Overview of Sciatica
Sciatica (pronounced sī-at-ĭ-kă) is a term often used to describe low back pain that spreads (radiates) through the hip, to the back of the thigh, and down the inside of the leg. There are many causes for low back pain; however, true sciatica is a symptom of inflammation or compression of the sciatic nerve.
The sciatic nerve is the largest nerve in the body. It originates in a bundle of nerves in the lower back (called the sacral plexus), and passes through the pelvis and down the back of each thigh. In the back of the thigh, the sciatic nerve branches into two smaller nerves called the tibial nerve and the peroneal nerve. The sciatic nerve carries impulses between nerve roots in the lower back and the muscles and nerves of the buttocks, thighs, and lower legs.
Nerve roots are extensions of the spinal nerves. They emerge from the spinal cord through spaces on both sides of the bony segments (vertebrae) in the backbone (spine). There are 31 pairs of nerve roots.
- eight pair originate in the neck (called the cervical spine)
- 12 pair originate in the upper back (called the thoracic spine)
- 5 pair originate in the lower back (called the lumbar spine)
- 5 pair originate in the lowest area of the back (called the sacral spine)
- 1 pair originate in the tailbone (coccyx)
Pressure or irritation in one of the nerve roots in the lumbar spine (which lead to the sciatic nerve) or compression of the sciatic nerve itself can cause sciatica.
Sciatica is a type of radiculopathy. Radiculopathies are disorders that affect the nerve roots or nerves. Compression of a nerve root often occurs as a result of damage to one of the discs between the vertebrae (called intervertebral discs). In some cases, sciatic pain radiates from other nerves in the body. This is called referred pain.
Pain associated with sciatica often is severe, sharp, and shooting. It may be accompanied by other symptoms, such as numbness, tingling, weakness, and sensitivity to touch. Sciatic pain usually occurs on one side of the body and may extend into the lower leg.
Incidence and Prevalence of Sciatica
Although low back pain is a common condition that affects as many as 80–90 percent of people during their lifetime, true sciatica occurs in about 5 percent of cases. Sciatica is more common between 30 and 50 years of age. Although the condition occurs in men and women about equally, some studies have shown that sciatica often is more severe in women.