Home > Encyclopedia of Nursing & Allied Health > Sciatica

Definition

Sciatica describes pain or discomfort in the distribution of the sciatic nerve or its components. This nerve runs from the lower part of the spinal cord, down the back of the leg, to the foot. Injury to, or pressure on, the sciatic nerve can cause the characteristic pain of sciatica—a sharp or burning pain that radiates from the lower back or hip, following the path of the sciatic nerve to the foot.

Description

The sciatic nerve is the largest and longest nerve in the body. It supplies sensation from the lower back to the foot. The nerve originates in the lumbar region of the spinal cord. As it branches off from the spinal cord, it passes between the bony vertebrae (the component bones of the spine) and runs through the pelvic girdle (hipbones). The nerve passes near the hip joint and continues down the back of the leg to the foot.

Sciatica is a fairly common disorder. Approximately 40% of the population suffers from it at some point in their lives; however, only about 1% experience any sensory or motor deficits. Sciatic pain has several root causes, and its treatment is directed to the underlying problem.

Of the identifiable causes of sciatic pain, lumbosacral (LS) radiculopathy and back strain are the most frequently suspected. The LS area is the lower part of the spine, and radiculopathy describes pain radiating from pressure on a spinal nerve roots. This area between the vertebrae (hard bones) is cushioned with a disk of shockabsorbing tissue. The spinal canal, comprising the spinal cord and other nerve roots, is hollow and lies in the middle of the spinal column. It is the disks between the vertebrae that enable the back to bend or flex.

A "ring" of cartilage, gristle-like in character, is found the outer edge of the disk (the annulus). The disk's center (nucleus) is a substance like gel. When a disk ruptures, or herniates, it does so because of wear-and-tear, excessive weight, poor posture, injury (perhaps due to improper lifting), or disease. The center nucleus pushes the outer edge of the disk into the spinal canal, putting pressure on the nerves. The spinal nerve root may become compressed by the shifted tissue or the vertebrae. This compression of the nerve root sends a pain signal to the brain. Although the injury is actually suffered by the nerve roots, the pain may be perceived as originating anywhere along the sciatic nerve. Further, if fragments of the disk lodge in the spinal canal, the nerves that control bowel and urinary functions may be damaged. Incontinence may result.

Sciatica is largely a symptom of a herniated disk. However, compression of the sciatic nerve can also present as muscle spasms in the lower back (back strain). In this case, pressure is placed on the sciatic nerve. In rare cases, infection, cancer, bone inflammation, or other diseases may cause pressure. Another possible cause of sciatica is piriformis syndrome.

As the sciatic nerve passes behind the hip joint, it shares the space with several muscles. One of these muscles, the piriformis muscle, is closely associated with the sciatic nerve. In some people, the nerve actually runs through the muscle. If this muscle is injured or has a spasm, it places pressure on the sciatic nerve, in effect, compressing it.

In many sciatica cases, the specific cause is never identified. About half of affected individuals recover from an episode within a month. Some cases persist and may require aggressive treatment. In other cases, the pain returns or becomes chronic.

Causes and symptoms

Patients with sciatica may experience low back pain, but the most common symptom is pain that radiates through one buttock and down the back of the leg. The most frequently identified cause of pain is compression or pressure on the sciatic nerve. The extent of the pain varies. Some patients describe pain that centers in the area of the hip; others feel discomfort all the way to the foot. The quality of the pain also varies; it may be described as tingling, burning, prickly, aching, or stabbing.

Onset of sciatica may be sudden, but it might also develop gradually. The pain may be intermittent or continuous. Certain activities (such as bending, coughing, sneezing, or sitting) can worsen the pain.

Sudden loss of bowel or bladder control, weakness in the legs, buttocks, or torso, as well as numbness that goes upwards from the toes or the feet, may indicate a sciatic condition.

Chronic pain may arise from more than simple compression of the nerve root. Discogenic pain, the result of injury to the innervated portions of the annulus fibrosus, is a common cause of sciatica. Pain is generally felt in the buttocks and in the posterior thigh.

According to some pain researchers, physical damage to a nerve is only half of the equation. A theory developed in 2001 proposes that some nerve injuries result when certain neurotransmitters and immune system chemicals that exacerbate and sustain a pain message. Even after the injury has healed or the damage has been repaired, the pain lingers. Effective management of this type of pain is difficult. Another theory that has been put forward is that back problems may be inherited. This theory presupposes that a genetic abnormality is responsible for a number of cases of spinal disk disease cases. This defect makes people susceptible to rupture when the back is strained. The investigators claimed that 25% of all cases of sciatica, lower back problems, and discomfort higher in the spine, might be attributable to this gene defect. When classic symptoms are absent, identification of the defect could enable diagnosis of disease, thereby facilitating the therapeutic process.

