The value of neuronavigated rTMS for the treatment of depression

Clinical implementation, barriers, and unmet needs of rTMS and neuro-navigation systems in stroke rehabilitation: a nationwide survey in South Korea

Objective

The objective of this study was to determine the implementation, clinical barriers, and unmet needs of repetitive transcranial magnetic stimulation (rTMS) and neuro-navigation systems for stroke rehabilitation.

Design

We employed a nationwide survey via Google Forms (web and mobile) consisting of 36 questions across rTMS and neuro-navigation systems, focusing on their implementation, perceptions, and unmet needs in stroke recovery. The survey targeted physiatrists registered in the Korean Society for Neuro-rehabilitation and in rehabilitation hospitals in South Korea.

Results

Of 1,129 surveys distributed, 122 responses were analyzed. Most respondents acknowledged the effectiveness of rTMS in treating post-stroke impairments; however, they highlighted significant unmet needs in standardized treatment protocols, guidelines, education, device usability, and insurance coverage. Unmet needs for neuro-navigation were also identified; only 7.4% of respondents currently used such systems, despite acknowledging their potential to enhance treatment accuracy. Seventy percent of respondents identified lack of prescription coverage, time and errors in preparation, and device cost as barriers to clinical adoption of neuro-navigation systems.

Conclusion

Despite recognition of the potential of rTMS in stroke rehabilitation, there is a considerable gap between research evidence and clinical practice. Addressing these challenges, establishing standardized protocols, and advancing accessible neuro-navigation systems could significantly enhance the clinical application of rTMS, offering a more personalized, effective treatment modality for stroke recovery.

Noninvasive brain stimulation in autism: review and outlook for personalized interventions in adult patients

Noninvasive brain stimulation (NIBS) has been increasingly investigated during the last decade as a treatment option for persons with autism spectrum disorder (ASD). Yet, previous studies did not reach a consensus on a superior treatment protocol or stimulation target. Persons with ASD often suffer from social isolation and high rates of unemployment, arising from difficulties in social interaction. ASD involves multiple neural systems involved in perception, language, and cognition, and the underlying brain networks of these functional domains have been well documented. Aiming to provide an overview of NIBS effects when targeting these neural systems in late adolescent and adult ASD, we conducted a systematic search of the literature starting at 631 non-duplicate publications, leading to six studies corresponding with inclusion and exclusion criteria. We discuss these studies regarding their treatment rationale and the accordingly chosen methodological setup. The results of these studies vary, while methodological advances may allow to explain some of the variability. Based on these insights, we discuss strategies for future clinical trials to personalize the selection of brain stimulation targets taking into account intersubject variability of brain anatomy as well as function.

Design and Validation of Miniaturized Repetitive Transcranial Magnetic Stimulation (rTMS) Head Coils

Repetitive transcranial magnetic stimulation (rTMS) is a rapidly developing therapeutic modality for the safe and effective treatment of neuropsychiatric disorders. However, clinical rTMS driving systems and head coils are large, heavy, and expensive, so miniaturized, affordable rTMS devices may facilitate treatment access for patients at home, in underserved areas, in field and mobile hospitals, on ships and submarines, and in space. The central component of a portable rTMS system is a miniaturized, lightweight coil. Such a coil, when mated to lightweight driving circuits, must be able to induce B and E fields of sufficient intensity for medical use. This paper newly identifies and validates salient theoretical considerations specific to the dimensional scaling and miniaturization of coil geometries, particularly figure-8 coils, and delineates novel, key design criteria. In this context, the essential requirement of matching coil inductance with the characteristic resistance of the driver switches is highlighted. Computer simulations predicted E- and B-fields which were validated via benchtop experiments. Using a miniaturized coil with dimensions of 76 mm × 38 mm and weighing only 12.6 g, the peak E-field was 87 V/m at a distance of 1.5 cm. Practical considerations limited the maximum voltage and current to 350 V and 3.1 kA, respectively; nonetheless, this peak E-field value was well within the intensity range, 60-120 V/m, generally held to be therapeutically relevant. The presented parameters and results delineate coil and circuit guidelines for a future miniaturized, power-scalable rTMS system able to generate pulsed E-fields of sufficient amplitude for potential clinical use.

Traumatic Brain Injury and Neuromodulation Techniques in Rehabilitation: A Scoping Review

BACKGROUND AND OBJECTIVES

Traumatic Brain Injury (TBI) is a condition in which an external force, usually a violent blow to the head, causes functional impairment in the brain. Neuromodulation techniques are thought to restore altered function in the brain, resulting in improved function and reduced symptoms. Brain stimulation can alter the firing of neurons, boost synaptic strength, alter neurotransmitters and excitotoxicity, and modify the connections in their neural networks. All these are potential effects on brain activity. Accordingly, this is a promising therapy for TBI. These techniques are flexible because they can target different brain areas and vary in frequency and amplitude. This review aims to investigate the recent literature about neuromodulation techniques used in the rehabilitation of TBI patients.

MATERIALS AND METHODS

The identification of studies was made possible by conducting online searches on PubMed, Web of Science, Cochrane, Embase, and Scopus databases. Studies published between 2013 and 2023 were selected. This review has been registered on OSF (JEP3S).

RESULTS

We have found that neuromodulation techniques can improve the rehabilitation process for TBI patients in several ways. Transcranial Magnetic Stimulation (TMS) can improve cognitive functions such as recall ability, neural substrates, and overall improved performance on neuropsychological tests. Repetitive TMS has the potential to increase neural connections in many TBI patients but not in all patients, such as those with chronic diffuse axonal damage.

CONCLUSIONS

This review has demonstrated that neuromodulation techniques are promising instruments in the rehabilitation field, including those affected by TBI. The efficacy of neuromodulation can have a significant impact on their lives and improve functional outcomes for TBI patients.

Effects of neuromodulation on cognitive and emotional responses to psychosocial stressors in healthy humans

Physiological and psychological stressors can exert wide-ranging effects on the human brain and behavior. Research has improved understanding of how the sympatho-adreno-medullary (SAM) and hypothalamic-pituitary-adrenocortical (HPA) axes respond to stressors and the differential responses that occur depending on stressor type. Although the physiological function of SAM and HPA responses is to promote survival and safety, exaggerated psychobiological reactivity can occur in psychiatric disorders. Exaggerated reactivity may occur more for certain types of stressors, specifically, psychosocial stressors. Understanding stressor effects and how the body regulates these responses can provide insight into ways that psychobiological reactivity can be modulated. Non-invasive neuromodulation is one way that responding to stressors may be altered; research into these interventions may provide further insights into the brain circuits that modulate stress reactivity. This review focuses on the effects of acute psychosocial stressors and how neuromodulation might be effective in altering stress reactivity. Although considerable research into stress interventions focuses on treating pathology, it is imperative to first understand these mechanisms in non-clinical populations; therefore, this review will emphasize populations with no known pathology and consider how these results may translate to those with psychiatric pathologies.

Transcranial Magnetic Stimulation and its Imaging Features in Patients With Depression, Post-traumatic Stress Disorder, and Traumatic Brain Injury

Transcranial magnetic stimulation (TMS) is a type of noninvasive neurostimulation used increasingly often in clinical medicine. While most studies to date have focused on TMS's ability to treat major depressive disorder, it has shown promise in several other conditions including post-traumatic stress disorder (PTSD) and traumatic brain injury (TBI). As different treatment protocols are often used across studies, the ability to predict patient outcomes and evaluate immediate and long-term changes using imaging becomes increasingly important. Several imaging features, such as thickness, connectedness, and baseline activity of a variety of cortical and subcortical areas, have been found to be correlated with a greater response to TMS therapy. Intrastimulation imaging can reveal in real time how TMS applied to superficial areas activates or inhibits activity in deeper brain regions. Functional imaging performed weeks to months after treatment can offer an understanding of how long-term effects on brain activity relate to clinical improvement. Further work should be done to expand our knowledge of imaging features relevant to TMS therapy and how they vary across patients with different neurological and psychiatric conditions.

Evidence and expert consensus based German guidelines for the use of repetitive transcranial magnetic stimulation in depression

INTRODUCTION

Non-invasive brain stimulation techniques such as repetitive transcranial magnetic stimulation (rTMS) offer a promising alternative to psychotherapeutic and pharmacological treatments for depression. This paper aims to present a practical guide for its clinical implementation based on evidence from the literature as well as on the experience of a group of leading German experts in the field.

