Effects of Hypnotic Analgesia and Transcranial Direct Current Stimulation on Pain Tolerance and Corticospinal Excitability in Individuals with Fibromyalgia: A Cross-Over Randomized Clinical Trial

Abstract

Objective

We compare the effect of HAS, a-tDCS on the left dorsolateral prefrontal cortex (l-DLPFC), and rest-testing on pain measures [(cold pressor test (CPT) (primary outcome) and heat pain threshold]. We also compare their effects on the motor evoked potential (MEP) (primary outcome), short intracortical inhibition (SICI), intracortical facilitation (ICF), and cortical silent period (CSP).

Methods

This randomized, blind, crossover trial included 18 women with fibromyalgia, aged from 18 to 65 years old. They received at random and in a crossover order a-tDCS over the l-DLPFC (2mA), HAS, or a rest-testing.

Results

HAS compared to a-tDCS increased the pain tolerance with a moderate effect size (ES) [Cohen’s f=−0.78; (CI 95%; −1.48 to −0.12)]. While compared to rest-testing, HAS increased the CPT with a large ES [Cohen’s f=−0.87; (CI 95%; −1.84 to −0.09)]. The a-tDCS compared to HAS increased the MEP amplitude with large ES [Cohen’s f=−1.73 (CI 95%; −2.17 to −0.17)]. Likewise, its ES compared to rest-testing in the MEP size was large [Cohen’s f=−1.03; (CI 95%; −2.06 to −0.08)].

Conclusion

These findings revealed that HAS affects contra-regulating mechanisms involved in perception and pain tolerance, while the a-tDCS increased the excitability of the corticospinal pathways. They give a subsidy to investigate their effect as approaches to counter regulate the maladaptive neuroplasticity involved in fibromyalgia.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier – NCT05066568.

Keywords:

• tDCS
• hypnosis
• hypnotic analgesia
• chronic pain
• fibromyalgia
• pain threshold
• cold pressor test
• CPM-test

Data Sharing Statement

After acceptance, the corresponding author accepts to submit the datasets underlying the results of this paper to the editorial office.

Acknowledgments

This manuscript was based on the author’s master dissertation intitulated “Effects of transcranial direct current stimulation and hypnotic suggestion in tolerance to pain and cortical excitability in fibromyalgia: a cross-over randomized clinical trial”. Reference: Corrêa BSC. Efeitos da estimulação transcraniana de corrente contínua e sugestão hipnótica na tolerância à dor e excitabilidade cortical na fibromialgia: um ensaio clínico randomizado cruzado. LUME UFRGS. 2022. http://hdl.handle.net/10183/238843. The authors would like to acknowledge Fundação de incentivo à Pesquisa (FIPE) at Hospital de Clínicas de Porto Alegre.

Disclosure

Dr Paulo RS Sanches reports a patent BR2020150164500 with royalties paid to Quark Medical. Dr Felipe Fegni reports grants from NIH and personal fees from Neurive, outside the submitted work. The authors declare no other conflicts of interest in this work.

Additional information

Funding

The present research was supported by the following Brazilian funding agencies: (i) Committee for the Development of Higher Education Personnel – CAPES PROEX (grant to BS with master scholarship, Grant #2020). (ii) National Council for Scientific and Technological Development – CNPq (grant to WC number: 420826/2018-1). (iii) Foundation for the Support of Research at Rio Grande do Sul (FAPERGS) Ministry of Science and Technology. National Council for Scientific and Technological Development – (CNPq)/ Health Secretary of state of Rio Grande do Sul, Brazil (SEARS) n. 03/2017 (PPSUS) (number: 17/2551-0001). (iv) Brazilian Innovation Agency (FINEP [Financiadora de Estudos e Projetos]) (process number 1245/13). (v) FINEP grant 0261/18 chamada pública MCTIC/FINEP/CT-INFRA 04/2018. (vi) Fundação de incentivo à Pesquisa (FIPE) at Hospital de Clínicas de Porto Alegre.