Motor neurone disease

Question 1

What is motor neuron disease (MND)?

Answer 1

• Neurodegenerative condition caused by loss of UMNs and LMNs in the CNS
• Cause:
  
  • Mostly sporadic
  • SOD1 gene mutation 20% of familial cases
  • Repeat sequence of C9orf72 gene on ch9 is associated with MND and frontotemporal dementia

Question 2

What is the most common type of MND?

Answer 2

Amyotrophic lateral sclerosis (ALS)

Question 3

Onset of MND?

Answer 3

• Average age of onset is 65
  
  • 10% present before 45
• More common in males

Question 4

Name some types of motor neuron disease?

Answer 4

• ALS
• Progressive muscular atrophy
• Primary lateral sclerosis
• Progressive bulbar palsy

Question 5

Describe ALS?

Answer 5

• Mixed LMN and UMN
  
  • Distal and proximal muscle wasting and weakness
  • Fasciculation
  • Spasticity, exaggerated reflexes, extensor plantars
  • Pyramidal tract features may predominate

Question 6

Describe Progressive muscular atrophy?

Answer 6

• Predominantly LMN
  
  • Weakness and wasting of distal muscles initially
  • Fasciculation
  • Tendon reflexes may be present

Question 7

Describe Primary lateral sclerosis?

Answer 7

• Predominantly UMN
  
  • Spasticity - few lower motor neuron signs
• Gradual progression

Question 8

Describe Progressive bulbar palsy?

Answer 8

• Predominantly cranial nerves
  
  • Early involvement of tongue, palate and pharyngeal muscles
  • Dysarthria/dysphagia
  • Wasting and fasciulations of tongue
  • Pyramidal signs may be present

Question 9

Name a common terminal event of MND?

Answer 9

Type II respiratory failure

Question 10

Describe cognitive impairment in MND?

Answer 10

• Up to 50% will have executive impairment
• 10% develop frontotemporal dementia (FTD)

Question 11

Symptoms on MND?

Answer 11

• Limb weakness, cramps, fasciculation
• Disturbance of speech/swallowing
• Cogntivie and behavioural features common (similar to FTD)

Question 12

What is dysarthria?

What is dysphagia?

Answer 12

Unclear execution of speech

Difficulty with swallowing

Question 13

Signs of MND?

Answer 13

• Muscle wasting
• Weakness of limbs, tongue, face and palate
• Pyrimidal tract invovlement
• External ocular muscles and sphincters remain intact

Question 14

What does pyrimidal tract involvement in MND cause?

Answer 14

• Spasticity
• Exaggerated tendon reflexes
• Extensor plantar responses

Question 15

Describe investigations into MND?

Answer 15

• Clinical features are often typical but treatable causes should be excluded
• Blood:
  
  • Mildly elevated creatine kinase
• Sensory and motor nerve conduction studies:
  
  • Normal but ampoutude of motor action potentials may be reduced due to axonal loss
• EMG:
  
  • Confirm widespread denervation and re-innervation
• Genetic testing:
  
  • SOD1, C9orf72

Question 16

Describe the management of MND?

Answer 16

• MDT
  
  • Physio, OT, speech therapist, dieticians, palliative care
• Riluzole
• Non-invasive ventilation
• Feeding by percutaneous gastrostomy

Question 17

Describe the use of Riluzole in MND?

Answer 17

• Licensed for ALS
• Glutamate release antagonist
• Prolongs median survivial by 2-3 months

Question 18

Describe the use of non-invasive ventilation in MND?

Answer 18

Signficantly prolongs survival and improves QoL

Question 19

Describe the mechanism of ALS?

Answer 19

• Mechanism of disease is unknown btu several theories exist:
  
  • Glutamate toxicity
  • Protein misfolding
  • Mitochondrial dysfunction

Question 20

Read this presentation of ALS

Answer 20

Question 21

Name some differentials for ALS?

Answer 21

• Cervical spondylosis w/ myelopathy and radiculopathy
  
  • Usually has bladder/bowel disturbances too
  • MRI C-spine shows cord compression
• Myasthenia gravis
  
  • Symptoms fluctuate
  • Acetylecholine receptor antibodies present