If it can, the future may be brighter for the thousands who suffer from crippling lower back pain caused by squeezed spinal nerves.

The study, funded by a new $1.2 million grant from the National Institutes of Health, will test the idea that electromyography, or EMG, can help doctors zoom in on the exact location where back pain originates -- without the uncertainty, false positives and higher cost of other tests.

That precision could allow patients to get the help they need.

EMG's promise for pinpointing the origin of pain comes from several years of U-M studies led by Andrew Haig, M.D., head of the U-M Spine Program and an associate professor of physical medicine & rehabilitation and of surgery at the U-M Medical School.

After working to make EMG easier for patients to have, and more precise, Haig and his colleagues won the new grant to perform a major study of EMG in diagnosing back pain -- possibly the first ever funded by NIH.

The U-M study will follow participants for more than a year, and use rigorous tests of EMG's accuracy. It will focus on spinal stenosis, a catch phrase for back pain that stems from narrowing of the channels and gaps through which nerves lead out of the spine to nearby muscles.

Spinal stenosis, which strikes thousands of people with arthritis and other conditions each year, can cause crippling lower-body pain and hamper a person's ability to work, play and walk.

"Many tests used today for back pain are not as accurate as we'd like and miss a lot of people who have back pain that could be treated by specific treatment methods," says Haig. "We've been applying modern research techniques to some of the ideas from 50 years ago, and we've standardized some of the tests.

"This study will let us compare EMG results from those with and without back pain for the first time, so that we can be confident it's giving us the right answers."

Haig and his colleagues hope their findings will give physicians a new tool to clear up the mystery of what's behind an individual's back pain. Since disabling back pain, including stenosis, strikes about 80 percent of Americans during their lives, any new aid could help millions.

Spinal stenosis accounts for a large portion of the back pain felt in the United States each year, along with herniated disks, muscle and ligament strains and joint irritation.

In stenosis, the swelling of joints from arthritis, the formation of bone spurs, the breakdown or displacement of bones in the spine or the natural anatomy a person is born with can make the passages in and near the spine become more narrow.

When a nerve leading from the spine is squeezed by a narrowed passage, the nerve doesn't get enough blood supply, and the muscle it connects to doesn't get enough of a signal to tell it what to do.

"The message from your brain going down through your spine gets choked off on the way down to your legs," explains Haig, adding that the result can be debilitating pain that extends throughout the back and lower body. Stenosis mainly strikes people over 50, and can last years.

In an effort to see the narrowing and its cause, doctors have turned to X-rays, and more recently to magnetic resonance imaging, or MRI, which can show tiny details of the spine's structures and nearby tissue, and allow measurements to be made. But, says Haig, "The problem is that we know that some people have very small canals and they don't have any symptoms at all, and some people's canals don't look all that bad on an MRI but they've got horrible pain. The MRI gives a great photograph, but it can't show function."

That's where EMG comes in. The test, commonly done on muscles throughout the body, uses tiny needles placed in the skin to measure the electrical signals that travel in nerves and allow them to "talk" to muscles. Haig and his colleagues have shown that EMG can work on tiny muscles, called paraspinal muscles, that connect to nerves that emerge from the spinal cord.

"It's a test that looks at whether the nerves themselves are actually functioning," Haig notes. "EMG allows us to listen to the electrical activity that the brain sends to the muscles, and to give little electrical stimulations to the nerves to time how long it takes to travel to the muscle. By putting those measurements together, and knowing about the person's anatomy, we can find out whether the person has a spinal disorder that's hurting the nerves."

After years of research, MRI scans have become an important part of back pain diagnosis, Haig explains. It shows doctors at UMHS and around the world where problems might be coming from. But still, MRIs often give false positives, or fail to find the exact spot where pain originates.

Haig likens it to taking a picture of damage to a car after a collision -- the photo gives useful but not complete information. Only by turning the key in the ignition can you tell whether the car still works. EMG, Haig explains, lets doctors get the kind of information about how the nerves are working that they can't get from an MRI.

U-M's back pain researchers have spent years developing and testing EMG's capabilities in back muscles, and standardizing it so they can tell what readings are normal for paraspinal muscles and what readings aren't. They have even cut the number of needles that must be placed in the skin by 75 percent -- good news for patients, because fewer needles means less pain during the test. The U-M team calls their technique "paraspinal mapping."

Now, with the new NIH funding, they will try to compare readings from 150 people -- some who have back pain but no exact diagnosis, some who have various forms of stenosis diagnosed on an MRI, and those of the same age who have no back problems.

The research subjects will not only help the team determine how well EMG can find the source of back pain -- they'll also receive specialized help for their own back pain, whatever the cause. The study may help researchers develop EMG into a low-cost follow-up -- or even replacement -- for spinal MRI.

The study will also look at how well EMG results correspond to participants' quality of life, their ability to walk and how much pain they report feeling. And, it will follow the participants for more than a year to see if the extent of the nerve damage shown on their first EMG can predict how much their symptoms worsen over time.

The study may even allow EMG's application to go beyond stenosis-related back pain, Haig predicts. The researchers will evaluate the idea that common strains of back muscles can lead to injured nerves as bones become temporarily unstable and joints swell, causing pain and, eventually, squeezing the nerves.

"I think EMG is going to play an important role in the diagnosis of back pain as a result of this research and research going on elsewhere," says Haig. "When doctors look at a scan and it doesn't make sense to them, they're going to go to EMG to find out the truth. In the next decade or so, it may really change how we deal with back pain."

Facts about back pain, spinal stenosis and EMG:

* As many as 80 percent of Americans have disabling back pain during their working lives.

* More than 12 million Americans annually see their doctors because of back pain.

* Most of the time, back pain will go away on its own. But for many people, back pain can persist for weeks, months, and even years, and can interfere with activities of everyday life.

* Proof of what is causing a person's back pain is found in only about 20 percent of cases.

* Stenosis means narrowing. Spinal stenosis is a narrowing of the passages, such as the spinal canal and the spaces between vertebrae, through which spinal nerves pass.

* Estimates say as many as 400,000 Americans may have spinal stenosis. This number is expected to grow as members of the baby boom generation reach their 50s and 60s.

* Spinal stenosis is most common in people over 50 years of age. However, it may occur in younger people who were born with a narrow spinal canal or who suffer a spine injury.

* Symptoms of spinal stenosis include: pain or numbness in the buttocks, thighs, or calves that is worse with walking or exercise; back pain that radiates to the legs; weakness of the legs; neck pain; and leg pain.

Electromyography, or EMG, was developed in the first part of the 20th century and first applied widely after World War II.

EMG measures electrical impulses in nerves and muscle to reveal problems in function caused by disease or physical factors.

Related websites:

U-M Health System, Health Topics A to Z: Back pain index

UMHS Spine Program

National Institute of Arthritis and Musculoskeletal and Skin Diseases: Spinal Stenosis

[Contact: Kara Gavin, Valerie Gliem]

11-Jun-2001