METHODS

The current evidence base for the use of rTMS in depression was examined via review of the literature. From the evidence and from clinical experience, recommendations for the use of rTMS in clinical practice were derived. All members of the of the German Society for Brain Stimulation in Psychiatry and all members of the sections Clinical Brain Stimulation and Experimental Brain Stimulation of the German Society for Psychiatry, Psychotherapy, Psychosomatics and Mental Health were invited to participate in a poll on whether they consent with the recommendations.

FINDINGS

Among rTMS experts, a high consensus rate could be identified for clinical practice concerning the setting and the technical parameters of rTMS treatment in depression, indications and contra-indications, the relation of rTMS to other antidepressive treatment modalities and the frequency and management of side effects.

Transcranial Magnetic Stimulation for the Neurological Patient: Scientific Principles and Applications

Non-invasive brain stimulation has been increasingly recognized for its potential as an investigational, diagnostic and therapeutic tool across the clinical neurosciences. Transcranial magnetic stimulation (TMS) is a non-invasive method of focal neuromodulation. Diagnostically, TMS can be used to probe cortical excitability and plasticity, as well as for functional mapping. Therapeutically, depending on the pattern employed, TMS can either facilitate or inhibit stimulated cortex potentially modulating maladaptive physiology through its effects on neuroplasticity. Despite this potential, applications of TMS in neurology have only been approved for diagnostic clinical neurophysiology, pre-surgical mapping of motor and language cortex, and the treatment of migraines. In this article, we discuss the principles of TMS and its clinical applications in neurology, including experimental applications in stroke rehabilitation, seizures, autism spectrum disorder, neurodegenerative disorders, movement disorders, tinnitus, chronic pain and functional neurological disorder. To promote increased cross-talk across neurology and psychiatry, we also succinctly review the TMS literature for the treatment of major depression and obsessive compulsive disorder. Overall, we argue that larger clinical trials that are better informed by circuit-level biomarkers and pathophysiological models will lead to an expansion of the application of TMS for patients cared for by neurologists.

The Use of Repetitive Transcranial Magnetic Stimulations for the Treatment of Post-Traumatic Stress Disorder: A Scoping Review

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive procedure in which brain neural activity is stimulated by the direct application of a magnetic field to the scalp. Despite its wide and continuous usage for the management of psychiatric disorders, the use of rTMS for post-traumatic stress disorder (PTSD) is not well established and evaluated by researchers. This scoping review seeks to explore the relevant literature available regarding the use of rTMS as a mode of treatment for PTSD, to map evidence in support of the use of rTMS for PTSD, and recommendations on future clinical and research work. Five databases were searched (MEDLINE, CINAHL, Psych INFO, SCOPUS, and EMBASE) to identify empirical studies and randomized controlled trials aimed at the treatment of PTSD with rTMS. A total of 10 studies were eligible for this review. The search results are up to date as of the date of the electronic data search of 20 December 2020. The frequencies applied in the studies ranged from low (1 Hz) to high (10 Hz) at different thresholds. Nine reported significant positive outcomes and PTSD symptoms improvement. rTMS was reported as well tolerated with no significant side effects. The application of rTMS for PTSD looks promising despite the diversity in terms of its outcomes and its clinical significance. Studies with well-defined stimulation parameters need to be conducted in the future.

Non-invasive brain stimulation in rehabilitation

Non-invasive brain stimulation (NIBS) has been seen more common in rehabilitation settings. It can be used for the treatment of stroke, spinal cord injury, traumatic brain injury and multiple sclerosis, as well as for some diagnostic neurophysiological measurements. Two major modalities of NIBS are transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). As an add-on therapy to conventional rehabilitative treatments, the main goal of NIBS is to create neuromodulation by inhibiting or activating neural activity in the targeted cortical region. Indications for therapeutic NIBS in neurorehabilitation are motor recovery, aphasia, neglect, dysphagia, cognitive disorders, spasticity, and central pain. The NIBS can be regarded a safe technique with appropriate patient selection and defined treatment parameters. This review provides an overview on NIBS modalities, specifically TMS and tDCS, the working mechanisms, the stimulation techniques, areas of use, neuronavigation systems and safety considerations.

Neuromodulation Treatments of Pathological Anxiety in Anxiety Disorders, Stressor-Related Disorders, and Major Depressive Disorder: A Dimensional Systematic Review and Meta-Analysis

BACKGROUND

Pathological anxiety is responsible for major functional impairments and resistance to conventional treatments in anxiety disorders (ADs), posttraumatic stress disorder (PTSD) and major depressive disorder (MDD). Focal neuromodulation therapies such as transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS) and deep brain stimulation (DBS) are being developed to treat those disorders.

METHODS

We performed a dimensional systematic review and meta-analysis to assess the evidence of the efficacy of TMS, tDCS and DBS in reducing anxiety symptoms across ADs, PTSD and MDD. Reports were identified through systematic searches in PubMed/Medline, Scopus and Cochrane library (inception to November 2020), followed by review according to the PRISMA guidelines. Controlled clinical trials examining the effectiveness of brain stimulation techniques on generic anxiety symptoms in patients with ADs, PTSD or MDD were selected.

RESULTS

Nineteen studies (RCTs) met inclusion criteria, which included 589 participants. Overall, focal brain activity modulation interventions were associated with greater reduction of anxiety levels than controls [SMD: -0.56 (95% CI, -0.93 to-0.20, I ² = 77%]. Subgroup analyses revealed positive effects for TMS across disorders, and of focal neuromodulation in generalized anxiety disorder and PTSD. Rates of clinical responses and remission were higher in the active conditions. However, the risk of bias was high in most studies.

CONCLUSIONS

There is moderate quality evidence for the efficacy of neuromodulation in treating pathological anxiety.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=233084, identifier: PROSPERO CRD42021233084. It was submitted on January 29th, 2021, and registered on March 1st, 2021. No amendment was made to the recorded protocol. A change was applied for the subgroup analyses based on target brain regions, we added the putative nature (excitatory/inhibitory) of brain activity modulation.

Effect of low-cost transcranial magnetic stimulation navigation on hotspot targeting and motor evoked potential variability in the biceps brachii

BACKGROUND

Transcranial magnetic stimulation (TMS) can monitor or modulate brain excitability. However, reliability of TMS outcomes depends on consistent coil placement during stimulation. Neuronavigated TMS systems can address this issue, but their cost limits their use outside of specialist research environments.

OBJECTIVE

The objective was to evaluate the performance of a low-cost navigated TMS approach in improving coil placement consistency and its effect on motor evoked potentials (MEPs) when targeting the biceps brachii at rest and during voluntary contractions.

METHODS

We implemented a navigated TMS system using a low-cost 3D camera system and open-source software environment programmed using the Unity 3D engine. MEPs were collected from the biceps brachii at rest and during voluntary contractions across two sessions in ten non-disabled individuals. Motor hotspots were recorded and targeted via two conditions: navigated and conventional.

RESULTS

The low-cost navigated TMS system reduced coil orientation error (pitch: 1.18°±1.2°, yaw: 1.99°±1.9°, roll: 1.18°±2.2° with navigation, versus pitch: 3.7°±5.7°, yaw: 3.11°±3.1°, roll: 3.8°±9.1° with conventional). The improvement in coil orientation had no effect on MEP amplitudes and variability.

CONCLUSIONS

The low-cost system is a suitable alternative to expensive systems in tracking the motor hotspot between sessions and quantifying the error in coil placement when delivering TMS. Biceps MEP variability reflects physiological variability across a range of voluntary efforts, that can be captured equally well with navigated or conventional approaches of coil locating.

The use of repetitive transcranial magnetic stimulation for treatment of obsessive-compulsive disorder: a scoping review

Purpose

This paper aims to explore the relevant literature available regarding the use of repetitive transcranial magnetic stimulation (rTMS) as a mode of treatment for obsessive-compulsive disorder (OCD); to evaluate the evidence to support the use of rTMS as a treatment option for OCD.

Design/methodology/approach

The authors electronically conducted data search in five research databases (MEDLINE, CINAHL, Psych INFO, SCOPUS and EMBASE) using all identified keywords and index terms across all the databases to identify empirical studies and randomized controlled trials. The authors included articles published with randomized control designs, which aimed at the treatment of OCD with rTMS. Only full-text published articles written in English were reviewed. Review articles on treatment for conditions other than OCD were excluded. The Covidence software was used to manage and streamline the review.

