Deep brain stimulation and ablation for obsessive compulsive disorder: evolution of contemporary indications, targets and techniques

Intraoperative valence testing to adjudicate between ventral capsule/ventral striatum and bed nucleus of the stria terminalis target selection in deep brain stimulation for obsessive-compulsive disorder

OBJECTIVE

Deep brain stimulation (DBS) is an accepted therapy for severe, treatment-refractory obsessive-compulsive disorder (trOCD). The optimal DBS target location within the anterior limb of the internal capsule, particularly along the anterior-posterior axis, remains elusive. Empirical evidence from several studies in the past decade has suggested that the ideal target lies in the vicinity of the anterior commissure (AC), either just anterior to the AC, above the ventral striatum (VS), or just posterior to the AC, above the bed nucleus of the stria terminalis (BNST). Various methods have been utilized to optimize target selection for trOCD DBS. The authors describe their practice of planning trajectories to both the VS and BNST and adjudicating between them with awake intraoperative valence testing to individualize permanent target selection.

METHODS

Eight patients with trOCD underwent awake DBS with trajectories planned for both VS and BNST targets bilaterally. The authors intraoperatively assessed the acute effects of stimulation on mood, energy, and anxiety and implanted the trajectory with the most reliable positive valence responses and least stimulation-induced side effects. The method of intraoperative target adjudication is described, and the OCD outcome at last follow-up is reported.

RESULTS

The mean patient age at surgery was 41.25 ± 15.1 years, and the mean disease duration was 22.75 ± 10.2 years. The median preoperative Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score was 39 (range 34-40). Two patients had previously undergone capsulotomy, with insufficient response. Seven (44%) of 16 leads were moved to the second target based on intraoperative stimulation findings, 4 of them to avoid strong negative valence effects. Three patients had an asymmetric implant (1 lead in each target). All 8 patients (100%) met full response criteria, and the mean Y-BOCS score reduction across the full cohort was 51.2% ± 12.8%.

CONCLUSIONS

Planning and intraoperatively testing trajectories flanking the AC-superjacent to the VS anteriorly and to the BNST posteriorly-allowed identification of positive valence responses and acute adverse effects. Awake testing helped to select between possible trajectories and identify individually optimized targets in DBS for trOCD.

Feasibility, acceptability and practicality of transcranial stimulation in obsessive compulsive symptoms (FEATSOCS): A randomised controlled crossover trial

BACKGROUND

Transcranial direct current stimulation (tDCS) is a non-invasive form of neurostimulation with potential for development as a self-administered intervention. It has shown promise as a safe and effective treatment for obsessive compulsive disorder (OCD) in a small number of studies. The two most favourable stimulation targets appear to be the left orbitofrontal cortex (L-OFC) and the supplementary motor area (SMA). We report the first study to test these targets head-to-head within a randomised sham-controlled trial. Our aim was to inform the design of future clinical research studies, by focussing on the acceptability and safety of the intervention, feasibility of recruitment, adherence to and tolerability of tDCS, and the size of any treatment-effect.

METHODS

FEATSOCS was a randomised, double-blind, sham-controlled, cross-over, multicentre study. Twenty adults with DSM-5-defined OCD were randomised to treatment, comprising three courses of clinic-based tDCS (SMA, L-OFC, Sham), randomly allocated and delivered in counterbalanced order. Each course comprised four 20-min 2 mA stimulations, delivered over two consecutive days, separated by a 'washout' period of at least four weeks. Assessments were carried out by raters who were blind to stimulation-type. Clinical outcomes were assessed before, during, and up to four weeks after stimulation. Patient representatives with lived experience of OCD were actively involved at all stages.

RESULTS

Clinicians showed willingness to recruit participants and recruitment to target was achieved. Adherence to treatment and study interventions was generally good, with only two dropouts. There were no serious adverse events, and adverse effects which did occur were transient and mostly mild in intensity. Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) scores were numerically improved from baseline to 24 h after the final stimulation across all intervention groups but tended to worsen thereafter. The greatest effect size was seen in the L-OFC arm, (Cohen's d = -0.5 [95% CI -1.2 to 0.2] versus Sham), suggesting this stimulation site should be pursued in further studies. Additional significant sham referenced improvements in secondary outcomes occurred in the L-OFC arm, and to a lesser extent with SMA stimulation.

