Abstract
Objectives: This paper aims to determine if hypnotic analgesia suggestion and transcranial direct-current stimulation (tDCS) have a differential effect on pain perception. We hypothesized that transcranial direct-current stimulation would be more effective than hypnotic analgesia suggestion at changing the descending pain modulating system, whereas the hypnotic suggestion would have a greater effect in quantitative sensory testing.Design: This is a randomized, double blind and crossover trial.Settings: All stages of this clinical trial were performed at the Laboratory of Pain and Neuromodulation of the Hospital de Clínicas de Porto Alegre.Subjects: Were included 24 healthy females aged from 18 to 45 years old, with a high susceptibility to hypnosis, according to the Waterloo-Stanford Group Scale of Hypnotic Susceptibility, Form C (15).Methods: The subjects received a random and crossover transcranial direct-current stimulation over the dorsolateral prefrontal cortex (2 mA for 20 min) and hypnotic analgesia (20 min).Results: Only hypnotic suggestion produced changes that are statistically significant from pre- to post-intervention in the following outcomes measures: heat pain threshold, heat pain tolerance, cold pressure test, and serum brain-derivate-neurotrophic-factor. The analysis showed a significant main effect for treatment (F = 4.32; P = 0.04) when we compared the delta-(Δ) of conditioned pain modulation task between the transcranial direct-current stimulation and hypnotic suggestion groups. Also, the change in the brain-derivate-neurotrophic-factor was positively correlated with the conditioned pain modulation task.Conclusion: The results confirm a differential effect between hypnotic suggestion and transcranial direct-current stimulation on the pain measures. They suggest that the impact of the interventions has differential neural mechanisms, since the hypnotic suggestion improved pain perception, whereas the transcranial direct-current stimulation increased inhibition of the descending pain modulating system.Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT03744897.Perspective: These findings highlight the effect of hypnotic suggestion on contra-regulating mechanisms involved in pain perception, while the transcranial direct-current stimulation increased inhibition of the descending pain modulating system. They could help clinicians comprehend the mechanisms involved in hypnotic analgesia and transcranial direct-current stimulation and thus may contribute to pain and disability management.
Highlights
The pain and emotion circuits are reciprocally interconnected, providing pro- and anti-nociceptive pain modulation (Price, 2000)
This study tested the following hypotheses: (i) hypnotic suggestion would have a superior effect on pain perception in response to the Quantitative Sensory Testing (QST) compared with anodal transcranial directcurrent stimulation (tDCS) applied to the left dorsolateral prefrontal cortex (DLPFC) and cathodic tDCS applied to the right DLPFC, as assessed by changes in the heat pain threshold ( -Heat pain threshold (HPT)), heat pain tolerance ( -HPTo) and the cold pressure test ( -cold-pressor test (CPT)). (ii) Anodic tDCS applied to the left DLPFC and cathodic tDCS applied to the right DLPFC would be superior to hypnotic suggestion at altering the descending pain modulating system (DPMS) function, as assessed by the delta ( )-value of the change on the NPS during a conditioned pain modulation (CPM)-test
Three subjects were excluded because we identified the presence of minor psychiatric disorders or scores on the Beck Depression Inventory-II (BDI-II) that were higher than the cutoff point of 12
Summary
The pain and emotion circuits are reciprocally interconnected, providing pro- and anti-nociceptive pain modulation (Price, 2000). Sensory information is primarily transmitted by the ascending pathway, providing the sensory components of the pain experience, top-down neuromodulator techniques can affect both ascending and descending pain processing pathways. These approaches include non-invasive brain stimulation (NIBS) methods, which can alter aberrant activities within the pain processing circuit (e.g., transcranial direct-current stimulation [tDCS]), and psychological pain interventions, which improve the cognitive and emotional components of pain (e.g., meditation and hypnotic suggestions). The dorsolateral prefrontal cortex (DLPFC) is a target for improving pain sensations and the emotional aspects linked to pain (Fregni et al, 2005; Nitsche et al, 2008; Silva et al, 2017). Anodal tDCS applied to the left DLPFC, with the cathode over the right DLPFC has been shown to either enhance neural activity and/or reduce neural activity in the right DLPFC (Brunoni et al, 2012)
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