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Bruno Schein,1,2 Gerardo Beltran,1â 3 Bárbara Regina França,1,2 Paulo RS Sanches,4 Danton P Silva Jr,4 Iraci Lucena Torres,5,6 Felipe Fegni,7 Wolnei Caumo1,2,5,8 1Post-Graduate Program in Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Rio Grande do Sul (RS), Brazil; 2Laboratory of Pain and Neuromodulation, Hospital de ClÃnicas de Porto Alegre (HCPA), Porto Alegre, RS, Brazil; 3Institute of Neurosciences, Universidad Catolica de Cuenca, Cuenca, Ecuador; 4Laboratory of Biomedical Engineer, HCPA, Porto Alegre, RS, Brazil; 5Pain and Palliative Care Service, HCPA, Porto Alegre, RS, Brazil; 6Laboratory of Pharmacology of Pain and Neuromodulation, Experimental Research Center, HCPA, Porto Alegre, RS, Brazil; 7Laboratory of Neuromodulation and Center for Clinical Research Learning, Physics and Rehabilitation Department, Spaulding Rehabilitation Hospital, Boston, MA, USA; 8Department of Surgery, School of Medicine, UFRGS, Porto Alegre, RS, BrazilCorrespondence: Wolnei Caumo, Laboratory of Pain and Neuromodulation, Hospital de ClÃnicas de Porto Alegre at UFRGS, Ramiro Barcelos, 2350 - CEP 90035-003 Bairro Rio Branco, Porto Alegre, RS, Brazil, Tel/Fax +55 51- 33598083, Email wcaumo@hcpa.edu.brObjective: 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) [Cohenâs f=â 0.78; (CI 95%; â 1.48 to â 0.12)]. While compared to rest-testing, HAS increased the CPT with a large ES [Cohenâs f=â 0.87; (CI 95%; â 1.84 to â 0.09)]. The a-tDCS compared to HAS increased the MEP amplitude with large ES [Cohenâs f=â 1.73 (CI 95%; â 2.17 to â 0.17)]. Likewise, its ES compared to rest-testing in the MEP size was large [Cohenâs f=â 1.03; (CI 95%; â 2.06 to â 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 â NCT05066568.Keywords: tDCS, hypnosis, hypnotic analgesia, chronic pain, fibromyalgia, pain threshold, cold pressor test, CPM-test |
