Fibromyalgia syndrome (FMS) is a highly prevalent, chronic musculoskeletal condition characterized by widespread pain and evoked pain at tender points. This study evaluated various aspects of body awareness in a sample of 14 women with FMS and 13 healthy controls, such as plasticity of the body schema, body esteem, and interoceptive awareness. To this end, the Rubber Hand Illusion (RHI), the Body Esteem Scale (BES), and the Body Perception Questionnaire (BPQ) were used, respectively. Consistent with increased plasticity of the body schema, FMS patients scored higher, with large or very large effect sizes, across all three domains evaluated in the RHI paradigm, namely proprioceptive drift and perceived ownership and motor control over the rubber hand. Scores on all items addressed by the BES were consistently lower among FMS subjects (2.52, SEM .19 vs 3.89, SEM .16, respectively, p < .01, Cohen’s d = .38-.66). In the FMS sample, BES scores assigned to most painful regions also were lower than those assigned to the remaining body sites (1.58, SEM .19 vs 2.87, SEM .18, respectively, p < .01). Significantly higher scores (p < .01, Cohen’s d = .51-.87) were found in the FMS sample across awareness (3.57 SEM .15 vs 1.87 SEM .11), stress response (3.76 SEM .11 vs 1.78 SEM .11), autonomic nervous system reactivity (2.59 SEM .17 vs 1.35 SEM .07), and stress style 2 (2.73 SEM .27 vs 1.13 SEM .04) subscales of the BPQ. Intensity of ongoing clinical pain was found to be strongly correlated with interoceptive awareness (r = .75, p = .002). The results suggest a disturbed embodiment in FMS, characterized by instability of the body schema, negatively biased cognitions regarding one’s own body, and increased vigilance to internal bodily cues. These manifestations may be interpreted as related with the inability of incoming sensory inputs to adequately update negatively biased off-line somatorepresentations stored as long-term memory.

Objective: Evidence suggests that there is an association between chronic pain and disruption of the body schema. We tested the hypothesis in fibromyalgia syndrome (FMS). Materials and Methods: We investigated distinct perceptual aspects of the body schema both in a sample of patients with FMS and in pain-free controls. Performances on the left/right judgment task were measured; tactile acuity was assessed by using the 2-point discrimination test. Furthermore, we evaluated sensations evoked by tactile stimulation with von Frey filaments to body parts that were experiencing pain. Anomalous sensations elicited by sensory-motor conflict (SMC) were also investigated. Results: Patients with FMS showed inferior performance on the right/left judgment task, both in terms of correct matches (75.38% vs. 89.67%, respectively; P<0.05) and response time (2.58 s vs. 1.89 s, respectively; P<0.05). Effect sizes were large and very large, respectively. Two-point discrimination thresholds were significantly higher (P<0.05) in participants from the FMS sample (mean of 49.71 mm, SD: 12.09 mm) relative to controls (mean of 37.36 mm, SD: 7.81 mm). Nine of 14 participants with FMS, but no control participants, reported referred sensations upon tactile stimulation, including tingling, pins and needles, weight, and cramps. Referral sites included regions both adjacent and remote to stimulated sites. Patients with FMS scored across all items within the administered questionnaire addressing anomalous sensations on the mirror setup (Cohen d=1.04 to 2.42 across all items), and FMS patients perceived pain during the SMC (the required statistical power for it to be statistically significant was 96% and for it to be recognized as a difference of means in pain item). Conclusion: Our present findings suggest a disrupted body schema and propensity to experiencing anomalous somatosensory sensations during SMC in people with FMS.

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