A follow-up MRI doesn't help evaluate results after treatment for sciatica, a new study finds. Sciatica is caused by pinching, irritation or damage in the sciatic nerve. Symptoms include pain or weakness in the lower back or leg. Most people feel better in a couple of months. Others need surgery to get relief. Doctors often order an MRI to show if there's a bulging (herniated) disk pressing on or irritating the nerve. The new study included nearly 300 people with sciatica. All of them showed signs of a bulging disk on an MRI scan. They received surgery or more conservative treatments, such as exercise. After a year, they were given follow-up MRIs. About 85% of people reported that their treatment was successful. But researchers couldn't tell from the MRIs who had good results and who didn't. About one-third of those with poor results still had a bulging disk, according to their MRI. But so did one-third of those with good results. The New England Journal of Medicine published the study March 14. An editorial in the journal noted that inflammation could cause symptoms, and an MRI would not show that cause. HealthDay News wrote about the study.

By Robert H. Shmerling, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

The sciatic nerve runs from the lower back to the leg. When it gets irritated, pinched or damaged, the result is sciatica. People with sciatica describe it as a sharp, burning pain traveling down the back of the leg.

News about better ways to detect, treat or monitor this condition is important because sciatica:

• Is common -- The estimated lifetime risk of sciatica ranges as high as 40%.
• Has no reliable cure -- Treatments are available (see below), but none offers immediate relief in every case. In many cases, time is the only "cure."
• Can reduce quality of life -- In some cases, sciatica is so severe that the person is temporarily bedbound.

People with sciatica who do not improve within a few days or weeks often have an MRI. These scans usually reveal that a disk is bulging and pinching a portion of the sciatic nerve near the spine.

It's rare that any serious or dangerous cause of pain is found, such as cancer or infection. In many cases, the scan shows normal results. Sometimes it finds something else (such as degenerative arthritis) that seems unrelated to the sciatica. This is a big problem with MRI scans, and imaging tests in general: Abnormalities found often have no connection to the symptoms.

Even so, it's common for doctors to repeat an MRI when someone with known sciatica caused by a bulging disk continues to have symptoms. After all, there could be a new problem or the disk bulging could have become worse.

A new study in the New England Journal of Medicine examined the practice of repeating an MRI for people with sciatica. In this study, the second scan was done a year after the first one showed a bulging disk. Here's what the study found:

• After one year, about 20% of those treated with surgery still had disk bulging. So did 60% of those treated without surgery. But disk bulging was equally likely in those who felt better and those who did not.
• Overall, 84% of study patients had mostly or completely recovered. This proportion was about the same whether people had disk bulging or not.

These results will not surprise doctors who see a lot of patients with sciatica. So why order MRIs at all for people with symptoms of sciatica? Good question!

This was a study of second MRIs for people who already had a first scan that showed a bulging disk. But that first MRI may not always be necessary, especially when symptoms of sciatica are typical and there's little reason to suspect a rare or serious condition. Treatment for sciatica is rarely changed by the MRI results.

What Changes Can I Make Now?

If you have sciatica, you have several treatments to consider:

• Rest, balanced with periods of limited activity
• Alternating hot and cold compresses
• Physical therapy to help you move better, strengthen the back and abdominal muscles and prevent future injury
• Other non-drug options, such as chiropractic care, acupuncture or yoga
• Pain relievers, such as acetaminophen or ibuprofen
• Medicines for nerve pain, such as amitriptyline or gabapentin
• Injections of an anesthetic plus a steroid
• Surgery, though this is usually a last resort

If you have symptoms of sciatica, should you have an MRI? Maybe. MRI is routinely ordered if your doctor suspects a serious cause for the symptoms or if surgery may be an option for you.

Before getting that MRI for sciatica, consider these facts:

• Sciatica is rarely caused by a dangerous condition that requires urgent diagnosis.
• Sciatica often gets better without treatment.
• MRI results are often normal among people with sciatica.
• MRIs often show abnormalities that have nothing to do with sciatica. This can lead to surgery that you don't need.

If your doctor recommends a test, such as an MRI, ask some basic questions:

• How will this test help me to get better?
• Is this test for diagnosis or something else?
• Is this test painful? Risky? Expensive?
• Is there another test that is safer, less risky or costs less that will provide the same information?
• What are the pros and cons of not having the test? What about delaying the test to see if the symptoms improve or go away on their own?

Thinking twice about medical tests is an important way to cut costs without reducing the quality of health care.

What Can I Expect Looking to the Future?

Health care costs and quality are being examined today as never before. So you can expect to hear more about studies that analyze the usefulness of common tests and treatments. This latest study is a good example of how testing that has become routine actually may be unnecessary.