Findings

Despite the inconsistencies in the published literature, the application of rTMS over the supplementary motor area and the orbitofrontal cortex has proven to be promising in efficacy and tolerability compared with other target regions such as the prefrontal cortex for the treatment of OCD. Despite the diversity in terms of the outcomes and clinical variability of the studies under review, rTMS appears to be a promising treatment intervention for OCD.

Research limitations/implications

The authors of this scoping review acknowledge several limitations. First, the search strategy considered only studies published in English and the results are up to date as the last day of the electronic data search of December 10, 2020. Though every effort was made to identify all relevant studies for the purposes of this review per the eligibility criteria, the authors still may have missed some relevant studies, especially those published in other languages.

Originality/value

This review brought to bare the varying literature on the application of rTMS and what is considered gaps in the knowledge in this area in an attempt to evaluate and provide information on the potential therapeutic effects of rTMS for OCD.

Repetitive Transcranial Magnetic Stimulation for the Treatment of Depression, Post-Traumatic Stress Disorder, and Suicidal Ideation in Military Populations: A Scholarly Review

INTRODUCTION

Military mental health conditions, such as depression, PTSD, and suicidal ideation, are currently understudied and undertreated. Repetitive transcranial magnetic stimulation (rTMS) is currently being considered as a treatment for these conditions; however, there exists a paucity of research in this area. This scholarly review will examine the limitations of the existing literature on the use of rTMS to treat depression, PTSD, and suicidal ideation in service members (SMs) and veterans.

MATERIALS AND METHODS

Publications that evaluated rTMS for the treatment of depression, PTSD, or suicidal ideation in military samples were identified via a PubMed search. Non-interventional rTMS studies, studies where the sample could not be confirmed to be primarily composed of SMs or veteran participants, studies without psychiatric outcome measures, and studies not published in a peer-reviewed journal were excluded from this review.

RESULTS

This literature search identified 20 total publications (eight primary analyses of randomized controlled trials (RCTs), one longitudinal analysis of an RCT, five open label trials, and six retrospective analyses of clinical data), inclusive of 879 participants. Eighteen studies utilized a protocol targeting the prefrontal cortex (PFC), and one of these also targeted the supplementary motor area (SMA) with the PFC (one study did not specify the stimulation site). Eight studies applied standard 10 Hz frequency stimulation, and four applied standard 1 Hz frequency stimulation. The remainder of studies applied alternative stimulation protocols including 5 Hz (two studies), 20 Hz (one study), a combination of 1 and 10 Hz (two studies), and theta burst stimulation (TBS) (two studies). Twelve studies reported significant results, including four RCTs, three open label studies, and five retrospective analyses.

CONCLUSIONS

rTMS offers a promising area of research for mental health conditions in military populations. However, the number of studies that focus specifically on this population are few in number and have many notable limitations. Further research is needed to validate the effectiveness of this tool for SMs and veterans.

Task-related functional magnetic resonance imaging-based neuronavigation for the treatment of depression by individualized repetitive transcranial magnetic stimulation of the visual cortex

To determine whether repetitive transcranial magnetic stimulation (rTMS) of the visual cortex (VC) provides effective and well-tolerated treatment and whether magnetic resonance imaging (MRI) measures functional change of the VC as a biomarker of therapeutic effect in major depressive disorder (MDD), we performed a sham-controlled, double-blind, randomized, three-arm VC rTMS treatment study in 74 MDD patients. Neuronavigated rTMS (10 Hz, 90% of resting motor threshold, 1,600 pulses over 20 min twice per day) was performed over the VC for five days. Clinical outcome was measured by Hamilton Depression Rating Scale (HAMD-24) at days 0, 1, 3, 5 and after terminating rTMS, with follow-up at four weeks. MRI was measured at days 0 and 5. The individualized group exhibited the greatest change in HAMD-24 scores after VC rTMS for 5 days (F=5.53, P=0.005), which were maintained during follow-up period (F=4.22, P=0.016). All patients reported good tolerance. Changes in VC task-related functional MRI correlated with symptomatic reduction in the individualized group. Treatment reduced the initially abnormal increase in resting state functional connectivity from the VC to the pre/subgenual anterior cingulate cortex at day 5, especially in the individualized group. We demonstrated therapeutic potential and good tolerance of VC rTMS in MDD patients, indicated by biomarkers of fMRI measurement.

Unilateral and bilateral repetitive transcranial magnetic stimulation for treatment-resistant depression: a meta-analysis of randomized controlled trials over 2 decades

BACKGROUND

Approximately 35% of people with depression do not respond to 2 courses of antidepressant medications of adequate dosage, and treatment-resistant depression (TRD) is still a major clinical concern with a great impact on patients, their families, society and the health system. The present meta-analysis evaluates antidepressant efficacy of unilateral and bilateral repetitive transcranial magnetic stimulation (rTMS) in patients with unipolar TRD.

METHODS

We searched for randomized controlled trials that compared rTMS with sham treatment and were published by Apr. 3, 2017. The primary outcome was improvement in depression scores measured using the Hamilton Rating Scale for Depression. The secondary outcomes were remission and response rates. Two independent review authors screened the studies and extracted the data.

RESULTS

Twenty-three studies met the inclusion criteria. Meta-analysis of the depression scores showed a weighted mean difference (WMD) of 3.36 (95% confidence interval [CI] 1.85–4.88) between unilateral rTMS and sham treatment. Stratified data showed that the effect was relatively higher when rTMS was used as an add-on to antidepressant medications (WMD 3.64, 95% CI 1.52–5.76) than when it was used as a stand-alone treatment (WMD 2.47, 95% CI 0.90–4.05). The WMD between bilateral rTMS and sham was 2.67 (95% CI 0.83–4.51), and all studies that contributed to this outcome used rTMS while participants were taking antidepressant medications. The pooled remission and response rates for unilateral rTMS versus sham treatment were 16.0% and 25.1% for rTMS and 5.7% and 11.0% for sham treatment, respectively. The pooled remission and response rates for bilateral rTMS versus sham treatment were 16.6% and 25.4% for rTMS and 2.0% and 6.8% for sham treatment, respectively.

CONCLUSION

This study suggests that rTMS has moderate antidepressant effects and appears to be promising in the short-term treatment of patients with unipolar TRD.

Limits and reproducibility of resting-state functional MRI definition of DLPFC targets for neuromodulation

BACKGROUND

Transcranial magnetic stimulation (TMS) is a noninvasive neuromodulation technique with therapeutic applications for the treatment of major depressive disorder (MDD). The standard protocol uses high frequency stimulation over the left dorsolateral prefrontal cortex (DLPFC) identified in a heuristic manner leading to moderate clinical efficacy. A proposed strategy to increase the anatomical precision in targeting, based on resting-state functional MRI (rsfMRI), identifies the subregion within the DLPFC having the strongest anticorrelated functional connectivity with the subgenual cortex (SGC) for each individual subject.

OBJECTIVE

In this work, we comprehensively test the reliability and reproducibility of this targeting method for different scan lengths on 100 subjects from the Human Connectome Project (HCP) where each subject had a four 15-min rsfMRI scan on 2 different days.

METHODS

We quantified the inter-scan and inter-day distance between the rsfMRI-guided DLPFC targets for each subject controlling for a number of expected sources of noise using volumetric as well as surface analyses.

RESULTS

Our results show that the average inter-day distance (with fMRI scans lasting 30 min on each day) is 25% less variable than the inter-scan distance, which uses 50% less data. Specifically, the inter-scan distance was more than 37 mm, while for the longer-scan, the inter-day distance had lower variability at 25 mm. Finally, we tested the same rsfMRI strategy using the nucleus accumbens (NAc) as a control region relevant to MDD but less susceptible to artifacts, using both volume and surface rsfMRI data. The results showed similar variability to the SGC-DLPFC functional connectivity. Moreover, our results suggest that a smoothing kernel with 12 mm full-width half maximum (FWHM) lead to more stable and reliable target estimates.

CONCLUSION

Our work provides a quantitative assessment of the topographic precision of this targeting method, describing an anatomical variability that may surpass the spatial resolution of some forms of focal TMS as it is commonly applied, and provides recommendations for improved accuracy.

