Amyotrophic lateral sclerosis (ALS) is a neurological condition that causes gradual loss of mobility in affected patients. ALS is also known as Lou Gehrig’s disease, named after the famous baseball player who died from the disease in 1941. Patients with ALS typically die from respiratory failure within three to five years of diagnosis.

ALS is characterized by the degradation and eventual death of motor neurons. These nerve cells transmit signals from the brain to the muscles involved in movement. Without the nerve signals, the muscles stop functioning and begin to waste away (atrophy). A patient is likely to experience muscle weakness that gradually progresses to complete loss of movement (paralysis). Most patients experience the first symptoms after the age of 40.

Anyone can develop ALS, but it is a rare condition. Fewer than 6,000 cases are diagnosed each year in the United States, according to the ALS Association.

The cause of most cases of ALS is unknown. Between 90 and 95 percent of patients have no family history of the disease. Of the remaining patients with ALS, approximately 20 percent of cases have been linked to a mutation in the SOD1 gene. It is thought that this mutation affects the way in which certain harmful elements are processed in the body, causing them to build up and consequently damage motor neurons. The disease may also be related to glutamate, a neurotransmitter that has been found in high levels in ALS patients.

ALS progresses slowly and its symptoms may not be noticed for some time. Symptoms are likely to include muscle weakness or twitching, slurred and/or nasal speech, and difficulty with chewing and swallowing. Patients are likely to trip more often and lose strength in their hands, which can affect fine motor skills, such as buttoning clothes and other such activities of daily living.

The diagnosis of ALS is usually based on the presence of symptoms. A family history of the disease accompanied by signs and symptoms is a strong indication of ALS. A physician may perform tests to exclude other possible causes of muscle weakness. These tests may include electromyography (EMG), nerve conduction velocity (NCV) studies and magnetic resonance imaging (MRI). Some tests may be repeated over time to monitor disease is progression.