BAsic information description A progressive breakdown of the cells of the spinal cord. This results in a gradual loss of muscle function. It involves the central nervous system and the muscle system, especially in the hands, forearms, legs, head, and neck. It usually affects people aged 40 to 60 years, and occurs more often in men than women. frequent signs and symptoms Muscle twitching and weakness. It begins in the hands and spreads to the arms and legs. The weakness then begins to...