Surgical neuroanatomy and programming in deep brain stimulation for obsessive compulsive disorder

Behavioral disorders in Parkinson disease: current view

Patients with Parkinson disease (PD) frequently experience several behavioral symptoms, such as anxiety, apathy, irritability, agitation, impulsive control and obsessive-compulsive or REM sleep behavior disorders, which can cause severe psychosocial problems and impair quality of life. Occurring in 30-70% of PD patients, these symptoms can manifest at early stages of the disease, sometimes even before the appearance of classic motor symptoms, while others can develop later. Behavioral changes in PD show distinct patterns of brain atrophy, dopaminergic and serotonergic deterioration, altered neuronal connectivity in frontostriatal, corticolimbic, default mode and other networks due to a cascade linking molecular pathologies and deficits in multiple behavior domains. The changes suggest a multi-system neurodegenerative process in the context of a specific α-synucleinopathy inducing a variety of biochemical and functional changes, the neurobiological basis and clinical relevance of which await further elucidation. This paper is intended to review the recent literature with focus on the main behavioral disturbances in PD patients, their epidemiology, clinical features, risk factors, animal models, neuroimaging findings, pathophysiological backgrounds, and treatment options of these deleterious lesions.

Microlesion Effect Induced by Electrode Implantation in the Posteroventral Globus Pallidus Interna for Severe Dystonic Tics

Background

Tourette syndrome (TS) is a neurologic condition characterized by motor and phonic tics. Dystonic tics, including blepharospasm, are considered atypical or unusual in severe TS.

Case Report

We report a severe case of TS with facial dystonic tics resembling blepharospasm in which the microlesion effect and a sustained therapeutic effect was observed with bilateral globus pallidus interna (GPi) deep brain stimulation (DBS).

Discussion

Bilateral GPi DBS can be beneficial for blepharospasm-like tics and severe symptoms of TS. The improvements seen can be explained by the microlesion effect induced by DBS lead placement in the GPi.

Precision Mapping of Thalamic Deep Brain Stimulation Lead Positions Associated With the Microlesion Effect in Tourette Syndrome

BACKGROUND

The microlesion effect refers to the improvement of clinical symptoms after deep brain stimulation (DBS) lead placement and is suggested to indicate optimal lead placement. Very few studies have reported its implications in neuropsychiatric disorders.

OBJECTIVE

To evaluate the magnitude of the microlesion effect in Tourette syndrome and the relationship between the microlesion effect and the anatomic location of implanted DBS leads.

METHODS

Six male patients were included. Their median age at surgery and follow-up period were 25 years (range, 18-47) and 12 months (range, 6-24), respectively. All patients were videotaped pre- and postoperatively, and tic frequencies were counted. We also analyzed the precision of lead placement and evaluated the normative connectome associated with the microlesion area.

RESULTS

The microlesion effect was observed as an improvement in tic symptoms in all patients, and the long-term clinical outcomes were favorable. The median motor tic frequency was 20.2 tics/min (range, 9.7-60) at baseline and decreased to 3.2 tics/min (1.2-11.3) in patients on postoperative day 1 ( P = .043) and to 5.7 tics/min (range, 1.9-16.6) in patients on postoperative day 7 ( P = .028). Phonic tic tended to improve immediately after surgery although the changes were not significant. Image analyses revealed that the precise position of the electrode was directed toward the anteromedial centromedian nucleus. Normative connectome analysis demonstrated connections between improvement-related areas and wide areas of the prefrontal cortex.

CONCLUSION

This study shows that the microlesion effect may seem as an immediate improvement after optimal DBS lead placement in patients with Tourette syndrome.

A review of neurophysiological effects and efficiency of waveform parameters in deep brain stimulation

Neurostimulation has diverse clinical applications and potential as a treatment for medically refractory movement disorders, epilepsy, and other neurological disorders. However, the parameters used to program electrodes-polarity, pulse width, amplitude, and frequency-and how they are adjusted have remained largely untouched since the 1970 s. This review summarizes the state-of-the-art in Deep Brain Stimulation (DBS) and highlights the need for further research to uncover the physiological mechanisms of neurostimulation. We focus on studies that reveal the potential for clinicians to use waveform parameters to selectively stimulate neural tissue for therapeutic benefit, while avoiding activating tissue associated with adverse effects. DBS uses cathodic monophasic rectangular pulses with passive recharging in clinical practice to treat neurological conditions such as Parkinson's Disease. However, research has shown that stimulation efficiency can be improved, and side effects reduced, through modulating parameters and adding novel waveform properties. These developments can prolong implantable pulse generator lifespan, reducing costs and surgery-associated risks. Waveform parameters can stimulate neurons based on axon orientation and intrinsic structural properties, providing clinicians with more precise targeting of neural pathways. These findings could expand the spectrum of diseases treatable with neuromodulation and improve patient outcomes.

