Sciatica

Sciatica is a term used to describe pain that travels along the path of the sciatic nerve. This nerve pathway begins in the lower back and extends down the leg.

The sensation is often described as a shooting or shock-like pain. It may travel down the back, the side, or the front of the leg. While it typically affects only one side of the body, some causes can result in pain on both sides. Symptoms can also include numbness or weakness in various parts of the leg and foot. Depending on how it is defined, between 1% and 40% of people may experience sciatica at some point.

The sciatic nerve is formed by several nerve roots from the spine. These roots include L4, L5, S1, S2, and S3. These roots merge in the pelvic cavity to form a structure called the sacral plexus. From this plexus, the sciatic nerve branches out. Sciatica occurs when there is pathology, or a medical issue, anywhere along this nerve pathway. This can happen inside the spine or outside the spine.

Most cases of sciatica are caused by a spinal disc herniation. This accounts for about 90% of cases, especially in people under age 50. Intervertebral discs sit between the bones of the spine to provide stability. Each disc has a tough outer ring called the anulus fibrosus. Inside this ring is a gelatinous center called the nucleus pulposus. As people age, the anulus fibrosus can weaken and tear. When a tear occurs, the nucleus pulposus can extrude through the opening. This material then presses against the lumbar or sacral nerve roots. This pressure causes inflammation and the characteristic shooting pain.

Another common cause is spinal stenosis, which is most frequent in people over age 50. This condition involves the narrowing of the spinal canal. The spinal canal is the space where the spinal cord and nerve roots reside. This narrowing can be caused by bone spurs, inflammation, or spondylolisthesis, which is the misalignment of vertebrae. When the space shrinks, it pinches the nerves. People with spinal stenosis often find that standing or sitting for long periods increases their pain. Conversely, bending forward may provide some relief.

Sciatica can also be caused by issues outside the spine, known as extraspinal causes. One such cause is piriformis syndrome. The piriformis is a muscle located in the buttock area near the sciatic nerve. In about 17% of people, the sciatic nerve actually runs through this muscle instead of beneath it. If the muscle spasms or becomes injured, it can compress the nerve. There is also a broader category called deep gluteal syndrome. This describes many different ways the nerve can be trapped in the hip area. These causes can include fibrous bands that restrict how the nerve moves.

Medical history shows that humans have understood this condition for a very long time. The 1st-century physician Dioscorides mentioned it in his work, Materia Medica. However, the first known modern use of the specific word "sciatica" dates back to 1451. Today, doctors use various methods to diagnose the cause. One common method is the straight-leg-raising test. During this test, a person lies on their back while their leg is lifted. If the person feels pain shooting below the knee, the test is considered positive.

In many instances, the body heals on its own with time. About 90% of sciatica cases resolve in less than six weeks. Initial treatment often focuses on pain medications, though evidence for their effectiveness is sometimes lacking. Doctors generally recommend that patients continue with normal activities as much as they are able. If the pain is severe or lasts longer than six weeks, surgery might be an option. Surgery is sometimes necessary if complications arise, such as a loss of bowel or bladder control. It is most common to see these symptoms in men between the ages of 40 and 59.