Patients with lower back pain that can't be traced to a specific physical cause may have abnormal pain-processing pathways in their brains, according to a new study led by University of Michigan researchers.
The effect, which as yet has no explanation, is similar to an altered pain perception effect in fibromyalgia patients recently reported by the same research team.
In fact, the study finds, people with lower back pain say they feel severe pain, and have measurable pain signals in their brains, from a gentle finger squeeze that barely feels unpleasant to people without lower back pain. People with fibromyalgia felt about the same pain from a squeeze of the same intensity.
But the squeeze's force must be increased sharply to cause healthy people to feel the same level of pain - and their pain signals register p in different brain areas.
The results, which will be presented Oct. 27 at the annual meeting of the American College of Rheumatology in New Orleans, may help lead researchers to important findings on lower back pain, and on enhanced pain perception in general.
Senior authors Richard Gracely, Ph.D., and Daniel Clauw, M.D., did the study at Georgetown University Medical Center and the National Institutes of Health, but are now continuing the work at the University of Michigan Health System. In May, they and their colleagues published a paper in the journal Arthritis and Rheumatism on pain perception in fibromyalgia patients.
To correlate subjective pain sensation with objective views of brain signals, the researchers used a super-fast form of MRI brain imaging, called functional MRI or fMRI. They looked at the brains of 15 people with lower back pain whose body scans showed no mechanical cause, such as a ruptured disk, for their pain. They also looked at 15 fibromyalgia patients and 15 normal control subjects.
As a result, they say, the study offers the first objective method for corroborating what lower back pain patients report they feel, and what's going on in their brains at the precise moment they feel it. And, it continues to give researchers a road map of the areas of the brain that are most - and least - active when patients feel pain. The researchers hope that further study on larger groups of patients will yield more information on altered pain processing.
"The fMRI technology gave us a unique opportunity to look at the neurobiology underlying tenderness, which is a hallmark of both lower back pain and fibromyalgia," says Clauw. "These results, combined with other work done by our group and others, have convinced us that some pathologic process is making these patients more sensitive. For some reason, still unknown, there's a neurobiological amplification of their pain signals."
Take that Valerie Hardcastle. (Actually, I'm not sure if this is the sort of thing she has in mind for the 'mentally caused pains' she rails against since she never bothers to give them a sharp characterization despite discussing several different alleged cases. I'd appreciate it if someone could explain it to me in the comments...)