Muscle atrophy

Definition

Muscle atrophy is the wasting or loss of muscle tissue.

Alternative Names

Muscle wasting; Wasting; Atrophy of the muscles

Considerations

There are two types of muscle atrophy.

• Disuse atrophy occurs from a lack of physical activity. In most people, muscle atrophy is caused by not using the muscles enough. People with seated jobs, medical conditions that limit their movement, or decreased activity levels can lose muscle tone and develop atrophy. This type of atrophy can be reversed with exercise and better nutrition. Bedridden people can have significant muscle wasting. Astronauts who are away from the Earth's gravity can develop decreased muscle tone after just a few days of weightlessness.
• The most severe type of muscle atrophy is neurogenic atrophy. It occurs when there is an injury to, or disease of, a nerve that connects to the muscle. This type of muscle atrophy tends to occur more suddenly than disuse atrophy.

Examples of diseases affecting the nerves that control muscles:

• Amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease)
• Guillain-Barre syndrome
• Neuropathy
• Polio (poliomyelitis)

Although people can adapt to muscle atrophy, even minor muscle atrophy usually causes some loss of movement or strength.

Common Causes

Some muscle atrophy occurs normally with aging. Other causes may include:

• Alcohol-associated myopathy
• Amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease)
• Burns
• Dermatomyositis and polymyositis
• Guillain-Barre syndrome
• Injury
• Long-term corticosteroid therapy
• Malnutrition
• Motor neuropathy (such as diabetic neuropathy)
• Muscular dystrophy
• Not moving (immobilization)
• Osteoarthritis
• Polio
• Rheumatoid arthritis  
• Spinal cord injury
• Stroke

Home Care

An exercise program (under the direction of a therapist or doctor) is recommended to help treat muscle atrophy. This may include exercises in water to reduce the muscle workload, and other types of rehabilitation.

People who cannot actively move one or more joints can do exercises using braces or splints.

Call your health care provider if

Call your doctor for an appointment if you have unexplained or long-term muscle loss. You can often see this when you compare one hand, arm, or leg to the other.

What to expect at your health care provider's office

The health care provider will perform a physical examination and ask questions about your medical history and symptoms, including:

• When did the muscle atrophy begin?
• Is it getting worse?
• What other symptoms do you have?

The doctor will look at your arms and legs and measure muscle size to try to determine which nerve or nerves are affected.

Tests that may be performed include:

• Blood tests
• CT scans
• Electromyography (EMG)
• MRI scans
• Muscle or nerve biopsy
• Nerve conduction studies
• X-rays

Treatment may include physical therapy, ultrasound therapy and, in some cases, surgery to correct a contracture.

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References

Chinnery PF. Muscle Diseases. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011: chap 429.