Effects of Low-Frequency Repetitive Transcranial Magnetic Stimulation of the Bilateral Parietal Cortex in Patients With Tourette Syndrome

A meta-analysis of transcranial magnetic stimulation in Tourette syndrome

There is growing enthusiasm for the treatment of neuropsychiatric disorders using neuromodulation. While some reports claim that transcranial magnetic stimulation (TMS) can be used to treat Tourette Syndrome (TS), little research exists to support this assertion. This meta-analysis examined the efficacy of TMS to reduce tic severity in patients with TS. Additionally, it explored the effect of TMS to reduce premonitory urge severity-the primary mechanism implicated in the frontline evidence-based treatment of TS. Five treatment comparisons were selected using PRISMA guidelines. All studies included were required to be (1) a randomized controlled trial, (2) compare TMS to a sham condition, and (3) have all participants meet diagnostic criteria for a persistent tic disorder and/or TS. A random effects model meta-analysis examined the efficacy of using TMS to reduce tic severity and explored the effect of TMS to reduce premonitory urge severity. TMS did not significantly reduce tic severity (g = 0.44; 95% CI = -0.17, 1.05; z = 1.40; p = 0.16), but a moderate reduction in premonitory urge severity was found (g = 0.63; 95% CI = 0.9, 1.17; z = 2.27; p < 0.02). Trials with larger sample sizes and a preponderance of women were found to have greater therapeutic effects of TMS for tic severity. There is limited support for the use of TMS to reduce tic severity, though reductions in premonitory urge severity were observed. Major limitations of the existing literature are examined, with a call for research investigating newer TMS protocols and their use as a treatment augmentation strategy.

Transcranial Magnetic Stimulation for Developmental Neuropsychiatric Disorders with Inflammation

BACKGROUND

Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique that may potentially be helpful for neuropsychiatric symptoms of developmental disorders with inflammatory aspects. TMS utilizes a varying magnetic field to induce electrical changes in the brain. Repetitive use of TMS modulates plasticity at multiple levels, particularly at the synapse and network level.

SUMMARY

As inflammation can affect synaptic plasticity negatively, TMS may theoretically be a tool to address this inflammation-induced dysfunction. There are also data to suggest that TMS can directly downregulate inflammation. Neuropsychiatric consequences of multiple disorders with inflammatory aspects, particularly neurodevelopmental disorders like autism, Tourette syndrome, and obsessive-compulsive disorder (OCD), maybe treated effectively with TMS. Treatment of OCD, treatment-resistant major depression, and nicotine cessation (all in adults) are currently FDA-cleared indications, while migraine is cleared for ages 12 and above.

KEY MESSAGES

TMS will likely continue to grow in terms of indications as research continues to assess what brain networks are dysfunctional in various disorders and it becomes clearer how to modulate these networks. TMS may thus be best understood as a technology platform that can be utilized to modulate different brain networks affected in neuropsychiatric disorders. TMS is likely to become an increasingly important tool in targeting brain networks that could become dysfunctional in part due to inflammation in the developing brain and addressing consequent neuropsychiatric symptoms.

Mapping a network for tics in Tourette syndrome using causal lesions and structural alterations

