Transcranial Magnetic Stimulation of the Supplementary Motor Area in the Treatment of Obsessive-Compulsive Disorder: A Multi-Site Study

Transcranial magnetic stimulation in the treatment of obsessive-compulsive disorder: current perspectives

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive neurostimulation technique receiving increasing attention in the treatment of different psychiatric disorders. Evidence for rTMS use in obsessive-compulsive disorder (OCD) is accumulating and informing further developments in the neurostimulation field, the latest being deep transcranial magnetic stimulation (dTMS). dTMS allows direct stimulation of deeper subcortical structures and larger brain volume than conventional rTMS. Underlying neurobiological mechanisms related to transcranial magnetic stimulation are still under evaluation, but appear to offer a novel "third" way of addressing symptoms via localized electrical stimulation compared to pharmacotherapy and psychotherapy approaches. This systematic review focuses on the effects of rTMS and dTMS stimulation on different brain targets in OCD. Brain areas included are the dorsolateral prefrontal cortex, supplementary motor area, orbitofrontal cortex/medial prefrontal cortex, and anterior cingulate cortex (ACC). Improved understanding of the therapeutic effects of rTMS in OCD will support fine-tuning of the method and help determine how we can best optimize the approach via rTMS or dTMS to achieve clinically relevant results.

Updated Review on the Clinical Use of Repetitive Transcranial Magnetic Stimulation in Psychiatric Disorders

With the ability to modulate cortical activity, repetitive transcranial magnetic stimulation (rTMS) is becoming increasingly important in clinical applications for psychiatric disorders. Previous studies have demonstrated its promising efficacy in depression and schizophrenia, and emerging evidence has also been found in patients with anxiety disorder, obsessive-compulsive disorder, and substance or food craving. However, the overall literature features some conflicting results, varied quality of studies, and a lack of consensus on optimal rTMS parameters. Besides, the efficacy of rTMS in patients with medication-resistant symptoms has drawn most attention from clinicians. Here we review multi-site studies and double-blind randomized controlled trials (RCTs) in single sites, as well as meta-analyses of RCTs in the last three years, in order to update evidence on efficacy and the optimal protocol of rTMS in psychiatric disorders, especially for medication-resistant symptoms.

Repetitive motor cortex stimulation reinforces the pain modulation circuits of peripheral neuropathic pain

Recent evidence indicates that motor cortex stimulation (MCS) is a potentially effective treatment for chronic neuropathic pain. However, the neural mechanisms underlying the attenuated hyperalgesia after MCS are not completely understood. In this study, we investigated the neural mechanism of the effects of MCS using an animal model of neuropathic pain. After 10 daily sessions of MCS, repetitive MCS reduced mechanical allodynia and contributed to neuronal changes in the anterior cingulate cortex (ACC). Interestingly, inhibition of protein kinase M zeta (PKMζ), a regulator of synaptic plasticity, in the ACC blocked the effects of repetitive MCS. Histological and molecular studies showed a significantly increased level of glial fibrillary acidic protein (GFAP) expression in the ACC after peripheral neuropathy, and neither MCS treatment nor ZIP administration affected this increase. These results suggest that repetitive MCS can attenuate the mechanical allodynia in neuropathic pain, and that the activation of PKMζ in the ACC may play a role in the modulation of neuropathic pain via MCS.

An updated meta-analysis: Short-term therapeutic effects of repeated transcranial magnetic stimulation in treating obsessive-compulsive disorder

BACKGROUND

This study was conducted to evaluate the short-term therapeutic effects of using repeated transcranial magnetic stimulation (rTMS) to treat obsessive-compulsive disorder (OCD) and to examine potential influencing factors.

METHOD

We searched the PubMed, EMBASE, CENTRAL, Wanfang, CNKI, and Sinomed databases on September 18, 2016 and reviewed the references of previous meta-analyses. Sham-controlled, randomized clinical trials using rTMS to treat OCD were included. Hedge's g was calculated for the effect size. Subgroup analyses and univariate meta-regressions were conducted.

RESULTS

Twenty studies with 791 patients were included. A large effect size (g=0.71; 95%CI, 0.55-0.87; P<0.001) was found for the therapeutic effect. Targeting the supplementary motor area (SMA) (g=0.56; 95%CI, 0.12-1.01; P<0.001), left dorsolateral prefrontal cortex (DLPFC) (g=0.47; 95%CI, 0.02-0.93; P=0.02), bilateral DLPFC (g=0.65; 95%CI, 0.38-0.92; P<0.001) and right DLPFC (g=0.93; 95%CI, 0.70-1.15; P<0.001), excluding the orbitofrontal cortex (OFC) (g=0.56; 95%CI, -0.05-1.18; P=0.07), showed significant improvements over sham treatments. Both low-frequency (g=0.73; 95%CI, 0.50-0.96; P<0.001) and high-frequency (g=0.70; 95%CI, 0.51-0.89; P<0.001) treatments were significantly better than sham treatments, with no significant differences between the effects of the two frequencies. The subgroup analyses indicated that patients who were non-treatment resistant, lacked concurrent major depressive disorder (MDD) and received threshold-intensity rTMS showed larger therapeutic effects than the corresponding subgroups. The subgroup analysis according to sham strategy showed that tilted coils yielded larger effects than sham coils. Meta-regression analyses revealed that none of the continuous variables were significantly associated with the therapeutic effects.

LIMITATIONS

Only short-term therapeutic effects were assessed in this study.

CONCLUSIONS

Based on this study, the short-term therapeutic effects of rTMS are superior to those of sham treatments. The site of stimulation, stimulation frequency and intensity and sham condition were identified as potential factors modulating short-term therapeutic effects. The findings of this study may inspire future research.