|Synonyms||Sciatic neuritis, sciatic neuralgia, lumbar radiculopathy|
|Anterior view showing the sciatic nerve going down the right leg|
|Symptoms||Pain going down the leg from the lower back, weakness or numbness of the affected leg|
|Complications||Loss of bowel or bladder control|
|Duration||90% of the time less than 6 weeks|
|Causes||Spinal disc herniation, spondylolisthesis, spinal stenosis, piriformis syndrome, pelvic tumor|
|Diagnostic method||Straight-leg-raising test|
|Treatment||Pain medications, surgery|
|Frequency||2–40% of people at some time|
Sciatica is a medical condition characterized by pain going down the leg from the lower back. This pain may go down the back, outside, or front of the leg. Onset is often sudden following activities like heavy lifting, though gradual onset may also occur. The pain is often described as shooting. Typically, symptoms are only on one side of the body. Certain causes, however, may result in pain on both sides. Lower back pain is sometimes present. Weakness or numbness may occur in various parts of the affected leg and foot.
About 90% of sciatica is due to a spinal disc herniation pressing on one of the lumbar or sacral nerve roots. Spondylolisthesis, spinal stenosis, piriformis syndrome, pelvic tumors, and pregnancy are other possible causes of sciatica. The straight-leg-raising test is often helpful in diagnosis. The test is positive if, when the leg is raised while a person is lying on their back, pain shoots below the knee. In most cases medical imaging is not needed. However, imaging may be obtained if bowel or bladder function is affected, there is significant loss of feeling or weakness, symptoms are long standing, or there is a concern for tumor or infection. Conditions that may present similarly are diseases of the hip and early herpes zoster (prior to rash formation).
Initial treatment typically involves pain medications. It is generally recommended that people continue with normal activity to the best of their abilities. Often all that is required for sciatica resolution is time; in about 90% of people symptoms resolve in less than six weeks. If the pain is severe and lasts for more than six weeks, surgery may be an option. While surgery often speeds pain improvement, its long term benefits are unclear. Surgery may be required if complications occur, such as loss of normal bowel or bladder function. Many treatments, including steroids, gabapentin, pregabalin, acupuncture, heat or ice, and spinal manipulation, have limited or poor evidence for their use.
Depending on how it is defined, less than 1% to 40% of people have sciatica at some point in time. It is most common during people's 40s and 50s, and men are more frequently affected than women. The condition has been known since ancient times. The first known use of the word sciatica dates from 1451.
The term "sciatica" usually describes a symptom—pain along the sciatic nerve pathway—rather than a specific condition, illness, or disease. Some use it to mean any pain starting in the lower back and going down the leg. Others use the term as a diagnosis (i.e. an indication of cause and effect) for nerve dysfunction caused by compression of one or more lumbar or sacral nerve roots from a spinal disc herniation. Pain typically occurs in the distribution of a dermatome and goes below the knee to the foot. It may be associated with neurological dysfunction, such as weakness and numbness. The pain is characteristically described as shooting or shock-like, quickly traveling along the course of the affected nerves.
Modifiable risk factors for sciatica include smoking, obesity, lower socioeconomic status, and occupation. Non-modifiable risk factors include increasing age, being male, and having a personal history of low back pain.
Spinal disc herniation
Spinal disc herniation pressing on one of the lumbar or sacral nerve roots is the most frequent cause of sciatica, being present in about 90% of cases. Disc herniation most often occurs during heavy lifting. Sciatica caused by pressure from a disc herniation and swelling of surrounding tissue can spontaneously subside if the tear in the disc heals and the pulposus extrusion and inflammation cease.
Other compressive spinal causes include lumbar spinal stenosis, a condition in which the spinal canal, the space the spinal cord runs through, narrows and compresses the spinal cord, cauda equina, or sciatic nerve roots. This narrowing can be caused by bone spurs, spondylolisthesis, inflammation, or a herniated disc, which decreases available space for the spinal cord, thus pinching and irritating nerves from the spinal cord that become the sciatic nerve. Sciatic pain due to spinal stenosis is most commonly brought on by standing, walking, or sitting for extended periods of time. However, pain can arise with any position or activity in severe cases. The pain is most commonly relieved by rest.
Piriformis syndrome is a controversial condition that, depending on the analysis, varies from a "very rare" cause to contributing up to 8% of low back or buttock pain. In a small population of people, the sciatic nerve runs through the piriformis muscle rather than beneath it. When the piriformis shortens or spasms due to trauma or overuse, it is posited that this causes compression of the sciatic nerve. Piriformis syndrome has colloquially been referred to as "wallet sciatica" since a wallet carried in a rear hip pocket compresses the buttock muscles and sciatic nerve when the bearer sits down. Piriformis syndrome may be suspected as a cause of sciatica when the spinal nerve roots contributing to the sciatic nerve are normal and no herniation of a spinal disc is apparent.
Sciatica may also occur during pregnancy, especially during later stages, as a result of the weight of the fetus pressing on the sciatic nerve during sitting or during leg spasms. While most cases do not directly harm the woman or the fetus, indirect harm may come from the numbing effect on the legs, which can cause loss of balance and falls. There is no standard treatment for pregnancy-induced sciatica.
Sciatica can also be caused by tumors impinging on the spinal cord or the nerve roots. Severe back pain extending to the hips and feet, loss of bladder or bowel control, or muscle weakness may result from spinal tumors or cauda equina syndrome. Trauma to the spine, such as from a car accident or hard fall onto the heel or buttocks, may also lead to sciatica. A relationship has been proposed with a latent Propionibacterium acnes infection in the intervertebral discs, but the role it plays is not yet clear.