Diagnosis

Establishing the diagnosis requires taking a thorough medical history and performing a focused physical examination. The patient is asked about the location, nature, and duration of the pain, and the details of any accidents, injuries or unusual activities that may have occurred prior to the onset of sciatica. This information provides clues that may point to back strain or injury to a specific location.

Back pain from disk disease, piriformis syndrome, and back strain must be differentiated from more serious conditions, such as cancer or infection. In spring 2001, Dr. T. S. J. Elliott, professor of microbiology at University Hospital in Birmingham, England, conducted a new study—the results of which were published in The Lancet. The doctor found hidden infections in 43 of 140 sciatica (30.7%) patients who suffered from persistent pain originating in the sciatic nerve. (The sciatic nerve of the leg is the largest nerve in the body.) Dr. Elliott believes that when the spine suffers a minor trauma, an organism enters the body. This organism causes sciatica that is continuous, with the resulting inflammation being caused by the infection. Further, he postulated that if imaging studies do not show injury, then there may be something to the physician's study.

More investigations need to be done, however, evaluating the success of antibiotics (used to fight infections) in treating sciatica. Lumbar spine stenosis, an overgrowth of the covering layers of the vertebrae that narrows the spinal canal, must also be considered.

A straight leg-raising test is often performed. The patient lies supine, and the health care provider raises the affected leg to various heights. This test pinpoints the location of the pain and may reveal whether it is caused by a disk problem. Other tests, such as observing the patient rotate the hip joint, may provide information about involvement of the piriformis muscle if the patient experience pain. Piriformis weakness is tested with additional leg-strength maneuvers.

Further tests may be conducted depending on the patient's history, results of the physical examination, and response to initial treatment. Diagnostic tests may include traditional x rays, magnetic resonance imaging (MRI), and computed tomography scans (CT scans). Other tests include electromyography (studies of the electrical activity generated as muscles contract), nerve conduction velocity testing, and evoked potential testing. Myelography, a more invasive test, involves injecting a contrast medium into the spinal subarachnoid space between the vertebrae and taking x-ray images of the spinal cord. Myelography is usually ordered when surgical treatment is considered. Since the advent of MRI, however, myelography is very rarely used. The MRI does not use ionizing radiation. Noninvasive, it produces excellent computerized images of soft tissues, such as seen in herniated discs and tumors. The MRI is based on nuclear magnetic resonance of atoms within the body; the atoms are generated by the use of radio waves. All these tests can reveal problems with the vertebrae, the disk, or the nerve itself.

Treatment

Pharmacological therapy—initial treatment for sciatica—focuses on pain relief. Regardless of the cause of the pain, analgesics (such as acetaminophen) may help relieve pain. Muscle relaxants are also used, but it hasn't been proved whether they really work. Furthermore, the side effects of muscle relaxants may be greater than their benefits, particularly in the elderly. Generally, pain relief is accomplished with nonsteroidal anti-inflammatory drugs (NSAIDs). It should be noted, however, that anti-inflammatory medications should be administered generally for only two to four weeks, and only if no medical contraindications are present. As of 2001, the Food and Drug Administration (FDA) had also approved labeling two newer drugs for the relief of pain; they are rofecoxib (Vioxx), a NSAID with selective cyclo-oxygenase 2 inhibition); and celecoxib (Celebrex). Both have fewer gastrointestinal side effects, but must be taken advisedly by the patient at risk for peptic ulcer disease.

If the pain is unremitting, opioids may be prescribed for short-term use or a local anesthetic may be injected directly into the lower back. Massage and heat application may be suggested as adjunct therapies.

If the pain is chronic, different pain relief medications are used to avoid long-term dosing of NSAIDs, muscle relaxants, and opioids. Antidepressant drugs, which have been shown to be effective in treating pain, may be prescribed in conjunction with a short-term course of a muscle relaxants or a NSAID. Local anesthetic injections, or epidural steroids, are used in selected cases.

As pain permits, physical therapy is introduced into the treatment regime. Stretching exercises that focus on the lower back, buttocks, and hamstring muscles are suggested. The exercises may also include identifying and practicing comfortable, pain-reducing positions. Corsets and braces may be useful in some cases, but there is not any clinical evidence for their general effectiveness as of 2001. However, they may be helpful in the prevention of exacerbation of sciatica as related to certain activities.

With less pain and the success of early therapy, the patient is encouraged to follow a long-term exercise program to maintain a healthy back and prevent re-injury. A physical therapist may suggest exercises and regular activity, such as water exercise or walking. Patients are instructed in proper posture and body mechanics as means of minimizing symptoms during light lifting, prolonged sitting or standing, and other activities.

If the pain is chronic and conservative treatment fails—suggesting that a disk fragment has lodged in the spinal canal and is pressing on the nerve (and perhaps causing a loss of function—surgery may be required. A procedure to repair a herniated disk or excise part, or all of the piriformis muscle, may be suggested, particularly if there is neurologic evidence of nerve or nerve-root damage (radiculopathy). It should be noted, however, that as of 2001, newer and minimally invasive procedures are available to relieve the pain of sciatica. A local anesthetic is used, and surgery is performed on an ambulatory basis. The recovery period is two to six weeks.

