Muscle Atrophy

Muscle atrophy is the slow degeneration or shrinkage of muscle and nerve tissue. The leading causes of muscle degeneration include aging, malnutrition, immobility, injuries and other diseases.

Disuse of muscles causes atrophy and can lead to immobility and bed rest, but it can be reversed by physical activity, depending upon the health of the individual. Malnutrition first causes fat loss, but prolonged starvation may lead to muscle degeneration which can be reversed by nutritional therapy. Age-related muscle degeneration is sarcopenia that can be slowed down by exercise.

Muscle atrophy or degeneration of muscle is not a disease itself but a symptom or sign for an underlying disease.

Types of Muscle Atrophy

There are three types of muscle atrophy:

1. Physiologic: This type of atrophy is caused due to less usage of the muscles. It can be reversed by nutrition and exercise. People who are bedridden, those who have a seated job, people who cannot move their limbs due to stroke, those who are in limited gravity, etc. are likely to have physiologic muscle atrophy.
2. Pathologic: Pathologic muscular atrophy is caused due to aging, starvation or consuming high amounts of corticosteroids.
3. Neurogenic: It is the most serious kind of muscular atrophy that is caused due to an injury or a disease caused to nerves connecting to muscles such as polio and Guillain-Barré syndrome.

Symptoms of Muscle Degeneration

The most significant symptom of muscle degeneration is the loss of muscle. However, the loss may be difficult to detect due to obesity.

The prominent symptom of muscle degeneration is increased weakness and inability to perform physical tasks depending on the affected muscle. Muscle degeneration of the leg muscles or the core causes difficulty in standing up from a seated position, increased falls and difficulty in climbing stairs and walking.

If the throat muscles are affected, it causes difficulty in swallowing. Similarly, a difficulty in breathing is observed when the diaphragm muscles are affected.

Causes of Muscle Degeneration

Muscles are the storage sites of amino acids. These are used up when either the demand is too high or supply is too low. However, if the metabolic demands are higher than the protein synthesis, it can result in muscle loss. The causes of muscle degeneration are as follows:

1. Immobility: Disuse of muscle due to bedrest or injuries can cause approximately 0.5-0.6% of muscle loss. Elderly people are more vulnerable to muscle degeneration due to immobility.
2. Cachexia: It is a muscle wasting syndrome that is caused due to complications of other diseases such as COPD, cancer, chronic kidney diseases and AIDS. Cachexia leads to continuous muscle loss that cannot be reversed entirely.
3. Sarcopenia: Sarcopenia is muscle loss due to aging. It reduces the mass of the muscle, strength and its quality. The extent of muscle loss depends on factors such as nutrition and exercise levels.
4. Intrinsic Muscle Diseases: Muscle diseases such as muscle dystrophy, myositis and amyotrophic lateral sclerosis can also lead to muscle degeneration.
5. Central Nervous System Damage: Damage in the neurons of the brain and spinal cord can lead to muscle degeneration.
6. Peripheral Nervous System Damage: Genetic or acquired diseases in the peripheral nerves that supply specific muscles can cause loss of muscle.
7. Medications: Medications such as glucocorticoids negatively affect the muscles and can cause muscle loss.
8. Endocrinopathies: Endocrinological diseases such as Cushing’s syndrome and hypothyroidism can cause muscle atrophy.

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Also Read:

• Short Notes on Disorders of Muscular System
• Types of Muscular Dystrophy – Causes, Symptoms, Treatment
• Structure, Functions and Types of Muscular Tissue
• MCQs on Muscular Dystrophy for NEET 2022
• Skeletal Muscles – Structure, Function and Types