Amyotrophic lateral sclerosis
(ALS), often referred to as "Lou Gehrig's
Disease," is a progressive neurodegenerative
disease that affects nerve cells in the brain
and the spinal cord. Motor neurons reach from
the brain to the spinal cord and from the spinal
cord to the muscles throughout the body. The
progressive degeneration of the motor neurons in
ALS eventually leads to their death. When the
motor neurons die, the ability of the brain to
initiate and control muscle movement is lost.
With voluntary muscle action progressively
affected, patients in the later stages of the
disease may become totally paralyzed.