Practical considerations in the development and refinement of subcallosal cingulate white matter deep brain stimulation for treatment-resistant depression

Deep brain stimulation for refractory major depressive disorder: a comprehensive review

Deep brain stimulation (DBS) has emerged as a promising treatment for select patients with refractory major depressive disorder (MDD). The clinical effectiveness of DBS for MDD has been demonstrated in meta-analyses, open-label studies, and a few controlled studies. However, randomized controlled trials have yielded mixed outcomes, highlighting challenges that must be addressed prior to widespread adoption of DBS for MDD. These challenges include tracking MDD symptoms objectively to evaluate the clinical effectiveness of DBS with sensitivity and specificity, identifying the patient population that is most likely to benefit from DBS, selecting the optimal patient-specific surgical target and stimulation parameters, and understanding the mechanisms underpinning the therapeutic benefits of DBS in the context of MDD pathophysiology. In this review, we provide an overview of the latest clinical evidence of MDD DBS effectiveness and the recent technological advancements that could transform our understanding of MDD pathophysiology, improve the clinical outcomes for MDD DBS, and establish a path forward to develop more effective neuromodulation therapies to alleviate depressive symptoms.

Prelemniscal Radiations as a Target for the Treatment of Parkinson Disease - Individual Variations in the Stereotactic Location of Fiber Components: A Probabilistic Tractography Study

OBJECTIVE

Prelemniscal radiation (Raprl) lesions and deep brain stimulation effectively control motor symptoms of Parkinson disease, but individual variations in the stereotactic location of its fiber components constitute a significant concern. The objective of this study was to determine individual variations in the stereotactic location of fiber tracts composing Raprl.

METHODS

Raprl fiber composition was determined in a group of 10 Parkinson patients and 10 matched controls using 3T magnetic resonance imaging, brain imaging processed for diffusion-weighted images, tract density imaging, and constrained spherical deconvolution. The stereotactic position of the point of maximal proximity (PMP), which is the point where the most significant number of fibers is concentrated in the smallest volume in the tractography, was evaluated in the right and left hemispheres of the same person, between individuals and between patients and controls for each tract in coordinates "x," "y," and "z." The stereotactic coordinates at which PMP of all tracts meet were statistically determined, representing the recommended aim for this target.

RESULTS

Stereotactic coordinates of the 3 fiber tracts composing Raprl, cerebellar-thalamic-cortical, globus pallidus-peduncle-pontine nucleus, and mesencephalic-orbital frontal cortex, did not vary between right and left hemispheres in the same person and between patients and controls. In contrast, PMP variability between individuals was significant, mainly for the mesencephalic-orbitofrontal tract. Therefore, probabilistic tractography can better determine individual variations to plan electrode trajectories.

CONCLUSIONS

Individual PMP variations for fiber tracts in Raprl, identified by probabilistic tractography, provide a platform for planning the stereotactic approach to conform volumes for deep brain stimulation and lesions.

A narrative review on invasive brain stimulation for treatment-resistant depression

While most patients with depression respond to pharmacotherapy and psychotherapy, about one-third will present treatment resistance to these interventions. For patients with treatment-resistant depression (TRD), invasive neurostimulation therapies such as vagus nerve stimulation, deep brain stimulation, and epidural cortical stimulation may be considered. We performed a narrative review of the published literature to identify papers discussing clinical studies with invasive neurostimulation therapies for TRD. After a database search and title and abstract screening, relevant English-language articles were analyzed. Vagus nerve stimulation, approved by the U.S. Food and Drug Administration as a TRD treatment, may take several months to show therapeutic benefits, and the average response rate varies from 15.2-83%. Deep brain stimulation studies have shown encouraging results, including rapid response rates (> 30%), despite conflicting findings from randomized controlled trials. Several brain regions, such as the subcallosal-cingulate gyrus, nucleus accumbens, ventral capsule/ventral striatum, anterior limb of the internal capsule, medial-forebrain bundle, lateral habenula, inferior-thalamic peduncle, and the bed-nucleus of the stria terminalis have been identified as key targets for TRD management. Epidural cortical stimulation, an invasive intervention with few reported cases, showed positive results (40-60% response), although more extensive trials are needed to confirm its potential in patients with TRD.

