title: A novel paradigm to evaluate conditioned pain modulation in fibromyalgia.
abstract: BACKGROUND
  Application of noxious stimulation to one body area reduces pain sensitivity in a remote body area through activation of an endogenous pain-inhibitory network, a behavioral phenomenon referred to as conditioned pain modulation (CPM). The efficiency of CPM is predictive of a variety of health outcomes, while impaired CPM has been associated with various chronic pain conditions. Current methods used to assess CPM vary widely, and interest in CPM method development remains strong. Here, we evaluated a novel method for assessing CPM in healthy controls and fibromyalgia (FM) patients using thumb pressure as both a test and conditioning stimulus.
  
  
  METHODS
  Sixteen female FM patients and 14 matched healthy controls underwent CPM testing with thumbnail pressure as the test stimulus, and either cold water or noxious pressure as the conditioning stimulus. CPM magnitude was evaluated as the difference in pain rating of the test stimulus applied before and during the conditioning stimulus.
  
  
  RESULTS
  In healthy controls, application of either pressure or cold water conditioning stimulation induced CPM as evidenced by a significant reduction in test stimulus pain rating during conditioning (P=0.007 andP=0.021, respectively). In contrast, in FM patients, neither conditioning stimulus induced a significant CPM effect (P>0.274). There was a significant difference in CPM magnitude for FM patients compared to healthy controls with noxious pressure conditioning stimulation (P=0.023); however, no significant difference in CPM was found between groups using cold water as a conditioning stimulus (P=0.269).
  
  
  CONCLUSIONS
  The current study demonstrates that thumbnail pressure can be used as both a test and conditioning stimulus in the assessment of CPM. This study further confirms previous findings of attenuated CPM in FM patients compared with healthy controls.
authors.affiliation: Department of Anesthesiology, Chronic Pain and Fatigue Research Center, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Schoen
authors.affiliation: Institute of Rheumatology, Tel Aviv Suorasky Medical Center, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Jacob N
authors.initials: JN
authors.lastname: Ablin
authors.affiliation: Department of Anesthesiology, Chronic Pain and Fatigue Research Center, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Ichesco
authors.affiliation: Department of Neurology, University of Pennsylvania, Philadelphia, PA.
authors.forename: Rupal J
authors.initials: RJ
authors.lastname: Bhavsar
authors.affiliation: Department of Anesthesiology, Chronic Pain and Fatigue Research Center, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Kochlefl
authors.affiliation: Department of Anesthesiology, Chronic Pain and Fatigue Research Center, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Harris
authors.affiliation: Department of Anesthesiology, Chronic Pain and Fatigue Research Center, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Clauw
authors.affiliation: Department of Endodontics, University of North Carolina - Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Gracely
authors.affiliation: Department of Anesthesiology, Chronic Pain and Fatigue Research Center, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Harte
keywords: cold pressor test; diffuse noxious inhibitory controls; pressure pain; quantitative sensory testing