- Muscle wasting or muscle atrophy is the loss of skeletal muscle mass which occur due to ageing, inactivity or due to various disease or underlying conditions. It can be partial or complete wasting of muscles.
- Skeletal muscle is one of the three muscle type in human body. They are attached to bone. They are responsible for many important functions and are responsible for endurance, physical performance and strength.
- It occurs when the nerve that control the muscle fiber is damaged or in bedridden people. When a person doesn’t use his muscle for long time, the muscle tissue waste away and can become loose or detached from the motor nerve. The person may experience loss of strength, decreased movement and paralysis.
Symptoms of muscle wasting
Some common symptoms associated with this condition includes:
- Reduced muscle strength.
- Decreased muscle size (one arm or leg is smaller or thinner than other).
- Loss of muscle coordination.
- Tingling or weakness of the extremities.
- Impaired balance while walking.
Causes of muscle wasting
Ageing:
- It is the common cause of gradual muscle wasting. Muscle loss with ageing is known as sarcopenia.
- As the age increases, people tend to lead more sedentary lifestyle and become less active which can cause degenerative loss of skeletal muscle mass.
Inactivity/Immobility
- If one remains inactive for prolonged period such as in coma, in bed rest due to injury or illness can cause muscle wasting. Elder people are more prone to muscle loss due to immobility.
- According to research, the rate of muscle atrophy from inactivity is 0.5-0.6% of total muscle mass per day and muscle wasting can develop within 10 days in healthy old adults during bed rest.
Malnutrition
- In people with malnutrition, muscle loss may occur due to inadequate nutritional intake leasing to muscle wasting. Malnutrition may be due to various reasons including eating disorders like anorexia, poor diet, persistent nausea or problem with absorbing nutrition from foods.
Medical conditions or disease
- Muscle loss may occur due to various neurological condition like cerebral palsy, stroke, neuropathy and spinal cord apathy. Amyotrophic lateral sclerosis, muscular dystrophy and multiple sclerosis may lead to muscle wasting.
- Amyotrophic lateral sclerosis is a progressive disease that affect nerve cells. Muscular dystrophy is a genetic condition leading to progressive muscle weakness and muscle wasting. Multiple sclerosis is autoimmune disease that affect myelin surrounding the nerve fibers and damage them.
- In person with osteoarthritis and rheumatoid arthritis, the pain may cause patient to lead sedentary lifestyle which may lead to muscle wasting. Several studies have shown that decrease in lower limb lean mass is frequent in osteoarthritic patients.
- Certain diseases can cause a complex muscle wasting syndrome called cachexia. It may be due to cancer, AIDS, chronic obstructive pulmonary disease (COPD), congestive heart failure (CHF) and chronic kidney disease.
Pathophysiology of muscle wasting
- The pathology may differ according to underlying cause. Generally, it occurs when protein degradation exceeds protein synthesis.
- A disbalance in proportion of anabolic and catabolic factors may alter nitrogen balance leading to protein depletion. There are different molecular mechanisms involved which are not completely understood.
- The two major pathways involved in protein degradation are the UPS (Ubiquitin Proteasome System) and the autophagy-lysosome pathway. UPS is responsible for degrading short-lived proteins and autophagy regulate levels of long-lived proteins in normal physiological condition.
- Several researches have shown that both pathways play important role in skeletal muscle wasting.
Diagnosis
- Diagnosis is based on physical examination, review of recent or old injuries and history of any medical condition. Tests to be performed may include blood test, X-rays, MRI (Magnetic Resonance Imaging), CT scan, electromyography, muscle or nerve biopsy and nerve conduction studies.
Treatment
- Treatment usually depends on the underlying cause.
- Exercise and physical therapy are more effective in muscle wasting due to immobility. If it is due to other disease treatment option may include hospitalization, medications, breathing support, feeding support, nutritional therapy or surgery.
- Focused ultrasound therapy is new technique in which beams of high frequency sound waves are used which stimulate muscle contraction and decrease muscle loss.
References
- Fanzani A, Conraads VM, Penna F, Martinet W. Molecular and cellular mechanisms of skeletal muscle atrophy: an update. J Cachexia Sarcopenia Muscle. 2012; 3(3): 163–179.
- Shorter E, Sannicandro AJ, Poulet B, Whysall KG. Skeletal Muscle Wasting and Its Relationship with Osteoarthritis: a Mini-Review of Mechanisms and Current Interventions. Current Rheumatology Reports. 2019; 21(40).
- Winslow MA, Hall SE. Muscle wasting: A review of exercise, classical and non‐classical RAS axes. J Cell Mol Med. 2019; 23(9): 5836–5845.
- https://www.healthline.com/health/muscle-atrophy#diagnosis