CONCLUSIONS

tDCS was acceptable, practicable to apply, well-tolerated and appears a promising potential treatment for OCD. The L-OFC represents the most promising target based on clinical changes, though the effects on OCD symptoms were not statistically significant compared to sham. SMA stimulation showed lesser signs of promise. Further investigation of tDCS in OCD is warranted, to determine the optimal stimulation protocol (current, frequency, duration), longer-term effectiveness and brain-based mechanisms of effect. If efficacy is substantiated, consideration of home-based approaches represents a rational next step.

TRIAL REGISTRATION

ISRCTN17937049. https://doi.org/10.1186/ISRCTN17937049.

Feasibility and acceptability of transcranial stimulation in obsessive-compulsive symptoms (FEATSOCS): study protocol for a randomised controlled trial of transcranial direct current stimulation (tDCS) in obsessive-compulsive disorder (OCD)

BACKGROUND

Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder which often proves refractory to current treatment approaches. Transcranial direct current stimulation (tDCS), a noninvasive form of neurostimulation, with potential for development as a self-administered intervention, has shown potential as a safe and efficacious treatment for OCD in a small number of trials. The two most promising stimulation sites are located above the orbitofrontal cortex (OFC) and the supplementary motor area (SMA).

METHODS

The aim of this feasibility study is to inform the development of a definitive trial, focussing on the acceptability, safety of the intervention, feasibility of recruitment, adherence and tolerability to tDCS and study assessments and the size of the treatment effect. To this end, we will deliver a double-blind, sham-controlled, crossover randomised multicentre study in 25 adults with OCD. Each participant will receive three courses of tDCS (SMA, OFC and sham), randomly allocated and given in counterbalanced order. Each course comprises four 20-min stimulations, delivered over two consecutive days, separated by at least 4 weeks' washout period. We will collect information about recruitment, study conduct and tDCS delivery. Blinded raters will assess clinical outcomes before, during and up to 4 weeks after stimulation using validated scales. We will include relevant objective neurocognitive tasks, testing cognitive flexibility, motor disinhibition, cooperation and habit learning.

DISCUSSION

We will analyse the magnitude of the effect of the interventions on OCD symptoms alongside the standard deviation of the outcome measure, to estimate effect size and determine the optimal stimulation target. We will also measure the duration of the effect of stimulation, to provide information on spacing treatments efficiently. We will evaluate the usefulness and limitations of specific neurocognitive tests to determine a definitive test battery. Additionally, qualitative data will be collected from participants to better understand their experience of taking part in a tDCS intervention, as well as the impact on their overall quality of life. These clinical outcomes will enable the project team to further refine the methodology to ensure optimal efficiency in terms of both delivering and assessing the treatment in a full-scale trial.

TRIAL REGISTRATION

ISRCTN17937049 . (date applied 08/07/2019). Recruitment (ongoing) began 23rd July 2019 and is anticipated to complete 30th April 2021.

Deep brain stimulation response in obsessive-compulsive disorder is associated with preoperative nucleus accumbens volume

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Preoperative MRI was associated with 12-months DBS treatment outcome in OCD patients.

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Larger nucleus accumbens volume was associated with larger clinical improvement.

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Machine learning analysis was not successful in predicting clinical improvement.

Background

Deep brain stimulation (DBS) is a new treatment option for patients with therapy-resistant obsessive–compulsive disorder (OCD). Approximately 60% of patients benefit from DBS, which might be improved if a biomarker could identify patients who are likely to respond. Therefore, we evaluated the use of preoperative structural magnetic resonance imaging (MRI) in predicting treatment outcome for OCD patients on the group- and individual-level.

Methods

In this retrospective study, we analyzed preoperative MRI data of a large cohort of patients who received DBS for OCD (n = 57). We used voxel-based morphometry to investigate whether grey matter (GM) or white matter (WM) volume surrounding the DBS electrode (nucleus accumbens (NAc), anterior thalamic radiation), and whole-brain GM/WM volume were associated with OCD severity and response status at 12-month follow-up. In addition, we performed machine learning analyses to predict treatment outcome at an individual-level and evaluated its performance using cross-validation.

