Sciatica

Alternative names
Neuropathy - sciatic nerve; Sciatic nerve dysfunction

Definition
Sciatica is a condition involving pain, weakness, numbness, or tingling in the leg. It is caused by injury to or compression of the sciatic nerve.

Causes, incidence, and risk factors

Sciatica is a form of peripheral neuropathy. It occurs when there is damage to the sciatic nerve, located in the back of the leg. This nerve controls the muscles of the back of the knee and lower leg and provides 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).

A problem in a single nerve group, such as the sciatic nerve, is classified as a mononeuropathy. The usual causes are direct trauma (often due to an injection into the buttocks), prolonged external pressure on the nerve, and pressure on the nerve from nearby body structures. It can also be caused by entrapment - pressure on the nerve where it passes through a narrow structure. The damage slows or prevents conduction of impulses through the nerve.

The sciatic nerve is commonly injured by fractures of the pelvis, gunshot wounds, or other trauma to the buttocks or thigh. Prolonged sitting or lying with pressure on the buttocks may also injure it. Systemic diseases, such as Diabetes, can typically damage many different nerves, including the sciatic nerve. The sciatic nerve may also be harmed by pressure from masses such as a tumor or abscess, or by bleeding in the pelvis.

In many cases, no cause can be identified.

Note: A ruptured lumbar disk in the spine may cause symptoms that simulate the symptoms of sciatic nerve dysfunction.

Symptoms

     
  • Sensation changes       o Of the back of the calf or the sole of the foot       o Numbness, decreased sensation       o Tingling, burning sensation       o Pain, may be severe       o Abnormal sensations  
  • Weakness of the knee or foot       o Difficulty walking       o Inability to move the foot (in severe cases)       o Inability to bend the knee (in severe cases)

Signs and tests

Sciatica might be revealed by a neuromuscular examination of the legs by a physician. There may be weakness of knee bending or foot movement, or difficulty bending the foot inward or down. Reflexes may be abnormal, with weak or absent ankle-jerk reflex. Pain down the leg can be reproduced by lifting the leg straight up off the examining table.

Tests that reveal sciatic nerve dysfunction may include:

     
  • EMG (a recording of electrical activity in muscles)  
  • Nerve conduction tests

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

Treatment

Treatment is aimed at maximizing mobility and independence. The cause of the nerve dysfunction should be identified and treated as appropriate. In some cases, no treatment is required and recovery is spontaneous.

Conservative treatment is usually appropriate if there was sudden onset, minimal sensation changes, no difficulty in movement, no history of trauma to the area, and no evidence of degeneration of the nerve axon.

Surgical removal of lesions that press on the nerve, such as a herniated disc, may relieve symptoms. In cases of severe injury to the nerve, such as laceration, recovery may be not possible or may be limited.

Injections can be used to reduce inflammation around the nerve. Over-the-counter or prescription analgesics may be needed to control nerve pain.

Various other medications may reduce the stabbing pains that some people experience, including phenytoin, carbamazepine, or tricyclic antidepressants such as amitriptyline. Steroids may help with nerve inflammation related to a herniated disc. 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. The use of braces, splints, orthopedic shoes, or other appliances may help compensate for lost or impaired function. Vocational counseling, occupational therapy, occupational changes, job retraining, or similar interventions may be recommended.

Expectations (prognosis)

If the cause of the sciatic nerve dysfunction can be identified and successfully treated, full recovery is possible. 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

Calling your health care provider

Call your health care provider if you have symptoms of this disorder. Nerve pain is very difficult to treat. If you have ongoing problems with pain, you may want to see a pain specialist to ensure that you have access to the widest range of treatment options.

Prevention

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

Johns Hopkins patient information

Last revised: December 4, 2012
by Janet G. Derge, M.D.

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