Motor neurone disease

Question 1

Describe the pathophysiology of MND.

Answer 1

Degeneration of motor neurones in:
The motor cortex
Cranial nerve nuclei 
Anterior horn cell 
There is NO sensory loss.

Question 2

Describe the pathophysiology of upper motor neurone disorders

Answer 2

Degeneration of motor cortex neurones.

Question 3

Describe the pathophysiology of mixed MNDs

Answer 3

Degeneration of cranial nerve nuclei neurons

Question 4

Describe the pathophysiology of lower MNDs

Answer 4

Anterior horn cell neuronal degeneration

Question 5

Which is the most common type of MND?

Answer 5

Amyotrophic lateral sclerosis

Question 6

Which type of MND affects UMNs?

Answer 6

Primary lateral sclerosis,

Question 7

Which type of MND affects LMNs?

Answer 7

Progressive muscular atrophy

Question 8

What is progressive bulbar palsy?

Answer 8

A rare type of MND.

Question 9

Which type of MND affects upper motor neurones of the corticobulbar tract?

Answer 9

Pseudobulbar palsy

[PTS]

Question 10

What investigations would you do if you suspect MND?

Answer 10

1. Clinical exam - UMN and LMN signs.
2. Electromyography (EMG) - shows neurophysiology
3. Nerve conduction studies (NCS) - shows denervation
4. MRI to exclude other causes
5. LP to exclude inflammatory causes eg infection/autoimmune (MS)

Question 11

What is the normal physiology of deciding on, and doing a movement?

Answer 11

1. Idea of movement in association areas
2. Activation of UMNs in precentral gyrus
3. Impulses travel to LMNs via corticospinal tracts
4. Modulation activity by the cerebellum and basal ganglia
5. Modification of movement based on sensory feedback.

Question 12

What makes up a motor unit?

Answer 12

LMN + its axon + supplied muscle fibres - FEWER fibres PER LMN the more SOPHISTOCATED the movement is.

Question 13

Describe the management of MND.

Answer 13

1. Riluzole: antiglutaminergic
2. MDT
3. Symptomatic tx:
   - amitriptyline for drooling
   - nil by mouth due to dysphagia (PEG)
   - GABA agonist eg baclofen/ ca inhibitor eg dantrolene for spasticity
   - analgesic ladder for joint pain
   - NIV for respiratory failure.

Question 14

How is muscle tone regulated?

Answer 14

1. Stretch receptors in muscle (muscle spindles)*?

Question 15

What are 3 clinical features of lower MNDs?

Answer 15

Everything goes down/ LOWERs:

1. Decreased muscle tone
2. Muscle wasting
3. Reflexes weaken
4. Fasciculation (contraction of motor units)

Question 16

What is the final common pathway?

Answer 16

The motor neurons by which nerve impulses from many central sources pass to a muscle or gland in the periphery. (medical-dictionary.thefreedictionary.com)

Question 17

What can damage the FCP?

Answer 17

Brainstem/SC: MND
Spinal roots: Prolapsed intervertebral disc, spinal tumours, malignant infltration
Peripheral nerves: axon demyelination/ degeneration
NMJ: Myasthaenia gravis, congenital
Muscle: weakness mostly affects proximal muscles.

Question 18

How would you differentiate MND from MS?

Answer 18

MS causes sensory loss, disturbances in eye movements and sphincter disturbances, none of which occur in MND.

Question 19

How would you differentiate myelopathy from MND?

Answer 19

If there is sensory loss, it is not MND.

Question 20

What is the pharmacology of riluzole?

Answer 20

Riluzole is an antiglutaminergic which inhibits glutamate release and inhibits NMDA receptors.

Question 21

What are the common side-effects of riluzole?

Answer 21

Nausea, weakness, decreased lung function.

Question 22

Give 3 risk factors for MND.

Answer 22

Male 3:2
Family history, esp in inherited form of MND.
Increasing age

Question 23

How does baclofen work?

Answer 23

Skeletal muscle relaxant, used to treat spasticity. Activates GABA receptor, blocking release of excitatory neurotransmitters.

Question 24

How does dantrolene work?

Answer 24

Inhibits calcium ion release to reduce skeletal muscle contraction.

Question 25

What is non-invasive ventilation?

Answer 25

Airway support administered through a nasal mask instead of an endotracheal tube.