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.