Symptoms of Amyotrophic Lateral Sclerosis
ALS results in muscles that are weak and soft, or stiff, tight and spastic. Muscle twitches and cramps are common; they occur because degenerating axons (long fibers extending from nerve-cell bodies) become "irritable." Symptoms may be limited to a single body region, or mild symptoms may affect more than one region. When ALS begins in the bulbar motor neurons, the muscles used for swallowing and speaking are affected first. Rarely, symptoms begin in the respiratory muscles.

As ALS progresses, symptoms become more widespread, and some muscles become paralyzed while others are weakened or unaffected. In late-stage ALS, most voluntary muscles are paralyzed.

The involuntary muscles, such as those that control the heartbeat, gastrointestinal tract and bowel, bladder and sexual functions are not directly affected in ALS. Sensations, such as vision, hearing and touch, are also unaffected.

In most cases, ALS does not affect a person’s thinking ability. However, some people with ALS develop some degree of cognitive (thinking) or behavioral abnormality. Usually, cognitive and behavioral symptoms in ALS range from mild (such that only close family members may notice a difference) to moderate.