How Does Repetitive Transcranial Magnetic Stimulation Influence the Brain in Depressive Disorders?: A Review of Neuroimaging Magnetic Resonance Imaging Studies

OBJECTIVE

Repetitive transcranial magnetic stimulation (rTMS) is a nonpharmacological technique used to stimulate the brain. It is a safe and proven alternative tool to treat resistant major depressive disorders (MDDs). Neuroimaging studies suggest a wide corticolimbic network is involved in MDDs. We researched observable changes in magnetic resonance imaging induced by rTMS to clarify the operational mechanism.

METHODS

A systematic search of the international literature was performed using PubMed and Embase, using papers published up to January 1, 2017. The following MESH terms were used: (depression or major depressive disorder) and (neuroimaging or MRI) and (rTMS or repetitive transcranial magnetic stimulation). We searched the databases using a previously defined strategy to identify potentially eligible studies.

RESULTS

Both structural and functional changes were observed on magnetic resonance imagings performed before and after rTMS. Various areas of the brain were impacted when rTMS was used. Although the results were very heterogeneous, a pattern that involved the anterior cingulate cortex and the prefrontal cortex emerged. These are known to be regions of interest in MDDs. However, the various parameters used in rTMS make any generalization difficult.

CONCLUSIONS

Repetitive transcranial magnetic stimulation helps to treat MDDs with good efficacy. Its effect on the brain, as observed in several neuroimaging studies, seems to impact on the structural and functional features of several networks and structures involved in major depressive disorders.

Accurate external localization of the left frontal cortex in dogs by using pointer based frameless neuronavigation

BACKGROUND

In humans, non-stereotactic frameless neuronavigation systems are used as a topographical tool for non-invasive brain stimulation methods such as Transcranial Magnetic Stimulation (TMS). TMS studies in dogs may provide treatment modalities for several neuropsychological disorders in dogs. Nevertheless, an accurate non-invasive localization of a stimulation target has not yet been performed in this species.

HYPOTHESIS

This study was primarily put forward to externally locate the left frontal cortex in 18 healthy dogs by means of a human non-stereotactic neuronavigation system. Secondly, the accuracy of the external localization was assessed.

ANIMALS

A total of 18 healthy dogs, drawn at random from the research colony present at the faculty of Veterinary Medicine (Ghent University), were used.

METHODS

Two sets of coordinates (X, Y, Z and X″, Y″, Z″) were compared on each dog their tomographical dataset.

RESULTS

The non-stereotactic neuronavigation system was able to externally locate the frontal cortex in dogs with accuracy comparable with human studies.

CONCLUSION AND CLINICAL IMPORTANCE

This result indicates that a non-stereotactic neuronavigation system can accurately externally locate the left frontal cortex and paves the way to use guided non-invasive brain stimulation methods as an alternative treatment procedure for neurological and behavioral disorders in dogs. This technique could, in analogy with human guided non-invasive brain stimulation, provide a better treatment outcome for dogs suffering from anxiety disorders when compared to its non-guided alternative.

A single session of repetitive transcranial magnetic stimulation of the prefrontal cortex reduces cue-induced craving in patients with gambling disorder

BACKGROUND

Gambling disorder (GD) is common and disabling addictive disorder. In patients with substance use disorders, the application of repetitive transcranial magnetic stimulation (rTMS) over the dorsolateral prefrontal cortex (DLPFC) offers promise to alleviate craving. We hypothesized that applying real compared to sham rTMS over the left DLPFC would reduce gambling craving in patients with GD.

METHODS

In a randomized sham-controlled crossover design, 22 treatment-seeking patients with GD received real or sham treatment with high frequency rTMS over the left DLPFC followed a week later by the other type of treatment. Before and after each rTMS session, participants rated their gambling craving (from 0 to 100) before and after viewing a gambling video used as a cue. We used the Yale-Brown Obsessive Compulsive Scale adapted for Pathological Gambling to assess gambling behavior before and 7 days after each rTMS session.

RESULTS

As compared to sham (mean +0.74; standard deviation±3.03), real rTMS significantly decreased cue-induced craving (-2.12±3.39; F_(1,19)=4.87; P=0.04; partial η²=0.05; 95% CI: 0.00-0.21). No significant effect of rTMS was observed on gambling behavior.

CONCLUSIONS

Patients with GD reported decreased cue-induced craving following a single session of high frequency rTMS applied over the left DLPFC. Further large randomized controlled studies are needed to determine the usefulness of rTMS in GD.

Transcranial Electrical Stimulation (tES) for the Treatment of Neuropsychiatric Disorders Across Lifespan

Abstract. Transcranial electrical stimulation (tES) is a safe, painless, and inexpensive noninvasive brain stimulation (NIBS) technique. tES has been shown to reduce symptoms in a variety of neuropsychiatric conditions such as depression, schizophrenia, anxiety, autism, and craving. There are many factors that can influence the effects of tES, such as current intensity, duration, baseline level of activity, gender, and age. Age is a critical variable, since the human brain undergoes several anatomic and functional changes across the lifespan. Therefore, tES-induced effects may not be the same across the lifespan. In this review we summarize the effects of tES, including tDCS, tACS, and tRNS, on clinical outcomes in several neuropsychiatric conditions, using a framework in which studies are organized according to the age of subjects. The use of tES in neuropsychiatric disorders has yielded promising results with mild, if any, adverse effects. Most of the published studies with tES have been conducted with tDCS in adult population. Future studies should focus on interventions guided by surrogate outcomes of neuroplasticity. A better understanding of neuroplasticity across the lifespan will help optimize current tES stimulation parameters, especially for use with children and elderly populations.

MRI Guided Brain Stimulation without the Use of a Neuronavigation System

A key issue in the field of noninvasive brain stimulation (NIBS) is the accurate localization of scalp positions that correspond to targeted cortical areas. The current gold standard is to combine structural and functional brain imaging with a commercially available "neuronavigation" system. However, neuronavigation systems are not commonplace outside of specialized research environments. Here we describe a technique that allows for the use of participant-specific functional and structural MRI data to guide NIBS without a neuronavigation system. Surface mesh representations of the head were generated using Brain Voyager and vectors linking key anatomical landmarks were drawn on the mesh. Our technique was then used to calculate the precise distances on the scalp corresponding to these vectors. These calculations were verified using actual measurements of the head and the technique was used to identify a scalp position corresponding to a brain area localized using functional MRI.

The use of repetitive transcranial magnetic stimulation for modulating craving and addictive behaviours: a critical literature review of efficacy, technical and methodological considerations

OBJECTIVES

Repetitive transcranial magnetic stimulation (rTMS) is a potential therapeutic intervention for the treatment of addiction. This critical review aims to summarise the recent developments with respect to the efficacy of rTMS for all types of addiction and related disorders (including eating disorders), and concentrates on the associated methodological and technical issues.

METHODS

The bibliographic search consisted of a computerised screening of the Medline and ScienceDirect databases up to December 2013. Criteria for inclusion were the target problem was an addiction, a related disorder, or craving; the intervention was performed using rTMS; and the study was a clinical trial.

RESULTS

Of the potential 638 articles, 18 met the criteria for inclusion. Most of these (11 of the 18) supported the efficacy of rTMS, especially in the short term. In most cases, the main assessment criterion was the measurement of craving using a Visual Analogue Scale.

DISCUSSION

The results are discussed with respect to the study limitations and, in particular, the many methodological and technical discrepancies that were identified. Key recommendations are provided.

Transcranial Magnetic Stimulation to Address Mild Cognitive Impairment in the Elderly: A Randomized Controlled Study

Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique with potential to improve memory. Mild cognitive impairment (MCI), which still lacks a specific therapy, is a clinical syndrome associated with increased risk of dementia. This study aims to assess the effects of high-frequency repetitive TMS (HF rTMS) on everyday memory of the elderly with MCI. We conducted a double-blinded randomized sham-controlled trial using rTMS over the left dorsolateral prefrontal cortex (DLPFC). Thirty-four elderly outpatients meeting Petersen's MCI criteria were randomly assigned to receive 10 sessions of either active TMS or sham, 10 Hz rTMS at 110% of motor threshold, 2,000 pulses per session. Neuropsychological assessment at baseline, after the last session (10th) and at one-month follow-up, was applied. ANOVA on the primary efficacy measure, the Rivermead Behavioural Memory Test, revealed a significant group-by-time interaction (p = 0.05), favoring the active group. The improvement was kept after one month. Other neuropsychological tests were heterogeneous. rTMS at 10 Hz enhanced everyday memory in elderly with MCI after 10 sessions. These findings suggest that rTMS might be effective as a therapy for MCI and probably a tool to delay deterioration.