Sciatica is generally caused by the compression of lumbar nerves L4 or L5 or sacral nerve S1. Less commonly, sacral nerves S2 or S3 or compression of the sciatic nerve itself may cause sciatica. In 90% of sciatica cases, this can occur as a result of a spinal disc bulge or herniation. Intervertebral spinal discs consist of an outer anulus fibrosus and an inner nucleus pulposus. The anulus fibrosus forms a rigid ring around the nucleus pulposus early in human development, and the gelatinous contents of the nucleus pulposus are thus contained within the disc. Discs separate the spinal vertebrae, thereby increasing spinal stability and allowing nerve roots to properly exit through the spaces between the vertebrae from the spinal cord. As an individual ages, the anulus fibrosus inevitably weakens and it becomes less rigid; thus, it is subsequently more likely to tear. When there is a tear in the anulus fibrosus, the nucleus pulposus may extrude through the tear and press against spinal nerves within the spinal cord, cauda equina, or exiting nerve roots, causing inflammation, numbness, or excruciating pain. Inflammation of spinal tissue can then spread to adjacent facet joints and cause facet syndrome, which is characterized by lower back pain and referred pain in the posterior thigh.
Other causes of sciatica secondary to spinal nerve entrapment include the roughening, enlarging, or misalignment (spondylolisthesis) of vertebrae, or disc degeneration that reduces the diameter of the lateral foramen through which nerve roots exit the spine. When sciatica is caused by compression of a dorsal nerve root, it is considered a lumbar radiculopathy or radiculitis when accompanied by an inflammatory response. Sciatica-like pain prominently focused in the buttocks can also be caused by compression of peripheral sections of the sciatic nerve usually from soft tissue tension in the piriformis or related muscles.
Sciatica is typically diagnosed by physical examination, and the history of the symptoms. Generally if a person reports the typical radiating pain in one leg as well as one or more neurological indications of nerve root tension or neurological deficit, sciatica can be diagnosed.
The most applied diagnostic test is the straight leg raise to produce Lasègue's sign, which is considered positive if pain in the distribution of the sciatic nerve is reproduced with passive flexion of the straight leg between 30 and 70 degrees. While this test is positive in about 90% of people with sciatica, approximately 75% of people with a positive test do not have sciatica. Straight raising the leg unaffected by sciatica may produce sciatica in the leg on the affected side; this is known as the Fajersztajn sign. The presence of the Fajersztajn sign is a more specific finding for a herniated disc than Lasègue's sign. Maneuvers that increase intraspinal pressure, such as coughing, flexion of the neck, and bilateral compression of the jugular veins, may worsen sciatica.
Imaging modalities such as computerised tomography or magnetic resonance imaging can help with the diagnosis of lumbar disc herniation. The utility of MR neurography in the diagnosis of piriformis syndrome is controversial.
Discography could be considered to determine a specific disc’s role in an individual’s pain. Discography involves the insertion of a needle into a disc to determine the pressure of disc space. Radiocontrast is then injected into the disc space to assess for visual changes that may indicate an anatomic abnormality of the disc. The reproduction of an individual’s pain during discography is also diagnostic.
Sciatica can be managed with a number of different treatments with the goal of restoring a person's normal functional status and quality of life. When the cause of sciatica is lumbar disc herniation (90% of cases), most cases resolve spontaneously over weeks to months. Initially treatment in the first 6–8 weeks should be conservative. More than 75% of sciatica cases are managed without surgery. Physical activity is often recommended for the conservative management of sciatica for persons that are physically able. However, the difference in outcomes between physical activity compared to bed rest have not been fully elucidated. In persons that smoke who also suffer from sciatica, smoking cessation should be strongly considered. Treatment of the underlying cause of nerve compression is needed in cases of epidural abscess, epidural tumors, and cauda equina syndrome.
There is no one medication regimen used to treat sciatica. Evidence supporting the use of opioids and muscle relaxants is poor. Low-quality evidence indicates that NSAIDs do not appear to improve immediate pain and all NSAIDs appear about equivalent in their ability to relieve sciatica. Nevertheless, NSAIDs are commonly recommended as a first-line treatment for sciatica. In those with sciatica due to piriformis syndrome, botulinum toxin injections may improve pain and function. While there is little evidence supporting the use of epidural or systemic steroids, systemic steroids may be offered to individuals with confirmed disc herniation if there is a contraindication to NSAID use. Low-quality evidence supports the use of gabapentin for acute pain relief in those with chronic sciatica. Anticonvulsants and biologics have not been shown to improve acute or chronic sciatica. Antidepressants have demonstrated some efficacy in treating chronic sciatica and may be offered to individuals who are not amenable to NSAIDs or who have failed NSAID therapy.
If sciatica is caused by a herniated disc, the disc's partial or complete removal, known as a discectomy, has tentative evidence of benefit in the short term. If the cause is spondylolisthesis or spinal stenosis, surgery appears to provide pain relief for up to two years.
Acupuncture has been shown to improve sciatica-related pain, though the supporting evidence is limited by small study samples. Low to moderate-quality evidence suggests that spinal manipulation is an effective treatment for acute sciatica. For chronic sciatica, the evidence supporting spinal manipulation as treatment is poor. Spinal manipulation has been found generally safe for the treatment of disc-related pain; however, case reports have found an association with cauda equina syndrome, and it is contraindicated when there are progressive neurological deficits.
Depending on how it is defined, less than 1% to 40% of people have sciatica at some point in time. Sciatica is most common during people's 40s and 50s and men are more frequently affected than women.
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