Critically Assessing the Unanswered Questions of How, Where, and When to Induce Plasticity in the Posttraumatic Stress Disorder Network With Transcranial Magnetic Stimulation

Extinction of traumatic memory, a primary treatment approach (termed exposure therapy) in posttraumatic stress disorder (PTSD), occurs through relearning and may be subserved at the molecular level by long-term potentiation of relevant circuits. In parallel, repetitive transcranial magnetic stimulation (TMS) is thought to work through long-term potentiation-like mechanisms and may provide a novel, safe, and effective treatment for PTSD. In a recent failed randomized controlled trial we emphasized the necessity of correctly identifying cortical targets, the directionality of TMS protocols, and the role of memory activation. Here, we provide a systematic review of TMS for PTSD to further identify how, where, and when TMS treatment should be delivered to alleviate PTSD symptoms. We conducted a systematic review of the literature by searching for repetitive TMS clinical trials involving patients with PTSD and outcomes. We searched MEDLINE through October 25, 2023, for "TMS and PTSD" and "transcranial magnetic stimulation and posttraumatic stress disorder." Thirty-one publications met our inclusion criteria (k = 17 randomized controlled trials, k = 14 open label). Randomized controlled trial protocols were varied in terms of TMS protocols, cortical TMS targets, and memory activation protocols. There was no clear superiority of low-frequency (k = 5) versus high-frequency (k = 6) protocols or by stimulation location. Memory provocation or exposure protocols (k = 7) appear to enhance response. Overall, TMS appears to be effective in treating PTSD symptoms across a variety of TMS frequencies, hemispheric target differences, and exposure protocols. Disparate protocols may be conceptually harmonized when viewed as potentiating proposed anxiolytic networks or suppressing anxiogenic networks.

Consensus review and considerations on TMS to treat depression: A comprehensive update endorsed by the National Network of Depression Centers, the Clinical TMS Society, and the International Federation of Clinical Neurophysiology

This article updates the prior 2018 consensus statement by the National Network of Depression Centers (NNDC) on the use of transcranial magnetic stimulation (TMS) in the treatment of depression, incorporating recent research and clinical developments. Publications on TMS and depression between September 2016 and April 2024 were identified using methods informed by PRISMA guidelines. The NNDC Neuromodulation Work Group met monthly between October 2022 and April 2024 to define important clinical topics and review pertinent literature. A modified Delphi method was used to achieve consensus. 2,396 abstracts and manuscripts met inclusion criteria for review. The work group generated consensus statements which include an updated narrative review of TMS safety, efficacy, and clinical features of use for depression. Considerations related to training, roles/responsibilities of providers, and documentation are also discussed. TMS continues to demonstrate broad evidence for safety and efficacy in treating depression. Newer forms of TMS are faster and potentially more effective than conventional repetitive TMS. Further exploration of targeting methods, use in special populations, and accelerated protocols is encouraged. This article provides an updated overview of topics relevant to the administration of TMS for depression and summarizes expert, consensus opinion on the practice of TMS in the United States.

Neuromodulation as a therapeutic approach for post-traumatic stress disorder: the evidence to date

INTRODUCTION

Post-traumatic stress disorder (PTSD) can have debilitating effects on quality of life, and conventional treatments show mixed results. Neuromodulation is emerging as a promising approach for treating PTSD. This review examines current neuromodulatory treatments for PTSD, and highlights methodologies, clinical outcomes, and gaps in the literature to help guide future research.

AREAS COVERED

A PubMed search identified 252 studies on PTSD and neuromodulation, of which 61 were selected for full review. These included 37 studies on repetitive transcranial magnetic stimulation (rTMS), 10 on transcranial direct current stimulation (tDCS),4 on deep brain stimulation (DBS) and 2 on focused ultrasound (FUS).