Results

Larger preoperative left NAc volume was associated with lower OCD severity at 12-month follow-up (p_FWE < 0.05). None of the individual-level regression/classification analyses exceeded chance-level performance.

Conclusions

These results provide evidence that patients with larger NAc volumes show a better response to DBS, indicating that DBS success is partly determined by individual differences in brain anatomy. However, the results also indicate that structural MRI data alone does not provide sufficient information to guide clinical decision making at an individual level yet.

The Psychopharmacology of Obsessive-Compulsive Disorder: A Preclinical Roadmap

This review evaluates current knowledge about obsessive-compulsive disorder (OCD), with the goal of providing a roadmap for future directions in research on the psychopharmacology of the disorder. It first addresses issues in the description and diagnosis of OCD, including the structure, measurement, and appropriate description of the disorder and issues of differential diagnosis. Current pharmacotherapies for OCD are then reviewed, including monotherapy with serotonin reuptake inhibitors and augmentation with antipsychotic medication and with psychologic treatment. Neuromodulatory therapies for OCD are also described, including psychosurgery, deep brain stimulation, and noninvasive brain stimulation. Psychotherapies for OCD are then reviewed, focusing on behavior therapy, including exposure and response prevention and cognitive therapy, and the efficacy of these interventions is discussed, touching on issues such as the timing of sessions, the adjunctive role of pharmacotherapy, and the underlying mechanisms. Next, current research on the neurobiology of OCD is examined, including work probing the role of various neurotransmitters and other endogenous processes and etiology as clues to the neurobiological fault that may underlie OCD. A new perspective on preclinical research is advanced, using the Research Domain Criteria to propose an adaptationist viewpoint that regards OCD as the dysfunction of a normal motivational system. A systems-design approach introduces the security motivation system (SMS) theory of OCD as a framework for research. Finally, a new perspective on psychopharmacological research for OCD is advanced, exploring three approaches: boosting infrastructure facilities of the brain, facilitating psychotherapeutic relearning, and targeting specific pathways of the SMS network to fix deficient SMS shut-down processes. SIGNIFICANCE STATEMENT: A significant proportion of patients with obsessive-compulsive disorder (OCD) do not achieve remission with current treatments, indicating the need for innovations in psychopharmacology for the disorder. OCD may be conceptualized as the dysfunction of a normal, special motivation system that evolved to manage the prospect of potential danger. This perspective, together with a wide-ranging review of the literature, suggests novel directions for psychopharmacological research, including boosting support systems of the brain, facilitating relearning that occurs in psychotherapy, and targeting specific pathways in the brain that provide deficient stopping processes in OCD.

Calcium imaging in freely-moving mice during electrical stimulation of deep brain structures

After decades of study in humans and animal models, there remains a lack of consensus regarding how the action of electrical stimulation on neuronal and non-neuronal elements - e.g. neuropil, cell bodies, glial cells, etc. - leads to the therapeutic effects of neuromodulation therapies. To further our understanding of neuromodulation therapies, there is a critical need for novel methodological approaches using state-of-the-art neuroscience tools to study neuromodulation therapy in preclinical models of disease. In this manuscript we outline one such approach combining chronic behaving single-photon microendoscope recordings in a pathological mouse model with electrical stimulation of a common deep brain stimulation (DBS) target. We describe in detail the steps necessary to realize this approach, as well as discuss key considerations for extending this experimental paradigm to other DBS targets for different therapeutic indications. Additionally, we make recommendations from our experience on implementing and validating the required combination of procedures that includes: the induction of a pathological model (6-OHDA model of Parkinson's disease) through an injection procedure, the injection of the viral vector to induce GCaMP expression, the implantation of the GRIN lens and stimulation electrode, and the installation of a baseplate for mounting the microendoscope. We proactively identify unique data analysis confounds occurring due to the combination of electrical stimulation and optical recordings and outline an approach to address these confounds. In order to validate the technical feasibility of this unique combination of experimental methods, we present data to demonstrate that 1) despite the complex multifaceted surgical procedures, chronic optical recordings of hundreds of cells combined with stimulation is achievable over week long periods 2) this approach enables measurement of differences in DBS evoked neural activity between anesthetized and awake conditions and 3) this combination of techniques can be used to measure electrical stimulation induced changes in neural activity during behavior in a pathological mouse model. These findings are presented to underscore the feasibility and potential utility of minimally constrained optical recordings to elucidate the mechanisms of DBS therapies in animal models of disease.

