Motor Neuron Disease

Question 1

What is MND?

Answer 1

Motor neurone disease is an umbrella term that encompasses a variety of specific diagnoses.

Motor neurone disease is a progressive, ultimately fatal condition where the motor neurones stop functioning.

There is no effect on the sensory neurones and patients should not experience any sensory symptoms.

Question 2

Types

Answer 2

Amylotropic lateral sclerosis (AML) is the most common and well known specific type of motor neurone disease. Stephen Hawking had amylotropic lateral sclerosis.

Progressive bulbar palsy is the second most common form of motor neurone disease. It affects primarily the muscles of talking and swallowing.

Progressive muscular atrophy: only lower motor neurone

Primary lateral sclerosis: progressive bilateral upper motor neuron weakness

Question 3

Pathophysiology

Answer 3

The exact cause is unclear although several mechanisms have been considered.

There is a genetic component and many genes have been linked with an increased risk of developing the condition. Taking a good family history is important as around 5-10% of cases are inherited.

There also seems to be an increased risk with smoking, exposure to heavy metals and certain pesticides.

There is progressive degeneration of both upper and lower motor neurones. The sensory neurones are spared.

Question 4

Clinical Features

Answer 4

Think of MND in those >40yrs (median UK age at onset is 60) with:

• stumbling spastic gait
• foot-drop ± proximal myopathy
• weak grip (door-handles don’t turn) and shoulder abduction (hair-washing is hard)
• aspiration pneumonia

Look for UMN signs: spasticity, brisk reflexes, upgoing plantars;

LMN signs: wasting, fasciculation of tongue, abdomen, back, thigh. Is speech or swallowing affected (bulbar signs)? Fasciculation is not enough to diagnose an LMN lesion: look for weakness too. Frontotemporal dementia occurs in ~25%

Question 5

Diagnosis

Answer 5

It is based on the clinical presentation and excluding other conditions that can cause motor neurone symptoms.

It should only be made by a specialist when there is certainty.

Question 6

Management

Answer 6

Unfortunately there are no effective treatments for halting or reversing the progression of the disease.

RILUZOLE can slow the progression of the disease and extend survival by a few months in AML. It is licensed in the UK and should be initiated by a specialist.

Non-invasive ventilation (NIV) used at home to support breathing at night improves survival and quality of life.

Supportive feeding via an NG or PEG may be indicated as bulbar disease progresses.

The key to management of the condition is supporting the person and their family.

Involving the multidisciplinary team (MDT) in supporting and maintaining their quality of life
Advanced directives to document the patients wishes as the disease progresses
End of life care planning
Patients usually die of respiratory failure or pneumonia