Massage is a recommended form of therapy, especially when the sciatic pain arises from muscle spasm. Patients may be able to relieve symptoms by icing the painful area as soon as pain occurs. The physical therapist or nurse may instruct the patient to place ice on the affected area for 20 minutes, several times a day. After two to three days, a hot water bottle or heating pad can replace the ice. Chiropractic or osteopathic therapy may offer solutions for relieving pressure on the sciatic nerve and the accompanying pain. Acupuncture and biofeed-back may also be useful as pain control methods.

Prognosis

Most cases of sciatica are treatable with pain medication and physical therapy. After four to six weeks of treatment, the patient should be able to resume normal activities.

Health care team roles

The diagnosis of sciatica is usually made by a PCP or a mid-level practitioner (physician assistant [PA] or nurse practitioner [NP]). Other physician specialists, such as neurologists, orthopedists, and physiatrists (specialists in physical medicine) also may provide consultative services. Radiologic technologists generally perform diagnostic imaging studies.

The treatment plan may involve physical therapists (PTs) and physical therapist assistants (PTAs), who instruct and supervise prescribed exercise programs. Patients also may be referred to specialists in orthotics, who prescribe appliances/apparatuses to support, align, prevent, or correct deformities, improve posture, or ease the function of movable body parts. Sometimes specialists work with ergonomics. The patient may be taught proper body mechanics at home and in the workplace.

Patient education

Patient education focuses on adhering to prescribed treatment, including exercise and body mechanics (above), and preventing future injuries. Nurses, PTs, PTAs, occupational therapists, and exercise physiologists may be involved in helping patients learn how to perform the activities of daily living (ADL) without exacerbating existing injuries.

Prevention

Some sources of sciatica are not preventable, such as disk degeneration, back strain resulting from pregnancy,

or accidental injuries from falls. Other sources of back strain, such as poor posture, overexertion, obesity, or wearing high heels, may be corrected or avoided. Smoking may also predispose patients to pain, as it the supply of blood to invertebral discs, and interferes with healing. An orthopedist with the Gwinnett Health System in Lawrenceville, Georgia, Dr. Walker states that "Smoking leads to drying and stiffness of the discs, making them more susceptible to injury, including herniation, and prolonged recovery time."

General suggestions for avoiding sciatica or preventing future episodes include sleeping on a firm mattress, using chairs with firm back supports, and sitting with both feet flat on the floor. Habitually crossing the legs while sitting may place excess pressure on the sciatic nerve. Sitting for prolonged periods of time also places pressure on the sciatic nerves, so patients are advised to take short breaks and move around during the workday, when on long trips, or in other situations that require sitting for extended lengths of time. When sitting for long periods, the patient should put his or her feet up on a low stool. If it is required that something be lifted without another person, the back should be kept straight and the legs should provide the lift. The knees should be bent, and the individual should get as close to the object as possible. This will reduce the load on the lower back. To give one a wider base of support and to distribute the weight of the object being lifted, the feet should be kept apart.

Regular exercise, such as swimming and walking, can build stamina, strengthen back muscles, improve flexibility, and improve posture. Exercise also helps to maintain proper body weight and lessens the likelihood of back strain.

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KEY TERMS

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Acupunture—The Chinese practice of piercing specific areas of the body along peripheral nerves with fine needles to relieve pain, to induce surgical anesthesia, and for therapeutic purposes.

Biofeedback—The process of furnishing an individual with information on the state of one or more physiologic variables, such as heart rate, blood pressure, or skin temperature. The goal is to enable the patient to gain some voluntary control over them.

Disk—Dense tissue between the vertebrae that acts as a shock absorber and prevents damage to nerves and blood vessels along the spine.

Electromyography—A diagnostic test in which a nerve's ability to conduct an impulse is measured.

Lumbosacral (LS)—Referring to the lower part of the backbone or spine.

Myelography—A medical test in which a special dye—a contrast medium—is injected the spinal subarachnoid space (through which cerebrospinal fluid [CSF] circulates, and across which extend delicate connective tissue pass) to make it visible on radiographic visualization.

NSAID—Nonsteroidal anti-inflammatory drugs are medications that produce analgesic and antiinflammatory effects.

Opioid—A synthetic narcotic that has opiate-like qualities, but is not derived from opium.

Orthotics—Serving to protect or to restore or improve function; relating to the use or application of an orthosis.

Piriformis—A muscle in the pelvic girdle that is closely associated with the sciatic nerve.

Radiculopathy—A condition in which the nerve root of a nerve has been injured or damaged.

Spasm—Involuntary contraction of a muscle.

Spinal subarachnoid space—Space through which which cerebrospinal fluid circulates, and across which extend delicate connective tissue pass.

Vertebrae—The component bones of the spine.

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Barbara Wexler