Sciatic neuropathy

Definition

Sciatica is a term given to any painful condition of the leg that originates in the lower back and descends down the leg. Because it tends to involve a single nerve tract it is designated as mononeuropathy (localized nerve disorder).

The cause of this pain is the neuropathy defined by the inflammation and swelling of the large sciatic nerve that originates from the exit of an intervertebral nerve plexus between one of the large lumbar vertebral discs. A portion of the sciatic nerve also originates from the sacrum. The name for the region from which this nerve emanates is the sacral plexus. It encompasses the lumbar vertebra L 4–5 through the sacral vertebra S 1–3. The intervertebral nerves join to form one of the larger nerve tracts in the body, the sciatic nerve. This nerve tract winds over the pelvic bones and down the proximal posterior side of the femurs (either right or left). From there it branches into the tibial and common peroneal nerve. Further branching produces the deep peroneal nerve.

An inflammation or irritation of this nerve can produce pain that ranges anywhere from mild discomfort to extreme distress. Many sufferers describe a constant pain that does not ease with change in body position or conventional medications. The pain can originate from a small area of the lower back to running along the hip, and down the leg past the ankle to the foot.

Additional symptoms of sciatic neuropathy that distinguish it from peripheral neuropathy include sensation changes. These occur on the soles of the foot and up the leg. They may include numbness and tingling and even a burning sensation. Difficulty in walking is common and, in serious conditions, there may be an inability to move the foot or knee.

Description

The most common source of inflammation of the sciatic nerve and its branches is injury to an intervertebral disc. This neuritis (nerve inflammation) may occur when pressure on the disc forces it to rupture, squeezing some of the softer more gelatinous interior against the nerve. In turn, this constant pressure begins to irritate the sciatic nerve until eventual swelling from inflammation occurs. The irritation is transmitted to the brain and the patient experiences constant or intermittent pain of varying degrees.

Depending on the degree of herniation to the disc, the pain may eventually go away or the patient may consider lower back surgery. Surgery is the most extreme form of treatment for this condition, as most cases will be relieved with exercise and anti-inflammatory medications. Healing may be slow and take up to six weeks.

A common source of sciatic neuropathy is wounding of the sciatic nerve. This condition presents itself when a person has been forced to lie down for extended lengths of time. The resulting pressure on the nerve and lack of movement produces neuropathy. This condition is often confused with tibial nerve dysfunction or common nerve dysfunction.

Wounds to the sciatic nerve may result from fractures of the pelvis, gunshots, or blunt objects such as a bat or stick. Car injuries may often produce damage to the sciatic nerve. Physiological damage can also result from diabetes or an abscess.

Another possible cause of pressure on the sciatic nerve is that imposed by a tumor. Again, surgery may be considered to treat this form of sciatica. The physician may offer alternative therapies to treat the tumor, but therapies are case dependent and vary widely. In cases where tumors are present, the primary cause of the sciatica usually requires treatment that is are not aimed specifically at resolving the sciatica.

Direct trauma to the sciatic nerve may also produce inflammation. A fall or a puncture from an injection could produce insult to the nerve tissues and result in sciatica. In these cases, the treatment is simple and effective. Movement and anti-inflammatory medications usually improve the situation until it eventually resolves.

Demographics

While there varying demographics regarding sciatica, there are conditions that may alert a physician to look for underlying cause of the condition. People under 20 or over 55 are often examined for additional symptoms of other disorders. Associated pain in the back of the chest is a concern along with recent major injury as the type sustained from a traffic injury.

Included in the groups of patients who receive additional examination when they complain of sciatica are those who have lost weight recently, have had cancer, are on steroids, have worsening pain, and those who have developed other nervous system disorders in the past.

Causes and symptoms

As previously noted, the most common cause of sciatica is a "slipped" or herniated disk, also called a prolapsed intervertebral disk (PID) or a herniated nucleus pulposus. Any trauma or injury to the nerve will result in swelling and inflammation. While this healing condition persists, the nerve will respond with pain, which in turn, will often reduce normal movement.

