• H Kaziyama Helena H Pain Center, Department of Neurology, University of São Paulo, São Paulo, Brazil. In, Julio Barbour, Ricardo Galhardoni, Valquíria Aparecida da Silva, Silvia R D Tesseroli de Siqueira, Clarice Listik, Gabriel José Dos Santos, Lin T Yeng, Marco Antonio Marcolin, Irina Raicher, Manoel J Teixeira, and Daniel Ciampi de Andrade.
• Pain Center, Department of Neurology, University of São Paulo, São Paulo, Brazil.
• Eur J Pain. 2020 Sep 1; 24 (8): 1635-1647.

BackgroundThe different phenotypic presentations of fibromyalgia (FM) have been infrequently studied and may have diagnostic and therapeutic implications. The aim of this study was to explore differences between FM patients with classical symmetric (s-FM) presentation and FM patients with marked asymmetric (a-FM) pain.MethodsWe performed two consecutive cross-sectional studies on FM patients and matched healthy volunteers (HV). FM patients were divided into a-FM (and s-FM groups according to their score of pain intensity on each body side; patients with a difference of ≥40 mm in VAS between left and right sides were classified as a-FM, otherwise classified as s-FM. Participants (FM = 32; HV = 31) were assessed for clinical, cortical excitability (CE), quantitative sensory testing (QST; study 1), and intraepidermal nerve fibre density (IENFD) determinations (study 2).ResultsWhile pain intensity did not significantly differ between s-FM and a-FM patients, pain interference in daily activities was significantly higher in the a-FM as compared to the s-FM group (54.7 ± 8.9 and 37.6 ± 13.5; p < .0001). PPT was significantly lower in the more painful side of a-FM as compared to the HV (27.7 ± 7.9 and 49.9 ± 13.0; p < .0001), while PPT in the less painful side of a-FM was significantly higher than PPT values in the s-FM (35.8 ± 8.3 and 27.7 ± 5.5; p = .031). S-FM and a-FM had significantly abnormal intracortical inhibition values on CE measurements compared to HV. There were no significant differences in IENFD between groups.ConclusionsWithin the current FM criteria, there exist different phenotypes with clinical, psychophysics, and neurophysiological findings that are not related to peripheral IENFD abnormalities.SignificanceCurrent fibromyalgia criteria may contain different phenotypes of fibromyalgia based on the lateralization of pain.© 2020 European Pain Federation - EFIC®.

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