Anatomical Connectivity-Based Strategy for Targeting Transcranial Magnetic Stimulation as Antidepressant Therapy

OBJECTIVES

Abnormal activity of the subgenual anterior cingulate cortex (sACC) is implicated in depression, suggesting the sACC as a potentially effective target for therapeutic modulation in cases resistant to conventional treatments (treatment-resistant depression, TRD). We hypothesized that areas in the prefrontal cortex (PFC) with direct fiber connections to the sACC may be particularly effective sites for treatment using transcranial magnetic stimulation (TMS). The aim of this study was to identify PFC sites most strongly connected to the sACC.

METHODS

Two neuroimaging data sets were used to construct anatomic and functional connectivity maps using sACC as the seed region. Data set 1 included magnetic resonance (MR) images from 20 healthy controls and Data set 2 included MR images from 15 TRD patients and 15 additional healthy controls. PFC voxels with maximum values in the mean anatomic connection probability maps were identified as optimal sites for TMS.

RESULTS

Both right and left PFC contained sites strongly connected to the sACC, but the coordinates (in Montreal Neurological Institute space) of peak anatomic connectivity differed slightly between hemispheres. The left PFC site connected directly to the sACC both anatomically and functionally, while the right PFC site was functionally connected to the posterior cingulate cortex (PCC).

CONCLUSIONS

Both left and right PFC are functionally connected to regions implicated in depression, the sACC and PCC, respectively. These bilateral PFC sites may be effective TMS targets to treat TRD.

White Matter Network Architecture Guides Direct Electrical Stimulation through Optimal State Transitions

Optimizing direct electrical stimulation for the treatment of neurological disease remains difficult due to an incomplete understanding of its physical propagation through brain tissue. Here, we use network control theory to predict how stimulation spreads through white matter to influence spatially distributed dynamics. We test the theory's predictions using a unique dataset comprising diffusion weighted imaging and electrocorticography in epilepsy patients undergoing grid stimulation. We find statistically significant shared variance between the predicted activity state transitions and the observed activity state transitions. We then use an optimal control framework to posit testable hypotheses regarding which brain states and structural properties will efficiently improve memory encoding when stimulated. Our work quantifies the role that white matter architecture plays in guiding the dynamics of direct electrical stimulation and offers empirical support for the utility of network control theory in explaining the brain's response to stimulation.

How Deep Brain Stimulation of the Nucleus Accumbens Affects the Cingulate Gyrus and Vice Versa

The nucleus accumbens (NA) and the cingulate gyrus (CG) are two vital limbic brain structures. They have attracted attention as deep brain stimulation (DBS) targets in the treatment of common refractory psychiatric illness. The primary purpose of this article was to review the current knowledge regarding the way that NA DBS affects the CG and vice versa. Methodologically, a thorough literature review was performed. According to the current literature, NA DBS modulates the function of several brain areas including the CG cortex. It specifically causes activation in the ipsilateral CG cortex and voltage-dependent reduction of its blood oxygenation. It also reverses anterior mid-CG cortex dysfunction and decreases metabolism in the subgenual CG. Moreover, NA DBS that induces mirth inhibits the function of the anterior CG cortex and enhances effective connectivity from anterior CG to the ventral striatum. On the other hand, although it is highly probable that CG DBS affects the NA, the exact nature of its effects remains unclear. Despite the increasing interest in psychiatric DBS, the available data on how NA DBS affects the CG and vice versa are restricted. This conclusion probably reflects the high complexity of the limbic circuits and necessitates further research.

Neuromodulation for Pain Management

Pain is a salient and complex sensory experience with important affective and cognitive dimensions. The current definition of pain relies on subjective reports in both humans and experimental animals. Such definition lacks basic mechanistic insights and can lead to a high degree of variability. Research on biomarkers for pain has previously focused on genetic analysis. However, recent advances in human neuroimaging and research in animal models have begun to show the promise of a circuit-based neural signature for pain. At the treatment level, pharmacological therapy for pain remains limited. Neuromodulation has emerged as a specific form of treatment without the systemic side effects of pharmacotherapies. In this review, we will discuss some of the current neuromodulatory modalities for pain, research on newer targets, as well as emerging possibility for an integrated brain-computer interface approach for pain management.

