Sifting the wheat from the chaff? Evidence for the existence of an asymmetric fibromyalgia phenotype

Abstract

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.

Tactile Detection in Fibromyalgia: A Systematic Review and a Meta-Analysis

“…95.7% of participants with fibromyalgia and 86.6% of pain-free controls were women [one study did not indicate the proportion of men and women ( 57 )]. Fourteen studies out of the 19 reported a mean pain intensity rating, either at the moment of the participation [ n = 10; ( 24 , 27 , 31 , 34 , 36 , 37 , 57 – 60 )] or within the last month prior [ n = 4; ( 30 , 33 , 35 , 61 )]. In nine studies, including five in the meta-analysis ( 32 , 57 , 59 , 61 , 62 ), individuals with fibromyalgia were instructed to stop taking their medication prior to their participation ( 27 , 30 , 32 , 33 , 57 , 59 , 61 – 63 ).…”

“…The TDT was assessed with Von Frey filaments in all studies except one ( 60 ) in which unspecified nylon filaments were used. For the TPT, five studies involved pinprick stimulators ( 27 , 28 , 30 , 32 , 35 , 36 , 61 ), five involved Von Frey filaments ( 34 , 37 , 57 , 62 , 63 ), one involved unspecified nylon filaments ( 60 ) and one involved disposable needles ( 59 ).…”

“…Out of the 19 studies, 15 used the method of limits ( 24 , 27 , 28 , 30 , 32 , 34 – 37 , 41 , 57 , 60 – 63 ), one the staircase method ( 58 ) and three did not report the method used ( 31 , 33 , 59 ). In the method of limits, the stimulus intensity increases or decreases continuously, and the participants have to say when they detect or stop detecting the stimulation ( 46 ), whereas in the staircase method, the stimulus intensity increases or decreases according to whether the participant detects the stimulus ( 64 ).…”

“…The most frequently stimulated site was the hand [13 studies ( 24 , 27 , 28 , 30 , 31 , 34 , 35 , 57 – 62 )], then the back [seven studies ( 27 , 28 , 30 , 33 , 37 , 60 , 61 )], the foot ( 30 , 35 , 36 ), the face ( 28 , 59 , 60 ) and the forearm ( 32 , 37 , 63 ); three studies each, and the elbow ( 58 ), the tibia ( 59 ), and the sternum ( 24 ) (one study each).…”

Abnormal sensory thresholds of dystonic patients are not affected by deep brain stimulation

“…The tests performed were already extensively used (Cury et al., 2016; Kaziyama et al., 2020; Lopes et al., 2018). Briefly, stimuli were applied on the thenar eminence of the asymptomatic limb (i.e.…”