Deep brain stimulation programming for intractable obsessive-compulsive disorder using a long pulse width

Introduction

Around 25% of patients with obsessive-compulsive disorder (OCD) do not respond to medication or psychotherapy, producing significant impairment and treatment challenges. Deep Brain Stimulation (DBS) has been shown in multiple blinded trials to be a safe and durable emerging option for treatment-refractory OCD. Intraoperative device interrogation offers a theoretical anchor for starting outpatient DBS programming; however, no definitive post-operative programming algorithm for psychiatrists exists currently.

Case

Here we present a 58-year-old female with childhood-onset, severe, intractable OCD with multiple failed trials of psychotherapy, medication, and electroconvulsive therapy. After interdisciplinary evaluation, she underwent bilateral electrode implantation targeting the anterior limb of the internal capsule, nucleus accumbens (ALIC/NAc). Intraoperative interrogation afforded sparse information about a preferred lead contact or current density target. Subsequent outpatient interrogation consisted of systematic and independent mapping using monopolar cathodic stimulation with constant current. Modulating bipolar and triple monopolar configurations, amplitude, and pulse width all failed to induce observable effects. Given negligible interrogation feedback, we created an electrical field through the ALIC bilaterally, using the three most ventral contacts to create triple monopoles, with a long pulse width and moderate amperage.

Conclusion

Three months post-programming, the patient reported significant improvement in OCD symptoms, particularly checking behaviors, with response sustained over the next several months. As with our case, the majority of DBS lead contacts do not induce affective or physiological markers in patients, complicating programming optimization. Here, we discuss an approach to titrating various stimulation parameters and purported mechanisms of physiological markers in DBS for OCD.

Connectivity-based parcellation of the amygdala and identification of its main white matter connections

The amygdala plays a role in emotion, learning, and memory and has been implicated in behavioral disorders. Better understanding of the amygdala circuitry is crucial to develop new therapies for these disorders. We used data from 200 healthy-subjects from the human connectome project. Using probabilistic tractography, we created population statistical maps of amygdala connectivity to brain regions involved in limbic, associative, memory, and reward circuits. Based on the amygdala connectivity with these regions, we applied k-means clustering to parcellate the amygdala into three clusters. The resultant clusters were averaged across all subjects and the main white-matter pathways of the amygdala from each averaged cluster were generated. Amygdala parcellation into three clusters showed a medial-to-lateral pattern. The medial cluster corresponded with the centromedial and cortical nuclei, the basal cluster with the basal nuclei and the lateral cluster with the lateral nuclei. The connectivity analysis revealed different white-matter pathways consistent with the anatomy of the amygdala circuit. This in vivo connectivity-based parcellation of the amygdala delineates three clusters of the amygdala in a mediolateral pattern based on its connectivity with brain areas involved in cognition, memory, emotion, and reward. The human amygdala circuit presented in this work provides the first step for personalized amygdala circuit mapping for patients with behavioral disorders.

Optimization of closed-loop electrical stimulation enables robust cerebellar-directed seizure control

Additional treatment options for temporal lobe epilepsy are needed, and potential interventions targeting the cerebellum are of interest. Previous animal work has shown strong inhibition of hippocampal seizures through on-demand optogenetic manipulation of the cerebellum. However, decades of work examining electrical stimulation-a more immediately translatable approach-targeting the cerebellum has produced very mixed results. We were therefore interested in exploring the impact that stimulation parameters may have on seizure outcomes. Using a mouse model of temporal lobe epilepsy, we conducted on-demand electrical stimulation of the cerebellar cortex, and varied stimulation charge, frequency and pulse width, resulting in over 1000 different potential combinations of settings. To explore this parameter space in an efficient, data-driven, manner, we utilized Bayesian optimization with Gaussian process regression, implemented in MATLAB with an Expected Improvement Plus acquisition function. We examined three different fitting conditions and two different electrode orientations. Following the optimization process, we conducted additional on-demand experiments to test the effectiveness of selected settings. Regardless of experimental setup, we found that Bayesian optimization allowed identification of effective intervention settings. Additionally, generally similar optimal settings were identified across animals, suggesting that personalized optimization may not always be necessary. While optimal settings were effective, stimulation with settings predicted from the Gaussian process regression to be ineffective failed to provide seizure control. Taken together, our results provide a blueprint for exploration of a large parameter space for seizure control and illustrate that robust inhibition of seizures can be achieved with electrical stimulation of the cerebellum, but only if the correct stimulation parameters are used.

Clinical recommendations for the care of people with treatment-refractory obsessive-compulsive disorder when undergoing deep brain stimulation

Deep brain stimulation is an emerging therapy for treatment-refractory obsessive-compulsive disorder patients. Yet, accessibility is limited, treatment protocols are heterogeneous and there is no guideline or consensus on the best practices. Here, we combine evidence from scientific investigations, expert opinions and our clinical expertise to propose several clinical recommendations from the pre-operative, surgical and post-operative phases of deep brain stimulation care for treatment-refractory obsessive-compulsive disorder patients. A person-centered and biopsychosocial approach is adopted. Briefly, we discuss clinical characteristics associated with response, the use of improved educational materials, an evaluative consent process, comprehensive programming by an expert clinician, a more global assessment of treatment efficacy, multi-disciplinary adjunct psychotherapy and the importance of peer support programs. Furthermore, where gaps are identified, future research suggestions are made, including connectome surgical targeting, scientific evaluation of hardware models and health economic data. In addition, we encourage collaborative groups of data and knowledge sharing by way of a clinical registry and a peer group of programming clinicians. We aim to commence a discussion on the determinants of deep brain stimulation efficacy for treatment-refractory obsessive-compulsive disorder patients, a rare and severe patient group, and contribute to more standardized and evidence-based practices.