Spatial versus angular resolution for tractography-assisted planning of deep brain stimulation

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Deep brain stimulation (DBS) benefits from precise targeting of white matter tracts.

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Better to increase spatial vs. angular resolution for separating parallel tracts.

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Scanning time trade-off between angular & spatial resolution depends on local anatomy.

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We recommend increased spatial resolution dMRI for tract-guided internal capsule DBS.

Given the restricted total scanning time for clinical neuroimaging, it is unclear whether clinical diffusion MRI protocols would benefit more from higher spatial resolution or higher angular resolution. In this work, we investigated the relative benefit of improving spatial or angular resolution in diffusion MRI to separate two parallel running white matter tracts that are targets for deep brain stimulation: the anterior thalamic radiation and the supero-lateral branch of the medial forebrain bundle. Both these tracts are situated in the ventral anterior limb of the internal capsule, and recent studies suggest that targeting a specific tract could improve treatment efficacy. Therefore, we scanned 19 healthy volunteers at 3T and 7T according to three diffusion MRI protocols with respectively standard clinical settings, increased spatial resolution of 1.4 mm, and increased angular resolution (64 additional gradient directions at b = 2200s/mm²). We performed probabilistic tractography for all protocols and quantified the separability of both tracts. The higher spatial resolution protocol improved separability by 41% with respect to the clinical standard, presumably due to decreased partial voluming. The higher angular resolution protocol resulted in increased apparent tract volumes and overlap, which is disadvantageous for application in precise treatment planning. We thus recommend to increase the spatial resolution for deep brain stimulation planning to 1.4 mm while maintaining angular resolution. This recommendation complements the general advice to aim for high angular resolution to resolve crossing fibers, confirming that the specific application and anatomical considerations are leading in clinical diffusion MRI protocol optimization.

Polydopamine Nanoparticles for Deep Brain Ablation via Near-Infrared Irradiation

Local resection or ablation remains an important approach to treat drug-resistant central neurological disease. Conventional surgical approaches are designed to resect the diseased tissues. The emergence of photothermal therapy (PTT) offers a minimally invasive alternative. However, their poor penetration and potential off-target effect limit their clinical application. Here, polydopamine nanoparticles (PDA-NPs) were prepared and characterized. Studies were performed to evaluate whether PDA-NPs combined with near-infrared (NIR) light can be used to ablate deep brain structures in vitro and in vivo. PDA-NPs were prepared with a mean diameter of ∼150 nm. The particles show excellent photothermal conversion efficiency. PDA-NPs did not show remarkable cytotoxicity against neuronal-like SH-SY5Y cell lines. However, it can cause significant cell death when combined with NIR irradiation. Transcranial NIR irradiation after PDA-NPs administration induced enhanced local hyperthermia as compared with NIR alone. Local temperature exceeded 60 °C after 6 min of irradiation plus PDA while it can only reach 48 °C with NIR alone. PTT with PDA (10 mg/mL, 3 μL) and NIR (1.5 W/cm²) can ablate deep brain structures precisely with an ablation volume of ∼6.5 mm³. Histological analysis confirmed necrosis and apoptosis in the targeted area. These results demonstrate the potential of NP-assisted PTT for the treatment against nontumorous central neurological diseases.

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.

Individual white matter bundle trajectories are associated with deep brain stimulation response in obsessive-compulsive disorder

BACKGROUND

The ventral anterior limb of the internal capsule (vALIC) is a target for deep brain stimulation (DBS) in obsessive-compulsive disorder (OCD). Conventional surgical planning is based on anatomical landmarks.

