Sciatica: Definition

Sciatica is a pain in the leg consequent to irritation of the sciatic nerve. Generally, the pain travels from the back of the thigh to the back of the calf, and also may extend upwards, to the hip, and downwards to the foot. In addition to pain, there may be numbness and difficulty in moving or controlling the leg. Typically, the symptoms are only felt on one side of the body.

Although sciatica is a relatively common form of low back pain and leg pain, the true meaning of the term often is misunderstood. Sciatica is a set of symptoms rather than a diagnosis for what is irritating the root of the nerve, causing the pain. This point is important, because treatment for sciatica or sciatic symptoms often will be different, depending upon the underlying cause of the symptoms.

The first cited use of the word "sciatica" was registered in 1450.

Sciatica: Causes

Sciatica is generally caused by the compression of a lumbar spine nerve root, and, far less commonly, by compression of the sciatic nerve itself. "True" sciatica, therefore, is caused by compression at the nerve root when it is considered a lumbar radiculopathy (or radiculitis when accompanied with an inflammatory response) from a spinal disc herniation (a herniated intervertebral disc in the spine), consequently either roughening and enlarging and/or misaligning of the vertebrae (spondylolisthesis), or degenerated discs (see Degenerative Disc Disease).

Sciatica may also be experienced in late pregnancy, primarily resulting from the uterus pressing on the sciatic nerve, and, secondarily, from the muscular tension and / or vertebral compression consequent to carrying the extra weight of the fetus, and the postural changes inherent to pregnancy.

"Pseudo-sciatica", which causes symptoms similar to spinal nerve root compression, is caused by the compression of peripheral sections of the nerve, usually from soft tissue tension in the piriformis or related muscles. The most predominant form of this condition is piriformis syndrome. In this condition, the piriformis muscle, located beneath the gluteal muscles, contracts spasmodically and strangles the sciatic nerve beneath the muscle. Another cause of sciatic symptoms is sacroiliac joint dysfunction. Unhealthy postural habits, such as excessive time sitting in chairs, and sleeping in the fetal position, along with insufficient stretching and exercise of the relevant myofascial areas, can lead to both the vertebral and soft tissue problems associated with sciatica.

Yet another source of sciatic symptoms is active trigger points of the lower back and the gluteus muscles. In this case, the referred pain is not, in fact, consequent to compression of the sciatic nerve, though the pain distribution down the buttocks and leg is similar. Trigger points occur when muscles become ischemic (low blood flow) due to injury or chronic muscular contraction. The most commonly associated muscles with trigger points triggering sciatic symptoms are: the quadratus lumborum, the gluteus medius, the gluteus minimus, and the deep hip rotators.

Sciatica: Treatment

One major cause of sciatica is a spinal disc herniation, pressing on the sciatic nerve. The spinal discs are composed of a spongiform cartilage with a liquid center. The discs separate the vertebrae, thereby allowing room for the sciatic nerve to properly exit through the sacral portion of the pelvis down into the leg. The discs cushion the spine from compressive forces, but are weak to pressure applied during rotational movements. That is why a person who bends to one side, at a bad angle, to pick up a piece of paper may more likely herniate a spinal disc than a person falling from a ladder and landing on his or her back. Compression of the sciatic nerve from a herniated disc occurs when the liquid center of the disc bulges outwards, tearing the external ring of fibers, and ballooning onto the nerve root, thus causing sciatica.

Surgial treatment for sciatica caused by disc herniation are treatments such as a Prosthetic Disc Nucleus, Disc Replacement Surgery, Nucleoplasty, a Discectomy and a Foraminotomy.

Other compressive spinal causes include Spinal Canal Stenosis (see Spinal Stenosis), a condition wherein the spinal canal (through which the spine runs) narrows and compresses spinal cord. This narrowing can decrease available space for the sciatic nerve to properly exit, thus pinching the nerve and irritating it with friction. The sciatic nerve runs through the piriformis muscle in the buttocks region. When the muscle shortens or spasms due to trauma, it can compress the sciatic nerve. This cause of sciatic symptoms is Piriformis Syndrome. The approach to treating sciatica is to reduce the compressive forces causing the pressure upon the sciatic nerve. This can be accomplished through traction and realignment therapeutic procedures in the case where the sciatica is spinal-related. Manual muscle stretching, massage, and mobilization techniques should be used when the sciatica is piriformis muscle-related. General therapeutic goals include helping the muscles loosen, thereby lessening pain, and to minimize inflammation.