An experienced physician makes a diagnosis by carefully evaluating the patient's medical history and by performing a thorough neurological examination. This test involves inserting electrodes into muscles and measuring the electrical signals. Occasionally, a muscle biopsy, in which a piece of muscle is removed under local anesthesia, may be necessary. In some situations, genetic testing may be done. ALS usually affects all of the body's muscles within three to five years from the onset of the disease.
Death results from paralysis of respiratory muscles.
Occasionally, though, the disease progresses very slowly, sometimes over a period of decades. Researchers are investigating reports of possible risk factors that may set off the disease. There are drugs that can control involuntary muscle twitching, disabling cramps and excessive saliva. In most parts of the world, ALS affects one in 10,000 people. About 30,000 people in the United States have ALS, and about 5,000 new cases are diagnosed annually.