Low-frequency repetitive transcranial magnetic stimulation on Parkinson motor function: a meta-analysis of randomised controlled trials

OBJECTIVES

Previous studies have demonstrated inconsistent findings regarding the efficacy of low-frequency repetitive transcranial magnetic stimulation (rTMS) in treating motor symptoms of Parkinson's disease (PD). Therefore, this meta-analysis was conducted to assess the efficacy of low-frequency rTMS.

METHODS

A comprehensive literature search (including PubMed, CCTR, Embase, Web of Science, CNKI, CBM-disc, NTIS,EAGLE, Clinical Trials, Current Controlled Trials, International Clinical Trials Registry) was conducted dating until June 2014. The key search terms ('Parkinson', 'PD', 'transcranial magnetic stimulation', 'TMS', 'RTMS' and 'noninvasive brain stimulation') produced eight high-quality randomised controlled trials (RCT) of low-frequency rTMS versus sham stimulation.

RESULTS

These eight studies, composed of 319 patients, were meta-analysed through assessment of the decreased Unified Parkinson's Disease Rating Scale (UPDRS part III) score. Pooling of the results from these RCTs yielded an effect size of -0.40 (95%CI=-0.73 to -0.06, p<0.05) in UPDRS part III, which indicated that low-frequency rTMS could have 5.05 (95%CI=-1.73 to -8.37) point decrease in UPDRS part III score than sham stimulation.

DISCUSSION

Low-frequency rTMS had a significant effect on motor signs in PD. As the number of RCTs and PD patients included here was limited, further large-scale multi-center RCTs were required to validate our conclusions.

Repetitive transcranial magnetic stimulation over the dorsolateral prefrontal cortex for treating posttraumatic stress disorder: an exploratory meta-analysis of randomized, double-blind and sham-controlled trials

OBJECTIVE

Repetitive transcranial magnetic stimulation (rTMS) applied to the dorsolateral prefrontal cortex (DLPFC) has yielded promising results as a treatment for posttraumatic stress disorder (PTSD). However, to date, no quantitative review of its clinical utility has been published.

METHOD

We searched for randomized and sham-controlled trials from 1995 to March 2013 using MEDLINE, Embase, PsycINFO, CENTRAL, and SCOPUS. We then performed an exploratory random effects meta-analysis.

RESULTS

Studies on rTMS applied to the right DLPFC included 64 adults with PTSD. The pooled Hedges g effect size for pre and post changes in clinician-rated and self-reported PTSD symptoms were, respectively, 1.65 (P < 0.001) and 1.91 (P < 0.001), indicating significant and large-sized differences in outcome favouring active rTMS. Also, there were significant pre and post decreases with active rTMS in overall anxiety (Hedges g = 1.24; P = 0.02) and depressive (Hedges g = 0.85; P < 0.001) symptoms. Dropout rates at study end did not differ between active and sham rTMS groups. Regarding rTMS applied to the left DLPFC, there is only one study published to date (using a high frequency protocol), and its results showed that active rTMS seems to be superior overall to sham rTMS.

CONCLUSIONS

Our exploratory meta-analysis shows that active rTMS applied to the DLPFC seems to be effective and acceptable for treating PTSD. However, the small number of subjects included in the analyses limits the generalizability of these findings. Future studies should include larger samples and deliver optimized stimulation parameters.

Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS)

A group of European experts was commissioned to establish guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS) from evidence published up until March 2014, regarding pain, movement disorders, stroke, amyotrophic lateral sclerosis, multiple sclerosis, epilepsy, consciousness disorders, tinnitus, depression, anxiety disorders, obsessive-compulsive disorder, schizophrenia, craving/addiction, and conversion. Despite unavoidable inhomogeneities, there is a sufficient body of evidence to accept with level A (definite efficacy) the analgesic effect of high-frequency (HF) rTMS of the primary motor cortex (M1) contralateral to the pain and the antidepressant effect of HF-rTMS of the left dorsolateral prefrontal cortex (DLPFC). A Level B recommendation (probable efficacy) is proposed for the antidepressant effect of low-frequency (LF) rTMS of the right DLPFC, HF-rTMS of the left DLPFC for the negative symptoms of schizophrenia, and LF-rTMS of contralesional M1 in chronic motor stroke. The effects of rTMS in a number of indications reach level C (possible efficacy), including LF-rTMS of the left temporoparietal cortex in tinnitus and auditory hallucinations. It remains to determine how to optimize rTMS protocols and techniques to give them relevance in routine clinical practice. In addition, professionals carrying out rTMS protocols should undergo rigorous training to ensure the quality of the technical realization, guarantee the proper care of patients, and maximize the chances of success. Under these conditions, the therapeutic use of rTMS should be able to develop in the coming years.

Response, remission and drop-out rates following high-frequency repetitive transcranial magnetic stimulation (rTMS) for treating major depression: a systematic review and meta-analysis of randomized, double-blind and sham-controlled trials

BACKGROUND

Meta-analyses have shown that high-frequency (HF) repetitive transcranial magnetic stimulation (rTMS) has antidepressant properties when compared with sham rTMS. However, its overall response and remission rates in major depression (MD) remain unclear. Thus, we have systematically and quantitatively assessed the efficacy of HF-rTMS for MD based on randomized, double-blind and sham-controlled trials (RCTs).

METHOD

We searched the literature from 1995 through to July 2012 using MEDLINE, EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials, SCOPUS, and ProQuest Dissertations & Theses. We used a random-effects model, odds ratios (ORs) and the number needed to treat (NNT).

RESULTS

Data from 29 RCTs were included, totaling 1371 subjects with MD. Following approximately 13 sessions, 29.3% and 18.6% of subjects receiving HF-rTMS were classified as responders and remitters, respectively (compared with 10.4% and 5% of those receiving sham rTMS). The pooled OR was 3.3 (p < 0.0001) for both response and remission rates (with associated NNTs of 6 and 8, respectively). Furthermore, we found HF-rTMS to be equally effective as an augmentation strategy or as a monotherapy for MD, and when used in samples with primary unipolar MD or in mixed samples with unipolar and bipolar MD. Also, alternative stimulation parameters were not associated with differential efficacy estimates. Moreover, baseline depression severity and drop-out rates at study end were comparable between the HF-rTMS and sham rTMS groups. Finally, heterogeneity between the included RCTs was not statistically significant.

CONCLUSIONS

HF-rTMS seems to be associated with clinically relevant antidepressant effects and with a benign tolerability profile.

PET-based confirmation of orientation sensitivity of TMS-induced cortical activation in humans

BACKGROUND

Currently, it is difficult to predict precise regions of cortical activation in response to transcranial magnetic stimulation (TMS). Most analytical approaches focus on applied magnetic field strength in the target region as the primary factor, placing activation on the gyral crowns. However, imaging studies support M1 targets being typically located in the sulcal banks.

OBJECTIVE/HYPOTHESIS

To more thoroughly investigate this inconsistency, we sought to determine whether neocortical surface orientation was a critical determinant of regional activation.

METHODS

MR images were used to construct cortical and scalp surfaces for 18 subjects. The angle (θ) between the cortical surface normal and its nearest scalp normal for ~50,000 cortical points per subject was used to quantify cortical location (i.e., gyral vs. sulcal). TMS-induced activations of primary motor cortex (M1) were compared to brain activations recorded during a finger-tapping task using concurrent positron emission tomographic (PET) imaging.

RESULTS

Brain activations were primarily sulcal for both the TMS and task activations (P < 0.001 for both) compared to the overall cortical surface orientation. Also, the location of maximal blood flow in response to either TMS or finger-tapping correlated well using the cortical surface orientation angle or distance to scalp (P < 0.001 for both) as criteria for comparison between different neocortical activation modalities.

CONCLUSION

This study provides further evidence that a major factor in cortical activation using TMS is the orientation of the cortical surface with respect to the induced electric field. The results show that, despite the gyral crown of the cortex being subjected to a larger magnetic field magnitude, the sulcal bank of M1 had larger cerebral blood flow (CBF) responses during TMS.

A systematic review and meta-analysis on the efficacy and acceptability of bilateral repetitive transcranial magnetic stimulation (rTMS) for treating major depression

BACKGROUND

Bilateral repetitive magnetic stimulation (rTMS) is a promising novel therapeutic intervention for major depression (MD). However, clinical trials to date have reported conflicting evidence concerning its overall efficacy, which might have resulted from low statistical power. Thus, meta-analytical approaches could be useful in examining this issue by allowing the integration of findings from multiple studies and thus producing more accurate estimates of the treatment effect.

