Is accelerated, high-dose theta burst stimulation a panacea for treatment-resistant depression?

Durability of clinical benefit with Stanford Neuromodulation Therapy (SNT) in treatment-resistant depression

BACKGROUND

Depression, the leading cause of disability worldwide, is a chronic disease characterized by a relapsing-remitting course. Acute treatments such as electroconvulsive therapy, ketamine, and repetitive transcranial magnetic stimulation are often effective at initiating remission, but relapse to a major depressive episode is common without ongoing interventions. Stanford Neuromodulation Therapy (SNT) produces high rates of remission after five days of acute treatment; however, the duration of this remission following a single course of SNT in people suffering from treatment-resistant depression is unknown, which poses a significant limit on clinical decision-making.

METHODS

Forty-six participants with treatment-resistant depression (TRD), received five days of SNT. Functional connectivity derived from resting-state functional MRI (fMRI) was used to individually target the region of the left dorsolateral prefrontal cortex most functionally anticorrelated with the subgenual anterior cingulate cortex. The 6-item Hamilton Depression Rating Scale (HDRS-6) was collected fortnightly for up to 24 weeks. Relapse was defined as two consecutive HDRS-6 scores of 5 or above.

RESULTS

Seventy percent (32 of 46) of participants entered remission the week following treatment. After 12 weeks of treatment, 15 of 46 (33 %) participants remained in remission. Of the participants who entered remission, 15 of 32 (47 %) remained in remission.

CONCLUSIONS

At 12 weeks, a subset of participants remained in remission, suggesting that the durability of SNT warrants further study. Comparisons with conventional rTMS should be interpreted cautiously given differences in study design, populations, and outcome measures.

Effects of accelerated intermittent theta-burst stimulation in modulating brain of Alzheimer's disease

Intermittent theta-burst stimulation (iTBS) is emerging as a noninvasive therapeutic strategy for Alzheimer's disease (AD). Recent advances highlighted a new accelerated iTBS (aiTBS) protocol, consisting of multiple sessions per day and higher overall pulse doses, in brain modulation. To examine the possibility of applying the aiTBS in treating AD patients, we enrolled 45 patients in AD at early clinical stages, and they were randomly assigned to either receive real or sham aiTBS. Neuropsychological scores were evaluated before and after treatment. Moreover, we detected cortical excitability and oscillatory activity changes in AD, by the single-pulse TMS in combination with EEG (TMS-EEG). Real stimulation showed markedly better performances in the group average of Auditory Verbal Learning Test scores compared to baseline. TMS-EEG revealed that aiTBS has reinforced this memory-related cortical mechanism by increasing cortical excitability and beta oscillatory activity underlying TMS target. We also found an enhancement of local natural frequency after aiTBS treatment. The novel findings implicated that high-dose aiTBS targeting left DLPFC is rapid-acting, safe, and tolerable in AD patients. Furthermore, TMS-related increase of specific neural oscillation elucidates the mechanisms of the AD cognitive impairment ameliorated by aiTBS.

Accelerated transcranial magnetic stimulation for major depressive disorder: A quick path to relief?

Transcranial magnetic stimulation (TMS) is a safe, tolerable, and evidence-based intervention for major depressive disorder (MDD). However, even after decades of research, nearly half of the patients with MDD fail to respond to conventional TMS, with responding slowly and requiring daily attendance at the treatment site for 4-6 weeks. To intensify antidepressant efficacy and shorten treatment duration, accelerated TMS protocols, which involve multiple sessions per day over a few days, have been proposed and evaluated for safety and viability. We reviewed and summarized the current knowledge in accelerated TMS, including stimulation parameters, antidepressant efficacy, anti-suicidal efficacy, safety, and adverse effects. Limitations and suggestions for future directions are also addressed, along with a brief discussion on the application of accelerated TMS during the COVID-19 pandemic. This article is categorized under: Neuroscience > Clinical Neuroscience.

Efficacy and safety of intermittent theta burst stimulation versus high-frequency repetitive transcranial magnetic stimulation for patients with treatment-resistant depression: a systematic review

Objective

Intermittent theta-burst stimulation (iTBS), which is a form of repetitive transcranial magnetic stimulation (rTMS), can produce 600 pulses to the left dorsolateral prefrontal cortex (DLPFC) in a stimulation time of just over 3 min. The objective of this systematic review was to compare the safety and efficacy of iTBS and high-frequency (≥ 5 Hz) rTMS (HF-rTMS) for patients with treatment-resistant depression (TRD).

Methods

Randomized controlled trials (RCTs) comparing the efficacy and safety of iTBS and HF-rTMS were identified by searching English and Chinese databases. The primary outcomes were study-defined response and remission.

Results

Two RCTs (n = 474) investigating the efficacy and safety of adjunctive iTBS (n = 239) versus HF-rTMS (n = 235) for adult patients with TRD met the inclusion criteria. Among the two included studies (Jadad score = 5), all were classified as high quality. No group differences were found regarding the overall rates of response (iTBS group: 48.0% versus HF-rTMS group: 45.5%) and remission (iTBS group: 30.0% versus HF-rTMS group: 25.2%; all Ps > 0.05). The rates of discontinuation and adverse events such as headache were similar between the two groups (all Ps > 0.05).

