Effects of bilateral sequential theta-burst stimulation on functional connectivity in treatment-resistant depression: First results

Magnetic resonance imaging connectivity features associated with response to transcranial magnetic stimulation in major depressive disorder

Transcranial magnetic stimulation (TMS) is an FDA-approved neuromodulation treatment for major depressive disorder (MDD), thought to work by altering dysfunctional brain connectivity pathways, or by indirectly modulating the activity of subcortical brain regions. Clinical response to TMS remains highly variable, highlighting the need for baseline predictors of response and for understanding brain changes associated with response. This systematic review examined brain connectivity features, and changes in connectivity features, associated with clinical improvement following TMS in MDD. Forty-one studies met inclusion criteria, including 1097 people with MDD. Most studies delivered one of two types of TMS to left dorsolateral prefrontal cortex and measured connectivity using resting-state functional MRI. The subgenual anterior cingulate cortex was the most well-studied brain region, particularly its connectivity with the TMS target or with the "executive control network" of brain regions. There was marked heterogeneity in findings. There is a need for greater understanding of how cortical TMS modulates connectivity with, and the activity of, subcortical regions, and how these effects change within and across treatment sessions.

Comparisons of Accelerated Continuous and Intermittent Theta Burst Stimulation for Treatment-Resistant Depression and Suicidal Ideation

BACKGROUND

Suicidal ideation is a substantial clinical challenge in treatment-resistant depression (TRD). Recent work demonstrated promising antidepressant effects in TRD patients with no or mild suicidal ideation using a specific protocol termed intermittent theta burst stimulation (iTBS). Here, we examined the clinical effects of accelerated schedules of iTBS and continuous TBS (cTBS) in patients with moderate to severe suicidal ideation.

METHODS

Patients with TRD and moderate to severe suicidal ideation (n = 44) were randomly assigned to receive accelerated iTBS or cTBS treatment. Treatments were delivered in 10 daily TBS sessions (1800 pulses/session) for 5 consecutive days (total of 90,000 pulses). Neuronavigation was employed to target accelerated iTBS and cTBS to the left and right dorsolateral prefrontal cortex (DLPFC), respectively. Clinical outcomes were evaluated in a 4-week follow-up period.

RESULTS

Accelerated cTBS was superior to iTBS in the management of suicidal ideation (pweek 1 = .027) and anxiety symptoms (pweek 1 = .01). Accelerated iTBS and cTBS were comparable in antidepressant effects (p < .001; accelerated cTBS: mean change at weeks 1, 3, 5 = 49.55%, 54.99%, 53.11%; accelerated iTBS: mean change at weeks 1, 3, 5 = 44.52%, 48.04%, 51.74%). No serious adverse events occurred during the trial. One patient withdrew due to hypomania. The most common adverse event was discomfort at the treatment site (22.73% in both groups).

CONCLUSIONS

These findings provide the first evidence that accelerated schedules of left DLPFC iTBS and right DLPFC cTBS are comparably effective in managing antidepressant symptoms and indicate that right DLPFC cTBS is potentially superior in reducing suicidal ideation and anxiety symptoms.

Computational Modeling of the Prefrontal-Cingulate Cortex to Investigate the Role of Coupling Relationships for Balancing Emotion and Cognition

Within the prefrontal-cingulate cortex, abnormalities in coupling between neuronal networks can disturb the emotion-cognition interactions, contributing to the development of mental disorders such as depression. Despite this understanding, the neural circuit mechanisms underlying this phenomenon remain elusive. In this study, we present a biophysical computational model encompassing three crucial regions, including the dorsolateral prefrontal cortex, subgenual anterior cingulate cortex, and ventromedial prefrontal cortex. The objective is to investigate the role of coupling relationships within the prefrontal-cingulate cortex networks in balancing emotions and cognitive processes. The numerical results confirm that coupled weights play a crucial role in the balance of emotional cognitive networks. Furthermore, our model predicts the pathogenic mechanism of depression resulting from abnormalities in the subgenual cortex, and network functionality was restored through intervention in the dorsolateral prefrontal cortex. This study utilizes computational modeling techniques to provide an insight explanation for the diagnosis and treatment of depression.

Targeting Symptom-Specific Networks With Transcranial Magnetic Stimulation

Increasing evidence suggests that the clinical effects of transcranial magnetic stimulation are target dependent. Within any given symptom, precise targeting of specific brain circuits may improve clinical outcomes. This principle can also be extended across symptoms-stimulation of different circuits may lead to different symptom-level outcomes. This may include targeting different symptoms within the same disorder (such as dysphoria vs. anxiety in patients with major depression) or targeting the same symptom across different disorders (such as primary major depression and depression secondary to stroke, traumatic brain injury, epilepsy, multiple sclerosis, or Parkinson's disease). Some of these symptom-specific changes may be desirable, while others may be undesirable. This review focuses on the conceptual framework through which symptom-specific target circuits may be identified, tested, and implemented.