METHOD

We searched the literature for randomized, double-blind and sham-controlled trials (RCTs) on bilateral rTMS for treating MD from 1995 to July 2012 using EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials, SCOPUS, and ProQuest Dissertations and Theses, and from October 2008 until May 2012 using Medline. The main outcome measures were response and remission rates. We used a random-effects model, odds ratios (ORs) and the number needed to treat.

RESULTS

Data were obtained from seven RCTs, totaling 279 subjects with MD. After an average of 12.9 (s.d. = 2.7) sessions, 24.7% (40/162) and 6.8% (8/117) of subjects receiving active bilateral rTMS and sham rTMS were classified as responders [OR 4.3, 95% confidence interval (CI) 1.95-9.52, p < 0.0001]. Also, 19% (23/121) and 2.6% (2/77) of subjects were remitters following active bilateral rTMS and sham rTMS, respectively (OR 6.0, 95% CI 1.65-21.8, p = 0.006). No difference between baseline mean depression scores for the bilateral and sham rTMS groups was found, and the former was comparable with the latter in terms of drop-out rates at study end. Furthermore, we did not find significant differences efficacy- and acceptability-wise between active bilateral and unilateral rTMS at study end. Finally, heterogeneity between the included RCTs was not significant, and the risk of publication bias was found to be low.

CONCLUSIONS

Bilateral rTMS is a promising treatment for MD as it provides clinically meaningful benefits that are comparable with those of standard antidepressants and unilateral rTMS. Furthermore, bilateral rTMS seems to be an acceptable treatment for depressed subjects.

Use of repetitive transcranial magnetic stimulation for treatment in psychiatry

The potential of noninvasive neurostimulation by repetitive transcranial magnetic stimulation (rTMS) for improving psychiatric disorders has been studied increasingly over the past two decades. This is especially the case for major depression and for auditory-verbal hallucinations in schizophrenia. The present review briefly describes the background of this novel treatment modality and summarizes evidence from clinical trials into the efficacy of rTMS for depression and hallucinations. Evidence for efficacy in depression is stronger than for hallucinations, although a number of studies have reported clinically relevant improvements for hallucinations too. Different stimulation parameters (frequency, duration, location of stimulation) are discussed. There is a paucity of research into other psychiatric disorders, but initial evidence suggests that rTMS may also hold promise for the treatment of negative symptoms in schizophrenia, obsessive compulsive disorder and post-traumatic stress disorder. It can be concluded that rTMS induces alterations in neural networks relevant for psychiatric disorders and that more research is needed to elucidate efficacy and underlying mechanisms of action.

Repetitive transcranial magnetic stimulation (rTMS) for obsessive-compulsive disorder (OCD): an exploratory meta-analysis of randomized and sham-controlled trials

OBJECTIVE

Randomized and sham-controlled trials (RCTs) on repetitive transcranial magnetic stimulation (rTMS) for treating obsessive-compulsive disorder (OCD) have yielded conflicting results that may be due to limited statistical power among individual studies. We pursued the present systematic review and meta-analysis to assess the efficacy of rTMS for OCD and to generate hypotheses for more robustly powered RCTs.

METHOD

We searched the literature for RCTs on rTMS for OCD from 1995 through December 2012 using MEDLINE, EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials, and SCOPUS. We then performed an exploratory random-effects meta-analysis with the main outcome measures as pre-post changes in Yale-Brown Obsessive Compulsive Scale (Y-BOCS) scores, response to treatment and overall dropout rates at study end.

RESULTS

Data were obtained from 10 RCTs, totaling 282 subjects with OCD. The pooled Hedges' g for pre-post Y-BOCS scores was 0.59 (z = 2.73, p = 0.006), indicating a significant and medium-sized difference in outcome favoring active rTMS. Furthermore, response rates were 35% and 13% for patients receiving active and sham rTMS, respectively (OR = 3.4, p = 0.002). Sub-group analyses indicated that LF-rTMS and rTMS protocols targeting non-DLPFC regions (i.e., orbitofrontal cortex or supplementary motor area) seem to be the most promising for reducing OCD-related symptoms. No differences on baseline depression scores or dropout rates at study end were observed between active and sham rTMS groups, although OCD severity at baseline was higher in the active group.

CONCLUSIONS

Our exploratory analyses show that active rTMS seems to be efficacious for treating OCD. Moreover, LF-rTMS and protocols targeting the orbitofrontal cortex or the supplementary motor area seem to be the most promising. Nevertheless, future RCTs on rTMS for OCD should include larger sample sizes and be more homogeneous in terms of demographic/clinical variables as well as stimulation parameters and brain targets.

Efficacy and acceptability of high frequency repetitive transcranial magnetic stimulation (rTMS) versus electroconvulsive therapy (ECT) for major depression: a systematic review and meta-analysis of randomized trials

Clinical trials comparing the efficacy and acceptability of high frequency repetitive transcranial magnetic stimulation (HF-rTMS) and electroconvulsive therapy (ECT) for treating major depression (MD) have yielded conflicting results. As this may have been the result of limited statistical power, we have carried out this meta-analysis to examine this issue. We searched the literature for randomized trials on head-to-head comparisons between HF-rTMS and ECT from January 1995 through September 2012 using MEDLINE, EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials, and SCOPUS. The main outcome measures were remission rates, pre-post changes in depression ratings, as well as overall dropout rates at study end. We used a random-effects model, Odds Ratios (OR), Number Needed to Treat (NNT), and Hedges' g effect sizes. Data were obtained from 7 randomized trials, totalling 294 subjects with MD. After an average of 15.2 HF-rTMS and 8.2 ECT sessions, 33.6% (38/113) and 52% (53/102) of subjects were classified as remitters (OR = 0.46; p = 0.04), respectively. The associated NNT for remission was 6 and favoured ECT. Also, reduction of depressive symptomatology was significantly more pronounced in the ECT group (Hedges' g = -0.93; p = 0.007). No differences on dropout rates for HF-rTMS and ECT groups were found. In conclusion, ECT seems to be more effective than HF-rTMS for treating MD, although they did not differ in terms of dropout rates. Nevertheless, future comparative trials with larger sample sizes and better matching at baseline, longer follow-ups and more intense stimulation protocols are warranted.

Therapeutic effects of non-invasive brain stimulation with direct currents (tDCS) in neuropsychiatric diseases

Neuroplasticity, which is the dynamic structural and functional reorganization of central nervous system connectivity due to environmental and internal demands, is recognized as a major physiological basis for adaption of cognition, and behavior, and thus of utmost importance for normal brain function. Pathological alterations of plasticity are increasingly explored as pathophysiological foundation of diverse neurological and psychiatric diseases. Non-invasive brain stimulation techniques (NIBS), such as repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS), are able to induce and modulate neuroplasticity in humans. Therefore, they have potential to alter pathological plasticity on the one hand, and foster physiological plasticity on the other, in neuropsychiatric diseases to reduce symptoms, and enhance rehabilitation. tDCS is an emerging NIBS tool, which induces glutamatergic plasticity via application of relatively weak currents through the scalp in humans. In the last years its efficacy to treat neuropsychiatric diseases has been explored increasingly. In this review, we will give an overview of pathological alterations of plasticity in neuropsychiatric diseases, gather clinical studies involving tDCS to ameliorate symptoms, and discuss future directions of application, with an emphasis on optimizing stimulation effects.

MRI-GUIDED NAVIGATION AND POSITIONING SOLUTION FOR REPETITIVE TRANSCRANIAL MAGNETIC STIMULATION

A MRI-guided navigation solution for repetitive transcranial magnetic stimulation (rTMS)was designed in this study which integrates optical positioning system to perform positioning and tracking of the magnetic stimulation coil in real-time. The system includes the following procedures: segmentation and 3D reconstruction of brain anatomy from T1-weighted (T1W) MRI, coil calibration and localization, spatial registration between the subject's head and the MRI data and 2D/3D navigation. The 2D/3D navigation provides the spatial relationship between actual sites of the coils and the cortical surface quantitively and allows visualization of the location and orientation of the coil over the brain/head. Verified through the experiments using a phantom human skull model and the head MRI data from a healthy human subject, the proposed navigation system was demonstrated to be flexible, safe, accurate and time efficient.

