What is amyotrophic lateral sclerosis?
Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a progressive wasting away of certain nerve cells of the brain and spinal column called motor neurons. The motor neurons control the voluntary muscles, which are the muscles that allow movement. ALS is a progressive, disabling disease. Walking, speaking, eating, swallowing, breathing, and other basic functions become more difficult with time. These problems can lead to injury, illness, and other complications.
Amyotrophic lateral sclerosis is one of a group of diseases known as motor neuron diseases. Neurons are nerve cells, and motor neurons are neurons that control movement. Movement occurs when neurons in the brain (upper motor neurons) send messages to neurons in the spinal cord (lower motor neurons). The lower motor neurons relay these messages to the specific muscles that carry out the movement. In some motor neuron diseases, only the upper motor neurons are affected, or only the lower motor neurons. In ALS, however, both upper and lower motor neurons are affected. The neurons die and stop sending messages to muscles. The muscles are unable to function without these messages and gradually become weaker. They waste away (atrophy) and twitch (fasciculate). Eventually all voluntary movement is lost, and muscles become paralyzed.
In amyotrophic lateral sclerosis, for unknown reasons, these neurons die, leading to a progressive loss of the ability to move virtually any of the muscles in the body. ALS affects "voluntary" muscles, those controlled by conscious thought, such as the arm, leg, and trunk muscles. Amyotrophic lateral sclerosis, in and of itself, does not affect sensation, thought processes, the heart muscle, or the "smooth" muscle of the digestive system, bladder, and other internal organs. Most people with ALS retain function of their eye muscles as well. However, various forms of ALS may be associated with a loss of intellectual function (dementia) or sensory symptoms.
"Amyotrophic" refers to the loss of muscle bulk, a cardinal sign of ALS. "Lateral" indicates one of the regions of the spinal cord affected, and "sclerosis" describes the hardened tissue that develops in place of healthy nerves. ALS affects approximately 30,000 people in the United States, with about 5,000 new cases each year. It usually begins between the ages of 40 and 70, although younger onset is possible. Men are slightly more likely to develop ALS than women.