ALS Home > Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis is a progressive neurological disease that causes voluntary muscles to weaken, waste away, and twitch uncontrollably. In the United States, approximately 20,000 people have this condition, and an estimated 5,000 are diagnosed each year. There is currently no cure, but treatment options can improve symptoms and extend a person's quality of life.

What Is Amyotrophic Lateral Sclerosis?

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a rapidly progressive, invariably fatal neurological disease. This disease attacks the nerve cells (neurons) responsible for controlling voluntary muscles. ALS belongs to a group of disorders known as motor neuron diseases, which are characterized by the gradual degeneration and death of motor neurons.

Understanding Motor Neurons

Motor neurons are nerve cells located in the brain, brainstem, and spinal cord. These nerve cells serve as controlling units and provide vital communication links between the nervous system and the voluntary muscles of the body. Messages from motor neurons in the brain (called upper motor neurons) are transmitted to motor neurons in the spinal cord (called lower motor neurons). From here, they are transmitted to particular muscles.

The Link Between Motor Neurons and Amyotrophic Lateral Sclerosis

In amyotrophic lateral sclerosis, both the upper motor neurons and the lower motor neurons degenerate or die, ceasing to send messages to the muscles. Unable to function, the muscles gradually weaken, waste away, and twitch. Eventually, the ability of the brain to start and control voluntary movement is lost.
Because amyotrophic lateral sclerosis affects only motor neurons, the disease does not impair a person's:
  • Mind
  • Personality
  • Intelligence
  • Memory.
Nor does it affect a person's ability to:
  • See
  • Smell
  • Taste
  • Hear
  • Recognize touch.
People with this condition usually maintain control of eye muscles and bladder and bowel functions.
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
Last updated/reviewed:
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