The motor neuron diseases (MNDs) are a group of progressive neurological disorders that destroy nerve cells. Normally, messages from nerve cells in the brain (called upper motor neurons) are transmitted to nerve cells in the brain stem and spinal cord (called lower motor neurons) and from them to particular muscles that selectively affect motor neurons, the cells that control voluntary muscle activity including speaking, walking, breathing, swallowing and general movement of the body.
There are different forms of motor neuron diseses(MND):-
1. ALS (amyotrophic lateral sclerosis) also called Lou Gehrig's which affects both upper and lower motor neurons. ALS is the most common form and accounts for approx. 60% to 70% of all cases.
2. PBP (progressive bulbar palsy) which affects the lower motor neurons of the brain stem, causing slurred speech and difficulty chewing and swallowing. PBP accounts for about 20% of all cases.
3. PMA (progressive muscular atrophy) which affects only lower motor neurons in the spinal cord. PMA accounts for the remaining 10% of cases.
4. PLS (primary lateral sclerosis) which affects only lower motor neurons. PLS is a very rare form of MND. PLS, unlike the other forms, is not fatal. In some very rare cases, patients with PLS eventually have ALS