Sciatic nerve dysfunction

Alternative names:

neuropathy - sciatic nerve

Definition:

A condition involving impaired movement and/or sensation in the leg, caused by damage to the sciatic nerve

Causes, incidence, and risk factors:

Sciatic nerve dysfunction is a form of peripheral neuropathy. It occurs when there is damage to the sciatic nerve, which is located in the leg and supplies the muscles of the back of the knee and lower leg. It supplies sensation to the back of the thigh, part of the lower leg, and the sole of the foot. Incomplete damage to the sciatic nerve may appear identical to damage to one of the branches of the sciatic nerve (tibial nerve dysfunction or common peroneal nerve dysfunction).

Dysfunction of a single nerve group, such as the sciatic nerve, is classed as mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although systemic disorders may occasionally cause isolated nerve damage (such as occurs with mononeuritis multiplex). The usual causes are direct trauma (often from an injection into the buttocks), prolonged external pressure on the nerve, and pressure on the nerve from nearby body structures. Entrapment involves pressure on the nerve where it passes through a narrow structure. The damage includes destruction of the myelin sheath of the nerve or destruction of part of the nerve cell (the axon). This damage slows or prevents conduction of impulses through the nerve.

The sciatic nerve is commonly injured by fractures of the pelvis or by gunshot wounds or other trauma to the buttocks or thigh. The nerve may be injured during intramuscular injections into the buttocks. It may also be injured by prolonged sitting or lying with pressure on the buttocks. It is commonly affected by systemic diseases causing polyneuropathy (damage to multiple nerves) such as diabetes mellitus or polyarteritis nodosa. It may be damaged by pressure from lesions such as a tumor, abscess, or bleeding in the pelvis. In many cases, no cause can be identified. These mechanical factors may be complicated by ischemia (lack of oxygen from decreased blood flow) in the area. A ruptured lumbar disk may cause symptoms that simulate the symptoms of sciatic nerve dysfunction.