Motor neurone disease

Question 1

Define motor neurone disease

Answer 1

A progressive neurodegenerative disorder of cortical, brainstem and spinal motor neurons (lower and upper motor neurons)

Question 2

What are the 4 subtypes of MND?

Answer 2

Subtypes:
○ Amyotrophic Lateral Sclerosis (ALS)
• AKA Lou Gehrig’s disease
• Combined generation of upper AND lower motor neurones resulting a mix
of LMN and UMN signs
- first sign presenting is in 1 limb eg foot drop, then progresses

○ Progressive Muscular Atrophy Variant
• Only LMN signs
• Better prognosis

○ Progressive Bulbar Palsy Variant
• Dysarthria
• Dysphagia
• Wasted fasciculating tongue
• Brisk jaw jerk reflex

○ Primary Lateral Sclerosis Variant
• UMN pattern of weakness
• Brisk reflexes
• Extensor plantar responses
• NO LMN signs

Question 3

Explain the aetiology/risk factors of motor neurone disease

Answer 3

• UNKNOWN
• Free radical damage and glutamate excitotoxicity have been implicated

• Pathology
○ Progressive motor neurone degeneration and death
○ Gliosis replacing lost neurones

• Associations
○ Frontotemporal lobar dementia

Question 4

Summarise the epidemiology of motor neurone disease

Answer 4

• RARE
• Incidence: 2/100,000
• Mean age of onset: 55 yrs
• 5-10% have a family history with autosomal dominant inheritance

Question 5

Recognise the presenting symptoms of motor neurone disease

Answer 5

• Weakness of limbs
• Speech disturbance (dysarthria - slurring or reduction in volume)
• Swallowing disturbance (e.g. choking on food)
• Behavioural changes (e.g. disinhibition, emotional lability)

Question 6

Recognise the signs of motor neurone disease on physical examination

Answer 6

• Combination of UMN and LMN signs

• UMN Features
○ Spastic weakness
○ Extensor plantar response - babinsky
○ Hyperreflexia
- dysarthria
- dysphagia

• LMN Features
○ Muscle wasting
○ Fasciculations
○ Flaccid weakness
○ Hyporeflexia
- dysphagia
- nasal speech

• Sensory examination - should be NORMAL

Question 7

Identify appropriate investigations for motor neurone disease

Answer 7

Clinical diagnosis

• Bloods
○ Mild elevation in CK
○ ESR
○ Anti-GM1 ganglioside antibodies -ve

• Electromyography (EMG); reduced amplitude, axonal loss
• Nerve conduction studies - often normal
• MRI - exclude cord compression and brainstem lesions
• Spirometry - assess respiratory muscle weakness

Question 8

Other symptoms of MND?

Answer 8

a weakened grip, which can cause difficulty picking up or holding objects

weakness at the shoulder that makes lifting the arm difficult

a “foot drop” caused by weak ankle muscles

dragging of the leg

if MND progresses far, sufferers can get to a stage where they are unable to walk talk eat or drink - so like locked in their bodies

Seeing hearing touching smelling preserved