Fibromyalgia, a brain-based disorder

Fibromyalgia is characterized by an abnormally lowered threshold of sensitivity to a variety of stimuli due to impairment in the brain's ability to properly process sensory signals, as reflected in a study just published in the journal Arthritis & Rheumatology. The authors state:

"Fibromyalgia (FM) is a disorder characterized by chronic pain and enhanced responses to acute noxious events. However, the sensory systems affected in FM may extend beyond pain itself, as FM patients show reduced tolerance to non-nociceptive sensory stimulation. Characterizing the neural substrates of multisensory hypersensitivity in fibromyalgia may thus provide important clues about the underlying pathophysiology of the disorder. The aim of this study was to characterize brain responses to non-nociceptive sensory stimulation in FM patients and its relationship to subjective sensory sensitivity and clinical pain severity."

The assessed the brain response to auditory, visual and tactile-motor stimulation in 35 women with fibromyalgia and 25 matched controls using functional magnetic resonance imaging (fMRI) and correlated this data with subjective hyper-sensitivity to daily sensory stimulation, spontaneous pain, and functional disability. The results demonstrated that subjects with fibromyalgia had a markedly lowered threshold of sensitivity to stimuli:

"Patients reported increased subjective sensitivity (increased unpleasantness) in response to multisensory stimulation in daily life. FMRI revealed that patients showed reduced task-evoked activation in primary/secondary visual and auditory areas and augmented responses in the insula and anterior lingual gyrus. Reduced responses in visual and auditory areas were correlated with subjective sensory hyper-sensitivity and clinical severity measures."

In other words, the neurons responsible for maintaining normal sensitivity to stimuli were not firing properly in the subjects with fibromyalgia. Quoted in Medscape Medical News, lead author Marina López-Solà, PhD, from the Department of Psychology and Neuroscience at the University of Colorado, Boulder stated:

"The brain seems to be hypoprocessing at a basic first level of cortical processing, then amplifying the signal at a later level."Recognizing the connection between pain and hypersensitivity may help clinicians who might otherwise dismiss symptoms of pain in a patient who, Dr. López-Solà said, seems to "complain basically about everything."

The authors conclude:

"FM patients showed strong attenuation of brain responses to non-painful events in early sensory cortices, accompanied by an amplified response at later stages of sensory integration in the insula. These abnormalities are associated with core fibromyalgia symptoms, suggesting that they may be part of the pathophysiology of the disease."