Conclusion

The antidepressant effects and safety of iTBS and HF-rTMS appeared to be similar for patients with TRD, although additional RCTs with rigorous methodology are needed.

A transdiagnostic review of safety, efficacy, and parameter space in accelerated transcranial magnetic stimulation

BACKGROUND

Accelerated transcranial magnetic stimulation (aTMS) is an emerging delivery schedule of repetitive TMS (rTMS). TMS is "accelerated" by applying two or more stimulation sessions within a day. This three-part review comprehensively reports the safety/tolerability, efficacy, and stimulation parameters affecting response across disorders.

METHODS

We used the PubMed database to identify studies administering aTMS, which we defined as applying at least two rTMS sessions within one day.

RESULTS

Our targeted literature search identified 85 aTMS studies across 18 diagnostic and healthy control groups published from July 2001 to June 2022. Excluding overlapping populations, 63 studies delivered 43,873 aTMS sessions using low frequency, high frequency, and theta burst stimulation in 1543 participants. Regarding safety, aTMS studies had similar seizure and side effect incidence rates to those reported for once daily rTMS. One seizure was reported from aTMS (0.0023% of aTMS sessions, compared with 0.0075% in once daily rTMS). The most common side effects were acute headache (28.4%), fatigue (8.6%), and scalp discomfort (8.3%), with all others under 5%. We evaluated aTMS efficacy in 23 depression studies (the condition with the most studies), finding an average response rate of 42.4% and remission rate of 28.4% (range = 0-90.5% for both). Regarding parameters, aTMS studies ranged from 2 to 10 sessions per day over 2-30 treatment days, 10-640 min between sessions, and a total of 9-104 total accelerated TMS sessions per participant (including tapering sessions). Qualitatively, response rate tends to be higher with an increasing number of sessions per day, total sessions, and total pulses.

DISCUSSION

The literature to date suggests that aTMS is safe and well-tolerated across conditions. Taken together, these early studies suggest potential effectiveness even in highly treatment refractory conditions with the added potential to reduce patient burden while also expediting response time. Future studies are warranted to systematically investigate how key aTMS parameters affect treatment outcome and durability.

Repetitive Transcranial Magnetic Stimulation-Associated Changes in Neocortical Metabolites in Major Depression: A Systematic Review

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We reviewed 12 studies that measured metabolites pre and post rTMS in MDD.

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Frontal lobe Glu, Gln, NAA, and GABA increased after rTMS.

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Increases in metabolites were often associated with MDD symptom improvement.

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We propose novel intracellular mechanisms by which metabolites are altered by rTMS.

Introduction

Repetitive Transcranial magnetic stimulation (rTMS) is an FDA approved treatment for major depressive disorder (MDD). However, neural mechanisms contributing to rTMS effects on depressive symptoms, cognition, and behavior are unclear. Proton magnetic resonance spectroscopy (MRS), a noninvasive neuroimaging technique measuring concentrations of biochemical compounds within the brain in vivo, may provide mechanistic insights.

Methods

This systematic review summarized published MRS findings from rTMS treatment trials to address potential neurometabolic mechanisms of its antidepressant action. Using PubMed, Google Scholar, Web of Science, and JSTOR, we identified twelve empirical studies that evaluated changes in MRS metabolites in a within-subjects, pre- vs. post-rTMS treatment design in patients with MDD.

Results

rTMS protocols ranged from four days to eight weeks duration, were applied at high frequency to the left dorsolateral prefrontal cortex (DLPFC) in most studies, and were conducted in patients aged 13-to-70. Most studies utilized MRS point resolved spectroscopy acquisitions at 3 Tesla in the bilateral anterior cingulate cortex and DLPFC. Symptom improvements were correlated with rTMS-related increases in the concentration of glutamatergic compounds (glutamate, Glu, and glutamine, Gln), GABA, and N-acetylated compounds (NAA), with some results trend-level.

Conclusions

This is the first in-depth systematic review of metabolic effects of rTMS in individuals with MDD. The extant literature suggests rTMS stimulation does not produce changes in neurometabolites independent of clinical response; increases in frontal lobe glutamatergic compounds, N-acetylated compounds and GABA following high frequency left DLPFC rTMS therapy were generally associated with clinical improvement. Glu, Gln, GABA, and NAA may mediate rTMS treatment effects on MDD symptomatology through intracellular mechanisms.