Deep brain stimulation for treatment-resistant depression: an integrative review of preclinical and clinical findings and translational implications

Although deep brain stimulation (DBS) is an established treatment choice for Parkinson's disease (PD), essential tremor and movement disorders, its effectiveness for the management of treatment-resistant depression (TRD) remains unclear. Herein, we conducted an integrative review on major neuroanatomical targets of DBS pursued for the treatment of intractable TRD. The aim of this review article is to provide a critical discussion of possible underlying mechanisms for DBS-generated antidepressant effects identified in preclinical studies and clinical trials, and to determine which brain target(s) elicited the most promising outcomes considering acute and maintenance treatment of TRD. Major electronic databases were searched to identify preclinical and clinical studies that have investigated the effects of DBS on depression-related outcomes. Overall, 92 references met inclusion criteria, and have evaluated six unique DBS targets namely the subcallosal cingulate gyrus (SCG), nucleus accumbens (NAc), ventral capsule/ventral striatum or anterior limb of internal capsule (ALIC), medial forebrain bundle (MFB), lateral habenula (LHb) and inferior thalamic peduncle for the treatment of unrelenting TRD. Electrical stimulation of these pertinent brain regions displayed differential effects on mood transition in patients with TRD. In addition, 47 unique references provided preclinical evidence for putative neurobiological mechanisms underlying antidepressant effects of DBS applied to the ventromedial prefrontal cortex, NAc, MFB, LHb and subthalamic nucleus. Preclinical studies suggest that stimulation parameters and neuroanatomical locations could influence DBS-related antidepressant effects, and also pointed that modulatory effects on monoamine neurotransmitters in target regions or interconnected brain networks following DBS could have a role in the antidepressant effects of DBS. Among several neuromodulatory targets that have been investigated, DBS in the neuroanatomical framework of the SCG, ALIC and MFB yielded more consistent antidepressant response rates in samples with TRD. Nevertheless, more well-designed randomized double-blind, controlled trials are warranted to further assess the efficacy, safety and tolerability of these more promising DBS targets for the management of TRD as therapeutic effects have been inconsistent across some controlled studies.

Orbital and Medial Prefrontal Cortex Functional Connectivity of Major Depression Vulnerability and Disease

BACKGROUND

Pathophysiology models of major depression (MD) center on the dysfunction of various cortical areas within the orbital and medial prefrontal cortex. While independent structural and functional abnormalities in these areas are consistent findings in MD, the complex interactions among them and the rest of the cortex remain largely unexplored.

METHODS

We used resting-state functional magnetic resonance imaging connectivity to systematically map alterations in the communication between orbital and medial prefrontal cortex fields and the rest of the brain in MD. Functional connectivity (FC) maps from participants with current MD (n = 35), unaffected first-degree relatives (n = 36), and healthy control subjects (n = 38) were subjected to conjunction analyses to distinguish FC markers of MD vulnerability and FC markers of MD disease.

RESULTS

FC abnormalities in MD vulnerability were found for dorsal medial wall regions and the anterior insula and concerned altered communication of these areas with the inferior parietal cortex and dorsal posterior cingulate, occipital areas and the brainstem. FC aberrations in current MD included the anterior insula, rostral and dorsal anterior cingulate cortex, and lateral orbitofrontal areas and concerned altered communication with the dorsal striatum, the cerebellum, the precuneus, the anterior prefrontal cortex, somatomotor cortex, dorsolateral prefrontal cortex, and visual areas in the occipital and inferior temporal lobes.

CONCLUSIONS

Functionally delineated parcellation maps can be used to identify putative connectivity markers in extended cortical regions such as the orbital and medial prefrontal cortex. The anterior insula and the rostral anterior cingulate cortex play a central role in the pathophysiology of MD, being consistently implicated both in the MD vulnerability and MD disease states.

