amyotrophic lateral sclerosis

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A chronic, progressive disease marked by gradual degeneration of the nerve cells in the spinal cord that control voluntary muscle movement, causing muscle weakness, atrophy, and eventual paralysis.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun pathology, neurology A chronic, progressive disease characterized by degeneration of the central nervous system and the loss of voluntary muscle control.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun thickening of tissue in the motor tracts of the lateral columns and anterior horns of the spinal cord; results in progressive muscle atrophy that starts in the limbs