Amyotrophic lateral sclerosis (ALS) is a progressive disease of the nervous system. It affects nerve cells in the brain and spinal cord called motor neurons. Motor neurons control muscle movement and ALS causes them to deteriorate and eventually die. The motor neurons lose the ability to send messages to the muscles in the body, affecting voluntary muscle movements. There have been recent advances in treating ALS, but current treatments can only slow disease progression. That is why it is important to diagnose ALS as early as possible.