Effect of anodal high-definition transcranial direct current stimulation on the pain sensitivity in a healthy population: a double-blind, sham-controlled study

Abstract

High-definition transcranial direct current stimulation (HD-tDCS) of brain areas related to pain processing may provide analgesic effects evident in the sensory detection and pain thresholds.The somatosensory sensitivity was assessed following HD-tDCS targeting the primary motor cortex (M1) and/or the dorsolateral prefrontal cortex (DLPFC). Eighty-one (40 females) subjects were randomly assigned to one of four anodal HD-tDCS protocols (20 min) applied on three consecutive days: Sham-tDCS, DLPFC-tDCS, M1-tDCS, and DLPFC&M1-tDCS (simultaneous tDCS of DLPFC and M1). Subjects and experimenter were blinded to the tDCS protocols. The somatosensory sensitivity were assessed each day, before and after each tDCS by detection and pain thresholds to thermal and mechanical skin stimulation, vibration detection thresholds, and pressureby the International Association for the Study of Pain. Unauthorized reproduction of this article is prohibited. 2021 4 pain thresholds. Subjects were effectively blinded to the protocol, with no significant difference in rates of whether they received real or placebo tDCS between the four groups. Compared with the Sham-tDCS, none of the active HD-tDCS protocols caused significant changes in detection or pain thresholds. Independent of tDCS protocols, pain and detection thresholds except vibration detection were increased immediately after the first tDCS protocol compared with baseline (P <0.05).Overall, the active stimulation protocols were not able to induce significant modulation of the somatosensory thresholds in this healthy population compared to sham-tDCS. Unrelated to the HD-tDCS protocol a decreased sensitivity was found after the first intervention, indicating a placebo effect or possibly habituation to the QST assessments. These findings add to the increasing literature of null-findings in the modulatory effects of HD-tDCS on the healthy somatosensory system.

Conditioning to Enhance the Effects of Repetitive Transcranial Magnetic Stimulation on Experimental Pain in Healthy Volunteers

“…Moreover, prior exposure to HPT equivalently increased post-intervention HPT across conditioning or intervention types. Similarly, in spite of experimental condition blinding, we observed a modest increase in baseline HPT between Visit 1 and Visit 2, which may reflect normal variability of HPT over time as pointed out in other studies (69,70), but also a possible "novelty effect" on Visit 1.…”

“…An important issue that was also observed in a recently published transcranial direct current stimulation (tDCS) study (69) was the high variability in baseline HPT from one visit to the other. In our study, we considered the potential confounding effects of several variables documented to influence the somatosensory system at baseline such as anxiety, depression, sleep, perceived stress, pain catastrophizing, and limited others at both visits such as medication and caffeine intake, circadian effects on QST and cortical excitability by performing both visits at the same time.…”

“…We nonetheless observed a significant difference between baseline HPT values from visit 1 to visit 2 across both groups, as heat pain thresholds at baseline in visit 2 were considerably higher than at visit 1 regardless of intervention order, which might have limited potential intervention-related improvement at visit 2. As noted by Kold and Graven-Nielsen (69), it is possible that the decreased heat sensitivity at the second visit could be due to some kind of habituation to the sensory testing, and perhaps to the intervention. As participants previously been exposed several times to rTMS and QST during the prior visit, the novelty and salience could have decreased, which may have increased mind wandering, reduce attention and thus decrease sensory experience (93).…”

Effects of transcranial direct current stimulation in pain and opioid consumption after spine surgery

“…Despite these limitations, a mild to moderate effect‐size was observed for tDCS in postoperative pain relief after spine surgery suggesting that more work is needed. Several novel tDCS techniques like high definition tDCS are beginning to demonstrate more promising effect for pain reduction could be useful for postoperative patient‐controlled analgesia (Kold & Graven‐Nielsen, 2021).…”

Mechanisms and manifestations in musculoskeletal pain: from experimental to clinical pain settings

“…In a large sham-controlled design with daily anodal tDCS applied to the primary motor cortex, dorsolateral prefrontal cortex, or both combined, the pain sensitivity (eg, pressure pain thresholds) was not affected in healthy participants. 121…”