Brain Stimulation For Obsessive-compulsive Disorder Research Articles

Clinical outcomes of deep brain stimulation for obsessive-compulsive disorder: Insight as a predictor of symptom changes.

Deep brain stimulation (DBS) is a safe and effective treatment option for people with refractory obsessive-compulsive disorder (OCD). Yet our understanding of predictors of response and prognostic factors remains rudimentary, and long-term comprehensive follow-ups are lacking. We aim to investigate the efficacy of DBS therapy for OCD patients, and predictors of clinical response. Eight OCD participants underwent DBS stimulation of the nucleus accumbens (NAc) in an open-label longitudinal trial, duration of follow-up varied between 9 months and 7 years. Post-operative care involved comprehensive fine tuning of stimulation parameters and adjunct multidisciplinary therapy. Six participants achieved clinical response (35% improvement in obsessions and compulsions on the Yale Brown Obsessive Compulsive Scale (YBOCS)) within 6-9 weeks, response was maintained at last follow up. On average, the YBOCS improved by 45% at last follow up. Mixed linear modeling elucidated directionality of symptom changes: insight into symptoms strongly predicted (P = 0.008) changes in symptom severity during DBS therapy, likely driven by initial changes in depression and anxiety. Precise localization of DBS leads demonstrated that responders most often had their leads (and active contacts) placed dorsal compared to non-responders, relative to the Nac. The clinical efficacy of DBS for OCD is demonstrated, and mediators of changes in symptoms are proposed. The symptom improvements within this cohort should be seen within the context of the adjunct psychological and biopsychosocial care that implemented a shared decision-making approach, with flexible iterative DBS programming. Further research should explore the utility of insight as a clinical correlate of response. The trial was prospectively registered with the ANZCTR (ACTRN12612001142820).

Perspectives on informed assent and bodily integrity in prospective deep brain stimulation for youth with refractory obsessive-compulsive disorder

Background Deep brain stimulation is approved for treating refractory obsessive-compulsive disorder in adults under the US Food and Drug Administration Humanitarian Device Exemption, and studies have shown its efficacy in reducing symptom severity and improving quality of life. While similar deep brain stimulation treatment is available for pediatric patients with dystonia, it is not yet available for pediatric patients with obsessive-compulsive disorder, although soon could be. The prospect of growing indications for pediatric deep brain stimulation raises several ethical concerns relating to bodily integrity, the ability to offer informed assent, and the role pediatric patients play in the decision-making process. Objective The aim of this study is to solicit and assess the views of stakeholders (children, parents, clinicians) on pediatric assent, autonomy, and bodily integrity in the context of potential pediatric deep brain stimulation for obsessive-compulsive disorder. Methods Semi-structured interviews were conducted with pediatric obsessive-compulsive disorder patients ( n = 21), caregivers of pediatric obsessive-compulsive disorder patients aged 14–18 ( n = 19), and clinicians with experience treating refractory obsessive-compulsive disorder ( n = 25). Interviews were transcribed and coded in MAXQDA 2018 and 2020 software and processed for thematic content analysis to isolate and compare specific themes. Results A majority of respondents (74%, 48/65) across all three stakeholder groups voiced that the decision-making process should be collaborative and involve everyone (clinicians: 84% or 21/25, caregivers 71% or 15/21, and patients 63% or 12/19). We identified a split between respondents’ views on who should have the final say in the event of disagreement (38% or 25/65 favored the patient versus 35% or 23/65 favoring caregivers). A split between respondents also emerged concerning the maturity relevant for deep brain stimulation decision-making, with 45% (29/65) favoring developmental maturity (age/physiological development) and 45% (29/65) favoring decisional maturity (capacity to understand and weigh information). A majority of clinicians indicated that they would not move forward with deep brain stimulation without securing patient assent (80% or 20/25), with some stating the only exception is if patient quality of life was very poor and/or they lacked insight. Both caregivers and patients expressed a significant respect for the patient's right to bodily integrity, with 67% of caregivers (14/21) and 68% of patients (13/19) justifying patient involvement in decision-making specifically with reference to infringements of bodily integrity. Conclusion Our findings demonstrate that despite broad agreement across stakeholders that the decision-making process for pediatric deep brain stimulation for obsessive-compulsive disorder should be collaborative and somehow involve pediatric patients, there is disagreement about what this process entails and what factors determine patient involvement in the process. However, there is agreement that children have a right to bodily and brain integrity, which should only be infringed upon in rare circumstances.

