Sciatica: Symptoms and Possible Causes
Is sciatica a spinal disorder or a symptom of a spinal disorder?
The term sciatica is commonly used to describe pain traveling in the distribution of the sciatic nerve—so it's more accurate to say that it's a symptom of a spinal disorder not a spinal disorder itself. The sciatic nerve is the largest nerve in the human body, about the diameter of a finger.Before jumping into the symptoms associated with sciatica, it's helpful to have an idea of where the sciatic nerve is and what it does.
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, helps with thigh extension).
The sciatic nerve then runs vertically downward into the back of the thigh, behind the knee and branches into the hamstring muscles (calf) and further downward to the feet.
- Symptoms of sciatica usually affect one side of the body.
- Pain from sciatic nerve compression may feel dull, sharp, burning, or accompanied by intermittent shocks of shooting pain beginning in the buttock and traveling downward into the back and/or side of the thigh and/or leg.
- Sciatica extends below the knee and may be felt in the feet.
- Sometimes symptoms of sciatic nerve compression include tingling and numbness.
- Sitting and trying to stand up may be painful and difficult.
- Coughing and sneezing can intensify the pain.
Nerve Compression Can Cause Sciatica
Compression of the sciatic nerve can cause any of the above-cited symptoms. Rarely is nerve damage permanent, and paralysis is seldom a danger since 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. If you are experiencing those symptoms right now, please seek immediate medical treatment.
Lumbar (low back) 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.
How Your Physician Diagnoses 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 studies. 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.