The role of the basal ganglia in the control of seizure

Epilepsy is a network disorder and each type of seizure involves distinct cortical and subcortical network, differently implicated in the control and propagation of the ictal activity. The role of the basal ganglia has been revealed in several cases of focal and generalized seizures. Here, we review the data that show the implication of the basal ganglia in absence, temporal lobe, and neocortical seizures in animal models (rodent, cat, and non-human primate) and in human. Based on these results and the advancement of deep brain stimulation for Parkinson's disease, basal ganglia neuromodulation has been tested with some success that can be equally seen as promising or disappointing. The effect of deep brain stimulation can be considered promising with a 76% in seizure reduction in temporal lobe epilepsy patients, but also disappointing, since only few patients have become seizure free and the antiepileptic effects have been highly variable among patients. This variability could probably be explained by the heterogeneity among the patients included in these clinical studies. To illustrate the importance of specific network identification, electrophysiological activity of the putamen and caudate nucleus has been recorded during penicillin-induced pre-frontal and motor seizures in one monkey. While an increase of the firing rate was found in putamen and caudate nucleus during pre-frontal seizures, only the activity of the putamen cells was increased during motor seizures. These preliminary results demonstrate the implication of the basal ganglia in two types of neocortical seizures and the necessity of studying the network to identify the important nodes implicated in the propagation and control of each type of seizure.

Use of deep brain stimulation for major affective disorders

The multifactorial etiology of major affective disorders, such as major depression and bipolar disorder, poses a challenge for identification of effective treatments. In a substantial number of patients, psychopharmacologic treatment does not lead to effective continuous symptom relief. The use of deep brain stimulation (DBS) for treatment-resistant patients is an investigational approach that has recently produced promising results. The recent development of safer stereotaxic neurosurgery, and the combination with functional neuroimaging to map the affected brain circuits, have led to the investigation of DBS as a potential strategy to treat major mood disorders. Several independent clinical studies have recently shown that chronic DBS treatment leads to remission of symptoms in a high number of treatment-resistant patients for major depression and bipolar disorder. In conclusion, the existing proof-of-principle that DBS can be an effective intervention for treatment-resistant depression opens new avenues for treatment. However, multicenter, randomized and blind trials need to confirm efficacy and be approved after the most recent failures. Patient selection and surgical-related improvements are key issues that remain to be addressed to help deliver more precise and customized treatment.

A randomized double-blind crossover trial of deep brain stimulation of the subcallosal cingulate gyrus in patients with treatment-resistant depression: a pilot study of relapse prevention

BACKGROUND

To date, antidepressant drugs show limited efficacy, leaving a large number of patients experiencing severe and persistent symptoms of major depression. Previous open-label clinical trials have reported significant sustained improvements with deep brain stimulation (DBS) of the subcallosal cingulate gyrus (SCG) in patients with severe, chronic treatment-resistant depression (TRD). This study aimed to confirm the efficacy and measure the impact of discontinuation of the electrical stimulation.

METHODS

We conducted a 6-month double-blind, randomized, sham-controlled crossover study in implanted patients with previous severe TRD who experienced full remission after chronic stimulation. After more than 3 months of stable remission, patients were randomly assigned to 2 treatment arms: the ON-OFF arm, which involved active electrode stimulation for 3 months followed by sham stimulation for 3 months, and the OFF-ON arm, which involved sham stimulation for 3 months followed by active stimulation for 3 months. The primary outcome measure was the difference in the 17-item Hamilton Rating Scale for Depression (HAMD-17) total score between sham and active stimulation.

RESULTS

We enrolled 5 patients in our trial. A Friedman repeated-measures analysis of variance revealed a significant effect of treatment (χ(2)1 = 5.0, p = 0.025) in patients with higher depression scores during sham stimulation. At the end of active stimulation, depression was remitted in 4 of 5 patients and none of them had experienced a relapse, whereas at the end of sham stimulation, 2 patients remained in remission, 2 relapsed and 1 showed a progressive worsening without reaching relapse criteria.

LIMITATIONS

The small sample size limited the statistical power and external validity.

CONCLUSION

These preliminary findings indicate that DBS of the SCG is an effective and safe treatment for severe forms of TRD and that continuous electrical stimulation is required to maintain therapeutic effects.

TRIAL REGISTRATION

NCT01268137 (ClinicalTrials.gov).

Activation of corticostriatal circuitry relieves chronic neuropathic pain

Neural circuits that determine the perception and modulation of pain remain poorly understood. The prefrontal cortex (PFC) provides top-down control of sensory and affective processes. While animal and human imaging studies have shown that the PFC is involved in pain regulation, its exact role in pain states remains incompletely understood. A key output target for the PFC is the nucleus accumbens (NAc), an important component of the reward circuitry. Interestingly, recent human imaging studies suggest that the projection from the PFC to the NAc is altered in chronic pain. The function of this corticostriatal projection in pain states, however, is not known. Here we show that optogenetic activation of the PFC produces strong antinociceptive effects in a rat model (spared nerve injury model) of persistent neuropathic pain. PFC activation also reduces the affective symptoms of pain. Furthermore, we show that this pain-relieving function of the PFC is likely mediated by projections to the NAc. Thus, our results support a novel role for corticostriatal circuitry in pain regulation.

