Question 22

features of carpal tunnel syndrome

Answer 22

Pins and needles
Numbness
Pain in sensory distribution of median nerve (digit 1,2,3)
Worse at night
Weakness in motor part of median nerve
Reduced pin prick sensation
Very severe  weakness of muscles in median nerve region

Question 23

polyneuropathy

Answer 23

multiple peripheral nerves become damaged

Question 24

clinical features of polyneuropathy

Answer 24

Symptoms are more diffused like in upper and lower limb
Pins and needles
Numbness 
Burning sensation
Tingling
Weakness if motor nerves involved

Question 25

causes of polyneuropathy

Answer 25

diabetes

Question 26

example of root pathology causing muscle weakness

Answer 26

radiculopathy

Question 27

radiculopathy

Answer 27

pinching of nerve at spinal level

Question 28

clinical features of radiculopathy

Answer 28

Sensory and motor symptoms in distribution of specific nerve root
Back pain if lower spinal problem
Neck pain if upper spinal problem

Question 29

why is dorsal root ganglion spared in most spine pathologies

Answer 29

it lies outside the spinal cord

Question 30

how to differentiate between spinal nerve pathologies or root pathologies

Answer 30

normal sensory and electrodiagnostic tests for spine pathologies as dorsal root ganglion lies outside of the spinal cord

Question 31

motor neuron disease

Answer 31

disease of motor neurones (upper or lower or both)

Question 32

clinical features of motor neurone disease

Answer 32

Painless
Progressive Bulbar palsy –> weakness in the tongue and the face and the palate
Dysphasia, dysarthria, nasal regurgitation and aspiration
Progressive muscle weakness

Question 33

causes of motor neuron disease

Answer 33

sporadic

5-15% genetic

Question 34

two main electrodiagnostic tests

Answer 34

nerve conduction studies (NCS)
needle electromyography (EMG)

Question 35

nerve conduction study - 2 types

Answer 35

median nerve sensory study

median nerve motor study

Question 36

median nerve sensory study

Answer 36

Electrodes on hand and arm - along median nerve
At wrist = recording electrodes
On thumb = stimulatory electrodes
Stimulate median nerve at thumb and response will be recorded at the median nerve at the wrist

Question 37

median nerve motor study

Answer 37

Electrodes on small muscle in hand supplied by median nerve = abductor pollicis brevis
Stimulatory electrodes on median nerve
Electric stimulus to median nerve and response is recorded from abductor pollicis brevis on the screen
= compound muscle action potential seen on the screen

Question 38

Electromyography (EMG)

Answer 38

A fine needle is inserted in a muscle
We record from motor units in the muscle
Activate the muscle (in this case to flex the bicep, bend the elbow)
Motor unit action potentials
By looking and listening to this activity, we can differentiate between different pathologies

Question 39

EMG findings: Spontaneous activity

Answer 39

When we insert the needle – any activity which is recorded when muscle is relaxed and not stimulated
E.g., fibrillation potentials and positive sharp waves

Question 40

Motor unit

Answer 40

number of muscle fibres supplied by a single motor neuron

Question 41

EMG findings: recruitment / interference patterns - NORMAL

Answer 41

In a normal person, there should be a screen full of motor action potential when muscle is contraction - there should be no gaps

Question 42

EMG findings: recruitment / interference patterns - nerve problems / denervation

Answer 42

if there are gaps / reduced interference pattern

Question 43

EMG findings: recruitment / interference patterns - muscle problems

Answer 43

with less effort, the screen can be seen to be pull but MUAP is smaller