Deep brain stimulation in the bed nucleus of the stria terminalis: A symptom provocation study in patients with obsessive-compulsive disorder

BACKGROUND

Deep brain stimulation (DBS) is an emerging therapy for treatment-resistant obsessive-compulsive disorder (OCD), and several targets for electrode implantation and contact selection have been proposed, including the bed nucleus of the stria terminalis (BST). Selecting the active electrode contacts (patients typically have four to choose from in each hemisphere), and thus the main locus of stimulation, can be a taxing process. Here, we investigated whether contact selection based purely on their neuroanatomical position in the BST is a worthwhile approach. For the first time, we also compared the effects of uni- versus bilateral BST stimulation.

METHODS

Nine OCD patients currently receiving DBS participated in a double-blind, randomized symptom provocation study to compare no versus BST stimulation. Primary outcomes were anxiety and mood ratings in response to disorder-relevant trigger images, as well as ratings of obsessions, compulsions, tendency to avoid and overall wellbeing. Furthermore, we asked whether patients preferred the electrode contacts in the BST over their regular stimulation contacts as a new treatment setting after the end of the task.

RESULTS

We found no statistically significant group differences between the four conditions (no, left, right and bilateral BST stimulation). Exploratory analyses, as well as follow-up data, did indicate that (bilateral) bipolar stimulation in the BST was beneficial for some patients, particularly for those who had achieved unsatisfactory effects through the typical contact selection procedure.

CONCLUSIONS

Despite its limitations, this study suggests that selection of stimulation contacts in the BST is a viable option for DBS in treatment-resistant OCD patients.

Developments in Deep Brain Stimulators for Successful Aging Towards Smart Devices—An Overview

This work provides an overview of the present state-of-the-art in the development of deep brain Deep Brain Stimulation (DBS) and how such devices alleviate motor and cognitive disorders for a successful aging. This work reviews chronic diseases that are addressable via DBS, reporting also the treatment efficacies. The underlying mechanism for DBS is also reported. A discussion on hardware developments focusing on DBS control paradigms is included specifically the open- and closed-loop “smart” control implementations. Furthermore, developments towards a “smart” DBS, while considering the design challenges, current state of the art, and constraints, are also presented. This work also showcased different methods, using ambient energy scavenging, that offer alternative solutions to prolong the battery life of the DBS device. These are geared towards a low maintenance, semi-autonomous, and less disruptive device to be used by the elderly patient suffering from motor and cognitive disorders.

Therapeutic Neurostimulation in Obsessive-Compulsive and Related Disorders: A Systematic Review

Invasive and noninvasive neurostimulation therapies for obsessive-compulsive and related disorders (OCRD) were systematically reviewed with the aim of assessing clinical characteristics, methodologies, neuroanatomical substrates, and varied stimulation parameters. Previous reviews have focused on a narrow scope, statistical rather than clinical significance, grouped together heterogenous protocols, and proposed inconclusive outcomes and directions. Herein, a comprehensive and transdiagnostic evaluation of all clinically relevant determinants is presented with translational clinical recommendations and novel response rates. Electroconvulsive therapy (ECT) studies were limited in number and quality but demonstrated greater efficacy than previously identified. Targeting the pre-SMA/SMA is recommended for transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS). TMS yielded superior outcomes, although polarity findings were conflicting, and refinement of frontal/cognitive control protocols may optimize outcomes. For both techniques, standardization of polarity, more treatment sessions (>20), and targeting multiple structures are encouraged. A deep brain stimulation (DBS) 'sweet spot' of the striatum for OCD was proposed, and CBT is strongly encouraged. Tourette's patients showed less variance and reliance on treatment optimization. Several DBS targets achieved consistent, rapid, and sustained clinical response. Analysis of fiber connectivity, as opposed to precise neural regions, should be implemented for target selection. Standardization of protocols is necessary to achieve translational outcomes.

Optimizing Deep Brain Stimulation Parameters in Obsessive-Compulsive Disorder

OBJECTIVES

Deep brain stimulation (DBS) is an innovative and effective treatment for patients with therapy-refractory obsessive-compulsive disorder (OCD). DBS offers unique opportunities for personalized care, but no guidelines on how to choose effective and safe stimulation parameters in patients with OCD are available. Our group gained relevant practical knowledge on DBS optimization by treating more than 80 OCD patients since 2005, the world's largest cohort. The article's objective is to share this experience.