Deep brain stimulation for psychiatric disorders: where we are now

Fossil records showing trephination in the Stone Age provide evidence that humans have sought to influence the mind through physical means since before the historical record. Attempts to treat psychiatric disease via neurosurgical means in the 20th century provided some intriguing initial results. However, the indiscriminate application of these treatments, lack of rigorous evaluation of the results, and the side effects of ablative, irreversible procedures resulted in a backlash against brain surgery for psychiatric disorders that continues to this day. With the advent of psychotropic medications, interest in invasive procedures for organic brain disease waned.

Diagnosis and classification of psychiatric diseases has improved, due to a better understanding of psychiatric patho-physiology and the development of disease and treatment biomarkers. Meanwhile, a significant percentage of patients remain refractory to multiple modes of treatment, and psychiatric disease remains the number one cause of disability in the world. These data, along with the safe and efficacious application of deep brain stimulation (DBS) for movement disorders, in principle a reversible process, is rekindling interest in the surgical treatment of psychiatric disorders with stimulation of deep brain sites involved in emotional and behavioral circuitry.

This review presents a brief history of psychosurgery and summarizes the development of DBS for psychiatric disease, reviewing the available evidence for the current application of DBS for disorders of the mind.

Neuroplasticity underlying the comorbidity of pain and depression

Acute pain induces depressed mood, and chronic pain is known to cause depression. Depression, meanwhile, can also adversely affect pain behaviors ranging from symptomology to treatment response. Pain and depression independently induce long-term plasticity in the central nervous system (CNS). Comorbid conditions, however, have distinct patterns of neural activation. We performed a review of the changes in neural circuitry and molecular signaling pathways that may underlie this complex relationship between pain and depression. We also discussed some of the current and future therapies that are based on this understanding of the CNS plasticity that occurs with pain and depression.

Different patterns of local field potentials from limbic DBS targets in patients with major depressive and obsessive compulsive disorder

The role of distinct limbic areas in emotion regulation has been largely inferred from neuroimaging studies. Recently, the opportunity for intracranial recordings from limbic areas has arisen in patients undergoing deep brain stimulation (DBS) for neuropsychiatric disorders including major depressive disorder (MDD) and obsessive compulsive disorder (OCD). Here we test the hypothesis that distinct temporal patterns of local field potential (LFP) activity in the human limbic system reflect disease state and symptom severity in MDD and OCD patients. To this end, we recorded LFPs via implanted DBS electrodes from the bed nucleus of stria terminalis (BNST area) in 12 patients (5 OCD, 7 MDD) and from the subgenual cingulate cortex in 7 MDD patients (CG25 area). We found a distinct pattern of oscillatory activity with significantly higher α-power in MDD compared with OCD in the BNST area (broad α-band 8-14 Hz; P<0.01) and a similar level of α-activity in the CG25 area as in the BNST area in MDD patients. The mean α-power correlated with severity of depressive symptoms as assessed by the Beck depression inventory in MDD (n=14, r=0.55, P=0.042) but not with severity of obsessive compulsive symptoms in OCD. Here we show larger α-band activity in MDD patients compared with OCD recorded from intracranial DBS targets. Our results suggest that α-activity in the limbic system may be a signature of symptom severity in MDD and may serve as a potential state biomarker for closed loop DBS in MDD.

