Neuromuscular Disorders: When Nerves and Muscles Fail to Work Together

Neuromuscular disorders affect the neuromuscular system. They can cause problems with:

• the nerves that control your muscles;
• the muscles themselves;
• the communication between nerves and muscles.

They can make muscles weak and waste away, and can cause spasms, twitching and pain.

Causes

Causes vary. Many of these disorders are genetic — inherited, running in families, or caused by a new mutation in a person's genes. Some are autoimmune diseases, and sometimes the cause is unknown. Many have no cure, but treatment may ease symptoms, improve mobility and lengthen life.

Four examples

Amyotrophic lateral sclerosis (ALS) attacks the neurons in the brain and spinal cord that send messages to the voluntary muscles — the ones you control, as in the arms and legs. It begins with mild problems such as trouble walking, running or writing, or speaking; in time people lose strength and cannot move, and when the chest muscles fail, they cannot breathe. It usually strikes between 40 and 60, and more men than women. Its cause is unknown; it can run in families but usually strikes at random. There is no cure, but medicines can relieve symptoms and sometimes prolong survival.

Muscular dystrophy (MD) is a group of more than 30 genetic diseases that weaken the muscles, worsening over time until walking and daily activities become hard; some types affect other organs too. Duchenne muscular dystrophy, the most common childhood form, is severe, affects boys more often than girls, and usually begins between ages 3 and 6.

Myasthenia gravis (MG) is a long-lasting autoimmune disease in which nerve signals to the voluntary muscles are blocked where nerves meet muscles. It weakens muscles used for eye and eyelid movement, facial expression, chewing, talking, swallowing, breathing and moving the limbs; the weakness worsens with activity and improves with rest.

Spinal muscular atrophy (SMA) is a group of genetic diseases that damage and kill motor neurons, the nerve cells in the spinal cord and lower brain that control movement of the arms, legs, face, chest, throat and tongue. As they die, muscles weaken and waste away, which can affect speaking, walking, swallowing and breathing. Its most severe and most common type, infantile-onset SMA, usually shows before 6 months of age.

Sources

• MedlinePlus, U.S. National Library of Medicine, "Neuromuscular Disorders." https://medlineplus.gov/neuromusculardisorders.html
• MedlinePlus summaries "Amyotrophic Lateral Sclerosis," "Muscular Dystrophy," "Myasthenia Gravis" and "Spinal Muscular Atrophy," used for the four examples: https://medlineplus.gov/amyotrophiclateralsclerosis.html, https://medlineplus.gov/musculardystrophy.html, https://medlineplus.gov/myastheniagravis.html, https://medlineplus.gov/spinalmuscularatrophy.html
• Rewritten in hubnx's own words.