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.

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. 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. 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%. 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.

The role of the dorsal anterior cingulate cortex in obsessive-compulsive disorder

Despite extensive research efforts, the pathophysiology of obsessive-compulsive disorder (OCD) is still largely unknown. The dorsal anterior cingulate cortex (dACC) plays an important role in cognitive control and is therefore hypothesized to contribute to the pathogenesis of OCD. In this review, we aim to gain a wider understanding of the specific functions of the dACC and its role in the pathophysiology of OCD. The dACC is part of the cortico-basal ganglia-thalamo-cortical loop, where it forms connections between sensory input streams, cognitive and affective processing regions, and structures that regulate behaviour. This position facilitates a broad function for the dACC in multiple domains, which center on goal-directed behaviour and reward-based learning. When presented with a certain threatening stimulus, the dACC instructs downstream structures to select actions to respond to this particular stimulus, based on previous experiences We hypothesize that hyperactivity of the dACC may impair goal-directed behaviour in OCD patients which in turn may lead to obsessive-compulsive symptoms by creating an over-reliance on threatening stimuli and inadequate selection of neutralizing actions. The working mechanisms of cognitive behavioural therapy, serotonergic medication, repetitive transcranial magnetic stimulation and deep brain stimulation in OCD may be in part explained by the normalization of the activity of the dACC within the cortico-basal ganglia-thalamo-cortical (CBGTC) loop.

Call to revise the Royal Australian and New Zealand College of Psychiatrists' clinical memorandum on deep brain stimulation for obsessive-compulsive disorder.

Call to revise the Royal Australian and New Zealand College of Psychiatrists' clinical memorandum on deep brain stimulation for obsessive-compulsive disorder.

Treating Obsessive-Compulsive Disorder by Invasively Modulating Thoughts, Feelings, or Both

The defining characteristic of pathological compulsions is that they are carried out to reduce momentary distress, even though performing the compulsive act or thought is rationally not in the individual’s true best interest. This inability to flexibly adapt is a prominent component of obsessive-compulsive disorder (OCD) and closely related illnesses such as Tourette syndrome and is also observed in substance use disorders ( 1 Figee M. Pattij T. Willuhn I. Luigjes J. van den Brink W. Goudriaan A. et al. Compulsivity in obsessive-compulsive disorder and addictions. Eur Neuropsychopharmacol. 2016; 26: 856-868 Crossref PubMed Scopus (111) Google Scholar ). Following the 20th century experience with ablative procedures such as capsulotomy, deep brain stimulation (DBS) was applied to the treatment of OCD. Electrodes are most commonly placed within the anterior limb of the internal capsule (ALIC), modulating cortico-basal ganglia-thalamo-cortical parallel white matter loops relevant to limbic, associative, and motor functions, respectively. ALIC stimulation has proven to be a highly effective treatment for severe OCD ( 2 Smith AH, Mayberg HS, Figee M (in press): Neuromodulation and psychiatric disorders. In: Nestler EJ, Charney DS, editors. Neurobiology of Mental Illness, 6th ed. New York: Oxford University Press. Google Scholar ). DBS to a different anatomical location, the subthalamic nucleus (STN), was initially developed for Parkinson’s disease, but positive early experience in patients with comorbid Parkinson’s disease and OCD led to research establishing high-frequency stimulation straight to the STN as clinically efficacious for OCD ( 3 Mallet L. Polosan M. Jaafari N. Baup N. Welter M.L. Fontaine D. et al. Subthalamic nucleus stimulation in severe obsessive-compulsive disorder. N Engl J Med. 2008; 359: 2121-2134 Crossref PubMed Scopus (687) Google Scholar ). In a similar manner, promising early pilot studies led to further exploration of other targets. These include the bed nucleus of the stria terminalis, the “extended amygdala” located between the ALIC and STN targets ( 4 Mosley P.E. Windels F. Morris J. Coyne T. Marsh R. Giorni A. et al. A randomised, double-blind, sham-controlled trial of deep brain stimulation of the bed nucleus of the stria terminalis for treatment-resistant obsessive-compulsive disorder. Transl Psychiatry. 2021; 11: 190 Crossref PubMed Scopus (38) Google Scholar ). More recently, evidence has emerged for the effectiveness of stimulation delivered deeper in the midbrain than the STN, adjacent to the ventral tegmental area (VTA)—a source of dopaminergic projections to the cortex (via the medial forebrain bundle [MFB]) and a recipient of proposed regulatory projections back from the cortex (via the “supralateral MFB”) ( 5 Meyer D.M. Spanier S. Kilian H.M. Reisert M. Urbach H. Sajonz B.E. et al. Efficacy of superolateral medial forebrain bundle deep brain stimulation in obsessive-compulsive disorder. Brain Stimul. 2022; 15: 582-585 Abstract Full Text Full Text PDF Scopus (3) Google Scholar ). SEE CORRESPONDING ARTICLE ON PAGE 1010 SEE CORRESPONDING ARTICLE ON PAGE 1010 The Rostral Zona Incerta: A Subcortical Integrative Hub and Potential Deep Brain Stimulation Target for Obsessive-Compulsive DisorderBiological PsychiatryVol. 93Issue 11PreviewThe zona incerta (ZI) is involved in mediating survival behaviors and is connected to a wide range of cortical and subcortical structures, including key basal ganglia nuclei. Based on these connections and their links to behavioral modulation, we propose that the ZI is a connectional hub for mediating between top-down and bottom-up control and a possible target for deep brain stimulation for obsessive-compulsive disorder. Full-Text PDF

