Deep brain stimulation of the subgenual cingulum and uncinate fasciculus for the treatment of posttraumatic stress disorder

Sex differences in long-term fear and anxiety-like responses to deep brain stimulation in a preclinical model of PTSD

Deep brain stimulation (DBS) is currently being investigated in patients and preclinical models of posttraumatic stress disorder (PTSD), but differences in behaviour according to sex remain elusive. We exposed female and male rats to fear conditioning and extinction. Thereafter, animals were treated with ventromedial prefrontal cortex DBS, followed by a battery of tests to measure fear and anxiety-like behaviour. As in our prior work, animals with high freezing scores during extinction (weak extinction; WE) were segregated from those with lower freezing scores (non-weak extinction; nWE), since the former population was previously shown to develop prolonged fear and anxiety-like responses. Vaginal lavages were collected after fear extinction to study the estrous cycle. After the experiments, brains were processed for the measurement of estrogen (ER) and progesterone receptors (PR) in the hypothalamus and hippocampus. We found that DBS-treated males had a more pronounced reduction in freezing than females during all recall sessions. In females, DBS induced an anxiolytic-like effect in the open field, while a reduction in the latency to feed during novelty suppressed feeding was noticed in both sexes. Noteworthy, a reduction in freezing during recall and anxiolytic-like responses following DBS were observed in males of all phenotypes, but only in nWE females. While no effect of the estrous cycle was noticed on fear memory, DBS-treated females in metestrus/diestrus during extinction had a more prominent response in the elevated plus maze. A similar expression of ERα, ERβ and PRβ in the hypothalamus and hippocampus was found in DBS-treated females and controls.

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.

White matter correlates of dissociation in a diverse sample of trauma-exposed women

Dissociation is a common response to trauma linked to functional brain disruptions in brain networks subserving emotion regulation and multisensory integration; however, structural neural correlates of dissociation are less known, particularly abnormalities in stress-sensitive white matter (WM) tracts. The present study examined associations between dissociation and WM microstructure, assessed via fractional anisotropy (FA), in a large, diverse sample of women recruited as part of a long-standing trauma study, the Grady Trauma Project (GTP). As part of GTP, 135 trauma-exposed women (18-62 years old, M=34.25, SD=12.96, 84% self-identifying as Black) were recruited, received diffusion tensor imaging, and completed the Multiscale Dissociation Inventory (MDI); FA values were extracted from ten major WM tracts of interest. Partial correlations were conducted to examine associations between dissociation facets (MDI total and subscales) and FA while covarying age and temporal signal-to-noise ratio; false discovery rate corrected p < 0.05 indicated statistical significance. FA in seven tracts showed significant negative associations with overall dissociation (MDI total score; rs<-0.19, pFDR<0.05); the corona radiata, corpus callosum, superior longitudinal fasciculus, thalamic radiation, anterior cingulum, fornix, and uncinate fasciculus. Among facets of dissociation, FA was most consistently associated with dissociative memory disturbance, showing a significant and negative association with all but one of tract of interest, (rs<-0.23, pFDR<0.05). Our findings indicated that dissociation severity was linked to proportionally lesser WM microstructural integrity in tracts involved with sensory integration, emotion regulation, memory, and self-referential processing. Disruptions in these pathways may underlie dissociative phenomena, representing important psychotherapeutic and neuromodulatory targets.

Novel Pharmacologic and Other Somatic Treatment Approaches for Posttraumatic Stress Disorder in Adults: State of the Evidence

Posttraumatic stress disorder (PTSD) is a highly prevalent psychiatric disorder that can become chronic and debilitating when left untreated. The most commonly recommended first-line treatments for PTSD among adults are individual trauma-focused psychotherapies. Other evidence-based treatments include specific antidepressant medications and non-trauma-focused psychotherapies. Despite the effectiveness of these available treatments, many patients' symptoms do not remit. This has led to the search for novel treatments for PTSD. In this review, the authors critically evaluate the data supporting several emerging pharmacological and other somatic interventions in the categories of medication-assisted psychotherapy, novel medication monotherapy strategies, and neuromodulation, selected because of the salience of their mechanisms of action to the pathophysiology of PTSD (e.g., MDMA-assisted psychotherapy, ketamine, cannabidiol, transcranial magnetic stimulation). The authors also evaluate the evidence for treatments that are the focus of increasing scientific or public interest (i.e., hyperbaric oxygen therapy, stellate ganglion block, neurofeedback). To date, the evidence supporting most novel pharmacological and somatic treatments for PTSD is preliminary and highly variable; however, the data for several specific treatments, such as transcranial magnetic stimulation, are encouraging.