Clinically meaningful efficacy and acceptability of low-frequency repetitive transcranial magnetic stimulation (rTMS) for treating primary major depression: a meta-analysis of randomized, double-blind and sham-controlled trials

Clinical trials on low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) over the right dorsolateral prefrontal cortex have yielded conflicting evidence concerning its overall efficacy for treating major depression (MD). As this may have been the result of limited statistical power of individual trials, we have carried the present systematic review and meta-analysis to examine this issue. We searched the literature for English language randomized, double-blind and sham-controlled trials (RCTs) on LF-rTMS for treating MD from 1995 through July 2012 using EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials, SCOPUS, and ProQuest Dissertations & Theses, and from October 2008 until July 2012 using MEDLINE. The main outcome measures were response and remission rates as well as overall dropout rates at study end. We used a random-effects model, odds ratios (ORs) and number needed to treat (NNT). Data were obtained from eight RCTs, totaling 263 subjects with MD. After an average of 12.6±3.9 rTMS sessions, 38.2% (50/131) and 15.1% (20/132) of subjects receiving active LF-rTMS and sham rTMS were classified as responders (OR=3.35; 95% CI=1.4-8.02; p=0.007). Also, 34.6% (35/101) and 9.7% (10/103) of subjects receiving active LF-rTMS and sham rTMS were classified as remitters (OR=4.76; 95% CI=2.13-10.64; p<0.0001). The associated NNT for both response and remission rates was 5. Sensitivity analyses have shown that protocols delivering >1200 magnetic pulses in total as well as those offering rTMS as a monotherapy for MD were associated with higher rates of response to treatment. No differences on mean baseline depression scores and dropout rates for active and sham rTMS groups were found. Finally, the risk of publication bias was low. In conclusion, LF-rTMS is a promising treatment for MD, as it provides clinically meaningful benefits that are comparable to those of standard antidepressants and high-frequency rTMS. Furthermore, LF-rTMS seems to be an acceptable intervention for depressed subjects.

rTMS as a Treatment of Alzheimer's Disease with and without Comorbidity of Depression: A Review

With an ever-increasing population of Alzheimer's disease (AD) patients worldwide, a noninvasive treatment for AD is needed. In this paper, the application of repetitive transcranial magnetic stimulus (rTMS) as a treatment for patients with probable AD is compared to the application of rTMS as a treatment for depression. Comorbidity of depression and dementia is discussed, as well as possible links between the two diseases. The possible confounding antidepressant effects of rTMS on cognitive improvements in AD patients are discussed.

Clinical utility of transcranial direct current stimulation (tDCS) for treating major depression: a systematic review and meta-analysis of randomized, double-blind and sham-controlled trials

OBJECTIVE

tDCS is a promising novel therapeutic intervention for major depression (MD). However, clinical trials to date have reported conflicting results concerning its efficacy, which likely resulted from low statistical power. Thus, we carried out a systematic review and meta-analysis on randomized, double-blind and controlled trials of tDCS in MD with a focus on clinically relevant outcomes, namely response and remission rates.

METHOD

We searched the literature for English language randomized, double-blind and sham-controlled trials (RCTs) on tDCS for treating MD from 1998 through July 2012 using MEDLINE, EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials and SCOPUS. We also consulted the Web of Science's Citations Index Expanded for the selected RCTs up to July 2012. The main outcome measures were response and remission rates. We used a random-effects model and Odds Ratios (OR).

RESULTS

Data were obtained from 6 RCTs that included a total of 200 subjects with MD. After an average of 10.8 ± 3.76 tDCS sessions, no significant difference was found between active and sham tDCS in terms of both response (23.3% [24/103] vs. 12.4% [12/97], respectively; OR = 1.97; 95% CI = 0.85-4.57; p = 0.11) and remission (12.2% [12/98] vs. 5.4% [5/92], respectively; OR = 2.13; 95% CI = 0.64-7.06; p = 0.22). Also, no differences between mean baseline depression scores and dropout rates in the active and sham tDCS groups were found. Furthermore, sensitivity analyses excluding RCTs that involved less than 10 treatment sessions or stimulus intensity of less than 2 mA did not alter the findings. However, tDCS used as monotherapy was associated with higher response rates when compared to sham tDCS (p = 0.043). Finally, the risk of publication bias in this meta-analysis was found to be low.

CONCLUSIONS

The clinical utility of tDCS as a treatment for MD remains unclear when clinically relevant outcomes such as response and remission rates are considered. Future studies should include larger and more representative samples, investigate how tDCS compares to other therapeutic neuromodulation techniques, as well as identify optimal stimulation parameters.

Equivalent brain SPECT perfusion changes underlying therapeutic efficiency in pharmacoresistant depression using either high-frequency left or low-frequency right prefrontal rTMS

BACKGROUND

Functional neuroimaging studies have suggested similar mechanisms underlying antidepressant effects of distinct therapeutics.

OBJECTIVE

This study aimed to determine and compare functional brain patterns underlying the antidepressant response of 2 distinct protocols of repetitive transcranial magnetic stimulation (rTMS).

METHODS

99mTc-ECD SPECT was performed before and after rTMS of dorsolateral prefrontal cortex in 61 drug-resistant right-handed patients with major depression, using high frequency (10Hz) left-side stimulation in 33 patients, and low frequency (1Hz) right-side stimulation in 28 patients. Efficiency of rTMS response was defined as at least 50% reduction of the baseline Beck Depression Inventory score. We compared the whole-brain voxel-based brain SPECT changes in perfusion after rTMS, between responders and non-responders in the whole sample (p<0.005, uncorrected), and separately in the subgroup of patients with left- and right-stimulation.

RESULTS

Before rTMS, the left- and right-prefrontal stimulation groups did not differ from clinical data and brain SPECT perfusion. rTMS efficiency (evaluated on % of responders) was statistically equivalent in the two groups of patients. In the whole-group of responder patients, a perfusion decrease was found after rTMS, in comparison to non-responders, within the left perirhinal cortex (BA35, BA36). This result was secondarily confirmed separately in the two subgroups, i.e. after either left stimulation (p=0.017) or right stimulation (p<0.001), without significant perfusion differences between these two subgroups.

CONCLUSIONS

These data show that distinct successful rTMS protocols induce equivalent brain functional changes associated to antidepressive efficiency, consisting to a remote brain limbic activity decrease within the left perirhinal cortex. However, these results will have to be confirmed in a double-blind randomized trial using a sham control group.

[Brain stimulation procedures. Transcranial magnetic stimulation, magnetic seizure therapy and deep brain stimulation]

Brain stimulation methods are promising treatment options in severe treatment-resistant psychiatric disorders. A safe and noninvasive method is transcranial magnetic stimulation, but the clinical application is not clear. Magnetic seizure therapy is a further development of transcranial magnetic stimulation, by which generalized seizures are induced under anaesthesia. Previous results with regard to the antidepressant effects and the fewer cognitive side effects were significant. Deep brain stimulation is an invasive procedure in which electrodes are stereotactically implanted in special brain areas. The effects in severe therapy-resistant obsessive-compulsive disorders and depressions are promising. However, the evaluation of ethical issues remains an important task.

The emerging use of brain stimulation treatments for psychiatric disorders

OBJECTIVE

The aim of this study was to review the current state of development and application of a wide range of brain stimulation approaches in the treatment of psychiatric disorders.

METHOD

The approaches reviewed include forms of minimally invasive magnetic and electrical stimulation, seizure induction, implanted devices and several highly novel approaches in early development.

RESULTS

An extensive range of brain stimulation approaches are now being widely used in the treatment of patients with psychiatric disorders, or actively investigated for this use. Both vagal nerve stimulation (VNS) and repetitive transcranial magnetic stimulation (rTMS) have been introduced into clinical practice in some countries. A small body of research suggests that VNS has some potentially long-lasting antidepressant effects in a minority of patients treated. rTMS has now been extensively investigated for over 15 years, with a large body of research now supporting its antidepressant effects. Further rTMS research needs to focus on defining the most appropriate stimulation methods and exploring its longer term use in maintenance protocols. Very early data suggest that magnetic seizure therapy (MST) has promise in the treatment of patients referred for electroconvulsive therapy: MST appears to have fewer side effects and may have similar efficacy. A number of other approaches including surgical and alternative forms of electrical stimulation appear to alter brain activity in a promising manner, but are in need of evaluation in more substantive patient samples.