Tics are sudden stereotyped movements or vocalizations. Cases of lesion-induced tics are invaluable, allowing for causal links between symptoms and brain structures. While a lesion network for tics has recently been identified, the degree to which this network translates to Tourette syndrome has not been fully elucidated. This is important given that patients with Tourette syndrome make up a large portion of tic cases; therefore, existing and future treatments should apply to these patients. The aim of this study was to first localize a causal network for tics from lesion-induced cases and then refine and validate this network in patients with Tourette syndrome. We independently performed 'lesion network mapping' using a large normative functional connectome (n = 1000) to isolate a brain network commonly connected to lesions causing tics (n = 19) identified through a systematic search. The specificity of this network to tics was assessed through comparison to lesions causing other movement disorders. Using structural brain coordinates from prior neuroimaging studies (n = 7), we then derived a neural network for Tourette syndrome. This was done using standard anatomical likelihood estimation meta-analysis and a novel method termed 'coordinate network mapping', which uses the same coordinates, yet maps their connectivity using the aforementioned functional connectome. Conjunction analysis was used to refine the network for lesion-induced tics to Tourette syndrome by identifying regions common to both lesion and structural networks. We then tested whether connectivity from this common network is abnormal in a separate resting-state functional connectivity MRI data set from idiopathic Tourette syndrome patients (n = 21) and healthy controls (n = 25). Results showed that lesions causing tics were distributed throughout the brain; however, consistent with a recent study, these were part of a common network with predominant basal ganglia connectivity. Using conjunction analysis, coordinate network mapping findings refined the lesion network to the posterior putamen, caudate nucleus, globus pallidus externus (positive connectivity) and precuneus (negative connectivity). Functional connectivity from this positive network to frontal and cingulate regions was abnormal in patients with idiopathic Tourette syndrome. These findings identify a network derived from lesion-induced and idiopathic data, providing insight into the pathophysiology of tics in Tourette syndrome. Connectivity to our cortical cluster in the precuneus offers an exciting opportunity for non-invasive brain stimulation protocols.

The Role of the Left Inferior Parietal Cortex in Gilles de la Tourette Syndrome—An rTMS Study

Increased activity in the left inferior parietal cortex (BA40) plays a role in the generation of tics in the Gilles de la Tourette syndrome (GTS). Thus, inhibitory repetitive transcranial magnetic stimulation (rTMS) applied to BA40 was hypothesized to alleviate symptoms in GTS. We investigated the immediate effects of single-session 1 Hz rTMS and sham stimulation delivered to the left BA40 on tics assessed with the Rush video protocol in 29 adults with GTS. There were no significant effects on tic symptoms following rTMS or sham stimulation. Moreover, there was no difference when comparing the effects of both stimulation conditions. Bayesian statistics indicated substantial evidence against an intervention effect. The left BA40 appears not to be a useful target for 1 Hz rTMS to modulate tic symptoms in GTS patients.

Tourette syndrome research highlights from 2021

We summarize selected research reports from 2021 relevant to Tourette syndrome that the authors consider most important or interesting. The authors welcome article suggestions and thoughtful feedback from readers.

Tourette Syndrome Treatment Updates: a Review and Discussion of the Current and Upcoming Literature

Purpose of Review

This study aims to examine the treatments currently available for Tourette syndrome (TS) and to discuss evolving therapies, spanning behavioral, pharmacologic, complementary and alternative medicine, and neuromodulation approaches.

Recent Findings

Behavioral therapies have undergone several modifications to improve accessibility, including transitioning to a virtual format which is particularly important in the current pandemic. There are several recent or ongoing pharmacologic studies that have shown promise including the selective D1 receptor antagonist ecopipam and various cannabinoid compounds. Adaptive DBS may enable the physiologic markers of tics to determine stimulation parameters and improve tic outcomes related to neuromodulation.

Summary

In recent years, there has been a wealth of research across multiple treatment domains in the TS field. This review highlights exciting and new potential options for the future treatment of patients with TS.

Therapeutic application of rTMS in neurodegenerative and movement disorders: A review

Transcranial magnetic stimulation (TMS) is a non-invasive form of brain stimulation that makes use of the magnetic field generated when an electric current passes through a magnetic coil placed over the scalp. It can be applied as a single stimulus at a time, in pairs of stimuli, or repetitively in trains of stimuli (repetitive TMS, rTMS). RTMS can induce changes in brain activity, whose after-effects reflect the processes of long-term potentiation and long-term depression, as certain protocols, namely those using low frequencies (≤1 Hz) seem to suppress cortical excitability, while those using high frequencies (>1 Hz) seem to enhance it. It is a technique with very few and mostly mild side-effects, whose effects can persist for long time periods, and as such, it has been studied as a potential treatment option in a multitude of neurodegenerative diseases, including those affecting movement. Although rTMS has received approval as a treatment strategy of only a few aspects in movement disorders in the latest guidelines, its further use seems to also be promising in their context. In this review, we gathered the available literature on the therapeutic application of rTMS in movement disorders, namely Parkinson's disease, Amyotrophic Lateral Sclerosis, Huntington's disease, Dystonia, Tic disorders and Essential Tremor.