Station 3.20: Motor neurone disease

Question 1

clinical signs

What are the clinical signs of Motor neurone disease?

Answer 1

• Inspection: wasting and fasciculation
• Tone: usually spastic but can be flaccid
• Power: weak
• Reflexes: absent and/or brisk. (Absent knee jerk with extensor plantar reflexes.)
• Sensory examination is normal
  * Speech: dysarthria may be bulbar (nasal, ‘Donald Duck’ speech, due to palatal weakness) or pseudo‐bulbar (‘hot potato’ speech, due to a spastic tongue).
• Tongue: wasting and fasciculation (bulbar) or a stiff spastic tongue with brisk jaw jerk (pseudo‐bulbar).
• There is no sensory, extra‐ocular muscle, cerebellar or extra‐pyramidal involvement. Sphincter and cognitive disturbance occasionally seen.

Question 2

discussions

Motor neurone disease discussion?

Answer 2

MND is a progressive disease of unknown aetiology
There is axonal degeneration of upper and lower motor neurones

Motor neurone disease may be classified into three types, although there is often some
overlap:

• **Amyotrophic lateral sclerosis **(50%): affecting the cortico‐spinal tracts predominantly producing spastic paraparesis or tetraparesis.
• Progressive muscular atrophy (25%): affecting anterior horn cells predominantly producing wasting, fasciculation and weakness. Best prognosis.
• Progressive bulbar palsy (25%): affecting lower cranial nerves and suprabulbar nuclei producing speech and swallow problems. Worst prognosis.

Question 3

discussions - Investigation

Clinical investigations Motor neurone disease?

Answer 3

• Clinical diagnosis
• EMG: fasciculation
• MRI (brain and spine): excludes the main differential diagnoses of cervical cord compression and myelopathy and brain stem lesions

Question 4

discussions - Treatment

What is the Treatment for Motor neurone disease?

Answer 4

• Supportive, e.g. PEG feeding and NIPPV
• Multidisciplinary approach to care
• Riluzole (glutamate antagonist): slows disease progression by an average of 3 months but does not improve function or quality of life and is costly

Question 5

discussions - Prognosis

What is the prognosis for Motor neurone disease?

Answer 5

• Most die within 3 years of diagnosis from bronchopneumonia and respiratory failure. Some disease variants may survive longer.
• Worst if elderly at onset, female and with bulbar involvement.

Question 6

discussions - Causes of generalized wasting of hand muscles

What is the Causes of generalized wasting of hand muscles for Motor neurone disease?

Answer 6

• Anterior horn cell
  ⚬ MND
  ⚬ Syringomyelia
  ⚬ Cervical cord compression
  ⚬ Polio
• Brachial plexus
  ⚬ Cervical rib
  ⚬ Pancoast’s tumour
  ⚬ Trauma
• Peripheral nerve
  ⚬ Combined median and ulnar nerve lesions
  ⚬ Peripheral neuropathy
• Muscle
  ⚬ Disuse atrophy, e.g. rheumatoid arthritis

Question 7

discussions - Fasciculation

What is the Fasciculation for Motor neurone disease?

Answer 7

• Visible muscle twitching at rest
• Cause: axonal loss results in the surviving axons recruiting and innervating more myofibrils than usual resulting in large motor units
• Seen commonly in MND and syringomyelia