EXPERT OPINION

The present review supports the potential of neuromodulation to reduce PTSD symptoms. rTMS and tDCS targeting the dlPFC appear effective through modulating neural circuits involved in fear processing and conditioning, however, literature varies regarding efficacy of stimulation frequencies and hemispheric targets. DBS targeting the amygdala or subcallosal cingulate white matter tracts improves treatment of refractory PTSD with sustained benefits, while FUS may improve symptoms through targeted modulation of brain structures such as the amygdala, though this technique is in the early stages of exploration. Future research should refine established neuromodulatory approaches and address gaps in emerging modalities to enhance treatment efficacy.

Common and divergent neuroimaging features in major depression, posttraumatic stress disorder, and their comorbidity

Posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) are common stress-related psychiatric disorders. Genetic and neurobiology research has supported the viewpoint that PTSD and MDD may possess common and disorder-specific underlying mechanisms. In this systematic review, we summarize evidence for the similarities and differences in brain functional and structural features of MDD, PTSD, and their comorbidity, as well as the effects of extensively used therapies in patients with comorbid PTSD and MDD (PTSD + MDD). These functional magnetic resonance imaging (MRI) studies highlight the (i) shared hypoactivation in the prefrontal cortex during cognitive and emotional processing in MDD and PTSD; (ii) higher activation in fear processing regions including amygdala, hippocampus, and insula in PTSD compared to MDD; and (iii) distinct functional deficits in brain regions involved in fear and reward processing in patients with PTSD + MDD relative to those with PTSD alone. These structural MRI studies suggested that PTSD and MDD share features of reduced volume in focal frontal areas. The treatment effects in patients with PTSD + MDD may correlate with the normalization trend of structural alterations. Neuroimaging predictors of repetitive transcranial magnetic stimulation response in patients with PTSD + MDD may differ from the mono-diagnostic groups. In summary, neuroimaging studies to date have provided limited information about the shared and disorder-specific features in MDD and PTSD. Further research is essential to pave the way for developing improved diagnostic markers and eventually targeted treatment approaches for the shared and distinct brain alterations presented in patients with MDD and PTSD.

Intermittent theta-burst stimulation to the right dorsolateral prefrontal cortex may increase potentiated startle in healthy individuals

Repetitive transcranial magnetic stimulation (rTMS) treatment protocols targeting the right dlPFC have been effective in reducing anxiety symptoms comorbid with depression. However, the mechanism behind these effects is unclear. Further, it is unclear whether these results generalize to non-depressed individuals. We conducted a series of studies aimed at understanding the link between anxiety potentiated startle and the right dlPFC, following a previous study suggesting that continuous theta burst stimulation (cTBS) to the right dlPFC can make people more anxious. Based on these results we hypothesized that intermittent TBS (iTBS), which is thought to have opposing effects on plasticity, may reduce anxiety when targeted at the same right dlPFC region. In this double-blinded, cross-over design, 28 healthy subjects underwent 12 study visits over a 4-week period. During each of their 2 stimulation weeks, they received four 600 pulse iTBS sessions (2/day), with a post-stimulation testing session occurring 24 h following the final iTBS session. One week they received active stimulation, one week they received sham. Stimulation weeks were separated by a 1-week washout period and the order of active/sham delivery was counterbalanced across subjects. During the testing session, we induced anxiety using the threat of unpredictable shock and measured anxiety potentiated startle. Contrary to our initial hypothesis, subjects showed increased startle reactivity following active compared to sham stimulation. These results replicate work from our two previous trials suggesting that TMS to the right dlPFC increases anxiety potentiated startle, independent of both the pattern of stimulation and the timing of the post stimulation measure. Although these results confirm a mechanistic link between right dlPFC excitability and startle, capitalizing upon this link for the benefit of patients will require future exploration.

Theta Burst Stimulation Is Not Inferior to High-Frequency Repetitive Transcranial Magnetic Stimulation in Reducing Symptoms of Posttraumatic Stress Disorder in Veterans With Depression: A Retrospective Case Series

OBJECTIVES

Two commonly used forms of repetitive transcranial magnetic stimulation (rTMS) were recently shown to be equivalent for the treatment of depression: high-frequency stimulation (10 Hz), a protocol that lasts between 19 and 38 minutes, and intermittent theta burst stimulation (iTBS), a protocol that can be delivered in just three minutes. However, it is unclear whether iTBS treatment offers the same benefits as those of standard 10-Hz rTMS for comorbid symptoms such as those seen in posttraumatic stress disorder (PTSD).

