• Stefania Ferraro, Licia Grazzi, Maria Luisa Mandelli, Domenico Aquino, Dagmar Di Fiore, Susanna Usai, Maria Grazia Bruzzone, Francesco Di Salle, Gennaro Bussone, and Luisa Chiapparini.
• Neuroradiology Department Headache Centre, Carlo Besta Neurological Institute-IRCCS Foundation, Milan, Italy. stefania.ferraro@istituto-besta.it
• Pain Med. 2012 Feb 1;13(2):255-62.

ObjectiveThe primary aim was to investigate functional differences between medication overuse headache (MOH) patients and controls with the purpose of evaluating the presence of a global alteration in the processing of noxious stimuli throughout the pain matrix. The secondary aim was to investigate whether activations in MOH patients normalize after medication withdrawal, which would suggest a possible role of the pain matrix in headache chronification.DesignFunctional magnetic resonance imaging was performed during painful mechanical stimulation in nine female patients with MOH immediately and at 6 months after beginning medication withdrawal, and in nine control participants.ResultsCompared with controls, immediately after beginning withdrawal, the MOH patients showed reduced pain-related activity across the primary somatosensory cortex, inferior parietal lobule, and supramarginal gyrus, as well as in regions of the lateral pathway of the pain matrix. At 6 months, these differences were no longer detectable.ConclusionOur findings suggest that significant functional changes occur in the lateral pain pathway in MOH patients. These could result from different processes: 1) cortical down-regulation aimed at reducing painful input to the cortex; 2) activity-dependent plasticity induced by excessive painful input during migraine attacks; and 3) direct effect of medication overuse. At 6 months after withdrawal, activity in these regions normalized, suggesting that no irreversible changes occur due to medication overuse.Wiley Periodicals, Inc.

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