MATERIALS AND METHODS

We provide guiding principles for optimizing DBS stimulation parameters in OCD and discuss the neurobiological and clinical basis.

RESULTS

Adjustments in stimulation parameters are performed in a fixed order. First, electrode contact activation is determined by the position of the electrodes on postoperative imaging. Second, voltage and pulse width are increased stepwise, enlarging both the chance of symptom reduction and of inducing side effects. Clinical evaluation of adjustments in stimulation parameters needs to take into account: 1) the particular temporal sequence in which the various OCD symptoms and DBS side-effects change; 2) the lack of robust response predictors; 3) the limited sensitivity of the Yale-Brown Obsessive-Compulsive Scale to assess DBS-induced changes in OCD symptoms; and 4) a patient's fitness for additional cognitive-behavioral therapy (CBT).

CONCLUSIONS

Decision-making in stimulation parameter optimization needs to be sensitive to the particular time-courses on which various symptoms and side effects change.

Deep Brain Stimulation for Obsessive-Compulsive Disorder: A Long Term Naturalistic Follow Up Study in a Single Institution

INTRODUCTION

Deep brain stimulation (DBS) is a proven, effective tool in the treatment of movement disorders. Expansion of indications for DBS into the realm of neuropsychiatric disorders, especially obsessive-compulsive disorder (OCD), has gained fervent interest, although data on appropriate clinical utilization remains limited.

METHODS

A retrospective, naturalistic study followed nine severely affected OCD patients (average YBOCs score before implantation 34.2 ± 2.5) treated with DBS of ventral capsule/ventral striatum, with average follow up of 54.8 months.

RESULTS

With chronic stimulation (years), a majority of the patients achieved significant benefits in obsessive-compulsive and depressive symptoms. Six patients experienced periods of OCD remission following implantation. Four of the six responders required more than 12 months to achieve response. Relief of major depressive symptoms occurred in four out of six patients with documented co-morbid depression. Settings required to achieve efficacy were higher than those typically utilized for movement disorders, necessitating increased impulse generator (IPG) battery demand. We found patients benefited from conversion to a rechargeable IPG to prevent serial operations for IPG replacement. For patients with rechargeable IPGs, the repetitive habit of recharging did not appear to aggravate or trigger new obsessive-compulsive behaviors or anxiety symptoms.

CONCLUSIONS

Our study supports and builds upon other research suggesting that DBS for OCD in a real-world setting can be implemented successfully and provide long-term benefit for severely affected OCD patients. Optimal patient selection and DBS programming criteria are discussed. The use of rechargeable IPGs appears to be both cost effective and well-tolerated in this population.

Effective Deep Brain Stimulation for Obsessive-Compulsive Disorder Requires Clinical Expertise

BACKGROUND

Deep brain stimulation (DBS) is an innovative treatment for severe obsessive-compulsive disorder (OCD). Electrodes implanted in specific brain areas allow clinicians to directly modulate neural activity. DBS affects symptomatology in a completely different way than established forms of treatment for OCD, such as psychotherapy or medication.

OBJECTIVE

To understand the process of improvement with DBS in patients with severe OCD.

METHODS

By means of open-ended interviews and participant observation we explore how expert clinicians involved in the post-operative process of DBS optimization evaluate DBS effects.

RESULTS

Evaluating DBS effect is an interactive and context-sensitive process that gradually unfolds over time and requires integration of different sources of knowledge. Clinicians direct DBS optimization toward a critical point where they sense that patients are being moved with regard to behavior, emotion, and active engagement, opening up possibilities for additional cognitive behavioral therapy (CBT).

DISCUSSION

Based on the theoretical framework of radical embodied cognitive science (RECS), we assume that clinical expertise manifests itself in the pattern of interaction between patient and clinician. To the expert clinician, this pattern reflects the patient's openness to possibilities for action ("affordances") offered by their environment. OCD patients' improvement with DBS can be understood as a change in openness to their environment. The threshold for patients to engage in activities is decreased and a broader range of daily life and therapeutic activities becomes attractive. Movement is improvement.

Comparative effectiveness of neuroablation and deep brain stimulation for treatment-resistant obsessive-compulsive disorder: a meta-analytic study

BACKGROUND

The safety and efficacy of neuroablation (ABL) and deep brain stimulation (DBS) for treatment refractory obsessive-compulsive disorder (OCD) has not been examined. This study sought to generate a definitive comparative effectiveness model of these therapies.

METHODS

A EMBASE/PubMed search of English-language, peer-reviewed articles reporting ABL and DBS for OCD was performed in January 2018. Change in quality of life (QOL) was quantified based on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) and the impact of complications on QOL was assessed. Mean response of Y-BOCS was determined using random-effects, inverse-variance weighted meta-analysis of observational data.

