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U-M study: Old test offers new hope for back pain sufferers


Developed during WWII, EMG provides an accurate means to diagnosis spinal stenosis.

ANN ARBOR, MI –A test that has been around since World War II is now providing that era’s baby boomer generation with a more definitive diagnosis for the back aches and pains that commonly come with age.

Andrew HaigResults from a new University of Michigan Health System study show that the electromyogram (EMG) test can accurately diagnosis spinal stenosis, reducing misdiagnosis of low back pain and other common neuromuscular conditions that can mimic symptoms, and even helping to avoid unnecessary back surgery.

The findings from this study are published in this month’s issue of Spine.

An estimated 400,000 Americans have spinal stenosis, a narrowing of spaces in the spine that results in pressure on the spinal cord and nerves and can lead to debilitating back pain or even paralysis if left untreated. And the number of people affected by spinal stenosis is only expected to grow as more baby boomers reach their 50s and 60s.

The problem, however, is that the symptoms of spinal stenosis are shared by many other diseases, including peripheral nerve disease and even arthritis in the joints, which can lead to costly misdiagnoses and unnecessary back surgery, says study lead author Andrew Haig, M.D., associate professor in the Department of Physical Medicine and Rehabilitation at the U-M Medical School.

“EMG plays an important role in the diagnosis of back pain because, unlike MRI (magnetic resonance imaging), EMG is more than a picture of a nerve – it can test nerve function and show if there is actual nerve damage,” says Haig. “The EMG is really going to help doctors to avoid unnecessary procedures because it proves that there is nerve damage in the people who clearly have it and can accurately diagnosis spinal stenosis.”

Although EMG has been around for about 60 years, there have been no controlled studies of EMG for spinal stenosis. Further, many past studies of spinal stenosis had only looked at asymptomatic patients, while others failed to include comparison groups for patients with back pain or symptoms of spinal stenosis.

For their study, Haig and his colleagues used 150 participants, ages 55 to 80, to determine how well EMG could find the source of back pain. Participants included those with low back pain but no MRI evidence of spinal stenosis, those with varying severity of spinal stenosis, and individuals who had no symptoms of either condition.

To test the accuracy of EMG, each patient first underwent a physical history, a physical examination and MRI. The data was then reviewed by a physiatrist, neurosurgeon and neuroradiologist, all of whom were masked to any outside information about the patients’ conditions, and a unanimous diagnosis was made about each patient’s condition.

Following the diagnosis, study participants underwent EMG testing. The EMG results were then compared against the initial diagnosis of the physiatrist, neurosurgeon and neuroradiologist.

The study found that EMG identified nerve or muscle disease in five participants whom medical experts all believed to have spinal stenosis.

In all, the results from the EMG show a substantial difference between the spinal stenosis patients and the two control groups, allowing experts to clearly distinguish spinal stenosis from low back pain. Additionally, EMG successfully detected common neuromuscular disease that can mimic spinal stenosis.

“Most doctors think of EMG as a simple test and incorrectly believe that it is sensitive for nerve damage, but cannot differentiate spinal stenosis form neuromuscular disease,” explains Haig. “But as this study shows, that’s not the case. In fact, EMG is an excellent test for spinal stenosis and other neuromuscular disorders using strict evidence-based criteria.”

As a result, MRI shouldn’t be used as the only proof that a patient has spinal stenosis, Haig says. Many patients, as this study shows, are misdiagnosed. Some of those patients instead were found to have some form of nerve illness.

Currently Haig and his colleagues are working to further the findings from this study. The team’s next study directly compares EMG and MRI to determine which test is best for detecting spinal stenosis. The research also looks to find if either test can predict what happens to people with back pain over time. Results from this study are expected to be published soon.

Along with Haig, co-authors from the U-M Health System were Henry C. Tong, M.D., MS; Karen S. J. Yamakawa, MS; Douglas J. Quint, M.D.; Julian T. Hoff, M.D.; Anthony Chiodo, M.D.; Jennifer A Miner, MBA; Vaishali R. Choksi, M.D.; and Michael E. Geisser, Ph.D.

This study was funded by National Institutes of Health grant 5ROI NF4 1855 02.
Reference: Spine, Vol. 30, No. 23.

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Written by Krista Hopson.


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