Motor neurone disease

Motor neurone disease is an incurable condition that causes the progressive degeneration of the nerve cells that control muscles.

Life expectancy varies but most people with motor neurone disease live just a few years beyond diagnosis. In New Zealand, approximately one in 15,000 people has motor neurone disease and more than 400 people are thought to have motor neurone disease at any one time.

Symptoms include muscle spasms; exaggerated reflexes; and the gradual wasting and weakness of muscles responsible for speech, chewing, and swallowing. As the condition progresses, people with motor neurone disease may be unable to walk, speak, use their arms and hands, or hold up their head.

General information

Motor neurons in the brain and spinal cord send electrical messages from the brain to the muscles to move the arms, legs, trunk, neck, and head. As motor neurons degenerate, the muscles do not work properly and gradually weaken and waste away. This muscle weakness and wasting affects speech, swallowing, movement, and breathing.

There are different forms of motor neurone disease. The three main forms are:

• Amyotrophic lateral sclerosis (ALS)
• Progressive muscular atrophy (PMA)
• Progressive bulbar palsy (PBP).

Each form is named according to the pattern of symptoms it presents. The most common form is ALS (also known as Lou Gehrig's disease). A fourth form of the disease, primary lateral sclerosis (PLS), is rare and often only provisionally diagnosed.

Most cases of motor neurone disease occur randomly, with no known cause. However, 5–10% of people have a family history of the disease, suggesting a genetic link in those cases.

Motor neurone disease is most commonly diagnosed in those over the age of 40 years, occurring mainly in those aged between 50 and 70 years. In some cases, though, symptoms can first appear in a person's 20s.

Usually the onset of motor neurone disease is gradual but younger patients may show a more rapid progression. The average life expectancy is two to four years from diagnosis but some people succumb within a matter of months, while others live up to 20 years or (in rare cases) beyond. Famous theoretical physicist Stephen Hawking defied the odds for 55 years following his ALS diagnosis in 1963 until his death in 2018.

Signs and symptoms

Initial symptoms depend on the form of the condition. However, the most common early sign is weakness in the arms and legs. This is often more pronounced on one side than the other. Other early signs of the condition include:

• Muscle twitching
• Muscle wasting
• An increasingly stiff, clumsy walk
• General fatigue
• Difficulty with chewing, swallowing, and speech.

Initially motor neurone disease may affect the upper motor neurons in the brain (causing muscle spasms and exaggerated reflexes) or the lower motor neurons in the brain stem and spinal cord (causing a gradual wasting and weakness of muscles required for speech, chewing, and swallowing). Eventually, both the upper and lower motor neurons will be affected.

As the condition progresses, people with motor neurone disease may not be able to:

• Walk
• Use their hands and arms
• Speak clearly, or at all
• Swallow
• Hold up their head.

Weakness of the respiratory muscles makes breathing and coughing difficult. Difficulty swallowing makes it more likely that food or saliva will be inhaled into the lungs. This increases the risk of infection in the lungs, which is often the cause of death for people with motor neurone disease.

Pain may be experienced. Musculoskeletal pain, pressure associated with immobility, and muscle cramps are the most common causes of pain. Motor neurone disease does not affect touch, sight, smell, hearing, or intellect. Additionally, the muscles that move the eyes are usually not affected.

In some cases, motor neurone disease is associated with frontotemporal dementia, which is a type of dementia that can affect personality and behaviour.

Diagnosis

There is no specific test for motor neurone disease, and it may be difficult to diagnose in the early stages. Diagnosis relies on a complete medical history and physical examination, as well diagnostic tests. If motor neurone disease is suspected, a referral to a neurologist (a doctor who specialises in the treatment of diseases of the nervous system) will be recommended.

A common test used in the diagnostic process is an electromyogram (EMG), which is an electrical test of muscle function. Another common test is a nerve conduction study (NCS), which assesses a nerve's ability to send a signal. Other tests that may be used to assist with the diagnosis and rule out other causes for the symptoms include blood tests and magnetic resonance imaging (MRI) scans.

Treatment

There is no cure for motor neurone disease and no treatment will significantly alter its course. Medications may be prescribed to control involuntary muscle twitching, muscle cramps, and excess saliva. However, treatment essentially focuses on retaining function and quality of life and providing comfort.

A disease-modifying drug called riluzole (Rilutek), which has the potential to modestly prolong survival in some patients, is available in New Zealand. The first funded treatment for motor neurone disease, riluzole is funded for people with ALS who meet certain criteria and can only be prescribed by a specialist, usually a neurologist.

Management of the condition will require input from a team of health professionals that may include:

• Family doctor
• Neurologist
• Respiratory specialist
• Gastroenterologist
• Physiotherapists
• Occupational therapists
• Speech and language therapists
• Nurse specialists and district nurses
• Dietitians
• Social workers
• Counsellors
• Palliative care specialists and hospice care
• Sleep technologists.

Together, and in conjunction with the patient and family, these health professionals will work to maintain mobility and make maximum use of the affected person’s abilities. Equipment to help overcome practical difficulties and communication problems is available.

The progressive nature of the condition means that most people will eventually require full time nursing care. When breathing becomes too difficult, a mechanical ventilator may be required to maintain breathing. While the use of a ventilator can prolong life and improve sleep, it will not alter the course of the condition, and many people with motor neurone disease therefore choose not to use ventilators for lengthy periods.

Support and information

The Motor Neurone Disease Association of New Zealand (Inc) provides support, advice, information, and advocacy for people living with the disease.

MND New Zealand

Phone: (09) 624 2148

Website: www.mnd.org.nz

References

O’Toole, M.T. (Ed.) (2017). Motor neuron disease. Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.

O’Toole, M.T. (Ed.) (2017). Amyotrophic lateral sclerosis (ALS). Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.

MND New Zealand (2018). Basic facts about MND (Web Page). Auckland: Motor Neurone Disease Association of New Zealand. https://mnd.org.nz/about-mnd/what-is-mnd/basic-facts-about-mnd/ [Accessed: 25/11/22]

MND New Zealand (2018). Type of MND (Web Page). Auckland: Motor Neurone Disease Association of New Zealand. https://mnd.org.nz/about-mnd/what-is-mnd/types-of-mnd/ [Accessed: 25/11/22]

National Institute of Neurological Disorders and Stroke (2022). Motor Neuron Diseases Information Page (Web Page). Bethesda, MD: National Institutes of Health Neurological Institute. https://www.ninds.nih.gov/Disorders/All-Disorders/Motor-Neuron-Diseases-Information-Page#disorders-r1 [Accessed: 25/11/22]

NHS (2021). Motor neurone disease (Web Page). Redditch: National Health Service (NHS)

England. https://www.nhs.uk/conditions/Motor-neurone-disease/ [Accessed: 25/11/22]

PHARMAC (2013). Approval of proposal to fund riluzole for amyotrophic lateral sclerosis (motor neurone disease), 11 September 2013 (Web Page). Wellington: Pharmaceutical Management Agency. https://www.pharmac.govt.nz/news/notification-2013-09-11-riluzole/ [Accessed 25/11/22]

PHARMAC (2014). First funded treatment for motor neurone disease, 30 September 2014 (Web Page). Wellington: Pharmaceutical Management Agency. https://pharmac.govt.nz/news-and-resources/news/first-funded-treatment-for-motor-neurone-disease/ [Accessed 25/11/22]

Last Reviewed: November 2022