451. Functional MRI Activation in Deep Brain Stimulation for Obsessive-Compulsive Disorder in Treatment Responders and Nonresponders

451. Functional MRI Activation in Deep Brain Stimulation for Obsessive-Compulsive Disorder in Treatment Responders and Nonresponders

Deep Brain Stimulation for Obsessive-Compulsive Disorder and Depression.

The field of stereotactic neurosurgery developed more than 70 years ago to address a therapy gap for patients with severe psychiatric disorders. In the decades since, it has matured tremendously, benefiting from advances in clinical and basic sciences. Deep brain stimulation (DBS) for severe, treatment-resistant psychiatric disorders is currently poised to transition from a stage of empiricism to one increasingly rooted in scientific discovery. Current drivers of this transition are advances in neuroimaging, but rapidly emerging ones are neurophysiological-as we understand more about the neural basis of these disorders, we will more successfully be able to use interventions such as invasive stimulation to restore dysfunctional circuits to health. Paralleling this transition is a steady increase in the consistency and quality of outcome data. Here, we focus on obsessive-compulsive disorder and depression, two topics that have received the most attention in terms of trial volume and scientific effort.

The Rostral Zona Incerta: A Subcortical Integrative Hub and Potential Deep Brain Stimulation Target for Obsessive-Compulsive Disorder

BackgroundThe zona incerta (ZI) is involved in mediating survival behaviors and is connected to a wide range of cortical and subcortical structures, including key basal ganglia nuclei. Based on these connections and their links to behavioral modulation, we propose that the ZI is a connectional hub for mediating between top-down and bottom-up control and a possible target for deep brain stimulation for obsessive-compulsive disorder. MethodsWe analyzed the trajectory of cortical fibers to the ZI in nonhuman and human primates based on tracer injections in monkeys and high-resolution diffusion magnetic resonance imaging in humans. The organization of cortical and subcortical connections within the ZI were identified in the nonhuman primate studies. ResultsMonkey anatomical data and human diffusion magnetic resonance imaging data showed a similar trajectory of fibers/streamlines to the ZI. Prefrontal cortex/anterior cingulate cortex terminals all converged within the rostral ZI, with dorsal and lateral areas being most prominent. Motor areas terminated caudally. Dense subcortical reciprocal connections included the thalamus, medial hypothalamus, substantia nigra/ventral tegmental area, reticular formation, and pedunculopontine nucleus and a dense nonreciprocal projection to the lateral habenula. Additional connections included the amygdala, dorsal raphe nucleus, and periaqueductal gray. ConclusionsDense connections with dorsal and lateral prefrontal cortex/anterior cingulate cortex cognitive control areas and the lateral habenula and the substantia nigra/ventral tegmental area, coupled with inputs from the amygdala, hypothalamus, and brainstem, suggest that the rostral ZI is a subcortical hub positioned to modulate between top-down and bottom-up control. A deep brain stimulation electrode placed in the rostral ZI would not only involve connections common to other deep brain stimulation sites but also capture several critically distinctive connections.

