Motor Neurone Disease

Question 1

Define Motor Neurone Disease and what are the 5 main types

Answer 1

Progressive neurodegenerative disorder or cortical, brainstem and spinal motor neurones (UMN and LMN)

• Amyotrophic lateral sclerosis (ALS)
• Progressive muscular atrophy variant
• Progressive bulbar palsy variant
• Pseudobulbar palsy
• Primary lateral sclerosis variant

Question 2

Aetiology/pathology of Motor Neurone Disease

Answer 2

Progressive motor neuron degeneration and death with gliosis replacing lost neurons

Associated with frontotemporal dementia

Question 3

Symptoms of Motor Neurone Disease

Answer 3

Progressive muscle weakness (focal or asymmetrical)
Dysphagia (choking on food, nasal regurgitation)
Dysarthria (slurring, dysphonia)
SOB
Behavioural changes (disinhibition, emotional lability)

(Oculomotor, sensory and autonomic function spared)

Question 4

Signs of Motor Neurone Disease on examination

Answer 4

Depends on subtype
Mostly both UMN and LMN signs
UMN: hypertonia, hyperreflexia, upgoing Babinski’s, clonus
LMN: hypotonia, hyporeflexia, fasciculations, tremor, muscle atrophy

Weakness
Wasting of thenar hand muscles (thumb base)
Tongue muscle wasting
NORMAL sensory exam

Question 5

What is the presentation for Amyotrophic lateral sclerosis (ALS)

Answer 5

UMN + LMN 
Most common  (50-60%)

Usually one limb initially (foot drop, clumsy hand)
Wasting seen
Fasciculations with brisk reflexes + upgoing plantars

Question 6

What is the presentation for Progressive muscular atrophy

Answer 6

LMN only
Best prognosis

Affects the distal muscles before the proximal

Question 7

What is the presentation for Progressive bulbar palsy variant

Answer 7

Cranial nerves
Worst prognosis

Tongue palsy: flaccid, fasciculating
Jaw: brisk jaw jerk (UMN) or absent jaw jerk (LMN)
Voice: nasal “donald duck” voice
Dysarthria and dysphagia

Question 8

What is the presentation for pseudobulbar palsy

Answer 8

UMN lesion of CN IX-XII

tongue: slow movement
Jaw: brisk jaw jerk
Voice: “Hot potato” speech

Question 9

What is the presentation for Primary lateral sclerosis (ALS)

Answer 9

Betz cell in motor cortex (mainly UMN)

UMN pattern of weakness
Brisk reflexes
Extensor planter response
No LMN signs

Question 10

Investigations for Motor Neurone Disease

Answer 10

EMG: acute and chronic denervation features (fibrillation potentials and +ve waves / motor unit potentials with large amplitude and long duration)
Nerve conduction studies: normal

CK: raised
Anti-GBM ganglioside Abs for multifocal motor, usually -ve

MRI: exclude cord or root compression + brainstem lesions

Spirometry: assess respiratory muscle weakness (FVC)