The main symptoms of ALS include muscle weakness, stiffness, and atrophy. Early signs, such as muscle twitches, cramps, stiffness, or weakness in one body part, can be subtle. Symptoms usually first appear in a hand or arm. This might look like difficulty with tasks including buttoning a shirt, turning a lock, or writing. In some cases, the disease begins by affecting one leg, causing trouble with walking or more frequent stumbling.
As the disease progresses, people with ALS have difficulty standing, moving, walking, swallowing, and speaking. Eventually, they lose their ability to breathe without the support of a ventilator.
The disease is not known to be associated with cognitive impairment, but recent studies suggest some people with ALS may develop a form of dementia that affects memory and decision-making.
ALS is ultimately fatal, typically due to respiratory failure when the muscles needed to breathe become too weak. On average, people with ALS survive about three to five years while about 10 percent will live 10 years or more.