Motor neuron disease

Question 1

What is motor neuron disease?

Answer 1

An untreatable and rapidly progressive neurodegenerative condition

Question 2

What are the clinical features of MND?

Answer 2

• Muscle weakness and wasting secondary to motor neuron degeneration
• Potentially problems with speech, swallow and breathing
• Upper and/or lower motor neuron signs without sensory problems
• Focal onset and continuous spread, finally generalised paresis
• Cognitive impairment

Question 3

What is the most common subtype of MND?

Answer 3

Amyotrophic lateral sclerosis (ALS)

Question 4

What causes MND and how common is it?

Answer 4

• 90% sporadic and 10% familial
• Genetic cause has been identified in up to 20% of sporadic and 60% of familial cases
• Slightly more common in males
• Lifetime risk is 1 in 400

Question 5

What is the average survival time for MND?

Answer 5

3 years

Question 6

ALS patients present with a combination of UMN and LMN signs. Name some of these

Answer 6

• UMN - increased tone, hyper-reflexia, extensor plantar responses, spastic gait, slowed movements
• LMN - muscle wasting, weakness, fasciculations, absent or reduced deep tendon reflexes

Question 7

How are UMN signs detected clinically?

Answer 7

• Spasticity
• Babinski sign
• Bulbar UMN signs - clonic jaw jerk, emotional lability
• Cervical and lumbar region - clonic deep tendon reflexes, preserved reflex in a weak, wasted limb, Hoffman reflex, hyper-reflexia
• Abdominal region - loss of superficial abdominal reflexes

Question 8

What is split hand syndrome?

Answer 8

Preferential wasting of thenar group is a typical pattern of atrophy seen in ALS

Question 9

What is the most common site of onset in MND?

Answer 9

• Extremities 70% (upper>lower)
• Bulbar 25%
• Thoracic 2%
• UMN 10%
• LMN 90%

Question 10

Describe the bulbar variant of MND

Answer 10

• Primary bulbar onset in about 25% of patients
• Women > Men (60-80 years)
• Always generalisation into ALS
• Therapeutic interventions - early communicator, nutritional support, care for URT

Question 11

ALS is the most common MND phenotype but what are some other phenotypes?

Answer 11

• Progressive muscular atrophy (PML) - 10% of cases
• Primary lateral sclerosis (PLS) - 1-3%
• Progressive bulbar palsy (PBP) - 1-2%

Question 12

There is a link between ALS and what type of dementia?

Answer 12

Frontotemporal dementia

Question 13

What are the diagnostic criteria for clinically definite ALS?

Answer 13

Upper and lower motor neuron signs in bulbar and at least two spinal regions (lumbosacral, thoracic or cervical) or UMN and LMN signs in 3 spinal regions

Question 14

How can the thoracic variant of MND present?

Answer 14

Fatigue, SOB at rest, pneumonia, neurogenic changes in paravertebral muscles on EMG

Question 15

What are some ALS variants with a more benign prognosis?

Answer 15

Flail arm syndrome, flail leg syndrome, primary lateral sclerosis, focal distal spinal muscular dystrophy, Kennedy’s disease

Question 16

If a patient presented with right sided foot drop then 6 months later right thigh weakness and then another 6 months later left sided foot drop on a history of decreased impulse control, social inadequacy, no insight and disinhibition what would be the likely diagnosis?

Answer 16

MND with frontotemporal dementia

Question 17

How is MND managed?

Answer 17

• Access to specialist MND services
• On-going management - communication needs, nutritional needs, respiratory needs
• Riluzole - used to extend life in patients with ALS