FINDINGS

Across 56 studies, totalling 681 cases (367 ABL; 314 DBS), ABL exhibited greater overall utility than DBS. Pooled ability to reduce Y-BOCS scores was 50.4% (±22.7%) for ABL and was 40.9% (±13.7%) for DBS. Meta-regression revealed no significant change in per cent improvement in Y-BOCS scores over the length of follow-up for either ABL or DBS. Adverse events occurred in 43.6% (±4.2%) of ABL cases and 64.6% (±4.1%) of DBS cases (p<0.001). Complications reduced ABL utility by 72.6% (±4.0%) and DBS utility by 71.7% (±4.3%). ABL utility (0.189±0.03) was superior to DBS (0.167±0.04) (p<0.001).

INTERPRETATION

Overall, ABL utility was greater than DBS, with ABL showing a greater per cent improvement in Y-BOCS than DBS. These findings help guide success thresholds in future clinical trials for treatment refractory OCD.

Deep Brain Stimulation for Obsessive Compulsive Disorder: Evolution of Surgical Stimulation Target Parallels Changing Model of Dysfunctional Brain Circuits

Obsessive compulsive disorder (OCD) is a common, disabling psychiatric disease characterized by persistent, intrusive thoughts and ritualistic, repetitive behaviors. Deep brain stimulation (DBS) is thought to alleviate OCD symptoms by modulating underlying disturbances in normal cortico-striato-thalamo-cortical (CSTC) circuitry. Stimulation of the ventral portion of the anterior limb of the internal capsule (ALIC) and underlying ventral striatum (“ventral capsule/ventral striatum” or “VC/VS” target) received U.S. FDA approval in 2009 for patients with severe, treatment-refractory OCD. Over the decades, DBS surgical outcome studies have led to an evolution in the electrical stimulation target. In parallel, advancements in neuroimaging techniques have allowed investigators to better visualize and define CSTC circuits underlying the pathophysiology of OCD. A critical analysis of these new data suggests that the therapeutic mechanism of DBS for OCD likely involves neuromodulation of a widespread cortical/subcortical network, accessible by targeting fiber bundles in the ventral ALIC that connect broad network regions. Future studies will include advances in structural and functional imaging, analysis of physiological recordings, and utilization of next-generation DBS devices. These tools will enable patient-specific optimization of DBS therapy, which will hopefully further improve outcomes.

Ablative neurosurgery and deep brain stimulation for obsessive-compulsive disorder

Despite advancements in pharmacotherapeutic and behavioral interventions, a substantial proportion of patients with obsessive-compulsive disorder (OCD) continue to have disabling and treatment-refractory illness. Neurosurgical interventions, including ablative procedures and deep brain stimulation (DBS), have emerged as potential treatment options in this population. We review the recent literature on contemporary surgical options for OCD, focusing on clinical aspects such as patient selection, presurgical assessment, and safety and effectiveness of these procedures. Given the invasiveness and limited evidence, these procedures have been performed in carefully selected patients with severe, chronic, and treatment-refractory illness. Along with informed consent, an independent review by a multidisciplinary team is mandated in many centers. Both ablative procedures and DBS have been found to be helpful in around half the patients, with improvement observed months after the procedure. Various targets have been proposed for either procedure, based on the dominant corticostriatal model of OCD. There is no strong evidence to recommend one procedure over the other. Hence, the choice of procedure is often based on the factors such as affordability, expertise, and reversibility of adverse effects. Surgery is not recommended as a standalone treatment but should be provided as part of a comprehensive package including medications and psychotherapeutic interventions. Available evidence suggest that the benefits of the procedure outweigh the risks in a treatment-refractory population. Advances in neurosurgical techniques and increasing knowledge of neurobiology are likely to bring about further progress in the efficacy, safety, and acceptability of the procedures.

Subthalamic theta activity: a novel human subcortical biomarker for obsessive compulsive disorder

Obsessive-compulsive disorder (OCD) is a common and serious psychiatric disorder. Although subthalamic nucleus deep brain stimulation (DBS) has been studied as a treatment for OCD patients the underlying mechanism of this treatment and the optimal method of stimulation are unknown. To study the neural basis of subthalamic nucleus DBS in OCD patients we used a novel, implantable DBS system with long-term local field potential sensing capability. We focus our analysis on two patients with OCD who experienced severe treatment-resistant symptoms and were implanted with subthalamic nucleus DBS systems. We studied them for a year at rest and during provocation of OCD symptoms (46 recording sessions) and compared them to four Parkinson's disease (PD) patients implanted with subthalamic nucleus DBS systems (69 recording sessions). We show that the dorsal (motor) area of the subthalamic nucleus in OCD patients displays a beta (25-35 Hz) oscillatory activity similar to PD patients whereas the ventral (limbic-cognitive) area of the subthalamic nucleus displays distinct theta (6.5-8 Hz) oscillatory activity only in OCD patients. The subthalamic nucleus theta oscillatory activity decreases with provocation of OCD symptoms and is inversely correlated with symptoms severity over time. We conclude that beta oscillations at the dorsal subthalamic nucleus in OCD patients challenge their pathophysiologic association with movement disorders. Furthermore, theta oscillations at the ventral subthalamic nucleus in OCD patients suggest a new physiological target for OCD therapy as well as a promising input signal for future emotional-cognitive closed-loop DBS.