OBJECTIVE/HYPOTHESIS

We hypothesized that treatment response depends on the location of the active DBS contacts with respect to individual white matter bundle trajectories. This study thus aimed to elucidate whether vALIC DBS can benefit from bundle-specific targeting.

METHODS

We performed tractography analysis of two fiber bundles, the anterior thalamic radiation (ATR) and the supero-lateral branch of the medial forebrain bundle (MFB), using diffusion-weighted magnetic resonance imaging (DWI) data. Twelve patients (10 females) who had received bilateral vALIC DBS for at least 12 months were included. We related the change in OCD symptom severity on the Yale-Brown obsessive-compulsive scale (Y-BOCS) between baseline and one-year follow-up with the distances from the active contacts to the ATR and MFB. We further analyzed the relation between treatment response and stimulation sites in standard anatomical space.

RESULTS

We found that active stimulation of the vALIC closer to the MFB than the ATR was associated with better treatment outcome (p = 0.04; r² = 0.34). In standard space, stimulation sites were largely overlapping between treatment (non)responders, suggesting response is independent of the anatomically defined electrode position.

CONCLUSION

These findings suggest that vALIC DBS for OCD may benefit from MFB-specific implantation and highlight the importance of corticolimbic connections in OCD response to DBS. Prospective investigation is necessary to validate the clinical use of MFB targeting.

Personality measures after gamma ventral capsulotomy in intractable OCD

BACKGROUND

Neurosurgeries such as gamma ventral capsulotomy (GVC) are an option for otherwise intractable obsessive-compulsive disorder (OCD) patients. In general, clinical and neuropsychological status both improve after GVC. However, its consequences on personality traits are not well-studied. The objective of this study was to investigate personality changes after one year of GVC in intractable OCD patients.

METHODS

The personality assessment was conducted using the Revised NEO Personality Inventory (NEO PI-R) and Cloninger's Temperament and Character Inventory (TCI) in 14 intractable OCD patients before and one year after GVC. Comparisons of personality features between treatment responders (n=5) and non-responders (n=9) were performed. Multiple linear regression was also used for predicting changes in clinical and global functioning variables.

RESULTS

Overall, no deleterious effect was found in personality after GVC. Responders had a reduction in neuroticism (p=0.043) and an increase in extraversion (p=0.043). No significant changes were observed in non-responders. Increases in novelty seeking and self-directedness, and decreases in persistence and cooperativiness predicted OCD symptom improvement. Similary, improvement in functioning was also predicted by hgher novelty seeking and self-directedness after GVC, whereas better functioning was also associated with lower reward dependence and cooperativeness after surgery.

CONCLUSIONS

The pattern of changes in personality traits after GVC was generally towards that observed in nonclinical population, and does not raise safety concerns.

History of psychosurgery at Sainte-Anne Hospital, Paris, France, through translational interactions between psychiatrists and neurosurgeons

Sainte-Anne Hospital is the largest psychiatric hospital in Paris. Its long and fascinating history began in the 18th century. In 1952, it was at Sainte-Anne Hospital that Jean Delay and Pierre Deniker used the first neuroleptic, chlorpromazine, to cure psychiatric patients, putting an end to the expansion of psychosurgery. The Department of Neuro-psychosurgery was created in 1941. The works of successive heads of the Neurosurgery Department at Sainte-Anne Hospital summarized the history of psychosurgery in France.

Pierre Puech defined psychosurgery as the necessary cooperation between neurosurgeons and psychiatrists to treat the conditions causing psychiatric symptoms, from brain tumors to mental health disorders. He reported the results of his series of 369 cases and underlined the necessity for proper follow-up and postoperative re-education, illustrating the relative caution of French neurosurgeons concerning psychosurgery.

Marcel David and his assistants tried to follow their patients closely postoperatively; this resulted in numerous publications with significant follow-up and conclusions. As early as 1955, David reported intellectual degradation 2 years after prefrontal leucotomies.

