Neuromuscular diseases affect the function of muscles due to problems with the nerves and muscles in your body. The most common sign of these diseases is muscle weakness. 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 (atrophy).