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, fatal disease. The course of the disease is different for everyone and some people live with ALS for many years. Walking, speaking, eating, swallowing, breathing, and other basic functions become more difficult with time. These problems can lead to injury, illness, and other complications.

In the United States and most other parts of the world, 1 to 2 people per 100,000 develop ALS each year. Men are affected slightly more often than women. Although ALS may occur at any age, it is most common in middle-aged and older adults.^{1, 2}

What causes ALS?

The cause of ALS is unknown. About 5% to 10% of people with ALS have an inherited form of the disease.³ ALS is not contagious.

What are the symptoms?

Over a period of months or years, ALS causes increasing muscle weakness, inability to control movement, and problems with speaking, swallowing, and breathing. The first sign of ALS is usually slight weakness in one leg, one hand, the face, or the tongue. Other problems may include increasing clumsiness and difficulty performing tasks that require precise movements of the fingers and hands. Frequent muscle twitching may occur. The weakness slowly spreads to the arms and legs over a period of months or years. As the nerves continue to waste away and decrease in number, the muscle cells that would normally be stimulated by those nerves also start to waste away, and the muscles weaken.

It is important to remember that having muscle weakness, fatigue, stiffness, and twitching doesn't necessarily mean that you have ALS.

How is ALS diagnosed?

ALS may be difficult to diagnose, and the diagnosis may not become clear until symptoms have progressed or until additional testing and observation have taken place.

If your health professional thinks you have ALS, you will likely be referred to a neurologist for diagnosis and treatment. ALS is diagnosed through a careful medical history, a detailed physical exam of the nervous system (neurologic exam), and tests that evaluate nerve and muscle function.

Tests needed to confirm the diagnosis include electromyogram (EMG) and nerve conduction studies. EMG helps measure how well and how quickly the nerves and muscles are working. Nerve conduction studies test nerve function.

Other tests may be needed to rule out other possible causes of the symptoms. These tests may include a nerve or muscle biopsy (tissue sample), blood tests, or imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI) scans.

How is it treated?