Distal median nerve dysfunction

Alternative names:

neuropathy - distal median nerve

Definition:

A form of peripheral neuropathy (disease of the nerves) involving impaired movement and/or sensation of the thumb caused by damage to the distal median nerve.

Causes, incidence, and risk factors:

Distal median nerve dysfunction occurs when there is damage to the distal portion of the median nerve, which travels down the arm and provides movement and sensation to the thumb. (The distal portion is the part closest to the hand.) Carpal tunnel syndrome, another form of median nerve dysfunction, is one of the more common peripheral neuropathies.

Dysfunction of a single nerve group, such as the distal median nerve, is classed as mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although occasionally systemic disorders may cause isolated nerve damage (such as occurs with mononeuritis multiplex). The usual causes are direct trauma, prolonged pressure on the nerve, and compression of the nerve by nearby body structures. Entrapment involves pressure on the nerve where it passes through a narrow structure.

Wrist fractures may injure the median nerve. The nerve may be compressed at the wrist because of tendonitis, arthritis, or conditions that affect connective tissue or cause deposits in the tissues (such as multiple myeloma, pregnancy, acromegaly, and hypothyroidism). In some cases, no detectable cause can be identified. These mechanical factors may be complicated by lack of oxygen from decreased blood flow (ischemia) in the area.

Carpal tunnel syndrome may be associated with entrapment of the nerve following prolonged or repeated pressure on the wrist area (such as may occur with repetitive wrist movements). This is a fairly common occupational or recreational injury.