What is MND?

Motor neurone disease (MND) is a neurological condition that causes progressive muscle weakness and wastage.

How common is it?

MND is relatively rare and affects approximately 2 in 100,000 people per year. The most likely people to suffer from MND are men between the ages of 50 and 70. Although women also suffer from this condition, men are two times more likely than women to be affected by MND.

Symptoms

The symptoms of MND are muscle weakness, accompanied by involuntary twitchiness and cramps. In the most common form of MND, called amyotrophic lateral sclerosis (ALS), these symptoms appear in the extremities first – arms, legs and hands. Weakness in the arms and hands may cause a person to drop or have trouble holding on to objects. A person’s ability to grip may diminish and the muscles can flatten, especially in the hands. Weakness in the legs may manifest as a sensation of being wobbly or unbalanced. This can also lead to falls as the legs lose their ability to support the person and give way.

The next muscles affected in ALS are in the mouth and throat area, causing speech and eating to become difficult as the ability to form words, chew and swallow deteriorates. This can also lead to chest infections, since improperly swallowed food particles can get lodged in the lungs. The neck muscles also weaken, making it difficult for the person to hold up their head.

Breathing also becomes problematic as these muscles weaken. Although treatments can help with breathing for a time, this symptom often leads to fatal respiratory failure.

In other forms of MND – progressive bulbar palsy (PBP), progressive muscular atrophy (PMA) and primary lateral sclerosis (PLS) – these symptoms can first surface in different parts of the body and progress in a different order. However, symptoms will eventually spread throughout the body and increase in severity in all forms of MND.

MND is unique among neurological disorders in that it does not affect bladder or bowel control or mental faculties (although a rare type of MND, which afflicts about 3 in every 5 million people, is linked to early dementia). The sensory nerves are also undamaged, leaving hearing, sight and all other senses intact.

Causes

Although the origins of MND are still unknown, it is occasionally found to run in families (about 5% of MND sufferers inherit the disease), which has led to theories that MND is genetic. Another theory posits that free radicals may lead to the nerve damage that causes the symptoms of MND.

Evidence also suggests that excess glutamate (a chemical that transmits nerve signals) may be responsible for MND. Too much glutamate can create an ‘excitotoxic’ state, or overstimulation thought to damage parts of the brain and spinal cord, which in turn causes the symptoms associated with MND.