Amyotrophic lateral sclerosis (ALS), also called motor neuron disease, is a progressive neurodegenerative condition. It attacks the motor neurons that carry signals from the brain and spinal cord to the muscles.
Early signs vary. Some people first notice weakness in a hand, a foot, or their voice. Cramping, twitching, or slurred speech can show up before more obvious changes. Over time, muscles weaken and atrophy. Eventually, the muscles that control breathing are affected.
ALS leads to the death of motor neurons at the cellular level. This happens due to mitochondrial failure, oxidative stress, chronic inflammation, and protein misfolding.