A set of symptoms including pain caused by general compression or irritation of one of five spinal nerve roots of each sciatic nerve—or by compression or irritation of the left or right or both sciatic nerves is called Sciatica. The term sciatica describes a symptom rather than a specific disease. Some use it to mean any pain starting in the lower back and going down the leg. Others use the term more specifically to mean a nerve dysfunction caused by compression of one or more lumbar or sacral nerve roots from a spinal disc herniation. It may be associated with neurological dysfunction, such as weakness. The pain is characteristically of shooting type, quickly traveling along the course of the nerve.
Spinal disc herniation pressing on one of the lumbar or sacral nerve roots is the primary cause of sciatica, being present in about 90% of cases. 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 spaces the spinal cord runs through narrows and compresses the spinal cord, cauda equina, or sciatic nerve roots. Piriformis syndrome is a condition that contributing to up to 8% of low back or buttock pain. In 15% of the population, the sciatic nerve runs through, or under the piriformis muscle rather than beneath it. When the muscle shortens or spasms due to trauma or overuse, it's posited that this causes compression of the sciatic nerve It 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 cause sciatica when the nerve root is normal. Sciatica may also occur during pregnancy as a result of the weight of the foetus pressing on the sciatic nerve during sitting or during leg spasms. Sciatica can also be caused by tumours 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 tumours or cauda equina syndrome. Trauma to the spine, such as from a car accident, may also lead to sciatica.
Symptoms include lower back pain, buttock pain, and numbness, pain or weakness in various parts of the leg and foot. Other symptoms include a "pins and needles" sensation, or tingling and difficulty moving or controlling the leg. Typically, symptoms only manifest on one side of the body. The pain may radiate above the knee, but does not always.
Sciatica is generally caused by the compression of lumbar nerves L4, or L5 or sacral nerves S1, S2, or S3, or by compression of the sciatic nerve itself. When sciatica is caused by compression of a dorsal nerve root (radix), it is considered a lumbar radiculopathy . This can occur as a result of a spinal disk bulge or spinal disc herniation or from roughening, enlarging, or misalignment of the vertebrae, or as a result of degenerated discs that can reduce the diameter of the lateral foramen through which nerve roots exit the spine.
The intervertebral discs (anulus fibrosus), form a ring surrounding the inner nucleus pulposus. When there is a tear in the anulus fibrosus, the nucleus pulp may extrude through the tear and press against spinal nerves within the spinal cord or exiting nerve roots, causing inflammation, numbness, excruciating pain.
Sciatica is diagnosed by physical examination, and the history of the symptoms.
The most applied diagnostic test is the straight leg raise. if pain in the distribution of the sciatic nerve is reproduced with between 30 and 70 degrees passive flexion of the straight leg, it is considered positive. While this test is positive in about 90% of people with sciatica, approximately 75% of people with a positive test do not have sciatica.
Imaging tests such as computerised tomography or magnetic resonance imaging can help with the diagnosis of lumbar disc herniation. The utility of MR neurography in the diagnoses of piriformis syndrome is controversial.
Although medicines are commonly prescribed for the treatment of sciatica, evidence for analgesics is poor. Specifically, NSAIDs do not appear to improve immediate pain. Evidence is also lacking in use of opioids and muscle relaxants. In those with sciatica due to piriformis syndrome, botulism toxin injections may improve pain and or function. There is little evidence for steroids, either epidural or by pill.