Motor Neurone Disease

Question 1

Define:

Answer 1

Progressive neurodegenerative disorder of cortical brainstem and spinal motor neurones (lower and upper neurones)

Does not affect the sensory neurones but selective for neurones in the motor cortex, cranial nerve nuclei and anterior horn cells.

Question 2

Aetiology/risk factors:

Answer 2

UNKNOWN.

Some association to free radical damage and glutamate excitatoxicty.

Progressive motor neurone death and degeneation

25% have frontal lobe dementia

Question 3

Epidemiology:

Answer 3

Rare

6/100,000

Mean onset of age in 55 yrs

FHx is common with autosomal dominant inheritence

Question 4

Symptoms:

Answer 4

Muscle weakness - proximal myopathy

Speech disturbance (slurring or reduction in volume)

Swallowing disturbance (choking on food)

Behaviour changes (emotional lability and disinhibition)

Question 5

Signs:

Answer 5

UMN and LMN signs

LMN:

• Fasciculation’s of the tongue, abdo, back and thigh
• Muscle wasting
• Hyporeflexia
• Flaccid weakness

UMN:

• Extensor plantar reflexes
• Spastic weakness
• Hyperreflexia

Sensory exam will be normal

Question 6

Investigations:

Answer 6

Bloods:

• CK (mildly elevated)
• ESR
• Anti-GM1

EMG

Nerve conduction studies - usually normal

MRI - to exclude cord compression and brainstem lesions

Spirometry to assess the resp weakness

LP to exclude any inflammatory causes

Question 7

What are the types of MND?

Answer 7

o Amyotrophic Lateral Sclerosis (ALS)
• AKA Lou Gehrig’s disease
• Combined degeneration = LMN and UMN signs

Progressive Muscular Atrophy Variant
• Only LMN signs = Better prognosis

Progressive Bulbar Palsy Variant
•	Only affects CN IX-XII
•	Dysarthria 
•	Dysphagia 
•	Wasted fasciculating tongue 
•	Brisk jaw jerk reflex 

Primary Lateral Sclerosis Variant
•	Loss of Betz cells in motor cortex
•	UMN pattern of weakness 
•	Brisk reflexes 
•	Extensor plantar responses 
•	NO LMN signs