Target-specific deep brain stimulation of the ventral capsule/ventral striatum for the treatment of neuropsychiatric disease

Deep brain stimulation (DBS) is a well-established therapy for Parkinson's disease and other movement disorders. An accumulating body of evidence supports the extension of DBS application for the treatment of refractory psychiatric disorders. The ventral capsule/ventral striatum (VC/VS) is the most common anatomical target for obsessive-compulsive disorder (OCD), addiction, and depression. However, no specific electrode is available for the clinical targeting of these areas for DBS. According to the anatomical features of the VC/VS, a novel electrode was developed for simultaneous and independently programmed stimulation of the nucleus accumbens (NAc) and the anterior limb of the internal capsule (ALIC). This VC/VS-specific electrode has the potential to enhance stimulus intensity, provide independent and flexible target stimulation.

Deep brain stimulation and treatment-resistant obsessive-compulsive disorder: A systematic review

INTRODUCTION

At least 10% of patients with Obsessive-compulsive Disorder (OCD) are refractory to psychopharmacological treatment. The emergence of new technologies for the modulation of altered neuronal activity in Neurosurgery, deep brain stimulation (DBS), has enabled its use in severe and refractory OCD cases. The objective of this article is to review the current scientific evidence on the effectiveness and applicability of this technique to refractory OCD.

METHOD

We systematically reviewed the literature to identify the main characteristics of deep brain stimulation, its use and applicability as treatment for obsessive-compulsive disorder. Therefore, we reviewed PubMed/Medline, Embase and PsycINFO databases, combining the key-words 'Deep brain stimulation', 'DBS' and 'Obsessive-compulsive disorder' 'OCS'. The articles were selected by two of the authors independently, based on the abstracts, and if they described any of the main characteristics of the therapy referring to OCD: applicability; mechanism of action; brain therapeutic targets; efficacy; side-effects; co-therapies. All the information was subsequently extracted and analysed.

RESULTS

The critical analysis of the evidence shows that the use of DBS in treatment-resistant OCD is providing satisfactory results regarding efficacy, with assumable side-effects. However, there is insufficient evidence to support the use of any single brain target over another. Patient selection has to be done following analyses of risks/benefits, being advisable to individualize the decision of continuing with concomitant psychopharmacological and psychological treatments.

CONCLUSIONS

The use of DBS is still considered to be in the field of research, although it is increasingly used in refractory-OCD, producing in the majority of studies significant improvements in symptomatology, and in functionality and quality of life. It is essential to implement random and controlled studies regarding its long-term efficacy, cost-risk analyses and cost/benefit.

Rechargeable Stimulators in Deep Brain Stimulation for Obsessive-Compulsive Disorder: A Prospective Interventional Cohort Study

BACKGROUND

From 1999 onwards, deep brain stimulation (DBS) has been proposed as an alternative to capsulotomy in refractory cases of obsessive-compulsive disorder (OCD). Although rechargeable implantable pulse generators (rIPGs) have been used extensively in DBS for movement disorders, there are no reports on rIPGs in patients with a psychiatric DBS indication, and even possible objections to their use.

OBJECTIVE

We aim to evaluate rIPGs in OCD in terms of effectiveness, applicability, safety, and need for IPG replacement.

METHODS

In this prospective before-after study recruiting from 2007 until 2012, OCD patients requiring at least one IPG replacement per 18 months were proposed to have a rIPG implanted at the next IPG depletion. OCD severity was the primary outcome. Ten patients were analyzed.

RESULTS

Psychiatric symptoms and global functioning remained stable in the two years after as compared to the two years before rIPG implantation. Over the same period, the prescribed OCD medication doses did not increase and the DBS stimulation parameters were largely unaltered. Until the end of the follow-up (mean 4¾ years; maximum seven years), the DBS-related surgery frequency decreased and there were no rIPG replacements. During the first few weeks after implantation, two patients obsessively checked the rIPG, but afterwards there were no signs of compulsively checking or recharging the rIPG. Two patients experienced rIPG overdischarges (five occurrences in total).

CONCLUSIONS

This is the first report on rIPGs in DBS for OCD patients. The use of rIPGs in this population appears to be effective, applicable, and safe and diminishes the need for IPG replacements.

Deep brain stimulation of the subthalamic nucleus in obsessive-compulsive disorder: Neuroanatomical and pathophysiological considerations

Obsessive-compulsive disorder (OCD) is among the most disabling chronic psychiatric disorders and has a significant negative impact on multiple domains of quality of life. For patients suffering from severe refractory OCD, deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been applied. Reviewing the literature of the last years we believe that through its central position within the cortico-basal ganglia-thalamocortical circuits, the STN has a coordinating role in decision-making and action-selection mechanisms. Dysfunctional information-processing at the level of the STN is responsible for some of the core symptoms of OCD. Research confirms an electrophysiological dysfunction in the associative and limbic (non-motor) parts of the STN. Compared to Parkinson׳s disease patients, STN neurons in OCD exhibit a lower firing rate, less frequent but longer bursts, increased burst activity in the anterior ventromedial area, an asymmetrical left-sided burst distribution, and a predominant oscillatory activity in the δ-band. Moreover, there is direct evidence for the involvement of the STN in both checking behavior and OCD symptoms, which are both related to changes in electrophysiological activity in the non-motor STN. Through a combination of mechanisms, DBS of the STN seems to interrupt the disturbed information-processing, leading to a normalization of connectivity within the cortico-basal ganglia-thalamocortical circuits and consequently to a reduction in symptoms. In conclusion, based on the STN׳s strategic position within cortico-basal ganglia-thalamocortical circuits and its involvement in action-selection mechanisms that are responsible for some of the core symptoms of OCD, the STN is a mechanism-based target for DBS in OCD.

