Motor neuron disease

Question 1

What is motor neuron disease?

Answer 1

Neurodegenerative disorder characterised by selective loss of neurons in the motor cortex, cranial nuclei and anterior horn cells

Question 2

Why is it easy to distinguish between MND and MS in terms of symptoms?

Answer 2

In MND, upper and lower motor neurons can be affected but there is no sensory loss or sphincter disturbance, thus distinguishing MND from MS and polyneuropathies

Question 3

How can we distinguish MND from MG? (What symptom or sign is never shown in MND?)

Answer 3

MND never affects eye movements, distinguishing from myasthenia gravis

Question 4

What is the most common clinical pattern of MND? Does this pattern produce upper or lower motor neurone signs?

Answer 4

Amyotrophic lateral sclerosis (80%)

→ Loss of motor neurons in motor cortex and the anterior horn of the cord, so combined UMN and LMN signs.

Question 5

Presentation of MND?

Answer 5

• stumbling spastic gait
• foot drop
• proximal myopathy
• weak grip
• shoulder abduction (washing hair is hard)
• aspiration pneumonia

Question 6

What signs do you expect in upper motor neuron lesions?

Answer 6

(everything goes up!)

• spasticity, brisk reflexes
• tendon reflexes and jaw jerk
• plantar responses (+ babinski sign)
• Characteristic pattern of limb muscle weakness (pyramidal) - upper limb extensor muscles weaker than flexors but lower limb flexors are weaker than extensors
• fine skilled movements are most severely impaired
• emotional lability may be present (crying, laughing)

Question 7

What signs do you expect from LMN lesions?

Answer 7

(everything goes down!)

• muscle wasting
• fasciculation of tongue, abdomen, back, thighs
• muscle tone is normal or reduced (flaccid)
• reflexes are depressed or absent

Question 8

What are bulbar signs?

Answer 8

Affecting speech or swallowing

Question 9

Causes of UMN pathology?

Answer 9

• vascular disease
• inflammatory MS
• compression of brain or spine by a tumour or degenerative spinal disease
• infiltration of corticospinal pathway by tumours
• neurodegenerative disease of UMN and or LMN = MND

Question 10

What can we use to diagnose MND?

Answer 10

No diagnostic test but we can do a brain and spinal cord MRI to exclude structural causes and LP to help exclude inflammatory causes.
Neurophysiology (EMG) can detect subclinical denervation and help exclude mimicking motor neuropathies
There is a definitive MND if there is lower and upper MN signs in 3 regions.

Question 11

Prognosis of MND?

Answer 11

Poor, <3 years post onset in half of patients

Question 12

Management of MND?

Answer 12

MDT - neurologist, palliative nurse, hospice, physio

Riluzole only medication shown to improve survival.