MATERIALS AND METHODS

In this retrospective case series, we analyzed treatment outcomes in veterans from the Veterans Affairs San Diego Healthcare System who received 10-Hz (n = 47) or iTBS (n = 51)-rTMS treatments for treatment-resistant depression between February 2018 and June 2022. We compared outcomes between these two stimulation protocols in symptoms of depression (using changes in the Patient Health Questionnaire-9 [PHQ-9]) and PTSD (using changes in the PTSD Checklist for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, or Patient Checklist [PCL]-5).

RESULTS

There was an imbalance of sex between groups (p < 0.05). After controlling for sex, we found no significant difference by stimulation protocol for depression (PHQ-9, F [1,94] = 0.16, p = 0.69, eta-squared = 0.002), confirming the original study previously noted. We also showed no difference by stimulation protocol of changes in PTSD symptoms (PCL-5, F [1,94] = 3.46, p = 0.067, eta-squared = 0.036). The iTBS group showed a decrease from 41.9 ± 4.4 to 25.1 ± 4.9 (a difference of 16.8 points) on the PCL-5 scale whereas the 10-Hz group showed a decrease from 43.6 ± 2.9 to 35.2 ± 3.2 on this scale (a difference of 8.4 points). Follow-up analyses restricting the sample in various ways did not meaningfully change these results (no follow-up analyses showed that there was a significant difference between stimulation protocols).

CONCLUSIONS

Although limited by small sample size, nonblind, and pseudorandomized assignment, our data suggest that iTBS is similar to 10-Hz stimulation in inducing reductions in PTSD symptoms and depression in military veterans.

Intensive rTMS for treatment-resistant depression patients with suicidal ideation: An open-label study

The advantages of intensive repetitive transcranial magnetic stimulation (rTMS) protocol are in the possible acute effect of the stimulation and in the possible reduction in the time required to achieve remission in depression. Here, we investigated the antidepressant effects and antisuicidal effects of a more intensive rTMS protocol for treatment-resistant depression (TRD) patients with suicidal ideation. Thirty-one outpatients were included in this study, including 22 military veterans and 9 non- militaries. The rTMS treatment consisted of 25 sessions, each session lasting 30 min (60 trains of 50 pulsations, 110 % resting motor threshold intensity) for a total of 3000 pulse. The total amount of stimulation (750,000 pulses) applied by our rTMS protocol was equivalent to that of a 5-week standard rTMS protocol. We found a significant effect of time on the 17-item Hamilton Depression Rating Scale (HAMD-17) scores and the Sheehan Disability Scale (SDS) scores. There was no difference in change in the HAMD-17 scores and SDS scores between the military veteran group and the non-military group between baseline and the week 4 assessment time point. The response rate of depression was 64.52 %, and the remission rate of depression was 51.61 % at day 5. 48.39 % and 35.48 % at week 4, respectively. All patients (100 %) met response criteria of suicidal ideation, and the remission rate was 87.09 % at day 5. The response rate was 83.87 % %, and the remission rate was 77.42 % at week 4. The accelerated high-dose rTMS treatment was well tolerated by all patients. Our intensive rTMS protocol is preliminarily safe and feasible. The TRD patients with suicidal ideation could benefit from much shorter exposure to this protocol with more efficacy in comparison with conventional rTMS protocol. In addition, intensive rTMS offers a promising treatment for military veteran populations.

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.

