Muscle Atrophy

Background

EarlyStages keyMuscle atrophy refers to a decrease in muscle mass that may arise secondary to a variety of diseases and conditions. Most commonly, muscle atrophy develops in the setting of continued disuse or prolonged immobility, such as seen in bedridden people and those living a sedentary lifestyle. While much less common, the most severe type of muscle atrophy occurs when there is an insult to the nerves that supply muscle fibers; this type of atrophy is referred to as neurogenic atrophy and generally has a faster onset than disuse atrophy. Several diseases are known to affect the nerves that control muscles including: Amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease), Guillain-Barre syndrome, Poliomyelitis, muscular dystrophy and motor neuropathy (i.e. diabetic neuropathy). Moreover, muscle atrophy is a co-morbidity of several common diseases including cancer, AIDS, congestive heart failure, COPD, and malnutrition.

Muscle atrophy from any cause generally manifests as muscle weakness, as the ability to exert force is related to muscle mass. In neurogenic atrophy, postural weakness with subsequent stooped posture is a common presenting symptom. Depending on the cause, atrophy may affect only one muscle or the entire body, and may be associated with numbness, pain and/or swelling of an injured area. Other symptoms may include back pain, difficulty with walking, limited range of motion, and even heart failure.

Current Treatment

Disuse atrophy can often be treated with restoration of appropriate exercise. Depending on severity, physical rehabilitation may be advised. In cases of severe muscle atrophy, anabolic steroids may also be utilized to promote muscle growth.

Muscle atrophy caused by nerve damage may require musculoskeletal manipulations, anti-inflammatory medications such as corticosteroids, and even surgery to reduce pressure on injured nerves. Low voltage electrical stimulation has also been used to stimulate denervated muscles in individuals with peripheral nerve damage. Unfortunately, in the case of incurable and progressive neurogenic diseases, treatment options are often limited and involve adequate pain management and mechanical aids to assist with daily living.

Focused Ultrasound Research

Pre-clinical research is currently being conducted to investigate the role of therapeutic ultrasound (US) in muscle atrophy. Studies have shown that the mechanical effects of pulsed focused ultrasound can stimulate targeted neurons that subsequently trigger the activation and propagation of neural signals. A recent study showed a decreased degree of muscle fiber atrophy in immobilized muscle tissue treated with pulsed focused ultrasound over a 4-week period, compared to the control group. This may partly be due to activation of satellite cells. Initial findings also suggest that focused ultrasound may prevent decreased joint mobility and collagen fibril movement that is associated with prolonged joint immobilization.

Notable Papers

Matsumoto Y, Nakano J, Oga S, Kataoka H, Honda Y, Sakamoto J, Okita M. The non-thermal effects of pulsed ultrasound irradiation on the development of disuse muscle atrophy in rat gastrocnemius muscle. Ultrasound Med Biol. 2014

Okita M, Nakano J, Kataoka H, Sakamoto J, Origuchi T, Yoshimura T. Effects of therapeutic ultrasound on joint mobility and collagen fibril arrangement in the endomysium of immobilized rat soleus muscle. Ultrasound Med Biol. 2009 Feb;35(2):237-44.

W. J. Tyler, Y. Tufail, M. Finsterwald, M. L. Tauchmann, E. J. Olson, and C. Majestic, “Remote excitation of neuronal circuits using low-intensity, low-frequency ultrasound.,” PLoS ONE, vol. 3, no. 10, Oct. 2008.


     

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