Sciatica: Symptoms and Possible Causes

Steven R. Garfin, M.D. Professor and Chair, Department of Orthopaedics University of California, San Diego San Diego, CA, USA

Is Sciatica a Disorder or a Symptom?

The term sciatica is commonly used to describe pain traveling in the distribution of the sciatic nerve. Sciatica is a symptom caused by a disorder occurring in the lumbar spine. The sciatic nerve is the largest nerve in the human body, about the diameter of a finger.

Sciatic nerve fibers begin at the 4th and 5th lumbar vertebra (L4, L5) and the first few segments of the sacrum. The nerve passes through the sciatic foramen just below the Piriformis muscle (rotates the thigh laterally), to the back of the extension of the hip and to the lower part of the Gluteus Maximus (muscle in the buttock, thigh extension). The sciatic nerve then runs vertically downward into the back of the thigh, behind the knee branching into the hamstring muscles (calf) and further downward to the feet.

 

Sciatica Symptoms

Usually sciatica affects one side of the body. The pain may be dull, sharp, burning, or accompanied by intermittent shocks of shooting pain beginning in the buttock traveling downward into the back or side of the thigh and/or leg. Sciatica then extends below the knee and may be felt in the feet. Sometimes symptoms include tingling and numbness. Sitting and trying to stand up may be painful and difficult. Coughing and sneezing can intensify the pain.

The Cause: Nerve Compression
Compression of the sciatic nerve can cause any of the above-cited symptoms. Rarely is nerve damage permanent and paralysis is seldom a danger as the spinal cord ends before the first lumbar vertebra. However, increasing trunk or leg weakness, or bladder and/or bowel incontinence is an indication of Cauda Equina Syndrome, a serious disorder requiring emergency treatment.

Lumbar spine disorders known to cause sciatic nerve compression include the following:

• Herniated discs are the most common cause of sciatica in the lumbar spine.
• Degenerative Disc Disease, a natural biological process associated with aging, is known to cause disc weakness that can be a precursor to a disc herniation.
• Lumbar Spinal Stenosis is a narrowing of one or more neural passageways due to disc degeneration and/or facet arthritis. The sciatic nerve may become impinged as a result of these changes.
• Isthmic Spondylolisthesis results from a stress fracture often at the 5th lumbar vertebra (L5). The fracture combined with disc space collapse may allow the vertebra to slip forward on the first sacral segment (S1). The slippage may cause the L5 nerve root to become pinched as it leaves the spine.

Spinal Tumors and Infections are other disorders that may compress the sciatic nerve, but this is rare.

There are other conditions, which may occur, and may mimic true sciatica but these are difficult to diagnose.

Diagnosis of Sciatica

The physician's examination includes the patient's medical history, a review of current medications, a physical and neurologic examination and, if warranted, x-rays, CT scan and/or MRI. A proper diagnosis requires an analysis of the patient's pain. The patient is often provided a Pain Diagram to illustrate pain distribution and sensation (eg, tingling and burning).

The physician's questions may include:

• "How did the pain develop?"
• "On a scale from 1 to 10, with 10 being the worst pain imaginable, rate your pain."
• "Is the pain worsened by walking uphill or downhill?"
• "How does the pain affect activities of daily living?"
• "What type of treatment has been tried and what was effective?"

The patient's range of motion is observed. Reflexes and muscle strength are tested. The physician may use one or more movement tests to determine the source or cause of the pain.