Shaping plasticity with non-invasive brain stimulation in the treatment of psychiatric disorders: Present and future

The final chapter of this book addresses plasticity in the setting of treating psychiatric disorders. This chapter largely focuses on the treatment of depression and reviews the established antidepressant brain stimulation treatments, focusing on plasticity and maladaptive plasticity. Depression is a unique neuropsychiatric disease in that the brain goes from a healthy state into a pathologic state, and then, with appropriate treatment, can return to health often without permanent sequelae. Depression thus differs fundamentally from neurodegenerative brain diseases like Parkinson's disease or stroke. Some have theorized that depression involves a lack of flexibility or a lack of plasticity. The proven brain stimulation methods for treating depression cause plastic changes and include acute and maintenance electroconvulsive therapy (ECT), acute and maintenance transcranial magnetic stimulation (TMS), and chronically implanted cervical vagus nerve stimulation (VNS). These treatments vary widely in their speed of onset and durability. This variability in onset speed and durability raises interesting, and so far, largely unanswered questions about the underlying neurobiological mechanisms and forms of plasticity being invoked. The chapter also covers exciting recent work with vagus nerve stimulation (VNS) that is delivered paired with behaviors to cause learning and memory and plasticity changes. Taken together these current and future brain stimulation treatments for psychiatric disorders are especially promising. They are unlocking how to shape the brain in diseases to restore balance and health, with an increasing understanding of how to effectively and precisely induce therapeutic neuroplastic changes in the brain.

A reexamination of motor and prefrontal TMS in tobacco use disorder: Time for personalized dosing based on electric field modeling?

OBJECTIVE

In this study, we reexamined the use of 120% resting motor threshold (rMT) dosing for transcranial magnetic stimulation (TMS) over the left dorsolateral prefrontal cortex (DLPFC) using electric field modeling.

METHODS

We computed electric field models in 38 tobacco use disorder (TUD) participants to compare figure-8 coil induced electric fields at 100% rMT over the primary motor cortex (M1), and 100% and 120% rMT over the DLPFC. We then calculated the percentage of rMT needed for motor-equivalent induced electric fields at the DLPFC and modeled this intensity for each person.

RESULTS

Electric fields from 100% rMT stimulation over M1 were significantly larger than what was modeled in the DLPFC using 100% rMT (p < 0.001) and 120% rMT stimulation (p = 0.013). On average, TMS would need to be delivered at 133.5% rMT (range = 79.9 to 247.5%) to produce motor-equivalent induced electric fields at the DLPFC of 158.2 V/m.

CONCLUSIONS

TMS would have to be applied at an average of 133.5% rMT over the left DLPFC to produce equivalent electric fields to 100% rMT stimulation over M1 in these 38 TUD patients. The high interindividual variability between motor and prefrontal electric fields for each participant supports using personalized electric field modeling for TMS dosing to ensure that each participant is not under- or over-stimulated.

SIGNIFICANCE

These electric field modeling in TUD data suggest that 120% rMT stimulation over the DLPFC delivers sub-motor equivalent electric fields in many individuals (73.7%). With further validation, electric field modeling may be an impactful method of individually dosing TMS.

Precision clinical trials: a framework for getting to precision medicine for neurobehavioural disorders

The goal of precision medicine (individually tailored treatments) is not being achieved for neurobehavioural conditions such as psychiatric disorders. Traditional randomized clinical trial methods are insufficient for advancing precision medicine because of the dynamic complexity of these conditions. We present a pragmatic solution: the precision clinical trial framework, encompassing methods for individually tailored treatments. This framework includes the following: (1) treatment-targeted enrichment, which involves measuring patients' response after a brief bout of an intervention, and then randomizing patients to a full course of treatment, using the acute response to predict long-term outcomes; (2) adaptive treatments, which involve adjusting treatment parameters during the trial to individually optimize the treatment; and (3) precise measurement, which involves measuring predictor and outcome variables with high accuracy and reliability using techniques such as ecological momentary assessment. This review summarizes precision clinical trials and provides a research agenda, including new biomarkers such as precision neuroimaging, transcranial magnetic stimulation-electroencephalogram digital phenotyping and advances in statistical and machine-learning models. Validation of these approaches - and then widespread incorporation of the precision clinical trial framework - could help achieve the vision of precision medicine for neurobehavioural conditions.

Accelerated Intermittent Theta Burst Stimulation in Late-Life Depression: A Possible Option for Older Depressed Adults in Need of ECT During the COVID-19 Pandemic

OBJECTIVE

Electroconvulsive therapy (ECT) is an essential psychiatric service with an important role in treating older adults with severe or treatment-resistant depression. During the COVID-19 pandemic, ECT services have be constrained by infection control measures. We report a case of a 66-year-old female patient with a severe major depressive episode who had previously responded to right unilateral ECT and was treated with two modified accelerated intermittent theta-burst stimulation (aiTBS) protocols.

METHODS

The two aiTBS courses consisted of eight daily sessions over five consecutive days, followed by gradual tapering, using 1,800 pulses per session pre-COVID-19 (first course), and 600 pulses per session during the pandemic (second course).

RESULTS

Moderate to severe baseline depressive symptoms reached remission levels after both courses.

CONCLUSION

The 600-pulses aiTBS treatment protocol reported here warrants further study and evaluation, but may be a potential option in cases where older adults with severe depressive symptoms cannot access ECT during the COVID-19 pandemic.