A potential target for noninvasive neuromodulation of PTSD symptoms derived from focal brain lesions in veterans

Neuromodulation trials for the treatment of posttraumatic stress disorder (PTSD) have yielded mixed results, and the optimal neuroanatomical target remains unclear. Here we analyzed three datasets to study brain circuitry causally linked to PTSD in military veterans. In veterans with penetrating traumatic brain injury, lesion locations that reduced probability of PTSD were preferentially connected to a circuit including the medial prefrontal cortex, amygdala and anterolateral temporal lobe. In veterans without lesions, PTSD was specifically associated with increased connectivity within this circuit. Reduced functional connectivity within this circuit after transcranial magnetic stimulation correlated with symptom reduction, even though the circuit was not directly targeted. This lesion-based 'PTSD circuit' may serve as a target for clinical trials of neuromodulation in veterans with PTSD.

Genetic evidence supports a causal relationship between air pollution and brain imaging-derived phenotypes

BACKGROUND

Observational studies have reported associations between air pollutants and brain imaging-derived phenotypes (IDPs); however, whether this relationship is causal remains uncertain.

METHODS

We conducted bidirectional two-sample Mendelian randomization (MR) analyses to explore the causal relationships between 5 types of air pollutants (N=423,796 to 456,380 individuals) and 587 reliable IDPs (N=33,224 individuals). Two-step MR was also conducted to assess whether the identified effects are mediated through the modulation of circulating cytokines (N=8293).

RESULTS

We found genetic evidence supporting the association of nitrogen oxides (NOx) with mean intra-cellular volume fraction (ICVF) in the left uncinate fasciculus (IVW β=-0.42, 95 % CI -0.62 to -0.23, P=1.51×10-5) and mean fractional anisotropy (FA) in the left uncinate fasciculus (IVW β=-0.42, 95 % CI -0.62 to -0.21, P=4.89×10-5). In further two-step MR analyses, we did not find evidence that genetic predictions of any circulating cytokines mediated the association between NOx and IDPs.

CONCLUSION

This study provides evidence for the association between air pollutants and brain IDPs, emphasizing the importance of controlling air pollution to improve brain health.

Deep brain stimulation of the amygdala for treatment-resistant combat post-traumatic stress disorder: Long-term results

Deep brain stimulation (DBS) holds promise for neuropsychiatric conditions where imbalance in network activity contributes to symptoms. Treatment-resistant Combat post-traumatic stress disorder (TR-PTSD) is a highly morbid condition and 50% of PTSD sufferers fail to recover despite psychotherapy or pharmacotherapy. Reminder-triggered symptoms may arise from inadequate top-down ventromedial prefrontal cortex (vmPFC) control of amygdala reactivity. Here, we report long-term data on two TR-PTSD participants from an investigation utilizing high-frequency amygdala DBS. The two combat veterans were implanted bilaterally with quadripolar electrodes targeting the basolateral amygdala. Following a randomized staggered onset, patients received stimulation with adjustments based on PTSD symptom severity for four years while psychiatric and neuropsychiatric symptoms, neuropsychological performance, and electroencephalography were systematically monitored. Evaluation of vmPFC-Amygdala network engagement was assessed with 18FDG positron emission tomography (PET). CAPS-IV scores varied over time, but improved 55% from 119 at baseline to 53 at 4-year study endpoint in participant 1; and 44%, from 68 to 38 in participant 2. Thereafter, during 5 and 1.5 years of subsequent clinical care respectively, long-term bilateral amygdala DBS was associated with additional, clinically significant symptomatic and functional improvement. There were no serious stimulation-related adverse psychiatric, neuropsychiatric, neuropsychological, neurological, or neurosurgical effects. In one subject, symptomatic improvement was associated with an intensity-dependent reduction in amygdala theta frequency power. In our two participants, FDG-PET findings were inconclusive regarding the hypothesized mechanism of suppression of amygdala hyperactivity. Our findings encourage further research to confirm and extend our preliminary observations.

