What Is Sciatica?Sciatica involves pain along the distribution of the sciatic nerve, the largest single nerve in the human body. The nerve begins in the lumbar region of the spine, goes deep and emerges just below the buttocks, and ends just above the posterior knee. Sciatica is not a medical diagnosis, but rather a symptom of underlying disease. The nerve is compressed or irritated in some way, leading to characteristic symptoms.
Sciatica symptoms include one or more of the following:
- Unilateral pain of a buttock or leg
- Pain made worse by sitting
- Tingling down the leg or foot
- Numbness in a leg or foot
- Muscle weakness in a leg or foot
Descriptions of the pain experienced with sciatica vary widely. Sciatica nerve pain can be described anywhere from burning to cramping. It can be infrequent and annoying to constant and excruciating. Exacerbating factors may include prolonged sitting, coughing, or sneezing. There is almost never any permanent sciatic nerve damage. The incidence of sciatica peaks in middle age.
What Causes Sciatica?Sciatica has a variety of possible etiologies. The most common cause is a herniated disc in the lumbar region of the spine. The gel-like contents of the disc leak out, or herniate, causing irritation of the sciatic nerve root. Other names for a herniated disc include slipped disc, bulging disc, ruptured disc, and protruding disc. A thorough medical history and physical examination with imaging studies (X-ray, MRI, or CT scan) provide the diagnosis in most patients.
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Other causes of sciatica include degenerative disc disease, piriformis syndrome, lumbar spinal stenosis, and spondylolisthesis.
Degenerative disc disease refers to the degeneration of discs in the back and is usually a result of aging. Piriformis syndrome refers to spasm of the piriformis muscle as it runs above the nerve root. Spinal stenosis results in a constriction of the sciatic nerve as it exits the spinal canal.
Spondylolisthesis occurs when a backbone, or vertebra, slips forward onto another. All of the etiologies referred to above cause compression or inflammation of the sciatic nerve root, the origin of sciatica.