Efficacy of non-invasive brain stimulation and neuronavigation for major depressive disorder: a systematic review and meta-analysis.

INTRODUCTION: Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are increasingly used for major depressive disorder (MDD). Most tDCS and rTMS studies target the left dorsolateral prefrontal cortex, either with or without neuronavigation. We examined the effect of rTMS and tDCS, and the added value of neuronavigation in the treatment of MDD. METHODS: A search on PubMed, Embase, and Cochrane databases for rTMS or tDCS randomized controlled trials of MDD up to 1 February 2023, yielded 89 studies. We then performed meta-analyses comparing tDCS efficacy to non-neuronavigated rTMS, tDCS to neuronavigated rTMS, and neuronavigated rTMS to non-neuronavigated rTMS. We assessed the significance of the effect in subgroups and in the whole meta-analysis with a z-test and subgroup differences with a chi-square test. RESULTS: We found small-to-medium effects of both tDCS and rTMS on MDD, with a slightly greater effect from rTMS. No significant difference was found between neuronavigation and non-neuronavigation. CONCLUSION: Although both tDCS and rTMS are effective in treating MDD, many patients do not respond. Additionally, current neuronavigation methods are not significantly improving MDD treatment. It is therefore imperative to seek personalized methods for these interventions.

Remotely supervised at-home delivery of taVNS for autism spectrum disorder: feasibility and initial efficacy.

Background: Transcutaneous auricular vagus nerve stimulation (taVNS) has potential clinical application for autism spectrum disorder (ASD). At-home sessions are necessary to allow delivery of repeated sessions, and remove burden on patients for daily visits, and reduce costs of clinic delivery. Our objective was to validate a protocol for remote supervised administration for home delivery of taVNS using specially designed equipment and platform. Methods: An open-label design was followed involving administration by caretakers to 12 patients with ASD (ages:7-16). Daily 1-h sessions over 2 weeks were administered under remote supervision. The primary outcome was feasibility, which was assessed by completion rate, stimulation tolerability, and confirmation of programmed stimulation delivery. The secondary measures were initial efficacy assessed by Childhood Anxiety Sensitivity Index-Revised (CASI-R), Parent Rated Anxiety Scale for Youth with ASD (PRAS-ASD), and Clinician Global Impression (CGI) scales. Sleep measures were also tracked using Cleveland Adolescent Sleep Questionnaire (CASQ). Results: Across 132 sessions, we obtained an 88.5% completion rate. A total of 22 expected adverse events were reported with headache being the most common followed by transient pain, itchiness, and stinging at the electrode site. One subject dropped out of the study unrelated to the stimulation or the study. Average scores of anxiety (CASI-R, PRAS-ASD, and CGI) and sleepiness (CASQ) were all improved at the 2 week time point. While not powered to determine efficacy, benefits were suggested in this open label pilot. Conclusion: Remotely supervised, proxy-administered, at-home delivery of taVNS is feasible in patients with ASD. Initial efficacy supports pursuing larger scale trials.

Feasibility of Direct Current stimulation through hair using a dry electrode: potential for transcranial Direct Current Stimulation (tDCS) application.

Conventional transcranial direct current stimulation (tDCS) protocols typically deliver 2 mA for 20-30 minutes. The most common administration uses a wet electrode approach which dries out in ~60 minutes at room temperature. This restricts its application to limited duration electrode-scalp contact use cases unless additional conductive media (saline, gel, or paste) is re-applied. This problem is further compounded by the subject's hair which not only presents administration challenges (interferes with electrode attachment and adhesion) but also acts as a conduit of current flow into the scalp resulting in current hotspots. This non-uniform current injection results in increased skin sensation. The aim of this study was to determine suitability of a commercially available hydrogel for DC delivery through hair. Experiments involved both non-clinical testing on an agar block and clinical testing on subjects' forearms. Electrodes were positioned on the posterior side of the forearm that has hair for the clinical testing. Typical dose as used in tDCS was delivered and pain scores were collected. Results indicate suitable current delivery performance and all subjects tolerated delivery with pain scores ranging between 0-6. Our study paves the way for future testing on the scalp for tDCS application.Clinical Relevance-This study demonstrates the possibility of delivering tDCS through hair via dry electrodes. Specific use cases that cannot use a traditional wet electrode approach stand to benefit from the results of our work.

Universal Transcranial Direct Current Stimulation (tDCS) Headset for targeting the bilateral Dorsolateral Prefrontal Cortex: Towards facilitating broader adoption.

Electrode position affects the brain current flow intensity and distribution induced by transcranial direct current stimulation (tDCS). The dorsolateral pre-frontal cortex (DLPFC) is a common target in neuropsychology and neuropsychiatry applications. A positioning scheme and subsequently a headgear has previously been developed to target the DLPFC automatically - devoid of any scalp ruler or neuronavigation method. This approach minimizes the time cost for pre-treatment measurements without compromising targeting accuracy and induced electric field focality. The goal of this study was to further develop this headgear to facilitate broader adoption while maintaining its core design elements intact. Briefly, we developed the headset to accommodate all adult head sizes (52-62 cm) rather than having multiple sizes, to have increased robustness, enhanced visual aesthetics, and have improved usability.We recruited 8 subjects and tested the accuracy of electrode placement on various head sizes. We also tested usability with the System Usability Scale (SUS) and asked the subjects to rate visual appeal. Our study demonstrated that the newly developed headset had greater usability and was more visually appealing than its predecessor without compromising targeting accuracy.Clinical Relevance- This study introduces a headset for routine tDCS administration targeting bilateral DLPFC. The headset is highly usable, robust, and is expected to facilitate home and high-volume use.

Galvanic Vestibular Stimulation Headset balancing robust and simple administration with subject comfort: A Usability Analysis.

The vestibular system is responsible for spatial orientation and stability. It can be stimulated with a weak electric current, a mechanism known as Galvanic Vestibular Stimulation (GVS). Typical GVS administration involves holding down electrodes on the mastoids either with a strap (or bandage) wrapped around the head or by positioning a self-adhesive electrode at the mastoid location. While the latter approach is simple to administer, it is limited to exposed skin application as hair impedes adhesion. The reduced access area limits total current delivery allowable due to increased skin sensation. Accordingly the former approach is more typically employed but leads to inconsistent and inaccurate electrode placement. As current flow pattern is directly influenced by electrode position, this results in inconsistent stimulation and replicability issues. The primary goal of this study was to test usability and comfort while developing a GVS-specific headset named "Mastoid Adjustable Robust Stimulation (MARS)" compared to a conventional elastic strap. We recruited 10 subjects, 5 operators and 5 wearers, and tested usability using the System Usability Scale (SUS) as well as comfort levels over a typical 20 minute stimulation session. Additional questions were answered by the operators and wearers on visual appeal, interference, slippage, and electrode placement. The results of this testing guided the development of a final version meeting our requirements of robustness, simple to administer, and subject comfort.Clinical Relevance-This study introduces a headset for routine Bilateral-Bipolar GVS administration that is highly usable and ensures both flexible and consistent electrode application over typical approaches.