Insertional effect following electrode implantation: an underreported but important phenomenon

Deep brain stimulation has revolutionized the treatment of movement disorders and is gaining momentum in the treatment of several other neuropsychiatric disorders. In almost all applications of this therapy, the insertion of electrodes into the target has been shown to induce some degree of clinical improvement prior to stimulation onset. Disregarding this phenomenon, commonly referred to as 'insertional effect', can lead to biased results in clinical trials, as patients receiving sham stimulation may still experience some degree of symptom amelioration. Similar to the clinical scenario, an improvement in behavioural performance following electrode implantation has also been reported in preclinical models. From a neurohistopathologic perspective, the insertion of electrodes into the brain causes an initial trauma and inflammatory response, the activation of astrocytes, a focal release of gliotransmitters, the hyperexcitability of neurons in the vicinity of the implants, as well as neuroplastic and circuitry changes at a distance from the target. Taken together, it would appear that electrode insertion is not an inert process, but rather triggers a cascade of biological processes, and, as such, should be considered alongside the active delivery of stimulation as an active part of the deep brain stimulation therapy.

A potential neuromodulation target for PTSD in Veterans derived from focal brain lesions

Neuromodulation trials for PTSD have yielded mixed results, and the optimal neuroanatomical target remains unclear. We analyzed three datasets to study brain circuitry causally linked to PTSD in military Veterans. After penetrating traumatic brain injury (n=193), lesions that reduced probability of PTSD were preferentially connected to a circuit including the medial prefrontal cortex (mPFC), amygdala, and anterolateral temporal lobe (cross-validation p=0.01). In Veterans without lesions (n=180), PTSD was specifically associated with connectivity within this circuit (p<0.01). Connectivity change within this circuit correlated with PTSD improvement after transcranial magnetic stimulation (TMS) (n=20) (p<0.01), even though the circuit was not directly targeted. Finally, we directly targeted this circuit with fMRI-guided accelerated TMS, leading to rapid resolution of symptoms in a patient with severe lifelong PTSD. All results were independent of depression severity. This lesion-based PTSD circuit may serve as a neuromodulation target for Veterans with PTSD.

BLA DBS improves anxiety and fear by correcting weakened synaptic transmission from BLA to adBNST and CeL in a mouse model of foot shock

Deep brain stimulation (DBS) in the basal lateral amygdala (BLA) has been established to correct symptoms of refractory post-traumatic stress disorder (PTSD). However, how BLA DBS operates in correcting PTSD symptoms and how the BLA elicits pathological fear and anxiety in PTSD remain unclear. Here, we discover that excitatory synaptic transmission from the BLA projection neurons (PNs) to the adBNST, and lateral central amygdala (CeL) is greatly suppressed in a mouse PTSD model induced by foot shock (FS). BLA DBS revises the weakened inputs from the BLA to these two areas to improve fear and anxiety. Optogenetic manipulation of the BLA-adBNST and BLA-CeL circuits shows that both circuits are responsible for anxiety but the BLA-CeL for fear in FS mice. Our results reveal that synaptic transmission dysregulation of the BLA-adBNST or BLA-CeL circuits is reversed by BLA DBS, which improves anxiety and fear in the FS mouse model.

Regional associations of white matter integrity and neurological, post-traumatic stress disorder and autonomic symptoms in Veterans with and without history of loss of consciousness in mild TBI

Background

Posttraumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI) share overlapping symptom presentations and are highly comorbid conditions among Veteran populations. Despite elevated presentations of PTSD after mTBI, mechanisms linking the two are unclear, although both have been associated with alterations in white matter and disruptions in autonomic regulation. The present study aimed to determine if there is regional variability in white matter correlates of symptom severity and autonomic functioning in a mixed sample of Veterans with and without PTSD and/or mTBI (N = 77).