BOLD fMRI response to therapeutic and nontherapeutic deep brain stimulation in obsessive-compulsive disorder

BOLD fMRI response to therapeutic and nontherapeutic deep brain stimulation in obsessive-compulsive disorder

Tractography-Based Modeling Explains Treatment Outcomes in Patients Undergoing Deep Brain Stimulation for Obsessive-Compulsive Disorder

BackgroundDeep brain stimulation (DBS) is an established and expanding therapy for treatment-refractory obsessive-compulsive disorder. Previous work has suggested that a white matter circuit providing hyperdirect input from the dorsal cingulate and ventrolateral prefrontal regions to the subthalamic nucleus could be an effective neuromodulatory target. MethodsWe tested this concept by attempting to retrospectively explain through predictive modeling the ranks of clinical improvement as measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) in 10 patients with obsessive-compulsive disorder who underwent DBS to the ventral anterior limb of internal capsule with subsequent programming uninformed by the putative target tract. ResultsRank predictions were carried out using the tract model by a team that was completely uninvolved in DBS planning and programming. Predicted Y-BOCS improvement ranks significantly correlated with actual Y-BOCS improvement ranks at the 6-month follow-up (r = 0.75, p = .013). Predicted score improvements correlated with actual Y-BOCS score improvements (r = 0.72, p = .018). ConclusionsHere, we provide data in a first-of-its-kind report suggesting that normative tractography-based modeling can blindly predict treatment response in DBS for obsessive-compulsive disorder.

Deep brain stimulation for obsessive-compulsive disorder: current situation

Deep brain stimulation for obsessive-compulsive disorder: current situation

Cognitive behavioral therapy in patients with deep brain stimulation for obsessive-compulsive disorder: a matched controlled study.

Deep brain stimulation (DBS) is effective for refractory obsessive-compulsive disorder (OCD). Post-operative cognitive behavioral therapy (CBT) may augment the effects of DBS, but previous results are conflicting. Here, we investigated whether CBT augments the effect of DBS for OCD. Patients with and without CBT following DBS of the ventral anterior limb of the internal capsule were included. First, we analyzed Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and Hamilton Depression Rating Scale (HAM-D) scores before, during and after CBT in all patients with CBT. Second, we matched patients with and without CBT based on clinical baseline variables and initial response to DBS and compared the course of Y-BOCS and HAM-D scores over the same timeframe. In total, 36 patients with and 16 patients without CBT were included. Average duration of CBT was 10.4 months (s.d. 6.4). In the 36 patients with CBT, Y-BOCS scores decreased on average by 3.8 points (14.8%) from start until end of CBT (p = 0.043). HAM-D scores did not decrease following CBT. Second, 10 patients with CBT were matched to 10 patients without CBT. In both groups, Y-BOCS scores decreased equally from start until end of CBT or over a similar timeframe (10% in CBT group v. 13.1% in no-CBT group, p = 0.741). Obsessive-compulsive symptoms decreased over time in patients with and without post-operative CBT. Therefore, further improvement may be attributed to late effects of DBS itself. The present study emphasizes the need for prospective randomized controlled studies, examining the effects of CBT.

Deep brain stimulation in obsessive-compulsive disorder: Results from meta-analysis

The aim of this work is to investigate the effectiveness of Deep Brain Stimulation (DBS) in patients with severe Obsessive Compulsive Disorder (OCD) who are resistant to pharmacological treatments, focusing on obsessive compulsive, depressive and anxiety symptoms as well as global function. A systematic review and meta-analysis including 25 studies (without language restrictions) from between 2003 and 2020 was performed. A total of 303 patients were evaluated twice (before and after DBS). After DBS treatment OCD patients with resistance to pharmacological treatments showed a significant improvement of obsessive-compulsive symptoms (25 studies; SMD=2.39; 95% CI, 1.91 to 2.87; P<0.0001), depression (9 studies; SMD= 1.19; 95%CI, 0.84 to 1.54; P<0.0001), anxiety (5 studies; SMD=1.00; 95%CI, 0.32 to 1.69; P=0.004) and functionality (7 studies; SMD=-3.51; 95%CI, -5.00 to -2.02; P=0.005) measured by the standardized scales: Yale Brown Obsessive Compulsive Scale (YBOCS), Hamilton Depression Rating Scale (HAM-D), Hamilton Anxiety Rating Scale (HAM-A) and Global Assessment of Function (GAF). Publication bias were discarded by using funnel plot. The main conclusions of this meta-analysis highlight the statistically significant effectiveness of DBS in patients with severe OCD who are resistant to conventional pharmacological treatments, underlying its role in global functioning apart from obsessive-compulsive symptoms.

