MRI's, Back Pain and Transparency

Over at the wonderful World's Fair, Ben Cohen has an interview with Kelly Joyce, author of the forthcoming Magnetic Appeal: MRI and the Myth of Transparency. Here is how Joyce summarizes the main argument of her book:

In the United States, MRI is socially constructed as a sacred technology--one that represents progress, certainty, and good health care. The technique's sacred status is achieved in part because cultural ideas link anatomical pictures and mechanical reproduction to transparency and truth. But, it is also achieved because information about contexts and actors is often missing from popular discussions of MRI. In Magnetic Appeal, I bring those contexts and actors back in to examine why MRI is perceived the way it is, how technologists and physicians make sense of and use the technology in clinical work, and how advertising, fear of litigation, reimbursement policies, and research funding all contribute to MRI in practice.

I'm always struck by how even neuroscientists who work with fMRI everyday, and are acutely aware of the limitations of the technology (the 3-5 second time lag, the messy data, the difficulty of imaging certain areas, the fidgety subjects, etc.) still use the same metaphor of transparency. They talk about "looking at the inside of the brain," or how the brain scanner is like a "window," or how they can "see what's happening in real time". Of course, fMRI is an incredibly powerful and potent tool which allows us an unprecedented understanding of the mind at work, but I get a little tired of all these visual analogies. Before we can "see" anything with fMRI, someone has to perform a tremendous amount of statistical analysis.

One of my favorite examples of MRI gone awry involves the diagnosis of back pain. (I wrote a longish article on the psychology of back pain for Best Life.) When MRI technology first appeared, in the late 1980's, the medical profession hoped that the use of MRI would revolutionize the treatment of lower back pain. Since doctors could finally image the spine and surrounding soft tissue in lucid detail, they should be able to offer precise diagnoses, locating the aggravated nerves and structural problems that caused the pain in the first place. This, in turn, would lead to better medical care.

Unfortunately, MRI's haven't solved the problem of back pain. While X-rays can only reveal tumors or problems with the vertebrae, MRI's can image spinal discs - the supple buffers between the vertebrae - in meticulous detail. After the imaging machines were first introduced, the diagnosis of various disc abnormalities began to skyrocket. The MRI pictures certainly looked bleak: people with pain seemed to have seriously degenerated discs, which everyone assumed caused inflammation of the local nerves. Doctors began administering epidurals to quiet the pain, and, if the pain still persisted, would surgically remove the necessary disc tissue.

The vivid images, however, were misleading. Those disc abnormalities are seldom the cause of chronic back pain. An infamous 1994 study published in The New England Journal of Medicine imaged the spinal regions of ninety-eight people with no back pain or any back related problems. The pictures were then sent to doctors who didn't know that the patients weren't in pain. The end result was shocking: two-thirds of normal patients exhibited "serious problems" like bulging, protruding or herniated discs. In 38 percent of these patients, the MRI revealed multiple damaged discs. Nearly 90 percent of these patients exhibited some form of "disc degeneration". These structural abnormalities are often used to justify surgery and yet nobody would advocate surgery for people without pain. The study concluded that, in most cases, "The discovery by MRI of bulges or protrusions in people with low back pain may be coincidental."

Or consider this: A large study published in the Journal of the American Medical Association (JAMA) randomly assigned 380 patients with back pain to undergo two different types of diagnostic analysis. One group received X-rays. The other group got diagnosed using MRI's, which give the doctor a much more detailed picture of the underlying anatomy.

Which group fared better? Did better pictures lead to better treatments? There was no difference in patient outcome: the vast majority of people in both groups got better. More information didn't lead to less pain. But stark differences emerged when the study looked at how the different groups were treated. Nearly 50 percent of MRI patients were diagnosed with some sort of disc abnormality, and this diagnosis led to intensive medical interventions. The MRI group had more doctor visits, more injections, more physical therapy and were more than twice as likely to undergo surgery. Although these additional treatments were very expensive, they had no measurable benefit.

Medical experts are now encouraging doctors not to order MRIs when diagnosing back pain. In the latest clinical guidelines issued by the American College of Physicians and the American Pain Society, doctors were "strongly recommended...not to obtain imaging or other diagnostic tests in patients with nonspecific low back pain." In too many cases, the expensive tests proved worse than useless.

The point is that, as Kelly Joyce points out, the metaphor of MRI - it was like a transparent window - seduced doctors into thinking the pictures were more revealing than they actually were. They assumed that these newly visible details (such as the degenerated discs) were the cause of back pain. The reality, however, turned out to be far more complicated.