Amyotrophic lateral sclerosis, or ALS, is a disease of the nerve cells in the brain and spinal cord that are responsible for voluntary muscle movement.

ALS is also known as Lou Gehrig's disease.

In about 10% of cases, ALS is caused by a genetic defect. In other cases, the cause of the nerve deterioration is unknown.

In ALS, nerve cells (neurons) waste away or die, and can no longer send messages to muscles. This eventually leads to muscle weakening, twitching, and an inability to move the arms, legs, and body. The condition slowly gets worse. When the muscles in the chest area stop working, it becomes hard or impossible to breathe on one's own. Persons with ALS eventually need a breathing machine.

ALS affects approximately 1 out of every 100,000 people.

Except for having a family member who has a hereditary form of the disease, there are no known risk factors.

Symptoms usually do not develop until after age 50. Persons with ALS have a loss of muscle strength and coordination that eventually gets worse (is progressive). This eventually makes the person unable to do routine activities, such as going up steps, getting out of a chair, or swallowing. Occasionally, breathing or swallowing muscles may be the first muscles affected.

As the disease gets worse, more muscle groups develop problems. However, ALS does not affect the senses (sight, smell, taste, hearing, touch) and it usually does not impact a person's ability to think or reason.

Symptoms include:

• Muscle weakness, decrease in muscle strength and coordination
  • Slowly starts
  • Slowly gets worse
  • Commonly involves one limb at first, such as the hand
  • Eventually, person has difficulty lifting, climbing stairs, and walking
• Paralysis
• Muscle cramps
• Voice changes, hoarseness
• Speech problems, such as a slow or abnormal speech pattern
• Difficulty swallowing, gags or chokes easily
• Difficulty breathing (increasing effort required to breathe)
• Head drop due to weak spinal and neck muscles

Additional symptoms that may be associated with this disease:

• Muscle contractions
• Muscle spasms
• Muscle atrophy
• Ankle, feet, and leg swelling
• Weight loss
• Drooling

A neuromuscular exam indicates weakness, often beginning in one area (such as shoulders or hips). There may be muscle tremors, spasms, twitching, or muscle atrophy (loss of tissue). Atrophy and twitching of the tongue are common.

The person's walk may be stiff or clumsy. Reflexes may be abnormal and may include loss of the gag reflex. Some patients have "emotional incontinence" in which it is hard to control crying or laughing.

Tests that may be done include:

• EMG to see which nerves are not functioning (sensory nerves are normal)
• Head CT or MRI of head to rule out other conditions
• Genetic test, if there is a family history of ALS
• Breathing test to see if respiratory muscles are affected.
• Blood tests to rule out other conditions that may cause similar symptoms