Researchers at the University of Colorado Boulder have discovered a neural signature that identified fibromyalgia with 93% accuracy, according to a 72-patient study in the journal Pain 2016 Aug 31. “This neural measure for fibromyalgia is composed of three brain-related submeasures that together identify [individuals with] fibromyalgia,” said lead author Marina López-Solà, PhD, a postdoctoral research associate in the Cognitive and Affective Control Laboratory at the university. “These results build off of other important previous work and have to be replicated using other samples of fibromyalgia patients. They represent a natural step in the evolution of our understanding of fibromyalgia as a disorder with an important brain component.”
Two of the submeasures detect brain abnormalities in response to painful pressure, and the other one identifies abnormalities in response to nonpainful multisensory stimulation, including visual, auditory and tactile-motor stimulation. “Together, the three do a good job in predicting fibromyalgia status in our work,” Dr. López-Solà said. “If validated in future samples, this would be an interesting way of characterizing patient subtypes, since different patients have different degrees of abnormality for each measure.”
The study consisted of 37 female patients with fibromyalgia, based on 1990 American College of Rheumatology criteria for chronic widespread musculoskeletal pain, and 35 female matched healthy controls.
Dr. López-Solà said some patients “express” the pressure–pain neural measures to a greater degree than the multisensory measure, whereas other patients express the multisensory neural measure. “These markers will be interesting to test the effects of different forms of treatment with potentially different effects in the brain alterations observed in these individual patients,” she said.
The study is the result of a collaboration between the University of Colorado Boulder and the Hospital del Mar in Barcelona, Spain. Steps included measuring thresholds and tolerance of the stimuli involved in the experiment and conducting MRI assessments for all patients and controls. Two types of stimulations were administered: painful pressure to the fingernail and visual, auditory and tactile-motor stimulation.
“The main finding of our study was that, indeed, we could say something about whether a particular subject in our sample was a patient or a healthy control using the brain measures we had developed with a different subset of the subjects,” Dr. López-Solà said. “We trained the models in one part of the sample and then tested whether the brain measures that we obtained could give us any valuable information about the remaining subjects—about whether these remaining subjects were fibromyalgia patients or healthy subjects. We found that the brain measures identified new patients or controls correctly in 93% of cases. That is clearly above chance.”
Dr. López-Solà and her colleagues were amazed by this high level of accuracy. “It was also surprising to us that patients seem to have a very remarkable abnormality in the processing of nonpainful multisensory stimulation that is bigger in magnitude than the alteration in the processing of painful pressure,” she said. “This is in line with previous work that we and others have done, and suggests that the complaints that fibromyalgia patients express about being annoyed by nonpainful sensory signals in daily life—such as noises from TV or sunlight, or even the contact of sheets in bed—fit well with our results showing strong abnormalities in the processing of these types of stimuli that are not painful in nature but that become unpleasant to patients.”
Implications for Treatment?
Daniel J. Clauw, MD, professor of anesthesiology, medicine and psychiatry at the University of Michigan in Ann Arbor, said the study builds upon many other studies, “showing that there is a characteristic neural signature seen on functional neuroimaging in conditions such as fibromyalgia. This particular signature emphasizes the fact that fibromyalgia patients are more sensitive to other sensory experiences, in addition to pain. These and similar studies continue to debunk the widely held—but inaccurate—view that we do not understand the pathophysiology of fibromyalgia.”
However, the current study “does not necessarily have any treatment implications because it did not administer or test any treatments,” Dr. Clauw said. “Still, this type of neuroimaging study could eventually be used to diagnose conditions such as fibromyalgia with more certainty than at present, where we look only at symptoms. These methods could also be used to follow an individual’s response to therapy, or even what drugs an individual might respond to.”
Dr. López-Solà said her study results suggest that different patient profiles, with different severities of clinical pain, mood symptoms, functional disability and other parameters, “may indeed have different profiles of underlying brain abnormalities. Such information might be worth considering when deciding which treatment is more optimal to which patient. This may one day be helpful to assess the effects of different forms of treatment in different patients, and might even recommend treatment selection on a biologically grounded basis.”
Dr. López-Solà acknowledged that much more research is required, including validating these brain-derived measures in different fibromyalgia samples and how different factors influence the measures. “For example, the patients that we used in our work were all sufficiently severe,” she said. “Would the marker also identify less severe patients? Similarly, can the marker identify patients with other forms of chronic pain, or is it relatively specific to individuals with fibromyalgia? Which chronic pain symptoms are better identified by this marker?”
By partnering with experts in the fields of neuroscience, clinical psychology, psychiatry, rheumatology, neurology and immunology, “we may be able to answer many of the questions remaining about the different ways in which the peripheral and central nervous system contribute to the generation and maintenance of chronic pain states,” Dr. López-Solà said.