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Muscle atrophy occurs when muscle mass decreases, causing limbs and other body parts to appear smaller than normal. Atrophy can result in symptoms such as weakness, balance problems, poor coordination, and numbness. There are three main types of muscle atrophy: neurogenic, physiological, and pathologic. Each has various and unique causes, some preventable, and some not.

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Genetics and Cellular Processes

Research indicates that muscle atrophy is caused by the failure or inhibition of muscle growth. Muscle tissue mass is controlled by cellular and protein turnover. When something interrupts this process, the muscle loses mass. Protein turnover seems to have more of an impact than cellular turnover, as loss of proteins can result in rapid and significant muscle loss.

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Neurogenic Muscle Atrophy

The most severe type of muscle atrophy is neurogenic. It occurs when a disease or injury affects the nerve connected to the muscle, interfering with its ability to function as normal. Serious medical conditions can cause neurogenic muscle atrophy, as can nerve damage from diabetes, alcohol, or toxins.

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Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis or ALS is a rare neurological disease that affects the motor nerve cells that control voluntary muscle movement. This progressive disease leads to muscle atrophy and eventually affects all of the voluntary muscles in the body until the brain can no longer initiate or control movements. ALS has no cure.

ALS lou gehrig's disease funky-data / Getty Images
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Guillain-Barré Syndrome

Guillain-Barré syndrome or GBS is a rare autoimmune disorder that causes the immune system to attack the nerves, leading to weakness, muscle atrophy, and even paralysis. Most people recover, but some have permanent nerve damage that causes permanent muscle loss. GBS is usually triggered by a GI or respiratory illness or, very rarely, an adverse reaction to a vaccine. It affects about 1 in 100,000 people each year in the U.S.

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Polio

Another disease that attacks the nerves and can lead to neurogenic muscle atrophy is poliomyelitis or polio. It is caused by a virus spread from person to person, and the symptoms can vary from none at all to full paralysis. Treatment centers on managing the symptoms while the infection runs its course, but the wide availability of the polio vaccine has reduced the number of cases dramatically.

polio patient legs Leif Skoogfors / Getty Images
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Physiologic Muscle Atrophy

Physiologic muscle atrophy is caused by underuse of the muscles and most often affects those who are immobile or bedridden because of a long-term illness, stroke, or other conditions affecting mobility or brain function. This type of muscle atrophy also occurs in people who spend a lot of time seated or have a sedentary lifestyle. Astronauts can also experience physiological muscle atrophy after spending extensive time in space.

bed rest atrophy Dana Neely / Getty Images
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Promising Research

Interesting research in ongoing into the relationship between mitochondrial dysfunction and physiologic muscular atrophy. The hope is that, in the future, advancements in this area can lead to therapeutic prevention of muscle wasting from disuse by protecting the mitochondria against the damage that occurs during prolonged periods of inactivity.

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Pathologic Muscle Atrophy

Pathologic muscle atrophy is caused by a condition or disease, but it is not the same as neurogenic muscle atrophy, which affects the nerves directly and the muscles peripherally. Rather, this type occurs due to aging, malnutrition, or high doses of corticosteroids. The latter can happen when a person takes this medication to treat a condition like asthma, arthritis, or COPD. As such, it is important that people with these conditions be informed about corticosteroid-induced muscle atrophy.

malnutrition muscle mass Zinkevych / Getty Images
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Testing

Testing for muscle atrophy will likely depend on what the doctor believes is the underlying cause. For example, blood tests can evaluate for malnutrition, while MRI and CT scans can identify issues in the brain or nerves. Nerve conduction studies test how well the nerves relay information and muscle biopsies can identify any issues within the muscles themselves.

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Diagnosis and Treatment

Testing is sometimes needed to confirm an underlying diagnosis, but the doctor will also ask a lot of questions about the characteristics of the muscle atrophy, as well. Most importantly, they need to know about any other symptoms and whether or not the muscle atrophy is progressing. There is usually no treatment for neurologic muscle atrophy, but physiologic and, at times, pathologic forms are treated with physical therapy to rebuild strength and encourage muscle growth.

physical therapy senior SetsukoN / Getty Images

Disclaimer

This site offers information designed for educational purposes only. You should not rely on any information on this site as a substitute for professional medical advice, diagnosis, treatment, or as a substitute for, professional counseling care, advice, diagnosis, or treatment. If you have any concerns or questions about your health, you should always consult with a physician or other healthcare professional.