Methods

Diffusion-weighted images were processed to extract fractional anisotropy (FA) values for major white matter structures. The PTSD Checklist-Military version (PCL-M) and Neurobehavioral Symptom Inventory (NSI) were used to determine symptom domains within PTSD and mTBI. Autonomic function was assessed using continuous blood pressure and respiratory sinus arrythmia during a static, standing angle positional test. Mixed-effect models were used to assess the regional specificity of associations between symptom severity and white matter, with FA, global symptom severity (score), and white matter tract (tract) as predictors. Additional interaction terms of symptom domain (i.e., NSI and PCL-M subscales) and loss of consciousness (LoC) were added to evaluate potential moderating effects. A parallel analysis was conducted to explore concordance with autonomic functioning.

Results

Results from the two-way Score × Tract interaction suggested that global symptom severity was associated with FA in the cingulum angular bundle (positive) and uncinate fasciculus (negative) only, without variability by symptom domain. We also found regional specificity in the relationship between FA and autonomic function, such that FA was positively associated with autonomic function in all tracts except the cingulum angular bundle. History of LoC moderated the association for both global symptom severity and autonomic function.

Conclusions

Our findings are consistent with previous literature suggesting that there is significant overlap in the symptom presentation in TBI and PTSD, and white matter variability associated with LoC in mTBI may be associated with increased PTSD-spectra symptoms. Further research on treatment response in patients with both mTBI history and PTSD incorporating imaging and autonomic assessment may be valuable in understanding the role of brain injury in treatment outcomes and inform treatment design.

Analysis of the influences of social isolation on cognition and the therapeutic potential of deep brain stimulation in a mouse model

Background

Social interaction is a fundamental human need. Social isolation (SI) can have negative effects on both emotional and cognitive function. However, it is currently unclear how age and the duration of SI affect emotion and recognition function. In addition, there is no specific treatment for the effects of SI.

Methods

The adolescence or adult mice were individually housed in cages for 1, 6 or 12 months and for 2 months to estabolish SI mouse model. We investigated the effects of SI on behavior in mice at different ages and under distinct durations of SI, and we explored the possible underlying mechanisms. Then we performed deep brain stimulation (DBS) to evaluate its influences on SI induced behavioral abnormalities.

Results

We found that social recognition was affected in the short term, while social preference was damaged by extremely long periods of SI. In addition to affecting social memory, SI also affects emotion, short-term spatial ability and learning willingness in mice. Myelin was decreased significantly in the medial prefrontal cortex (mPFC) and dorsal hippocampus of socially isolated mice. Cellular activity in response to social stimulation in both areas was impaired by social isolation. By stimulating the mPFC using DBS, we found that DBS alleviated cellular activation disorders in the mPFC after long-term SI and improved social preference in mice.

Conclusion

Our results suggest that the therapeutic potential of stimulating the mPFC with DBS in individuals with social preference deficits caused by long-term social isolation, as well as the effects of DBS on the cellular activity and density of OPCs.

A pilot study of closed-loop neuromodulation for treatment-resistant post-traumatic stress disorder

The neurophysiological mechanisms in the human amygdala that underlie post-traumatic stress disorder (PTSD) remain poorly understood. In a first-of-its-kind pilot study, we recorded intracranial electroencephalographic data longitudinally (over one year) in two male individuals with amygdala electrodes implanted for the management of treatment-resistant PTSD (TR-PTSD) under clinical trial NCT04152993. To determine electrophysiological signatures related to emotionally aversive and clinically relevant states (trial primary endpoint), we characterized neural activity during unpleasant portions of three separate paradigms (negative emotional image viewing, listening to recordings of participant-specific trauma-related memories, and at-home-periods of symptom exacerbation). We found selective increases in amygdala theta (5-9 Hz) bandpower across all three negative experiences. Subsequent use of elevations in low-frequency amygdala bandpower as a trigger for closed-loop neuromodulation led to significant reductions in TR-PTSD symptoms (trial secondary endpoint) following one year of treatment as well as reductions in aversive-related amygdala theta activity. Altogether, our findings provide early evidence that elevated amygdala theta activity across a range of negative-related behavioral states may be a promising target for future closed-loop neuromodulation therapies in PTSD.