Needle electromyogram (EMG), a relatively low-tech and inexpensive test in use since World War II, may be making a comeback. The old test may be more effective than magnetic resonance imaging (MRI) at detecting an increasingly common cause of back pain known as spinal stenosis, according to a 2006 study led by Andrew Haig, MD, an associate professor in the department of physical medicine and rehabilitation at the University of Michigan Medical School in Ann Arbor.

Marked by a narrowing of spaces in the spine, spinal stenosis results in pressure on the spinal cord and nerves. As a result, people with spinal stenosis experience debilitating back pain or even paralysis, if it’s left untreated. Close to 400,000 Americans have this condition, and the number is expected to increase as more baby boomers hit their 50s and 60s.

An EMG can help doctors better differentiate spinal stenosis from other conditions, like arthritis, herniated discs or peripheral nerve disease, and stave off unnecessary exploratory back surgery, explains Dr. Haig. MRIs tend to show arthritis, because most people older than 50 have some degeneration of their vertebrae, when the pain might really be due to spinal stenosis.

The study followed 150 people who had low back pain but no MRI evidence of spinal stenosis, varying severity of spinal stenosis or symptoms of either condition. Each patient was examined by a doctor and had an MRI. Then physiatrists, neurosurgeons and neuroradiologists came to a unanimous diagnosis about each patient’s condition. Following the diagnosis, the people had EMG testing and results were compared against the initial diagnosis. EMG clearly determined spinal stenosis diagnosis from other causes of low back pain.