Usefulness of functional magnetic resonance imaging in the evaluation of pain. Practical application in fibromyalgia

Functional neuroimaging has helped to define the neural circuit involved in modulating of pain perception and response. Pain is a highly subjective experience that is difficult to measure objectively due to its varied expression. The fibromyalgia (FM) is a syndrome representative and prevalent of chronic functional pain, although it has a highly controversial diagnosis. For years, many health professionals have found that the FM would be typecast as a functional disorder and patients have had the perception of a systematic loss of interest and legitimacy from the medical field. Its symptoms could not be explained solely by an alteration of peripheral mechanisms of pain or by a specific central alteration. However, functional neuroimaging studies with functional magnetic resonance imaging (fMRI) have allowed to objectify their brain response to pain. The outcome validate an altered brain response to pain based on an increased activation of the neural matrix of pain, with longer time in brain areas involved in the emotional dimension of pain processing, and altered inhibitory mechanisms of endogenous nociceptive stimulation. These results allow us to advance the understanding of pathophysiological central mechanisms and open a new line of research to develop effective new treatments in the pathology of FM. However, the clinical use of fMRI for the diagnosis of fibromyalgia is not yet well established or defined.