ALS is the most severe disease in the group of degenerative diseases affecting the motor neurons. The disease is rare and incurable. It is also known as "Lou Gehrig Disease" after an American baseball player who suffered from the disease in the thirties. In England, it is known as motor neuron disease (MND), and in France as Charcot's disease.
ALS affects the motor nerve cells (motor neurons), through which the brain oversee the operation of most voluntary muscles in the body. Nerve cells are destroyed and as a result they can not activate the muscles, causing their weakness to complete paralysis. The disease can damage the muscles responsible for operation of the limbs, swallowing, speech and breathing, not in any particular order. There is usually no harm to cognitive performance.
A small portion of ALS cases are hereditary, when a specific family has one or more cases of the disease.