Role of functional imaging in the development and refinement of invasive neuromodulation for psychiatric disorders

Deep brain stimulation (DBS) is emerging as a powerful tool for the alleviation of targeted symptoms in treatment-resistant neuropsychiatric disorders. Despite the expanding use of neuropsychiatric DBS, the mechanisms responsible for its effects are only starting to be elucidated. Several modalities such as quantitative electroencephalography as well a intraoperative recordings have been utilized to attempt to understand the underpinnings of this new treatment modality, but functional imaging appears to offer several unique advantages. Functional imaging techniques like positron emission tomography, single photon emission computed tomography and functional magnetic resonance imaging have been used to examine the effects of focal DBS on activity in a distributed neural network. These investigations are critical for advancing the field of invasive neuromodulation in a safe and effective manner, particularly in terms of defining the neuroanatomical targets and refining the stimulation protocols. The purpose of this review is to summarize the current functional neuroimaging findings from neuropsychiatric DBS implantation for three disorders: treatment-resistant depression, obsessive-compulsive disorder, and Tourette syndrome. All of the major targets will be discussed (Nucleus accumbens, anterior limb of internal capsule, subcallosal cingulate, Subthalamic nucleus, Centromedial nucleus of the thalamus-Parafasicular complex, frontal pole, and dorsolateral prefrontal cortex). We will also address some apparent inconsistencies within this literature, and suggest potential future directions for this promising area.

Deep brain stimulation of the human reward system for major depression--rationale, outcomes and outlook

Deep brain stimulation (DBS) as a putative approach for treatment-resistant depression (TRD) has now been researched for about a decade. Several uncontrolled studies--all in relatively small patient populations and different target regions-have shown clinically relevant antidepressant effects in about half of the patients and very recently, DBS to a key structure of the reward system, the medial forebrain bundle, has yielded promising results within few days of stimulation and at much lower stimulation intensities. On the downside, DBS procedures in regions are associated with surgical risks (eg, hemorrhage) and psychiatric complications (suicidal attenuation, hypomania) as well as high costs. This overview summarizes research on the mechanisms of brain networks with respect to psychiatric diseases and--as a novelty--extrapolates to the role of the reward system in DBS for patients with treatment-resistant depression. It further evaluates relevant methodological aspects of today's research in DBS for TRD. On the scientific side, the reward system has an important yet clearly under-recognized role in both neurobiology and treatment of depression. On the methodological side of DBS research in TRD, better animal models are clearly needed to explain clinical effects of DBS in TRD. Larger sample sizes, long-term follow-up and designs including blinded sham control are required to draw final conclusions on efficacy and side effects. Practical research issues cover study design, patient tracking, and the discussion of meaningful secondary outcome measures.

Treatment of depression with deep brain stimulation works by altering in specific ways the conscious perception of the core symptoms of sadness or anhedonia, not by modulating network circuitry

An important advance in the management of treatment-resistant depression has recently been reported: deep brain stimulation (DBS) of the subgenual cingulate (Brodmann area 25 or Cg 25) or the nucleus accumbens (NAcc). These treatments produce a response rate, meaning significant clinical improvement, of about 50%, but only a few patients are returned completely to normal. The authors of these papers generally attribute the therapeutic response to restoration of an altered or perturbed neural network. In contrast, the idea advanced here is that DBS works by altering conscious perception of the core symptoms of sadness and anhedonia, not by modulating network circuitry. In the case of Cg25, the crucial thing about this site is that it is where conscious perception of sadness localizes. However, the stimulus frequency of DBS (130Hz) was too fast to support consciousness, which is associated with gamma frequencies (35-85Hz). Therefore, the imposed rapid frequency instantaneously blocked the subjective experience of sadness. In the case of the NAcc, the treatment worked by stimulating hot zones in the NAcc, which, in animal models, are known to intensify the perception of pleasure. This magnifier effect on the perception of pleasure was able to alleviate anhedonia. The response was not instantaneous but could begin within hours. In both cases, patients' realization that a core symptom had been relieved led to a moderate overall improvement in other symptoms.

Deep brain stimulation (DBS) at the interface of neurology and psychiatry

Deep brain stimulation (DBS) is an emerging interventional therapy for well-screened patients with specific treatment-resistant neuropsychiatric diseases. Some neuropsychiatric conditions, such as Parkinson disease, have available and reasonable guideline and efficacy data, while other conditions, such as major depressive disorder and Tourette syndrome, have more limited, but promising results. This review summarizes both the efficacy and the neuroanatomical targets for DBS in four common neuropsychiatric conditions: Parkinson disease, Tourette syndrome, major depressive disorder, and obsessive-compulsive disorder. Based on emerging new research, we summarize novel approaches to optimization of stimulation for each neuropsychiatric disease and we review the potential positive and negative effects that may be observed following DBS. Finally, we summarize the likely future innovations in the field of electrical neural-network modulation.