What is ALS?

Amyotrophic lateral sclerosis (a-mi-o-TROE-fik LAT-ur-ul skluh-ROE-sis), or ALS, is a nervous system (neurological) disease that causes muscle weakness and impacts physical function.

ALS is often called Lou Gehrig's disease, after the famous baseball player who was diagnosed with it. ALS is a type of motor neuron disease that causes nerve cells to gradually break down and die. In the United States, ALS is sometimes called motor neuron disease.

In most cases, doctors don't know why ALS occurs. A small number of cases are inherited.

ALS often begins with muscle twitching and weakness in an arm or leg, or sometimes with slurring of speech. Eventually, ALS can affect your ability to control the muscles needed to move, speak, eat and breathe. ALS can't be cured and eventually leads to death.

Symptoms

Early signs and symptoms of ALS include:

• Difficulty walking, tripping or difficulty doing your normal daily activities
• Weakness in your leg, feet or ankles
• Hand weakness or clumsiness
• Slurring of speech or trouble swallowing
• Muscle cramps and twitching in your arms, shoulders and tongue
• Difficulty holding your head up or keeping a good posture

The disease frequently begins in your hands, feet or limbs, and then spreads to other parts of your body. As the disease advances, your muscles become progressively weaker. This weakness eventually affects chewing, swallowing, speaking and breathing.

However, ALS doesn't usually affect your bowel or bladder control, your senses, or your thinking ability. It's possible to remain actively involved with your family and friends.

Causes

In ALS, the nerve cells that control the movement of your muscles gradually die, so your muscles progressively weaken and begin to waste away.

ALS is inherited in 5 to 10 percent of cases. The other cases appear to occur randomly.

Researchers are studying several possible causes of ALS, including:

• Gene mutation. Various genetic mutations can lead to inherited ALS, which appears nearly identical to the noninherited form.
• Chemical imbalance. People with ALS generally have higher than normal levels of glutamate, a chemical messenger in the brain, around the nerve cells in their spinal fluid. Too much glutamate is known to be toxic to some nerve cells.
• Disorganized immune response. Sometimes a person's immune system begins attacking some of his or her body's own normal cells, which may lead to the death of nerve cells.

Protein mishandling. Mishandled proteins within the nerve cells may lead to a gradual accumulation of abnormal forms of these proteins in the cells, eventually causing the nerve cells to die.