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Cerebellar transcranial magnetic stimulation: the role of coil geometry and tissue depth.

ABSTRACT: While transcranial magnetic stimulation (TMS) coil geometry has important effects on the evoked magnetic field, no study has systematically examined how different coil designs affect the effectiveness of cerebellar stimulation.The depth of the cerebellar targets will limit efficiency. Angled coils designed to stimulate deeper tissue are more effective in eliciting cerebellar stimulation.Experiment 1 examined basic input-output properties of the figure-of-eight, batwing and double-cone coils, assessed with stimulation of motor cortex. Experiment 2 assessed the ability of each coil to activate cerebellum, using cerebellar-brain inhibition (CBI). Experiment 3 mapped distances from the scalp to cerebellar and motor cortical targets in a sample of 100 subjects' structural magnetic resonance images.Experiment 1 showed batwing and double-cone coils have significantly lower resting motor thresholds, and recruitment curves with steeper slopes than the figure-of-eight coil. Experiment 2 showed the double-cone coil was the most efficient for eliciting CBI. The batwing coil induced CBI only at higher stimulus intensities. The figure-of-eight coil did not elicit reliable CBI. Experiment 3 confirmed that cerebellar tissue is significantly deeper than primary motor cortex tissue, and we provide a map of scalp-to-target distances.The double-cone and batwing coils designed to stimulate deeper tissue can effectively stimulate cerebellar targets. The double-cone coil was found to be most effective. The depth map provides a guide to the accessible regions of the cerebellar volume. These results can guide coil selection and stimulation parameters when designing cerebellar TMS studies.

SUBMITTER: Hardwick RM

PROVIDER: S-EPMC4180011 | biostudies-literature | 2014 Sep-Oct

REPOSITORIES: biostudies-literature

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Cerebellar transcranial magnetic stimulation: the role of coil geometry and tissue depth.

Hardwick Robert M RM Lesage Elise E Miall R Chris RC

Brain stimulation 20140506 5

<h4>Background</h4>While transcranial magnetic stimulation (TMS) coil geometry has important effects on the evoked magnetic field, no study has systematically examined how different coil designs affect the effectiveness of cerebellar stimulation.<h4>Hypothesis</h4>The depth of the cerebellar targets will limit efficiency. Angled coils designed to stimulate deeper tissue are more effective in eliciting cerebellar stimulation.<h4>Methods</h4>Experiment 1 examined basic input-output properties of t ...[more]

PMID: 24924734

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Project description:BackgroundThe current study aims to systematically assess and compare the antidepressant outcomes of repetitive transcranial magnetic stimulation (rTMS) with the figure-of-eight (F8)-coil and deep transcranial magnetic stimulation (DTMS) with the H1-coil in studies matched on stimulation frequency in unipolar major depressive disorder (MDD).MethodsElectronic search of Medline and PsycInfo identified 19 studies with stimulation frequency of 18-20 Hz using F8-coil (k = 8 randomised sham-controlled trials, RCTs, k = 3 open-label; n = 168 patients) or H1-coil (k = 1 RCT, k = 7 open-label; n = 200). Depression severity (the primary outcome) and response/remission rates (the secondary outcomes) were assessed at session 10.ResultsEffects pooled with random-effects meta-analysis showed a large reduction in depression severity, 29% response, and 15% remission rates after 10 sessions of active stimulation with either coil relative to baseline. Reduction in depression severity was greater in studies with younger patients using either coil. The comparison between coils showed a larger reduction in depression severity in H1-coil vs. F8-coil studies (independent of the study design or the concurrent pharmacotherapy) and a trend towards higher remission rates in F8-coil vs. H1-coils studies. These effects are based on a low volume of studies, are not controlled for placebo, and may not be clinically-relevant. The stimulation protocols differed systematically because stimulation was more focal but less intense (80-110% of the resting motor threshold, MT) in the F8-coil studies and less focal but more intense (120% MT) in the H1-coil studies. Two seizures occurred in the H1-coil studies relative to none in the F8-coil studies.ConclusionWhen matched on frequency, the higher-intensity and less focal stimulation with the H1-coil reduces depression more than the lower-intensity and more focal stimulation with the F8-coil. Head-to-head trials should compare the antidepressant outcomes of F8-coil and H1-coil to identify the most optimal stimulation protocols for acute and longer-lasting efficacy.

Project description:BackgroundRepetitive transcranial magnetic stimulation, a non-invasive brain stimulation technique, can manage cerebellar ataxia (CA) by suppressing cerebral cortical excitability. Hence, this study aimed to summarize the efficacy and safety of rTMS for CA patients by meta-analysis.MethodsThe PubMed, Embase, Web of Science, and Cochrane Library databases were searched for eligible studies published till 20 May 2023. Weighted mean difference (MD) and 95% confidence intervals (CIs) were used to assess the effect of rTMS treatment. Additionally, the quality of the included studies and the risk of bias were evaluated using the Physiotherapy Evidence Database (PEDro) scale.ResultsOverall, eight studies involving 278 CA patients were included in this meta-analysis. rTMS could significantly improve the Scale for the Assessment and Rating of Ataxia (SARA) (MD: -2.00; 95% CI: -3.97 to -0.02, p = 0.05), International Cooperative Ataxia Rating Scale (ICARS) (MD: -3.96; 95% CI: -5.51 to -2.40, p < 0.00001), Timed Up-and-Go test (TUG) (MD: -1.54; 95% CI: -2.24 to -0.84, p < 0.0001), 10-m walk test (10 MWT) (MD10-m steps: -2.44; 95% CI: -4.14 to -0.73, p = 0.005), and Berg Balance Scale (BBS) (MD: 2.59; 95% CI: 1.15-4.03, p = 0.0004) as compared to sham stimulation. Active rTMS was not significantly different from sham rTMS in changing the duration (MD10-m time: -1.29; 95% CI: -7.98 to 5.41, p = 0.71). No severe adverse events were observed in both sham stimulation and active rTMS groups.ConclusionThis meta-analysis provides limited evidence that rTMS may be beneficial in treating CA patients. However, these findings should be treated with caution due to the limitations of the smaller sample size and the inconsistent approach and target of rTMS treatment. Therefore, more large-scale RCTs are required to further validate our analytical findings.Systematic review registrationhttps://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=295726, identifier: CRD42022295726.

Dataset Information

Cerebellar transcranial magnetic stimulation: the role of coil geometry and tissue depth.

Publications

Cerebellar transcranial magnetic stimulation: the role of coil geometry and tissue depth.

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