Rarely, sciatic neuropathy has been reported after surgical procedures that required the patient to be immobilized in the operating room for long periods of time or in positions that may have irritated the sciatic nerve.

Diagnosis

Sciatica is in itself a symptom of some other condition which must be diagnosed by a physician. The root causes of the disorder may vary. Only a professional who is trained in recognizing the information provided by the patient and laboratory results can determine if or whether the condition is an isolated symptom or a symptom of a more general or serious disorder of the patient.

Although the diagnosis is based primarily upon symptoms of pain, the physician will usually test for muscle strength, reflexes and flexibility while considering a diagnosis of sciatic neuropathy. Areas of spinal problems that may cause sciatic nerve irritation or compression are usually visible on MRI or CT images. Occasionally, further nerve function tests may be necessary.

Treatment team

Physicians are the first contact to be made in a treatment team. It is the physician who must first make the diagnosis. A radiologist or laboratory technician may take x rays of the area to look for bone spurs of disk protrusions. Once the diagnosis is made the pharmacist may be called to provide appropriate medication for treatment. In more severe cases, a physical therapist may be used to keep the patient active and performing physical tasks that help reduce the pain. With intractable pain, a neurosurgeon may be consulted for surgery.

Treatment

The immediate treatment of most cases of sciatica is to recommend medications specific to the inflammation. Staying active is also highly recommended, while avoiding activities that put pressure on the back. Studies have found that a simple combination of anti-inflammatory medication such as ibuprofen and mild exercise, such as walking, are effective treatment for most cases of common sciatica. Sometimes an epidural injection (an injection to the epidural space of the spine) may provide pain relief. Surgery for a herniated disk is an aggressive alternative, and includes more risk.

Recovery and rehabilitation

The majority of patients suffering with sciatica recover in a few weeks to six or seven weeks. While the pain may be intense for some sufferers, it is usually temporary. With treatment, person has an excellent chance for reduction or resolution of the neuropathy pain of sciatica.

Clinical trials

A large clinical trial testing the effectiveness of new drug therapies is being conducted by the National Institute of Dental and Craniofacial Research (NIDCR). This may seem like an unlikely group to sponsor such a trial, but any study that examines the effectiveness of medication on nerves may be of great aid to patients suffering from sciatica. Information on additional clinical trials can be found at the United States government website for clinical trials: <http://www.clinicaltrials.gov>.

Prognosis

The prognosis for the pain relief of most cases of sciatica is excellent. With a combined use of anti-inflammatory drugs and mild exercise, such as walking, sciatica can be reduced and even eliminated. If the underlying cause is more serious, the prognosis varies with the degree of severity and type of condition.

Special concerns

One of the myths associated with sciatica is the need to rest in bed. In fact, mild exercise is one of the best treatments for the pain. Prolonged sitting is a primary cause of many cases of sciatica. If a job requires extended periods of sitting, it is wise to take short walks or perform mild stretches to keep compression of the lower lumbar vertebrae from occurring.

Resources

BOOKS

Burn, Lois. Back and Neck Pain: The Facts. New York: Oxford University Press, 2000.

Fishman, Lauren, and Carol Ardman. Back Pain: How to Relieve Low Back Pain and Sciatica. New York: W. W. Norton & Company, 1999.

OTHER

National Library of Medicine. "Sciatica." MEDLINE plus. (February 11, 2004). <http://www.nlm.nih.gov/medlineplus/sciatica.html>.

ORGANIZATIONS

American Chronic Pain Association (ACPA). P.O. Box 850, Rocklin, CA 95677. (916) 632-0922 or (800) 533-3231; Fax: (916) 632-3208. [email protected]. <http://www.theacpa.org/>.

National Institute of Arthritis and Musculoskeletal and Skin Dieseases (NIAMS). National Institutes of Health, Bldg. 31, Rm. 4C05, Bethesda, MD 20892. (301) 496-8188; Fax: (540) 862-9485. [email protected]. <http://www.niams.nih.gov/index.htm>.

Brook Ellen Hall, PhD