Sciatic nerve dysfunction

Causes and Risks:
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.

Prevention:
Prevention varies depending on the cause of the nerve damage. Avoid prolonged sitting or lying with pressure on the buttocks.

Symptoms:



Signs and Tests:
A neuromuscular examination of the legs indicates sciatic nerve dysfunction. There may be weakness of knee flexion (bending), weakness of foot movements, difficulty bending the foot inward (inversion), or bending the foot down (plantar flexion). Reflexes may be abnormal, with weak or absent ankle-jerk reflex.

Tests that reveal sciatic nerve dysfunction may include:

Tests are guided by the suspected cause of the dysfunction, as suggested by the history, symptoms presented, and pattern of symptom development. They may include various blood tests, X-rays, scans, or other tests and procedures.

Treatment:
Treatment is aimed at maximizing mobility and independence.

The cause should be identified and treated as appropriate. In some cases, no treatment is required and recovery is spontaneous.

If there is no history of trauma to the area, conservative treatment is indicated by sudden onset, minimal sensation changes and no difficulty in movement, and no evidence on testing of degeneration of the nerve axon.

Surgical removal of lesions that press on the nerve may benefit some cases.

control of symptoms:
Over-the-counter or prescription analgesics may be needed to control pain ( neuralgia ).

Various other medications may reduce the stabbing pains that some persons experience, including phenytoin, carbamazepine, or tricyclic antidepressants such as amitriptyline. Whenever possible, their use should be avoided or minimized to reduce the risk of medication side effects.

Physical therapy exercises may be appropriate for some people to maintain muscle strength.

Orthopedic assistance may maximize the ability to walk. This may include use of braces, splints, orthopedic shoes, or other appliances.

Vocational counseling, occupational therapy, occupational changes, job retraining, or similar interventions may be recommended.

Prognosis:
If the cause of the sciatic nerve dysfunction can be identified and successfully treated, there is a possibility of full recovery. The extent of disability varies from no disability to partial or complete loss of movement or sensation. Nerve pain may be severe and persist for a prolonged period of time.

Complications:

  • partial or complete loss of leg movement
  • partial or complete loss of sensation in the leg
  • recurrent or unnoticed injury to the leg
  • side effects of medications (see the specific medication)



Call Your Healthcare Provider:
Call your health care provider if you have symptoms of this disorder.