Jean Talairach, a psychiatrist who eventually trained as a neurosurgeon, was the first to describe anterior capsulotomy in 1949. He operated in several hospitals outside of Paris, including the Sarthe Psychiatric Hospital and the Public Institution of Mental Health in the Lille region. He developed stereotactic surgery, notably stereo-electroencephalography, for epilepsy surgery but also to treat psychiatric patients using stereotactic lesioning with radiofrequency ablation or radioactive seeds of yttrium-90.

The evolution of functional neurosurgery has been marked by the development of deep brain stimulation, in particular for obsessive-compulsive disorder, replacing the former lesional stereotactic procedures.

The history of Sainte-Anne Hospital’s Neurosurgery Department sheds light on the initiation—yet fast reconsideration—of psychosurgery in France. This relatively more prudent attitude toward the practice of psychosurgery compared with other countries was probably due to the historically strong collaboration between psychiatrists and neurosurgeons in France.

Anterior Cingulate Implant for Obsessive-Compulsive Disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is a brain disorder with a lifetime prevalence of 2.3%, causing severe functional impairment as a result of anxiety and distress, persistent and repetitive, unwanted, intrusive thoughts (obsessions), and repetitive ritualized behavior (compulsions). Approximately 40%-60% of patients with OCD fail to satisfactorily respond to standard treatments. Intractable OCD has been treated by anterior capsulotomy and cingulotomy, but more recently, neurostimulation approaches have become more popular because of their reversibility.

OBJECTIVE

Implants for OCD are commonly being used, targeting the anterior limb of the internal capsula or the nucleus accumbens, but an implant on the anterior cingulate cortex has never been reported.

METHODS

We describe a patient who was primarily treated for alcohol addiction, first with transcranial magnetic stimulation, then by implantation of 2 electrodes overlying the rostrodorsal part of the anterior cingulate cortex bilaterally.

RESULTS

Her alcohol addiction developed as she was relief drinking to self-treat her OCD, anxiety, and depression. After the surgical implant, she underwent placebo stimulation followed by real stimulation of the dorsal anterior cingulate cortex, which dramatically improved her OCD symptoms (decrease of 65.5% on the Yale-Brown Obsessive Compulsive Drinking Scale) as well as her alcohol craving (decrease of 87.5%) after 36 weeks of treatment. Although there were improvements in all the scores, there was only a modest reduction in the patient's weekly alcohol consumption (from 50 units to 32 units).

CONCLUSIONS

Based on these preliminary positive results we propose to further study the possible beneficial effect of anterior cingulate cortex stimulation for intractable OCD.

A Review of Therapeutic Ablation Modalities

Understanding basic science and technical aspects is essential for scientists and engineers to develop and enhance ablative modalities, and for clinicians to effectively apply therapeutic ablative techniques. An overview of ablative modalities, anatomical locations, and indications for which ablations are performed is presented. Specifically, basic concepts, parameter selection, and underlying biophysics of tissue injury of five currently used therapeutic ablative modalities are reviewed: radiofrequency ablation (RFA), cryoablation (CRA), microwave ablation (MWA), high-intensity focused ultrasound (HIFU), and chemical ablation (CHA) (ablative agents: acetic acid, ethanol, hypertonic sodium chloride, and urea). Each ablative modality could be refined for expanding applications, either independently or in combination, for future therapeutic use.

Anaesthesia for deep brain stimulation: a review

PURPOSE OF REVIEW

Deep brain stimulation (DBS) is a well tolerated and efficacious surgical treatment for movement disorders, chronic pain, psychiatric disorder, and a growing number of neurological disorders. Given that the brain targets are deep and small, accurate electrode placement is commonly accomplished by utilizing frame-based systems. DBS electrode placement is confirmed by microlectrode recordings and macrostimulation to optimize and verify target placement. With a reliance on electrophysiology, proper anaesthetic management is paramount to balance patient comfort without interfering with neurophysiology.

RECENT FINDINGS

To achieve optimal pain control, generous amounts of local anaesthesia are instilled into the planned incision. During the opening and closing states, conscious sedation is the prevailing method of anaesthesia. The preferred agents are dexmedetomidine, propofol, and remifentanil, as they affect neurocognitive testing the least, and shorter acting. All the agents are turned off 15-30 min prior to microelectrode recording. Dexmedetomidine has gained popularity in DBS procedures, but has some considerations at higher doses. The addition of ketamine is helpful for pediatric cases.

