Amyotrophic lateral sclerosis (ALS), also called Lou Gehrig's disease, is a progressive, fatal neurological disease affecting as many as 20,000 Americans with 5,000 new cases occurring in the United States each year. The disorder belongs to a class of disorders known as motor neuron diseases. ALS occurs when specific nerve cells in the brain and spinal cord that control voluntary movement gradually degenerate. The loss of these motor neurons causes the muscles under their control to weaken and waste away, leading to paralysis. ALS manifests itself in different ways, depending on which muscles weaken first. Symptoms may include tripping and falling, loss of motor control in hands and arms, difficulty speaking, swallowing and/or breathing, persistent fatigue, and twitching and cramping, sometimes quite severely. ALS strikes in mid-life. Men are about one-and-a-half times more likely to have the disease as women. There is no cure for ALS; nor is there a proven therapy that will prevent or reverse the course of the disorder. The Food and Drug Administration (FDA) recently approved riluzole, the first drug that has been shown to prolong the survival of ALS patients. Patients may also receive supportive treatments that address some of their symptoms. ALS is usually fatal within five years after diagnosis.