Abstract
To compare the analgesic effects of stimulation of the anterior cingulate cortex (ACC) or the posterior superior insula (PSI) against sham deep (d) repetitive (r) transcranial magnetic stimulation (TMS) in patients with central neuropathic pain (CNP) after stroke or spinal cord injury in a randomized, double-blinded, sham-controlled, 3-arm parallel study. Participants were randomly allocated into the active PSI-rTMS, ACC-rTMS, sham-PSI-rTMS, or sham-ACC-rTMS arms. Stimulations were performed for 12 weeks, and a comprehensive clinical and pain assessment, psychophysics, and cortical excitability measurements were performed at baseline and during treatment. The main outcome of the study was pain intensity (numeric rating scale [NRS]) after the last stimulation session. Ninety-eight patients (age 55.02 ± 12.13 years) completed the study. NRS score was not significantly different between groups at the end of the study. Active rTMS treatments had no significant effects on pain interference with daily activities, pain dimensions, neuropathic pain symptoms, mood, medication use, cortical excitability measurements, or quality of life. Heat pain threshold was significantly increased after treatment in the PSI-dTMS group from baseline (1.58, 95% confidence interval [CI] 0.09-3.06]) compared to sham-dTMS (-1.02, 95% CI -2.10 to 0.04, p = 0.014), and ACC-dTMS caused a significant decrease in anxiety scores (-2.96, 95% CI -4.1 to -1.7]) compared to sham-dTMS (-0.78, 95% CI -1.9 to 0.3; p = 0.018). ACC- and PSI-dTMS were not different from sham-dTMS for pain relief in CNP despite a significant antinociceptive effect after insular stimulation and anxiolytic effects of ACC-dTMS. These results showed that the different dimensions of pain can be modulated in humans noninvasively by directly stimulating deeper SNC cortical structures without necessarily affecting clinical pain per se. NCT01932905.
Highlights
Participants were randomly allocated into the active posterior superior insula (PSI)-rTMS, anterior cingulate cortex (ACC)-rTMS, sham-PSI-rTMS, or sham-ACC-rTMS arms
Active rTMS treatments had no significant effects on pain interference with daily activities, pain dimensions, neuropathic pain symptoms, mood, medication use, cortical excitability measurements, or quality of life
Heat pain threshold was significantly increased after treatment in the PSI-deep rTMS (dTMS) group from baseline (1.58, 95% confidence interval [CI] 0.09–3.06]) compared to sham-dTMS (−1.02, 95% CI −2.10 to 0.04, p = 0.014), and ACC-dTMS caused a significant decrease in anxiety scores (−2.96, 95% CI −4.1 to −1.7]) compared to sham-dTMS (−0.78, 95% CI −1.9 to 0.3; p = 0.018)
Summary
Participants were randomly allocated into the active PSI-rTMS, ACC-rTMS, sham-PSI-rTMS, or sham-ACC-rTMS arms. We assessed randomization effectiveness by evaluating balance regarding baseline variables, comparing the 2 interventions and the control arms. Results from balancing were evaluated through 1-way analysis of variance and χ2 tests According to these results, data from both sham arms were pooled together into a single sham arm for comparisons with PSI and ACC active dTMS arms as previously reported.[32] To evaluate intervention efficacy (NRS), we performed a series of generalized linear models and generalized estimating equation models to evaluate the association between all previously reported outcomes in the 2 intervention arms and the sham. The effect size of the study was calculated from the effects of the 3 arms on pain intensity
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