Deep brain stimulation for movement disorders: update on recent discoveries and outlook on future developments

Modern deep brain stimulation (DBS) has become a routine therapy for patients with movement disorders such as Parkinson's disease, generalized or segmental dystonia and for multiple forms of tremor. Growing numbers of publications also report beneficial effects in other movement disorders such as Tourette's syndrome, various forms of chorea and DBS is even being studied for Parkinson's-related dementia. While exerting remarkable effects on many motor symptoms, DBS does not restore normal neurophysiology and therefore may also have undesirable side effects including speech and gait deterioration. Furthermore, its efficacy might be compromised in the long term, due to progression of the underlying disease. Various programming strategies have been studied to try and address these issues, e.g., the use of low-frequency rather than high-frequency stimulation or the targeting of alternative brain structures such as the pedunculopontine nucleus. In addition, further technical developments will soon provide clinicians with an expanded choice of hardware such as segmented electrodes allowing for a steering of the current to optimize beneficial effects and reduce side effects as well as the possibility of adaptive stimulation systems based on closed-loop concepts with or without accompanying advances in programming and imaging software. In the present article, we will provide an update on the most recent achievements and discoveries relevant to the application of DBS in the treatment of movement disorder patients and give an outlook on future clinical and technical developments.

A novel combinational approach of microstimulation and bioluminescence imaging to study the mechanisms of action of cerebral electrical stimulation in mice

Deep brain stimulation (DBS) is used to treat a number of neurological conditions and is currently being tested to intervene in neuropsychiatric conditions. However, a better understanding of how it works would ensure that side effects could be minimized and benefits optimized. We have thus developed a unique device to perform brain stimulation (BS) in mice and to address fundamental issues related to this methodology in the pre-clinical setting. This new microstimulator prototype was specifically designed to allow simultaneous live bioluminescence imaging of the mouse brain, allowing real time assessment of the impact of stimulation on cerebral tissue. We validated the authenticity of this tool in vivo by analysing the expression of toll-like receptor 2 (TLR2), corresponding to the microglial response, in the stimulated brain regions of TLR2-fluc-GFP transgenic mice, which we further corroborated with post-mortem analyses in these animals as well as in human brains of patients who underwent DBS to treat their Parkinson's disease. In the present study, we report on the development of the first BS device that allows for simultaneous live in vivo imaging in mice. This tool opens up a whole new range of possibilities that allow a better understanding of BS and how to optimize its effects through its use in murine models of disease.

DTI-based deterministic fibre tracking of the medial forebrain bundle

BACKGROUND

Deep brain stimulation (DBS) of the medial forebrain bundle (MFB) was reported to reduce symptoms in psychiatric disorders. The aim of our study was to find standardised parameters for diffusion tensor imaging (DTI) based fibre tracking to reliably visualise the MFB.

METHODS

Twenty-two cerebral hemispheres in 11 patients were investigated. Three different regions of interest (ROIs) were defined as seed regions for fibre tracking: the ipsilateral and contralateral superior cerebellar peduncle (SCP) and the nucleus raphe dorsalis (NRD). From each seed region the fibres were followed separately through the ventral tegmental area (VTA = second ROI) and their further courses and volumina were documented and compared. Minimal fibre length was set at 30 mm and the FA threshold at 0.12.

RESULTS

The fibre tracts starting in seed regions in the ipsilateral SCP and the NRD follow a similar course along the lateral wall of the third ventricle (hypothalamus) and the anterior limb of the internal capsule (ALIC) to inferior fronto-medial brain areas. These fibres are in accordance with the course of the MFB as described in various anatomical atlases. Consistently, a branch leaves the main fibre tract laterally to take a course through the capsula externa to the temporo-parietal cortex. Fibre tracts starting from the contralateral SCP follow a more superior and lateral course, including the dentato-rubro-thalamic and the pyramidal tract.

CONCLUSIONS

Deterministic fibre tracking with standardised ROIs provides constant and reproducible delineations of the medial forebrain bundle. Its visualisation might help to adjust targeting in DBS for psychiatric disorders.

