Background & Aims

Fibromyalgia (FM) is a chronic pain syndrome characterized by widespread, severe musculoskeletal pain resulting from central nervous system (CNS) dysfunction and other symptoms such as fatigue and mood disturbances. The pathogenesis of FM is thought to be primarily due to nociplastic pain mechanisms, which primarily involve changes in pain signal processing in the CNS and are typified by allodynia and hyperalgesia in the absence of obvious tissue damage or inflammation. It causes increased pain sensitivity. On the other hand, there are many people who suffer from localized musculoskeletal pain (MSP) for a long time, and it is assumed that some kind of functional change in the nervous system is caused in these cases as well. Therefore, this study aimed to compare the pain sensitivity characteristics of FM and MSP patients using a multimodal approach, and to deepen our understanding of the pathophysiology of FM and MSP.

Methods

This study included patients with FM (n=25) and MSP (n=23). Participants were assessed for self-reported pain using the numerical rating scale (NRS), pressure pain threshold (PPT) at the painful site, temporal summation of pain (TSP), conditioned pain modulation (CPM), and central sensitization-related symptoms (CSS) assessed by the central sensitization inventory (CSI), along with cognitive-emotional measures. Statistical analyses were conducted to compare each measure between FM and MSP groups. Furthermore, within the FM group, a cluster analysis was performed based on PPT reference values and CSI severity, according to international criteria for nociplastic pain, with subsequent comparison of characteristics between clusters.

Results

Both FM and MSP groups reported severe pain, with no significant differences in NRS scores observed between them. CPM was significantly lower in the FM group compared to the MSP patients, but no significant differences were found in TSP, the pain catastrophizing scale, or the pain self-efficacy questionnaire. CSI and the hospital anxiety and depression scale were significantly higher in the FM group than the MSP group. Cluster analysis within the FM group identified two clusters: cluster 1 with low PPT and mild CSI, and cluster 2 with low PPT and severe CSI. However, there were no significant differences in TSP, CPM, or cognitive-emotional measures between the two clusters.

Conclusions

In this study, both FM and MSP patients exhibited severe subjective pain levels. However, FM was inferred to have significant CSS and an endogenous pain suppression system compared to MSP. Within the FM group, significant reductions in PPT and CPM were observed almost without exception, but there was no relationship between the degree of CSS and central sensitization. Thus, although central sensitization plays an important role in the increased sensitivity to pain seen in FM, the presence of CSS does not necessarily define central sensitization in FM, which may be influenced more by psychological factors than neurological etiology.

References

1) Siracusa R, Paola RD, Cuzzocrea S, et al. Fibromyalgia: Pathogenesis, Mechanisms, Diagnosis and Treatment Options Update. Int J Mol Sci 2021;22(8):3891.
2) Arnold LM, Choy E, Clauw DJ, et al. Fibromyalgia and Chronic Pain Syndromes: A White Paper Detailing Current Challenges in the Field. Clin J Pain 2016;32(9):737-46.
3) Kosek E, Clauw D, Nijs J, et al. Chronic nociplastic pain affecting the musculoskeletal system: clinical criteria and grading system. Pain 2021;162(11):2629-2634.
4) Staud R, Godfrey MM, Riley JL, et al. Efficiency of pain inhibition and facilitation of fibromyalgia patients is not different from healthy controls: Relevance of sensitivity-adjusted test stimuli. Br J Pain. 2023;17(2):182-194.

Presenting Author

Takako Matsubara

Poster Authors

Takako Matsubara

PT

Kobe Gakuin University

Lead Author

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Takafumi Hattori

Kobe Gakuin University

Lead Author

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Yukiko Shiro

Nagoya Gakuin University

Lead Author

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Keiko OWARI

Pain Relief Surgery and Multidisciplinary Pain Center, Aichi Medical University Hospital

Lead Author

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Hidemi Niwa

Pain Relief Surgery and Multidisciplinary Pain Center, Aichi Medical University Hospital

Lead Author

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Chiaki Tanaka

Pain Relief Surgery and Multidisciplinary Pain Center, Aichi Medical University Hospital

Lead Author

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Shuhei Nagai

Pain Relief Surgery and Multidisciplinary Pain Center, Aichi Medical University Hospital

Lead Author

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Hironori Saisu

Pain Relief Surgery and Multidisciplinary Pain Center, Aichi Medical University Hospital

Lead Author

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Takahiro Ushida

Multidisciplinary Pain Center, Aichi Medical University

Lead Author

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Topics

  • Specific Pain Conditions/Pain in Specific Populations: Fibromyalgia