Hyperexcitability in pain matrices in patients with fibromyalgia

Objective. Emerging evidence associates fibromyalgia (FM) with pain system dysfunction. In this study, using laser evoked potentials (LEPs) and paired laser stimuli, we tested excitability in the pain matrices and sought possible changes in patients with FM. Methods. In 20 patients with FM and 15 healthy subjects, after recording control nociceptive system-mediated A delta- and C-fibre-related LEPs, we measured excitability in the pain matrices by testing the A delta-LEP conditioned by a preceding C-LEP. Results. No difference was found in control LEP amplitudes for A delta- or C-fibres between patients and healthy subjects. Conversely, the A delta-LEP amplitude, conditioned by a preceding C-LEP, was significantly higher in patients than in healthy subjects (p<0.001). Conclusion. Objective evidence from increased conditioned A delta-LEP amplitudes reflecting hyperexcitability in the pain matrices in FM, provides diagnostically useful information and might help in developing new therapeutic approaches.