CONCLUSIONS

It appears likely that the range of psychiatric treatments available for patients will grow over the coming years to progressively include a number of novel brain stimulation techniques.

Robust real-time robot-world calibration for robotized transcranial magnetic stimulation

BACKGROUND

For robotized transcranial magnetic stimulation (TMS), the magnetic coil is placed on the patient's head by a robot. As the robotized TMS system requires tracking of head movements, robot and tracking camera need to be calibrated. However, for robotized TMS in a clinical setting, such calibration is required frequently. Mounting/unmounting a marker to the end effector and moving the robot into different poses is impractical. Moreover, if either system is moved during treatment, recalibration is required.

METHODS

To overcome this limitation, we propose to directly track a marker at link three of the articulated arm. Using forward kinematics and a constant marker transform to link three, the calibration can be performed instantly.

RESULTS

Our experimental results indicate an accuracy similar to standard hand-eye calibration approaches. It also outperforms classical hand-held navigated TMS systems.

CONCLUSION

This robust online calibration greatly enhances the system's user-friendliness and safety.

Role of COMT, 5-HT(1A) , and SERT genetic polymorphisms on antidepressant response to Transcranial Magnetic Stimulation

BACKGROUND

Transcranial Magnetic Stimulation (TMS) is an effective technique in the treatment of depression, specifically in drug-resistant patients. However, there is little data available on the influence of genetic variables on TMS response.

METHODS

We analyzed the role of three genetic polymorphisms that affected the antidepressant response: serotonin transporter promoter region (SERTPR) polymorphism, 5-HT(1A) serotonergic receptor promoter region polymorphism (rs6295), and the coding region of COMT gene polymorphism (rs4680). Ninety patients with a major depressive drug-resistant episode due to a Major Depressive Disorder or to a Bipolar Disorder were included in our study. Patients underwent high frequency TMS, focused on the left prefrontal cortex, for 2 weeks. At study completion, the response rate was 45.5%. Effects of gene polymorphisms on clinical improvement were analyzed with an analysis of variance with each gene (SERTPR, 5-HT(1A) , and COMT) as factors and the Hamilton Rating Scale for Depression variation from baseline to the end of the treatment as a dependent variable.

RESULTS

We found a significant model in which three factors were not significant (diagnosis, COMT, and SERTPR), whereas factor 5-HT(1A) showed a significant influence on the outcome, with patients with C/C genotype showing a greater improvement than G/G and C/G and no difference between G/G and C/G.

CONCLUSION

According to our data, 5-HT(1A) polymorphism may play a role in influencing TMS response. The effect of COMT and SERTPR did not reach statistical significance. The analysis of these and other candidate genes in larger samples could help explain genetic influence on TMS response.

Age predicts low-frequency transcranial magnetic stimulation efficacy in major depression

BACKGROUND

Transcranial magnetic stimulation (TMS) effectiveness in major depression has so far been studied mainly with high-frequency (>1 Hz) administration (HF-TMS). However, some available studies with low-frequency TMS (LF-TMS) have provided similar response rates to HF-TMS with better tolerance, but the evidence is mixed and controversial.

METHODS

Randomized, controlled, two arm, clinical trial. 34 Major Depression patients were randomly assigned to receive 20 sessions of real or sham TMS of the right dorsolateral prefrontal cortex as adjuvant treatment to pharmacotherapy. The main stimulation parameters were 20 trains at 110% of the motor threshold for 60 s at a frequency of 1 Hz. Blinded external evaluators administered the Hamilton Depression Rating Scale.

RESULTS

Both treatment groups significantly improved, although there were no statistical differences between them. In the real TMS group patients age inversely correlated with improvement of depressive symptoms at the end of the study (r=-0683 p=0.002). The percentage of decrease in scores on the Hamilton Scale was greater in subjects younger than 45 years old vs. others (41.3 +/- 22.6 vs. 15.1 +/- 15.8; t=2.8 df=16, p=0.011). These real TMS subgroups did not differ significantly in their history of previous depressive disorders, or in the refractoriness indicators of the current episode.

LIMITATIONS

Small size and highly refractory sample.

CONCLUSION

Only younger patients benefited from LF-rTMS as adjuvant treatment to antidepressants in this study.

Transcranial magnetic stimulation in Alzheimer's disease: a neurophysiological marker of cortical hyperexcitability

Recently, neuropathological studies have shown an important motor cortex involvement in Alzheimer's disease (AD), even in its early stages, despite the lack of clinically evident motor deficit. Transcranial magnetic stimulation (TMS) studies have demonstrated that cortical excitability is enhanced in AD patients. This cortical hyperexcitability is believed to be a compensatory mechanism to execute voluntary movements, despite the progressive impairment of associative cortical areas. At present, it is not clear if these motor cortex excitability changes might be the expression of an involvement of intracortical excitatory glutamatergic circuits or an impairment of inhibitory cholinergic and, to a lesser extent, gabaergic activity. Although the main hypothesis for the pathogenesis of AD remains the degeneration of the basal forebrain cholinergic neurons, the development of specific TMS protocols, such as the paired-pulse TMS and the study of the short-latency afferent inhibition, points out the role of other neurotransmitters, such as gamma-amino-butyric acid, glutamate and dopamine. The potential therapeutic effect of repetitive TMS in restoring or compensating damaged cognitive functions, might become a possible rehabilitation tool in AD patients. Based on different patterns of cortical excitability, TMS may be useful in discriminating between physiological brain aging, mild cognitive impairment, AD and other dementing disorders. The present review provides a perspective of these TMS techniques by further understanding the role of different neurotransmission pathways and plastic remodelling of neuronal networks in the pathogenesis of AD.

The effects of repetitive transcranial magnetic stimulation in the treatment of depression

Repetitive transcranial magnetic stimulation (rTMS) is currently emerging as one of the first fundamentally new treatments in psychiatric practice for a considerable number of years. Research into the use of rTMS for the treatment of patients with depression has now been conducted for over 15 years. The aim of this article was to review the development of rTMS treatment for depression and the current state of evidence supporting its use. The vast majority of the trials conducted on the technique have evaluated the efficacy of high-frequency rTMS applied to the left dorsolateral prefrontal cortex using a set of parameters very similar to those originally described in the mid-1990s. This 'standard' form of rTMS clearly appears to have antidepressant efficacy, and its effects have now been confirmed in several large-scale clinical trials and a number of meta-analyses: response is better than that of sham stimulation, although the number of responders to treatment is relatively modest. A wide range of alternative forms of rTMS have been, or are currently being, evaluated. Low-frequency stimulation applied to the right prefrontal cortex appears to have similar efficacy to standard treatment and it is possible that the bilateral approaches may prove more effective. Novel methods of stimulation, such as priming stimulation, theta-burst stimulation and deep TMS, appear to be promising although require further evaluation. Significant benefit appears likely to accumulate through the use of methods that involve a more reliable targeting of prefrontal brain regions. Research is also required to evaluate the long-term effects of rTMS treatment, its use as a maintenance therapy and to establish reliable predictors of response to treatment.

Transcranial magnetic stimulation in Alzheimer's disease: a neurophysiological marker of cortical hyperexcitability

Recently, neuropathological studies have shown an important motor cortex involvement in Alzheimer's disease (AD), even in its early stages, despite the lack of clinically evident motor deficit. Transcranial magnetic stimulation (TMS) studies have demonstrated that cortical excitability is enhanced in AD patients. This cortical hyperexcitability is believed to be a compensatory mechanism to execute voluntary movements, despite the progressive impairment of associative cortical areas. At present, it is not clear if these motor cortex excitability changes might be the expression of an involvement of intracortical excitatory glutamatergic circuits or an impairment of inhibitory cholinergic and, to a lesser extent, gabaergic activity. Although the main hypothesis for the pathogenesis of AD remains the degeneration of the basal forebrain cholinergic neurons, the development of specific TMS protocols, such as the paired-pulse TMS and the study of the short-latency afferent inhibition, points out the role of other neurotransmitters, such as gamma-amino-butyric acid, glutamate and dopamine. The potential therapeutic effect of repetitive TMS in restoring or compensating damaged cognitive functions, might become a possible rehabilitation tool in AD patients. Based on different patterns of cortical excitability, TMS may be useful in discriminating between physiological brain aging, mild cognitive impairment, AD and other dementing disorders. The present review provides a perspective of these TMS techniques by further understanding the role of different neurotransmission pathways and plastic remodelling of neuronal networks in the pathogenesis of AD.