EMG ‘Hides in Plain Sight’ in Spinal Stenosis Diagnosis

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By Miki Fairley

Back pain wears many disguises; unmasking the real culprit can require some skillful detective work to arrive at an accurate diagnosis and thus, accurate treatment. Frequently, the perpetrator is spinal stenosis.

Spinal stenosis- a narrowing of the spinal canal-can cause pain and other difficulties if nerves become inflamed at points of increased pressure.

An estimated 400,000 Americans suffer from spinal stenosis, with conditions ranging from asymptomatic to disabled. The condition, most often caused by the wear and tear of aging, generally becomes more painful over time.

Spinal stenosis most often affects the cervical and lumbar areas. Patients with lumbar spinal stenosis may experience pain, weakness, or numbness in the legs and buttocks; cervical stenosis can cause similar symptoms in the shoulders, arms, and legs; other symptoms may be hand clumsiness and balance and gait difficulties.

Conservative treatment options include rest; painkilling and anti-inflammatory medications; orthotic support, such as a thoracolumbar spinal orthosis, which keeps the spine in some flexion; and gradual, appropriate exercise. Also helpful are using a pushcart when shopping, gently leaning forward when sitting, avoiding prolonged standing, and avoiding sleeping on the back without pillows under the knees.

If these treatments fail, surgery may be the next option and can offer an 80-85 percent chance of improvement, according to medical experts.

Unmasking Copycats

But here's the catch: other conditions, including polyneuropathy, myopathy, and joint pain from osteoarthritis, can mimic spinal stenosis symptoms-which can lead to painful, expensive, and unnecessary surgery.

This is where a diagnostic detective-a test dating back to World War II-has been waiting in the wings, "hiding in plain sight." Although the much newer, high-tech magnetic resonance imaging (MRI) test has been a favored diagnostic tool, a research study at the University of Michigan, Ann Arbor, has revealed that an electromyogram (EMG) test is highly accurate in diagnosing spinal stenosis and differentiating it from conditions that mimic its symptoms. Unlike an MRI, which simply shows a picture of the nerves, an EMG tests nerve function to determine if actual nerve damage is present, points out study lead author Andrew Haig, MD, professor in the Department of Physical Medicine and Rehabilitation at the University of Michigan Medical School. EMG also proved its efficacy in more accurately unmasking and diagnosing other conditions and diseases that previously had been misdiagnosed as spinal stenosis. For instance, one patient who had been previously diagnosed as having spinal stenosis was shown actually to have Charcot-Marie-Tooth disease.

"We've had a collection of cases in which doctors using MRI diagnosed spinal stenosis, operated, but later another disorder was found which was clearly causing the symptoms," says Haig. "Thus the operation was useless. So it's very important that clinicians don't rely on MRI alone to determine if that patient requires treatment."

Research Study

For their study, Haig and his colleagues used 150 participants, ages 55 to 80. 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.

Andrew Haig performs the EMG test on a patient.
Andrew Haig performs the EMG test on a patient.

To test the accuracy of EMG, each patient first underwent an evaluation including medical history, a physical examination, and MRI testing. 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 from neuromuscular disease," explains Haig. "In fact, EMG is an excellent test for spinal stenosis and other neuromuscular disorders using strict evidence-based criteria." Thus, EMG testing has proved its rightful place as a less expensive, more accurate addition to the diagnostic tool armentarium.

Findings from the study were published in the journal Spine in late 2005, and additional analysis was reported in the Journal of Bone and Joint Surgery in 2006. Knowledge about the efficacy of the test has been spreading, although Haig would like to see much more awareness on the part of surgeons. The increased attention has garnered Haig and his team several awards in the past year, including the Foundation for Physical Medicine and Rehabilitation Education Research Fund's "Best Research Paper" (established investigator) published by a physiatrist in any peer-reviewed journal in topics related to the field of physical medicine and rehabilitation; "Best Paper," awarded by the Association of Academic Physiatrists (AAP); and the Blue Cross Blue Shield of Michigan's "Best Clinical Research Award."

Of course, no single diagnostic tool is foolproof. "Clinical diagnosis should always be done using a combination of the patient's clinical presentation, his or her clinical evaluation, and results of diagnostic tests," notes University of Michigan researcher Henry Tong, MD.

Says Haig, "When cancer or other life-threatening conditions are ruled out, it's critical that patients especially don't let the findings of diagnostic tests alone drive their decision to have surgery or other invasive treatments. Patients, therapists, and doctors need to be aware that these tests don't prove how much you hurt or how disabled you are. You shouldn't just let a picture tell you what to do with your body."

Some information for this article was obtained from the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM), www.aanem.org; the University of Michigan, www.umich.edu; Spine Universe, www.spineuniverse.com; and St. Mary's Health System, www.stmarys.org

Miki Fairley is a contributing editor for   The O&P EDGE and a freelance writer based in southwest Colorado. She can be contacted via e-mail at  miki.fairley@gmail.com