What is Muscular Atrophy, and What Causes Denervation and Disuse Atrophy?

What does atrophy mean, and what causes atrophy of a muscle?

The definition of Atrophy, according to Human Anatomy and Physiology (Marieb, 8th Edition) is "reduction in size or wasting away of an organ or cell resulting from disease or lack of use". Atrophy is also referred to as "muscle wasting".

Atrophy of a muscle can occur in 2 ways – from disuse or denervation.

Disuse atrophy will occur when a person is unable to use a muscle for any number of reasons. It is very common when a limb has been cast from a break or fraction, or a person has been on bed rest for a extended length of time. Once a person is mobile again, or a cast has been removed, the client should undergo a rehabilitation process designed to challenge and strengthen the involved structures. Assuming that the atrophy was only caused by lack of use, the patient will eventually regain strength and normal size of the muscle.

Denervation atrophy occurs when the nerve supply to a muscle is interrupted and the muscle no longer receives signals or stimulus from the nervous system. This type of atrophy can occur from injury to the central nervous system, as in a spinal cord injury, or in the peripheral nervous system, such as a broken bone which damages surrounding nerve. Damage does not necessitously mean a complete severing of the nerve, in which case nerve tissue is not known to regenerate. Damage will occur in varying degrees of severity, and may be a result of compression (impingement), crushing or partial tearing. If this is the case, with proper care and rehabilitation the injury will heal and muscle strength can be regained.

Why is this important to a Massage Therapist?

Massage therapists are specialists in treating the dysfunctions of the musculoskeletal system, and understanding the anatomy of the involved structures is key to providing a successful treatment. Odds are that you will see quite a few conditions through your career that will either cause, or have the potential to cause, muscle atrophy. Conditions such as chronic Thoracic Outlet Syndrome or Carpal Tunnel Syndrome may cause denervation atrophy due to impingement or compression of the ulnar nerve root and median nerve respectably, and can be successfully resolved once the underlying cause of the compression has been addressed.

Atrophied tissue is very fragile, and deep techniques are contraindicated until the condition of the tissue improves. Initially, the primary goal of treatment for atrophied tissue is to increase circulation and to stimulate the nerves – this can be accomplished by gentle dry brushing, followed up by light stimulating techniques such as stroking, effleurage or c-scooping. Great care must be taken if there has been crushing or teething of the nerve, as any local techniques which apply pressure or traction can disrupt the healing of the injury.

It is highly recommended that you consult with the client's physician, physiotherapist or chiropractor to verify the cause of atrophy, and that you work under his or her supervision and guidance if the atrophy is caused by denervation.