• Chad M Brummett, Andrew G Lohse, Alex Tsodikov, Stephanie E Moser, Taha S Meraj, Jenna Goesling, Michael Hooten, and Afton L Hassett.
• From the *Department of Anesthesiology, Division of Pain Medicine, University of Michigan Medical School, †University of Michigan Medical School, and ‡Department of Biostatistics, School of Public Health, University of Michigan, Ann Arbor, MI; and §Department of Anesthesiology, Mayo Clinic, Rochester, MN.
• Reg Anesth Pain Med. 2015 May 1;40(3):249-54.

Background And ObjectivesFacet interventions for spine pain have high failure rates, and preprocedural prediction of response is nearly impossible. A potential explanation may be aberrant central pain processing as that existing in conditions like fibromyalgia. To test this hypothesis, we conducted a retrospective study investigating the impact of having characteristics of fibromyalgia on the acute analgesic response to a first diagnostic medial branch block (MBB).MethodsWe evaluated the analgesic responses of 187 patients that underwent MBB. Patients were categorized as "fibromyalgia-positive" or "fibromyalgia-negative" using the 2011 fibromyalgia survey criteria. Preprocedural and postprocedural pain scores and patient-completed pain diaries up to 24 hours postprocedure were collected. A linear mixed model was used to study longitudinal effects of MBB on pain responses.ResultsFibromyalgia-positive patients had a worse preprocedural pain phenotype (ie, greater pain severity, higher levels of depressive and anxiety symptoms, reduced function). Binary categorization of fibromyalgia status was not associated with a difference in immediate postprocedural pain relief; however, the longitudinal analgesic response across time varied significantly between groups (P = 0.0005). Fibromyalgia-negative subjects showed the expected steep decline in pain scores, followed by gradual return to baseline, whereas a more aberrant pattern was noted in the fibromyalgia-positive group. Pain scores for fibromyalgia-negative patients were also lower by -1.07 (SE = 0.37) on average after the MBB (P = 0.005).ConclusionsCharacteristics of fibromyalgia may indicate pain that is more centralized in nature, a factor that may explain the aberrant analgesic response to this peripheral intervention. This may have implications for future prediction of treatment response, although prospective studies are needed.

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