Diseases & Conditions

Amyotrophic Lateral Sclerosis

Overview, Causes, & Risk Factors

Amyotrophic lateral sclerosis, also known as ALS, is a progressive disease of the nervous system. Nerve cells, called neurons, are located in the spinal cord and brain and normally give signals to muscles. ALS causes these neurons to degenerate, or break down. So, when neurons stop sending signals to muscles, the muscles atrophy, which means they weaken and shrink. This may progress to paralysis. Spasticity is increased muscle tone that can make it hard to coordinate movement, and it may also develop as a result of ALS.

What is going on in the body?

The muscle weakness in ALS can affect the muscles of the limbs or of the tongue, mouth, and throat. The nerves that connect the brain and spinal cord, called motor neurons, can also degenerate.

What are the causes and risks of the disease?

Cases that run in families are often due to a defect on one of the chromosomes, the structures that hold genetic information. Otherwise, the cause of ALS is not known.

Symptoms & Signs

What are the signs and symptoms of the disease?

Weakness often starts in one arm or leg and progresses to the other limbs. Muscles may atrophy or have cramps or twitches. Hands, arms, and legs can become clumsy and stiff. The person may have trouble swallowing, and speech may be slurred. ALS does not usually affect bowel and bladder control until late in the course of the disease.

Diagnosis & Tests

How is the disease diagnosed?

The diagnosis is based on special tests. One test that is used is electromyography or EMG for short. Another is a nerve conduction study, or NCV. A neurological exam and a clinical history are also used. Other diseases that mimic ALS, such as conditions known as cervical spinal or lumbar stenosis, must be ruled out.

Prevention & Expectations

What can be done to prevent the disease?

There is no known way to prevent ALS.

What are the long-term effects of the disease?

ALS is usually progressive. Half of people with ALS die within 3 years, and 90% die within 6 years.

What are the risks to others?

Genetic counseling is advised in the inherited forms of the disease.

Treatment & Monitoring

What are the treatments for the disease?

There is no effective treatment for ALS. The drug riluzole may add 3 months to life expectancy. Creatine may help improve strength. Physical, occupational, and speech therapy are helpful. Baclofen, tizanidine, and diazepam may help to relax spastic muscles. Feeding tubes are often needed in the end stages of the disease. A ventilator, or breathing machine, can be used to prolong the life of someone with ALS. However, most people with ALS prefer not to use a ventilator to prolong their lives.

What are the side effects of the treatments?

There are very few side effects from the medicines used for people with ALS. Sedation is probably the most common side effect.

What happens after treatment for the disease?

Treatment usually does not extend life. It can ease pain or discomfort and spasticity and help with general care.

How is the disease monitored?

The disease is monitored by a healthcare provider. Any new or worsening symptoms should be reported to the provider.


Author:Michael Curiel, MD
Date Written:
Editor:Crist, Gayle P., MS, BA
Edit Date:12/18/01
Reviewer:Adam Brochert, MD
Date Reviewed:12/17/01