Common Disorders of the Muscular System

Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease)

Amyotrophic Lateral Sclerosis (ALS), also called Lou Gehrig’s Disease, is a disease that causes the nerve cells in both the upper and lower parts of the body to stop working and die. The nerves lose the ability to stimulate specific muscles, which causes the muscles to become weak and leads to paralysis. No one knows what causes most cases of ALS, but scientists have been studying factors such as heredity, environmental exposures, diet, and injuries that could be linked with ALS. Although the actual number of cases is unknown, reports suggest fewer than 30,000 people in the United States have ALS. Every year, about 5,000 people are diagnosed with the disease.^[1]

Cerebral Palsy

Cerebral palsy is a group of conditions that affect movement and posture caused by damage to the developing brain, most often before or right after birth. Symptoms appear during infancy or the preschool years and vary from very mild to severe. Children with cerebral palsy may have exaggerated reflexes. The arms, legs and trunk may appear floppy, or they may have stiff muscles, known as spasticity. Symptoms also can include irregular posture, uncontrolled movements, a walk that’s not steady, or some combination of these. Cerebral palsy may make it hard to swallow. It can also cause eye muscle imbalance, in which the eyes don’t focus on the same object. Epilepsy, blindness, or deafness also might affect some people with cerebral palsy. There is no cure, but treatments can help improve function. The symptoms of cerebral palsy may vary during the child’s development, but the condition generally stays the same over time.^[2]

Fibromyalgia

Fibromyalgia is a disorder characterized by widespread musculoskeletal pain accompanied by fatigue, sleep, memory, and mood issues. Researchers believe that fibromyalgia amplifies pain sensations by affecting the way the brain and spinal cord process pain signals. Symptoms often begin after an event, such as physical trauma, surgery, infection or significant psychological stress. In other cases, symptoms gradually develop over time with no single triggering event. Women are more likely to develop fibromyalgia than men. Many people who have fibromyalgia also have tension headaches, temporomandibular joint (TMJ) disorders, irritable bowel syndrome, anxiety and depression. While there is no cure for fibromyalgia, a variety of medications can help control symptoms. Exercise, relaxation and stress-reduction measures also may help.^[3]

Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a progressive weakening of the skeletal muscles. It is one of several diseases collectively referred to as “muscular dystrophy.” DMD is caused by a lack of the protein dystrophin, which helps the thin filaments of myofibrils bind to the sarcolemma. Over time, as muscle damage accumulates, muscle mass is lost, and greater functional impairments develop. DMD is an inherited disorder primarily affecting males. It is usually diagnosed in early childhood. DMD usually first appears as difficulty with balance and movement and then progresses to an inability to walk. It continues progressing upward in the body from the lower extremities to the upper body, where it affects the muscles responsible for breathing and circulation. It ultimately causes death due to respiratory failure, and those afflicted do not usually live past their twenties.^[4]

Myasthenia Gravis

Myasthenia gravis is a chronic neuromuscular disease that causes weakness in the skeletal muscles. Myasthenia gravis is an autoimmune disease, which means that the body’s immune system mistakenly attacks healthy cells or proteins needed for normal functioning. Symptoms commonly associated with myasthenia gravis include weakness of the eye muscles (ocular myasthenia), drooping of one or both eyelids (ptosis), blurred or double vision (diplopia), changes in facial expressions, difficulty swallowing, shortness of breath, impaired speech (dysarthria), and weakness in the arms, hands, fingers, legs, and neck. Myasthenia gravis affects both men and women and occurs across all racial and ethnic groups. It most commonly impacts young adult women (under 40) and older men (over 60), but it can occur at any age, including childhood. Myasthenia gravis is not inherited or contagious. Occasionally, the disease may occur in more than one member of the same family. Myasthenia gravis is caused by an error in how nerve signals are sent to muscles, specifically when communication between the nerve and muscle is interrupted at the neuromuscular junction. Currently, there is no known cure for myasthenia gravis. Most people with myasthenia gravis live an average life expectancy. There are some treatments available to help reduce and improve muscle weakness.^[5]

Poliomyelitis (Polio)

Polio is a highly infectious disease caused by a virus. It invades the nervous system and can cause total paralysis in a matter of hours. The virus is transmitted by person-to-person spread mainly through the fecal-oral route or, less frequently, by a common source (for example, contaminated water or food) and multiplies in the intestine. Initial symptoms are fever, fatigue, headache, vomiting, stiffness of the neck and pain in the limbs. One in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralyzed, 5–10% die when their breathing muscles become immobilized. Polio mainly affects children under 5 years of age. However, anyone of any age who is unvaccinated can contract the disease. There is no cure for polio, it can only be prevented. Polio vaccine, given multiple times, can protect a child for life. There are two vaccines available: oral polio vaccine and inactivated polio vaccine. Both are effective and safe.^[6]

Tendinitis

Tendinitis is the inflammation of a tendon, the thick band of fibrous connective tissue that attaches a muscle to a bone. The condition causes pain and tenderness in the area around a joint. Most often, the condition results from repetitive motions over time that strain the tendons, but on rare occasions a sudden injury can cause tendinitis. Individuals who perform the same movements over and over again are often at the greatest risk of tendinitis. Some examples of this include tennis and golfer’s elbow, jumper’s knee, and swimmer’s shoulder. In all cases, overuse of the joint causes a microtrauma that initiates the inflammatory response and causes pain. Because connective tissue in the tendon does not have abundant blood supply, tendinitis heals slowly.^[7]

Box

Watch this animation to learn more about tendinitis, a painful condition caused by swollen or injured tendons.

Tetanus

Tetanus is a serious disease of the nervous system caused by a toxin-producing bacterium. The bacteria affects the neuromuscular junction and causes muscle contractions, particularly of the jaw and neck muscles. Tetanus is commonly known as lockjaw. Severe complications of tetanus can be life-threatening. There’s no cure for tetanus. Treatment focuses on managing symptoms and complications until the effects of the tetanus toxin resolve. Because of the widespread use of vaccines, cases of tetanus are rare in the United States and other parts of the developed world. The disease remains a threat to people who aren’t up to date on their vaccinations. It’s more common in developing countries.^[8]