title: Pain processing in medication overuse headache: a functional magnetic resonance imaging (fMRI) study.
abstract: OBJECTIVE
  The 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.
  
  
  METHODS
  Functional 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.
  
  
  RESULTS
  Compared 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.
  
  
  CONCLUSIONS
  Our 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.
authors.affiliation: Neuroradiology Department Headache Centre, Carlo Besta Neurological Institute-IRCCS Foundation, Milan, Italy. stefania.ferraro@istituto-besta.it
authors.forename: Stefania
authors.initials: S
authors.lastname: Ferraro
authors.forename: Licia
authors.initials: L
authors.lastname: Grazzi
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Mandelli
authors.forename: Domenico
authors.initials: D
authors.lastname: Aquino
authors.forename: Dagmar
authors.initials: D
authors.lastname: Di Fiore
authors.forename: Susanna
authors.initials: S
authors.lastname: Usai
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Bruzzone
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Salle
authors.forename: Gennaro
authors.initials: G
authors.lastname: Bussone
authors.forename: Luisa
authors.initials: L
authors.lastname: Chiapparini
mesh_terms: D000328:Adult; D059350:Chronic Pain / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D051271:Headache Disorders, Secondary / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009415:Nerve Net / Q000503:physiopathology*; D013375:Substance Withdrawal Syndrome / Q000175:diagnosis / Q000503:physiopathology*