Family doctor

Overview

Motor neurone disease is also known a ALS (amyotrophic lateral sclerosis). In North America it is often called Lou Gehrig's disease, named after a famous baseball player who developed the condition. Motor neurone disease refers to a group of conditions where the nerves that supply muscles degenerate. These nerves exist in the brain, spinal cord and in the nerves travelling from the spinal cord to the muscles. Motor neurone disease can take different forms depending upon which groups of nerves if most affected.

What are the symptoms of motor neurone disease ?

This depends upon which nerves are most affected. The muscles supplied by the nerves lose their bulk and become weak. People with the disorder often develop cramps. They may also notice twitching or jumping of the muscles. It is important to know that twitching and jumping of muscles alone is quite normal in many people, particularly in the calf muscles.

The disorder commonly begins in one limb. The person with the condition notices that the limb is becoming progressively weaker. There is no numbness, and, apart from cramps, no pain. As the weakness progresses the muscle starts to shrink.

If the main loss of nerves is in the spinal cord, the person may notice stiffness. A common pattern of motor neurone disease is a loss of the spinal cord nerves causing stiffness and clumsiness of the legs and a loss of the nerves to the muscles in the arms causing weakness and shrinkage of the arm muscles.

If the disorder begins in the nerves to speaking and swallowing, the person may first develop slurred speech and a tendency to choke on food.

How common is motor neurone disease ?

About 40-50 people develop motor neurone disease in NZ each year. The average age of onset is 55. Uncommonly, it develops in young people.

How long do people survive motor neurone disease ?

The average length of survival is 2-4 years. Occasionally, people live longer.

How is the diagnosis made ?

A neurologist should make the diagnosis. Most important are the neurologist's assessment of the history and physical examination. The neurologist will probably order extra tests including blood tests, electrical tests of the nerves and muscles known as EMG (electromyography), and, in some patients, a scan of the spinal cord. An important feature of the diagnosis is progression of the disease. For that reason it is sometimes impossible to make the diagnosis with certainty in the early stages. If that is the case, the neurologist will wish to re-examine the person after an interval of weeks or months.

What causes motor neurone disease ?

About 5% of people with motor neurone disease have a hereditary disorder. Approximately 60 different gene abnormalities have been found causing these familial cases. In the other 90% of people, we do not know what causes the disease.

While familial motor neurone disease is rare, it offers special clues as to the possible underlying cause of motor neurone disease. In some patients with familial disease, there are gene mutations in the body's defence systems against free radicals. Free radicals can attack and destroy nerve cells. This information has given an important clue as to possible treatments that may be developed in motor neurone disease to combat free radicals and, hopefully, slow the progression of the disorder.

What is affected in motor neurone disease ?

Mobility

The limbs become very weak and people have difficulty walking. Weakness of the arms can cause difficulty with dressing and other self care. Eventually the person becomes bed-bound.

Speaking and swallowing

If the disorder is concentrated on the nerves to the mouth and face the person may develop slurred speech. They may also have difficulty with choking on food. This problem is almost universal in advanced motor neurone disease.

Breathing

Eventually, motor neurone disease affects the muscles of breathing. This causes progressive shortness of breath and a tendency to develop chest infections.

What is the treatment of motor neurone disease ?

Currently there is no cure for the condition. The medication riluzole slightly slows the progression of the disorder. Rizuzole has a very modest effect on the disorder. For this reason it is not funded for NZ patients.

The main treatment of motor neurone disease is control of the symptoms.

Cramps

Cramps can be controlled with Vitamin E, certain anti-convulsant medications and quinine.

Mobility

Physiotherapy and occupational therapy assessments are often useful. The physiotherapist along with an occupational therapist can advise on various aids for mobility such as walking sticks and frames or wheelchairs.

Swallowing disorders

People with motor neurone disease who develop swallowing disorders should have an assessment by a speech language therapist. The therapists can advise on alterations in the consistency and nature of various foods to assist with swallowing. If swallowing is a prominent part of the disorder, then certain people benefit from a feeding tube either passed through the nose and down into the stomach or through the abdominal wall. This is known as a PEG. If weight loss is a problem, then a dietitian can often provide helpful advice.

Breathing difficulties

Appropriate sleeping positions and physiotherapy to clear chest secretions can often help breathing difficulties. Very occasionally patients benefit from a special breathing apparatus that can be worn in bed overnight to help the breathing process. This is a complicated issue as patients can become dependent on the breathing machine. Sometimes this leads to inappropriate prolongation of the disease. Before a breathing machine is started, the person with motor neurone disease and the family must understand clearly that there will come a time when the breathing support should be discontinued.

What are future trends in motor neurone disease ?

The discovery of genes for motor neurone disease is very exciting and encouraging. By understanding the functions of these genes, it is possible for scientists to determine the abnormal process causing the degeneration of the nerves. Once that process is understood, medications can be developed to stop or slow that process. While riluzole is not very effective for motor neurone disease, the fact that it works at all suggests that more powerful or effective medications will be developed in the future.

Support in New-Zealand.

Yes. NZ has an active Motor Neurone Disease Association. There are branches throughout NZ. The National Office can be reached at P O Box 2129, Wellington, ph: 04-473-5555, fax: 04-499-4675, email: mndanz@xtra.co.nz.