Accelerated Theta Burst Stimulation: Safety, Efficacy, and Future Advancements

Theta burst stimulation (TBS) is a noninvasive brain stimulation technique that can be used to modulate neural networks underlying psychiatric and neurological disorders. TBS can be delivered intermittently or continuously. The conventional intermittent TBS protocol is approved by the U.S. Food and Drug Administration to treat otherwise treatment-resistant depression, but the 6-week duration limits the applicability of this therapy. Accelerated TBS protocols present an opportunity to deliver higher pulse doses in shorter periods of time, thus resulting in faster and potentially more clinically effective treatment. However, the acceleration of TBS delivery raises questions regarding the relative safety, efficacy, and durability compared with conventional TBS protocols. In this review paper, we present the data from accelerated TBS trials to date that support the safety and effectiveness of accelerated protocols while acknowledging the need for more durability data. We discuss the stimulation parameters that seem to be important for the efficacy of accelerated TBS protocols and possible avenues for further optimization.

The future of brain circuit-targeted therapeutics

The principle of targeting brain circuits has drawn increasing attention with the growth of brain stimulation treatments such as transcranial magnetic stimulation (TMS), deep brain stimulation (DBS), and focused ultrasound (FUS). Each of these techniques can effectively treat different neuropsychiatric disorders, but treating any given disorder depends on choosing the right treatment target. Here, we propose a three-phase framework for identifying and modulating these targets. There are multiple approaches to identifying a target, including correlative neuroimaging, retrospective optimization based on existing stimulation sites, and lesion localization. These techniques can then be optimized using personalized neuroimaging, physiological monitoring, and engagement of a specific brain state using pharmacological or psychological interventions. Finally, a specific stimulation modality or combination of modalities can be chosen after considering the advantages and tradeoffs of each. While there is preliminary literature to support different components of this framework, there are still many unanswered questions. This presents an opportunity for the future growth of research and clinical care in brain circuit therapeutics.

Effects of bilateral sequential theta-burst stimulation on 5-HT1A receptors in the dorsolateral prefrontal cortex in treatment-resistant depression: a proof-of-concept trial

Theta-burst stimulation (TBS) represents a brain stimulation technique effective for treatment-resistant depression (TRD) as underlined by meta-analyses. While the methodology undergoes constant refinement, bilateral stimulation of the dorsolateral prefrontal cortex (DLPFC) appears promising to restore left DLPFC hypoactivity and right hyperactivity found in depression. The post-synaptic inhibitory serotonin-1A (5-HT1A) receptor, also occurring in the DLPFC, might be involved in this mechanism of action. To test this hypothesis, we performed PET-imaging using the tracer [carbonyl-11C]WAY-100635 including arterial blood sampling before and after a three-week treatment with TBS in 11 TRD patients compared to sham stimulation (n = 8 and n = 3, respectively). Treatment groups were randomly assigned, and TBS protocol consisted of excitatory intermittent TBS to the left and inhibitory continuous TBS to the right DLPFC. A linear mixed model including group, hemisphere, time, and Hamilton Rating Scale for Depression (HAMD) score revealed a 3-way interaction effect of group, time, and HAMD on specific distribution volume (VS) of 5-HT1A receptor. While post-hoc comparisons showed no significant changes of 5-HT1A receptor VS in either group, higher 5-HT1A receptor VS after treatment correlated with greater difference in HAMD (r = -0.62). The results of this proof-of-concept trial hint towards potential effects of TBS on the distribution of the 5-HT1A receptor. Due to the small sample size, all results must, however, be regarded with caution.

Accelerated theta-burst transcranial magnetic stimulation of the bilateral dorsolateral prefrontal cortex in a patient with post-traumatic stress disorder and major depressive disorder: Case report

BACKGROUND

Theta-burst transcranial magnetic stimulation has demonstrated promising effectiveness as treatment for post-traumatic stress disorder (PTSD) and depression. However, the effect of accelerated theta-burst stimulation (TBS) in comorbid with PTSD and depression remains unknown.

CASE PRESENTATION

We report a case of a 25-year-old woman with PTSD and depression whose symptoms markedly improved after continuous TBS of the right dorsolateral prefrontal cortex (DLPFC) and intermittent TBS (iTBS) over the left DLPFC, and then with 20 min break before the 2nd iTBS session.

CONCLUSIONS

Accelerated TBS over the bilateral DLPFC may improve severe PTSD and depression. Accelerated TBS may have more improvement of depression symptoms than PTSD symptoms. Further trials are warranted to investigate the effect and safety for patients with complicated PTSD and depression.