Motor Neurone Disease

Question 1

What is MND?

Answer 1

Progressive neurodegenerative disorder of motor neurons (LMN + UMNs)

Question 2

Name 4 subtypes of MND

Answer 2

Amyotrophic Lateral Sclerosis (ALS)

Progressive Muscular Atrophy

Progressive Bulbar Palsy

Primary Lateral Sclerosis

Question 3

Describe Amyotrophic Lateral Sclerosis

Answer 3

Most common type of MND
Combined degeneration of UMN + LMNs resulting a mix of signs
Typically LMN signs in arms + UMN signs in legs

Question 4

In familial cases of ALS, which gene is responsible?

Answer 4

Lies on Chr21 + codes for superoxide dismutase

Question 5

Describe Progressive Muscular Atrophy

Answer 5

Only LMN signs e.g. flail arm/ foot.
Affects distal muscles before proximal
Better prognosis
~10% of MND

Question 6

Describe Progressive Bulbar Palsy

Answer 6

Loss of function of brainstem nuclei
Worst prognosis
~20% of MND

Question 7

Describe Primary Lateral Sclerosis

Answer 7

UMN pattern of weakness
Brisk reflexes
Extensor plantar responses.
NO LMN signs
~1% of MND
Slow progression, normal-ish life expectancy

Question 8

What causes MND?

Answer 8

UNKNOWN
Free radical damage + glutamate excitotoxicity have been implicated as mutations in SOD1 gene

Question 9

What condition is MND associated with?

Answer 9

Frontotemporal lobar dementia

Question 10

What is the epidemiology of MND?

Answer 10

4 in 100,000
M > F 2:1
Mean age of onset: 65y
5-10% have FH with AD inheritance

Question 11

How does MND usually present?

Answer 11

Asymmetric limb weakness
+/- functional effect; loss of dexterity/ falls/ trips

Question 12

List 4 signs of MND

Answer 12

UMN + LMN signs, often affecting several regions asymmetrically
Wasting of small hand muscles/ tibialis anterior
Fasciculations
Absence of sensory S/S

Question 13

List 5 late symptoms of MND

Answer 13

Cognitive impairment ~frontotemporal dementia
Autonomic Sx
Respiratory failure
Dysphagia
Sphincter dysfunction

Question 14

4 features of progressive bulbar palsy

Answer 14

Dysarthria
Dysphagia.
Wasted, fasciculating tongue (LMN).
Brisk jaw jerk reflex (UMN)

Question 15

What LMN signs are seen in MND?

Answer 15

Muscle wasting
Fasciculations (esp. thighs)
Flaccid weakness
Hyporeflexia

Question 16

What UMN signs are seen in MND?

Answer 16

Spastic weakness
Extensor plantar response
Hyperreflexia

Question 17

Which muscles are not affected/ signs not seen in MND?

Answer 17

Doesn’t affect external ocular muscles
No cerebellar signs
Abdominal reflexes usually preserved

Question 18

What investigations are necessary for diagnosing MND?

Answer 18

Clinical dx
Can do Ix to r/o other differentials

Question 19

What is seen on nerve conduction studies in MND?

Answer 19

Normal motor conduction
(excludes neuropathy)

Question 20

What is seen on electromyography in MND?

Answer 20

Reduced number of action potentials with increased amplitude

Question 21

What is excluded by MRI in suspected MND?

Answer 21

Cervical cord compression
Brainstem lesions
Myelopathy

Question 22

What blood tests are requested when suspecting MND to rule out other differentials?

Answer 22

Vitamin B12 + folate levels
HIV serology
Lyme disease serology
Creatine kinase assay
Serum protein electrophoresis
Anti-GM1 antibodies (multifocal motor neuropathy with conduction block)
Urinary hexosaminidase-A assay (Tay-Sachs)

Question 23

What conservative management strategies can be used in MND?

Answer 23

Exercise programme: maintains ROM, prevents contractures + stiffness

Resp physio

Dietetic support

Question 24

What pharmacological management is used in MND?

Answer 24

Riluzole
Prevents stimulation of glutamate receptors
Prolongs life by ~3 months

Question 25

What intervention is offered for respiratory impairment in MND?

Answer 25

Non-invasive ventilation (BIPAP) at night
Survival benefit of ~7 months

Question 26

What is the prognosis in MND?

Answer 26

50% dead within 3y

Question 27

How should nutrition be provided in late stages of MND?

Answer 27

Percutaneous gastrostomy tube
a/w prolonged survival

Question 28

What can be used for muscle spasticity in MND?

Answer 28

Quinine
Baclofen

Question 29

What can be used for excessive saliva in MND?

Answer 29

Glycopyrronium bromide