Motor Neurone Disease

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.

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.

Other types of motor neurone disease to be aware of are progressive muscular atrophy and primary lateral sclerosis.

 

Pathophysiology

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. 

 

Presentation

The typical patient is a late middle aged (e.g. 60) man, possibly with an affected relative. There is an insidious, progressive weakness of the muscles throughout the body affecting the limbs, trunk, face and speech. The weakness is often first noticed in the upper limbs. There may be increased fatigue when exercising. They may complain of clumsiness, dropping things more often or tripping over. They can develop slurred speech (dysarthria).

Signs of lower motor neurone disease:

  • Muscle wasting
  • Reduced tone
  • Fasciculations (twitches in the muscles)
  • Reduced reflexes

 

Signs of upper motor neurone disease:

  • Increased tone or spasticity
  • Brisk reflexes
  • Upgoing plantar responses

 

Diagnosis

The diagnosis of motor neurone disease needs to be made very carefully. 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. Unfortunately, the diagnosis is often delayed, which causes considerable anxiety and stress.

 

Management

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.

Edaravone is currently used in the United States but not the UK. Recent studies suggest it has the potential to slow the progression of the disease and it may come in to use in the future.

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

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

  • Effectively breaking bad news
  • 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

 

Last updated April 2019
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