Neuro - Motor Neurone Disease

Question 1

What is MND? Name 4 types

Answer 1

• Umbrella term encompassing a variety of specific disease
• Progressive degeneration of motor neurones in motor cortex and anterior horns of spinal cord + degeneration of cells within the somatic motor nuclei of the cranial nerves within the brain stem. There is also an effect on the cognitive centres and cerebellum + extrapyramidal pathways.

Types:

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

Question 2

What is the pathogenesis is of MND?

Answer 2

• Majority of cases are sporadic with no family Hx
• Familial cases: 5-10%
• Risk factors: smoking, heavy metal exposure and pesticides

Question 3

What symptoms would point towards a diagnosis of MND?

Answer 3

• Fasciculations
• Mixture of LMN and UNM signs
• Wasting of small hand muscles/tibias anterior is common
• No sensory sx as sensory neurones are spared
• Doesn’t affect external ocular muscles
• No cerebellum signs

Question 6

What is Amylotropic lateral sclerosis?

Answer 6

• Most common form (50% of patients)
• Typically LMN signs in arms and UMN signs in legs but this is variable
• Onset of disease is focal, distal and asymmetrical and progresses in segmental fashion from one limb to another.
• M>F
• Mean age onset is 60, mean duration of survival is 3 years

Question 7

What is Progressive bulbar palsy?

Answer 7

• Palsy of the tongue, muscles of chewing/swallowing and facial muscles due to loss of function of brain stem motor nuclei
• Prominent fasciculations + wasting in tongue + weak palate and nasal regurgitation and nasal voice.
• Bulbar: refers to lower brain stem motor nuclei.
• Carries the worst prognosis due to risk of aspiration

Question 8

What is progressive muscular atrophy?

Answer 8

• associated with LMN signs but tendon reflexes tend to be preserved.
• Often begins asymmetrically in small muscles of hands and feet and spread
• Affects distal muscles before proximal
• Eventually get UMN signs with time
• Carries best prognosis

Question 9

What is primary lateral sclerosis?

Answer 9

• Small number of patients may present solely with UMN signs, typically in legs before progressing to involve arms/bulbar muscles.
• Slower progression of disease
• Eye movement and sphincter are never affected

Question 10

How is MND managed?

Answer 10

• There is no effective treatment for halting/reversing the progression of the disease
• Riluzole: can slow progression by a few months in AML (need regular LFT checks)
• NIV: used at home to support breathing at night and improves survival and QoL
• MDT approach
• Advanced directives to document the patient wishes as disease progressive
• Careful end of life planning
• Patients usually die of respiratory failure/pneumonia

Question 11

Describe features of UMN and LMN lesions

Answer 11

Upper motor neurone lesion

• Spastic paralysis
• No wasting
• No fasciculations
• Brisk reflexes
• Clonus
• Extensor plantar response (Babinski)

Lower motor neurone lesions

• Flaccid paralysis
• Muscle wasting
• Fasciculations present
• Reduced/absent reflexes
• Flexor/absent plantar response

Question 12

How is MND diagnosed?

Answer 12

• Careful diagnosis based on clinical presentation and exclusion of other conditions that can cause MN symptoms
• MRI spine and brain: exclude cervical cord compression and myelopathy
• EMG: will show decreased number of action potentials with an increased amplitude
• Nerve conduction studies: normal motor conduction