Post-traumatic stress disorder: a psychiatric disorder requiring urgent attention

Post-traumatic stress disorder (PTSD) is a severe and heterogenous psychiatric disorder that was first defined as a mental disorder in 1980. Currently, the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-5) and the International Classification of Diseases 11th Edition (ICD-11) offer the most widely accepted diagnostic guidelines for PTSD. In both diagnostic categories, experiencing a traumatic event (TE) is the necessary criterion for diagnosing PTSD. The TEs described in the DSM-5 include actual or threatened death, serious injury, sexual violence, and other extreme stressors, either directly or indirectly. More than 70% of adults worldwide are exposed to a TE at least once in their lifetime, and approximately 10% of individuals develop PTSD after experiencing a TE. The important features of PTSD are intrusion or re-experiencing fear memories, pervasive sense of threat, active avoidance, hyperarousal symptoms, and negative alterations of cognition and mood. Individuals with PTSD have high comorbidities with other psychiatric diseases, including major depressive disorder, generalized anxiety disorder, and substance use disorder. Multiple lines of evidence suggest that the pathophysiology of PTSD is complex, involving abnormal neural circuits, molecular mechanisms, and genetic mechanisms. A combination of both psychotherapy and pharmacotherapy is used to treat PTSD, but has limited efficacy in patients with refractory PTSD. Because of the high prevalence, heavy burden, and limited treatments, PTSD is a psychiatric disorder that requires urgent attention. In this review, we summarize and discuss the diagnosis, prevalence, TEs, pathophysiology, and treatments of PTSD and draw attention to its prevention.

Transcranial Magnetic Stimulation for Post-traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is a psychiatric disorder that causes significant functional impairment and is related to altered stress response and reinforced learned fear behavior. PTSD has been found to impact three functional networks in the brain: default mode, executive control, and salience. The executive control network includes the dorsolateral prefrontal cortex (DLPFC) and lateral PPC. The salience network involves the anterior cingulate cortex, anterior insula, and amygdala. This latter network has been found to have increased functional connectivity in PTSD. Transcranial Magnetic Stimulation (TMS) is a technique used in treating PTSD and involves stimulating specific portions of the brain through electromagnetic induction. Currently, high-frequency TMS applied to the left dorsolateral prefrontal cortex (DLPFC) is approved for use in treating major depressive disorder (MDD) in patients who have failed at least one medication trial. In current studies, high-frequency stimulation has been shown to be more effective in PTSD rating scales posttreatment than low-frequency stimulation. The most common side effect is headache and scalp pain treated by mild analgesics. Seizures are a rare side effect and are usually due to predisposing factors. Studies have been done to assess the overall efficacy of TMS. However, results have been conflicting, and sample sizes were small. More research should be done with larger sample sizes to test the efficacy of TMS in the treatment of PTSD. Overall, TMS is a relatively safe treatment. Currently, the only FDA- approved to treat refractory depression, but with the potential to treat many other conditions.

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.

The Effects of Functionally Guided, Connectivity-Based rTMS on Amygdala Activation

While repetitive transcranial magnetic stimulation (rTMS) is widely used to treat psychiatric disorders, innovations are needed to improve its efficacy. An important limitation is that while psychiatric disorders are associated with fronto-limbic dysregulation, rTMS does not have sufficient depth penetration to modulate affected subcortical structures. Recent advances in task-related functional connectivity provide a means to better link superficial and deeper cortical sources with the possibility of increasing fronto-limbic modulation to induce stronger therapeutic effects. The objective of this pilot study was to test whether task-related, connectivity-based rTMS could modulate amygdala activation through its connectivity with the medial prefrontal cortex (mPFC). fMRI was collected to identify a node in the mPFC showing the strongest connectivity with the amygdala, as defined by psychophysiological interaction analysis. To promote Hebbian-like plasticity, and potentially stronger modulation, 5 Hz rTMS was applied while participants viewed frightening video-clips that engaged the fronto-limbic network. Significant increases in both the mPFC and amygdala were found for active rTMS compared to sham, offering promising preliminary evidence that functional connectivity-based targeting may provide a useful approach to treat network dysregulation. Further research is needed to better understand connectivity influences on rTMS effects to leverage this information to improve therapeutic applications.