The brain is linked to the rest of the body by nerves (neurones) which have been likened to electrical wiring; some carry impulses to the brain (the sensory nerves) while others carry messages from the brain to the muscles, to make the muscles work and contract - these are called the motor nerves or neurones. In MND these motor nerves degenerate so that the muscles supplied by them lose their strength. 

The illness is not infectious and normally affects people over 40 years of age, most commonly between 50 and 80 years.

The number of people in Scotland who will develop MND in one year is approximately 2.2 per 100,000 of the population (incidence): this means that about I00 people develop this condition in Scotland every year.

There is a small subgroup of people with MND (about 5%) in which the disease does seem to have run in the family, but in the vast majority of people, there is no chance of the children of people with MND being affected.

The disease will present in different ways depending on the location of the nerve cells involved. Doctors commonly use three main terms for Motor Neurone Disease but there is considerable overlap among the three forms as the disease progresses.

It must be stressed that MND affects individual people differently and not everyone will suffer all the symptoms. The rate of progression of the disease will also be individual to each person affected.