SUMMARY

DBS is a robust surgical treatment for a variety of neurological disorders. Appropriate anaesthetic agents that achieve patient comfort without interfering with electrophysiology are paramount.

Evolution of Movement Disorders Surgery Leading to Contemporary Focused Ultrasound Therapy for Tremor

Progressively less invasive neurosurgical approaches for the treatment of movement disorders have evolved, beginning with open craniotomy for placement of lesions within pyramidal structures followed by refined stereotactic ablation of extrapyramidal targets that encouraged nondestructive electrode stimulation of deep brain structures. A noninvasive approach using transcranial high-energy focused ultrasound has emerged for the treatment of intractable tremor. The ability to target discreet intracranial sites millimeters in size through the intact skull using focused acoustic energy marks an important milestone in movement disorders surgery. This article describes the evolution of magnetic resonance-guided focused ultrasound for ventrolateral thalamotomy for tremor.

Mechanisms of deep brain stimulation

Deep brain stimulation (DBS) is widely used for the treatment of movement disorders including Parkinson's disease, essential tremor, and dystonia and, to a lesser extent, certain treatment-resistant neuropsychiatric disorders including obsessive-compulsive disorder. Rather than a single unifying mechanism, DBS likely acts via several, nonexclusive mechanisms including local and network-wide electrical and neurochemical effects of stimulation, modulation of oscillatory activity, synaptic plasticity, and, potentially, neuroprotection and neurogenesis. These different mechanisms vary in importance depending on the condition being treated and the target being stimulated. Here we review each of these in turn and illustrate how an understanding of these mechanisms is inspiring next-generation approaches to DBS.

A programmable high-voltage compliance neural stimulator for deep brain stimulation in vivo

Deep brain stimulation (DBS) is one of the most effective therapies for movement and other disorders. The DBS neurosurgical procedure involves the implantation of a DBS device and a battery-operated neurotransmitter, which delivers electrical impulses to treatment targets through implanted electrodes. The DBS modulates the neuronal activities in the brain nucleus for improving physiological responses as long as an electric discharge above the stimulation threshold can be achieved. In an effort to improve the performance of an implanted DBS device, the device size, implementation cost, and power efficiency are among the most important DBS device design aspects. This study aims to present preliminary research results of an efficient stimulator, with emphasis on conversion efficiency. The prototype stimulator features high-voltage compliance, implemented with only a standard semiconductor process, without the use of extra masks in the foundry through our proposed circuit structure. The results of animal experiments, including evaluation of evoked responses induced by thalamic electrical stimuli with our fabricated chip, were shown to demonstrate the proof of concept of our design.

Analysis of gene expression changes in the rat hippocampus after deep brain stimulation of the anterior thalamic nucleus

Deep brain stimulation (DBS) surgery, targeting various regions of the brain such as the basal ganglia, thalamus, and subthalamic regions, is an effective treatment for several movement disorders that have failed to respond to medication. Recent progress in the field of DBS surgery has begun to extend the application of this surgical technique to other conditions as diverse as morbid obesity, depression and obsessive compulsive disorder. Despite these expanding indications, little is known about the underlying physiological mechanisms that facilitate the beneficial effects of DBS surgery. One approach to this question is to perform gene expression analysis in neurons that receive the electrical stimulation. Previous studies have shown that neurogenesis in the rat dentate gyrus is elicited in DBS targeting of the anterior nucleus of the thalamus(1). DBS surgery targeting the ATN is used widely for treatment refractory epilepsy. It is thus of much interest for us to explore the transcriptional changes induced by electrically stimulating the ATN. In this manuscript, we describe our methodologies for stereotactically-guided DBS surgery targeting the ATN in adult male Wistar rats. We also discuss the subsequent steps for tissue dissection, RNA isolation, cDNA preparation and quantitative RT-PCR for measuring gene expression changes. This method could be applied and modified for stimulating the basal ganglia and other regions of the brain commonly clinically targeted. The gene expression study described here assumes a candidate target gene approach for discovering molecular players that could be directing the mechanism for DBS.