MND is the name given to a group of similar illnesses. These illnesses all cause damage to the nerves called motor neurones. Motor neurones are the nerves which carry the messages from our brain to our muscles. Without these messages the muscles stop working.
There are three main types of MND:
- Amyotrophic Lateral Sclerosis (ALS)
ALS is the most common form of MND and affects both upper and lower motor neurones.
This means someone may experience both muscle weakness and muscle stiffness in any part of their body. Although the majority of people with ALS are over the age of forty, about 10% of those affected are younger. In general the disease tends to be much slower progressing in the under forties than in older age groups.
For around 25% of people diagnosed with MND, their first symptom is a problem with their speech, which is diagnosed as Progressive Bulbar Palsy (PBP). Some people regard this as a sub-type of ALS. The early symptoms of PBP normally involve slurring of speech due to loss of nerves to the mouth and tongue, and early development of swallowing difficulties is also common.
- Progressive Muscular Atrophy (PMA)
PMA affects the lower motor neurones and causes muscle wasting (atrophy) and weakness, loss of weight and muscle-twitching. The average life expectancy for someone diagnosed with PMA is usually longer than the life expectancy of those with ALS.
- Primary Lateral Sclerosis (PLS)
PLS affects the upper motor neurones and causes increased muscle tension. This results in stiffness of the limbs, known as spasticity, especially in the legs. This form of MND typically affects people over the age of 50. It is a very rare type of MND which progresses slowly, with life expectancy usually normal or near normal.