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There are several different types of MND. These are probably all part of the same disease, but the ways in which they start and progress are somewhat different.

Amyotrophic lateral sclerosis (ALS)
This is the most common form of the disease. It leads to weakness and speech and swallowing difficulties. There is often widespread fasciculation of muscles. Knee and ankle jerks commonly occur. Men are more frequently affected than women in a ratio of 3:2.

Progressive muscular atrophy (PMA)
This is much less common, and tends to progress more slowly, than ALS. It produces muscular wasting and atrophy, but spasms and spasticity do not occur. Fasciculations are present in most muscles. Many people with this form of MND may develop amyotrophic lateral sclerosis later. Men are more likely to have this form of the disease than women in a ratio of 5:1.

Progressive bulbar palsy
The muscles of the throat, tongue and face are mainly affected, but the eye muscles are not affected. There is difficulty with talking, swallowing, coughing, and clearing the throat. As with all forms of MND, in the late stages of the disease, breathing will also be affected. People with this syndrome may laugh and cry for no apparent reason. This is because the centre in the brainstem that controls the physical expression of the emotions is affected by the disease. The person doesn’t necessarily feel more emotional.

Primary lateral sclerosis
This is a very rare form of the disease in which spasticity occurs without wasting or fasciculation. Only a few cases have ever been described.

Familial MND (familial ALS/FALS)
In about eight per cent of cases of MND it is found that someone else in the family has had the disease. This proportion is fairly constant across the world, except in populations where first-cousin marriages are common, e.g. some Muslim societies; or where the population has been isolated for centuries, as in certain parts of northern Scandinavia. These factors lead to an increased frequency of genetic disorders. A genetic link, involving an enzyme known as superoxide dismutatse (SOD1), has been detected in about 20 per cent of the families where more than one case of MND has occurred. It is also suspected that other, as yet unknown, inherited genetic fingerprinting may make certain people more likely than others to develop the disease.

Juvenile ALS (MND)
There are very rare examples of the disease developing in children. This is a special type MND in which there is also a genetic link.