Sciatica Patient Information Fact Sheet

What is sciatica?
Sciatica is a general term referring to pain that occurs along the sciatic nerve. The sciatic nerve is the largest nerve in the body (about the width of a finger) and starts in the lower spine. It divides and passes behind each hip, down the buttock and back of each leg to the foot and finally to the big toe. Sciatic pain can be felt anywhere along the pathway of this nerve. There are many causes for this type of pain, which may be very different in character from back pain (although this may also be present). Sciatica and related back problems do tend to run in families.

What are the symptoms of sciatica?
Sciatica usually affects only one side of the body, although low back pain may be present at the same time. The pain radiates down the nerve, often to the buttock or leg. It can range in severity from a tingling feeling to severe, shooting pain, which makes standing up nearly impossible. The leg or foot may be numb or weak and there may be an inability to move the foot or bend the knee. In severe cases, bladder or bowel function may be affected. Anything that causes the nerve to be stretched can produce pain. Coughing, sneezing and sitting all make the pain worse. Sciatica often lasts for six weeks or more.

What causes sciatica?
Sciatica may be caused by the sciatic nerve becoming pinched between the vertebrae of the spine. It may also arise if the space in which the nerve lies becomes narrowed by arthritis or by swelling due to a sprain in the area. Very rarely, a blood clot, abscess or growth may push on the nerve, causing sciatica. A common cause of sciatica is a prolapsed lumbar disc. The prolapsed disc may bulge into the vertebral canal and compress the nerve roots. This may happen as a result of a poor lifting technique or lifting something too heavy. Digging the garden or other forms of strenuous exercise may also put pressure on a disc. The pain may begin as mild attacks of back pain and the back may become slowly more stiff and painful or, as is more usually the case, it may start as a sudden severe pain across the back that radiates down one side.

What tests confirm a diagnosis of sciatica?
A physical examination may be all that is necessary to make the diagnosis. X-rays are often not very helpful. A computerized tomographic (CT) scan or a magnetic resonance imaging (MRI) scan may be necessary to diagnose the cause of the sciatica, especially if there are complications or if symptoms are slow to resolve.