116 Altered peripheral axonal properties in fibromyalgia

Abstract

IntroductionFibromyalgia (FM), a common chronic widespread pain syndrome with neurological symptoms affecting ∼10% of the population worldwide. Whereas small fibre neuropathy is a recognized part of FM, surprisingly little is known about large fibre neuropathy. The present study investigates the sensory and motor axonal properties using novel nerve excitability testing (NET) to seek a better understanding of the pathogenesis of this painful disorder.Methods25 FM patients were recruited from the Wan Fang Hospital in Taiwan who fulfilled the American College of Rheumatology diagnostic criteria.1 NCS, pain scores, blood tests and NET were performed in all patients and patients with factors that may confound the results of NET were excluded. Control data were obtained from age and gender-matched healthy controls (HC) who had no neurological deficits or known pain disorders.ResultsThe FM group showed an increase in superexcitability (p<0.05), subexcitability (p<0.05) and over-shoot during hyperpolarizing threshold electrotonus (p<0.05) in the sensory excitability profiles in contrast to HC. However, motor nerve excitability profiles showed no significant difference.ConclusionsAlterations in the sensory axonal parameters can be detected while NCS is normal, these findings are compatible with the concept that the sensory system is mainly involved in the pathogenesis of FM. Results implied probable hypofunction of the paranodal fast K+ channel in the sensory axons, known to be associated with the generation of pain.2 Our study highlights the advantage of NET over NCS, in the early detection of axonal dysfunction and may provide further understandings of future therapeutic treatment.ReferencesWolfe F, Clauw DJ, Fitzcharles MA, Goldenberg DL, Hauser W, Katz RS, Mease P, Russell AS, Russell IJ, Winfield JB. Fibromyalgia criteria and severity scales for clinical and epidemiological studies: a modification of the ACR Preliminary Diagnostic Criteria for Fibromyalgia. J Rheumatol 2011;38(6):1113–1122.Kuwabara S, Misawa S. Pharmacologic intervention in axonal excitability: in vivo assessment of nodal persistent sodium currents in human neuropathies. Curr Mol Pharmacol 2008;1(1):61–67.