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ShareOctober 1, 2006 — Electromyography (EMG) detects the electrical potential generated by muscle cells, and can test nerve function. EMG can help physiatrists pin down the cause of back pain in cases such as spinal stenosis -- a narrowing of the spinal column -- in which the diagnosis can be tricky just relying on imaging techniques such as MRI.
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ANN ARBOR, Mich. -- A simple everyday move moved Timothy Pickens to unimaginable pain.
"I reached down to touch the computer mouse and shut it off, and I just tipped myself a little bit to reach down and it just grabbed," Pickens says. Now he's working to get his back back in shape.
Pickens is one of 400,000 people living with spinal stenosis, a narrowing of the spinal column. But for many, years of misdiagnosis keeps them in pain. Back pain is one of the most common medical complaints, but it can be one of the hardest to diagnose.
Carolyn Koski has lived with back pain her entire life. "Numbness, balance, fatigue, dizziness," she says. Doctors diagnosed her with spinal stenosis, but physiatrist Andrew Haig used an EMG to reveal the real problem -- nerve disease.
MRIs are what most doctors use to look at your spine, but an MRI scan can only give a picture of the nerve. "It's kinda like looking at a photograph of a car to see if it has dents," Dr. Haig, of University of Michigan in Ann Arbor, tells DBIS.
What an MRI doesn't show is pain.
An old test is breaking new ground when it comes to finding out what's hurting your back. An EMG records the electrical activity of muscles and can actually test nerve function and find out if anything hurts.
"It's more like putting the key in the engine to see if the car works or not. There are lots of dented cars that work just fine," Dr. Haig says.
Dr. Haig believes more doctors are not using EMG to test for back pain because the results are harder to read and takes more time to diagnose.
BACKGROUND: A test that has been around since World War II is now providing Baby Boomers with a more definitive diagnosis for back aches and pains. Results from a new University of Michigan Health System study show that the electromyogram (EMG) test can accurately diagnose spinal stenosis, and may even help avoid unnecessary back surgery. Unlike an MRI (magnetic resonance imaging), the electromyogram is more than a mere picture of a nerve. It can test nerve function to see if there is actual nerve damage, one of the primary symptoms of spinal stenosis.
HOW EMG WORKS: An electromyogram (EMG) is a test that records the electrical activity of muscle. At rest, muscle tissue doesn't produce electrical current, but when muscles are active, they do. The amount of current produced is usually proportional to how active the muscles are -- that is, the more a muscle works, the more electricity it produces. So an EMG can help distinguish between muscle conditions that are due to the muscles themselves, and weaknesses that result from certain nerve disorders. Needle electrodes are inserted through the skin into the muscle tissue, prompting electrical activity, which can be measured to determine a baseline. The patient is then asked to flex and relax the muscle. The resulting current is recorded on an electromyograph and printed out so doctors can analyze the data for abnormalities.
ABOUT SPINAL STENOSIS: 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, usually in the upper or lower back. This condition can lead to debilitating back pain or even paralysis if left untreated. It is commonly misdiagnosed as other conditions that have similar symptoms, such as peripheral nerve disease or arthritis in the joints. The primary cause of spinal degeneration is arthritis, which affects the cartilage hat cushions the ends of bones in the joints. As we age, that cartilage begins to deteriorate and its smooth surface becomes rough, and may rub painfully on bone. The body may produce bony growths called spurs in response, in an attempt to repair the damage, and these can sometimes narrow the spinal canal.
THE STUDY: Until now there haven't been any controlled studies of EMG for spinal stenosis. The Michigan study found that EMG identified muscle disease in five participants whom medical experts all believed to have spinal stenosis. In all, the results from the EMG showed a substantial difference between those patients with spinal stenosis and the two control groups, allowing experts to clearly distinguish spinal stenosis from low back pain. EMG also successfully detected common neuromuscular disease that can mimic spinal stenosis.
The American Association of Physicists in Medicine contributed to the information contained in the TV portion of this report.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.
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