Motor Neurone Disease

Question 1

Definition

Answer 1

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

Question 2

Subtypes

Answer 2

o 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

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

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

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

Question 3

Aetiology

Answer 3

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

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

• Associations
o Frontotemporal lobar dementia

Question 4

Epidemiology

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

Presenting symptoms

Answer 5

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

Question 6

Signs on physical examination (LMN features)

Answer 6

• Combination of UMN and LMN signs

• LMN Features
o Muscle wasting
o Fasciculations
o Flaccid weakness
o Hyporeflexia

Question 7

Signs on physical examination (UMN features)

Answer 7

• UMN Features
o Spastic weakness
o Extensor plantar response
o Hyperreflexia

• Sensory examination - should be NORMAL

Question 8

Investigations

Answer 8

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

• Electromyography (EMG)
• Nerve conduction studies - often normal
• MRI - exclude cord compression and brainstem lesions
• Spirometry - assess respiratory muscle weakness