A neuromuscular disorder is a term that encompasses many different medical conditions that impair the functioning of the muscles. Neuromuscular disorders affect the nerves that control voluntary muscles and the nerves that communicate sensory information back to the brain. Nerve cells (neurons) send and receive electrical messages to and from the body to help control voluntary muscles. When the neurons become unhealthy or die, communication between the nervous system and muscles breaks down. As a result, muscles weaken and waste away.