Smile without euphoria induced by deep brain stimulation: a case report

Poststroke central pain (PSCP) can be a debilitating medication-refractory disorder. We report a single case where right unilateral ventral capsule/ventral striatum (VC/VS) deep brain stimulation was used to treat PSCP and inadvertently induced a smile without euphoria. The patient was a 69 year-old woman who had a stroke with resultant dysesthesia and allodynia in her left hemibody and also a painful left hemibody dystonia. In her case, VC/VS stimulation induced a smile phenomenon, but without a euphoric sensation. This phenomenon was different from the typical smile responses we have observed in obsessive-compulsive disorder cases. This difference was considered to be possibly attributable to impairment in the emotional smile pathway.

Light and chemical control of neuronal circuits: possible applications in neurotherapy

Millions of people worldwide suffer from diseases that result from a failure of central pathways to regulate behavioral and physiological processes. Advances in genetics and pharmacology have already allowed us to appreciate that rather than this dysregulation being systemic throughout the brain, it is usually rooted in specific subsets of dysfunctional cells within discrete neurological circuits. This article discusses the advent of opto- and chemogenetic tools and how they are providing the means to dissect these circuits with a degree of temporal and spatial sensitivity not previously possible. We also highlight the potential applications for treating disease and the key developments likely to have the greatest impact over the next 5 years.

Interventional psychiatry: why now?

Interventional psychiatry offers substantial therapeutic benefits in some neuropsychiatric disorders and enormous potential in treating others. However, as interventional diagnostics and therapeutics require specialized knowledge and skill foreign to many psychiatrists, the emerging subspecialty of interventional psychiatry must be more formally integrated into the continuum of psychiatric training to ensure both safe application and continued growth. By establishing training paradigms for interventional psychiatry, academic medical centers can help fill this knowledge gap. The cultivation of a properly trained cohort of interventional psychiatrists will better meet the challenges of treatment-resistant psychiatric illness through safe and ethical practice, while facilitating a more informed development and integration of novel neuromodulation techniques.

Deep brain stimulation for treatment-resistant depression: systematic review of clinical outcomes

Major depressive disorder (MDD) is a widespread, severe, debilitating disorder that markedly diminishes quality of life. Medication is commonly effective, but 20-30 % of patients are refractory to medical therapy. The surgical treatment of psychiatric disorders has a negative stigma associated with it owing to historical abuses. Various ablative surgeries for MDD have been attempted with marginal success, but these studies lacked standardized outcome measures. The recent development of neuromodulation therapy, especially deep brain stimulation (DBS), has enabled controlled studies with sham stimulation and presents a potential therapeutic option that is both reversible and adjustable. We performed a systematic review of the literature pertaining to DBS for treatment-resistant depression to evaluate the safety and efficacy of this procedure. We included only studies using validated outcome measures. Our review identified 22 clinical research papers with 5 unique DBS approaches using different targets, including nucleus accumbens, ventral striatum/ventral capsule, subgenual cingulate cortex, lateral habenula, inferior thalamic nucleus, and medial forebrain bundle. Among the 22 published studies, only 3 were controlled trials, and 2, as yet unpublished, multicenter, randomized, controlled trials evaluating the efficacy of subgenual cingulate cortex and ventral striatum/ventral capsule DBS were recently discontinued owing to inefficacy based on futility analyses. Overall, the published response rate to DBS therapy, defined as the percentage of patients with > 50 % improvement on the Hamilton Depression Rating Scale, is reported to be 40-70 %, and outcomes were comparable across studies. We conclude that DBS for MDD shows promise, but remains experimental and further accumulation of data is warranted.

A neurochemical closed-loop controller for deep brain stimulation: toward individualized smart neuromodulation therapies

Current strategies for optimizing deep brain stimulation (DBS) therapy involve multiple postoperative visits. During each visit, stimulation parameters are adjusted until desired therapeutic effects are achieved and adverse effects are minimized. However, the efficacy of these therapeutic parameters may decline with time due at least in part to disease progression, interactions between the host environment and the electrode, and lead migration. As such, development of closed-loop control systems that can respond to changing neurochemical environments, tailoring DBS therapy to individual patients, is paramount for improving the therapeutic efficacy of DBS. Evidence obtained using electrophysiology and imaging techniques in both animals and humans suggests that DBS works by modulating neural network activity. Recently, animal studies have shown that stimulation-evoked changes in neurotransmitter release that mirror normal physiology are associated with the therapeutic benefits of DBS. Therefore, to fully understand the neurophysiology of DBS and optimize its efficacy, it may be necessary to look beyond conventional electrophysiological analyses and characterize the neurochemical effects of therapeutic and non-therapeutic stimulation. By combining electrochemical monitoring and mathematical modeling techniques, we can potentially replace the trial-and-error process used in clinical programming with deterministic approaches that help attain optimal and stable neurochemical profiles. In this manuscript, we summarize the current understanding of electrophysiological and electrochemical processing for control of neuromodulation therapies. Additionally, we describe a proof-of-principle closed-loop controller that characterizes DBS-evoked dopamine changes to adjust stimulation parameters in a rodent model of DBS. The work described herein represents the initial steps toward achieving a “smart” neuroprosthetic system for treatment of neurologic and psychiatric disorders.