P.0826 Deep brain stimulation for obsessive-compulsive disorder: concerns and barriers among Portuguese psychiatrists

P.0826 Deep brain stimulation for obsessive-compulsive disorder: concerns and barriers among Portuguese psychiatrists

Effect of brain target and stimulation paradigm on response to deep brain stimulation in obsessive-compulsive disorder

Effect of brain target and stimulation paradigm on response to deep brain stimulation in obsessive-compulsive disorder

Pressing ethical issues in considering pediatric deep brain stimulation for obsessive-compulsive disorder

BackgroundRefractory obsessive-compulsive disorder (OCD) among adults is the first psychiatric indication of deep brain stimulation (DBS) to receive an FDA Humanitarian Device Exemption (HDE). Given the HDE approval and encouraging evidence that has since emerged, exploration of DBS for OCD may expand to adolescents in the future. More than 100,000 adolescents in the U.S. suffer from refractory OCD, and there is already a precedent for the transition of DBS in adults to children in the case of dystonia. However, the risk-benefit analysis of pediatric DBS for OCD may be more complex and raise different ethical questions compared to pediatric DBS for dystonia. ObjectiveThis study aimed to gain insight into pressing ethical issues related to using DBS in adolescents with OCD. MethodsSemi-structured interviews were conducted with clinicians (n = 25) caring for pediatric patients with refractory OCD. Interview transcripts were coded with MAXQDA 2018 software and analyzed using thematic content analysis to identify emergent themes. ResultsFive central themes were identified in clinician responses, three of which were exacerbated in the pediatric DBS setting. Clinicians expressed concerns related to conditions of decision-making including adolescents' capacity to assent (80%), the lack of evidence about the outcomes and potential unknown effects of using DBS in adolescents with OCD (68%), and the importance of exhausting other treatment options before considering DBS (20%). ConclusionsStrategies to address clinician concerns include implementation of validated decision support tools and further research into the outcomes of pediatric DBS for OCD to establish clear guidelines for patient selection.

Neuromodulation via Deep Brain Stimulation in Obsessive-Compulsive Disorder—Present and Perspectives

Obsessive-compulsive disorder (OCD) is a highly heterogeneous condition. Obsessions and compulsions can vary substantially between patients (e.g., washing, checking, mental rituals, hoarding). Likewise, the neuropsychological mechanism underlying compulsivity can be manifold (e.g., harm avoidance, habit formation, cognitive inflexibility, behavioral disinhibition). While some patients experience a mild waxing and waning of symptoms in adulthood, others develop a severe chronic disorder from early childhood.

Patient-specific connectomic models correlate with, but do not reliably predict, outcomes in deep brain stimulation for obsessive-compulsive disorder.

Deep brain stimulation (DBS) of the ventral internal capsule/ventral striatum (VCVS) is an emerging treatment for obsessive-compulsive disorder (OCD). Recently, multiple studies using normative connectomes have correlated DBS outcomes to stimulation of specific white matter tracts. Those studies did not test whether these correlations are clinically predictive, and did not apply cross-validation approaches that are necessary for biomarker development. Further, they did not account for the possibility of systematic differences between DBS patients and the non-diagnosed controls used in normative connectomes. To address these gaps, we performed patient-specific diffusion imaging in 8 patients who underwent VCVS DBS for OCD. We delineated tracts connecting thalamus and subthalamic nucleus (STN) to prefrontal cortex via VCVS. We then calculated which tracts were likely activated by individual patients' DBS settings. We fit multiple statistical models to predict both OCD and depression outcomes from tract activation. We further attempted to predict hypomania, a VCVS DBS complication. We assessed all models' performance on held-out test sets. With this best-practices approach, no model predicted OCD response, depression response, or hypomania above chance. Coefficient inspection partly supported prior reports, in that capture of tracts projecting to cingulate cortex was associated with both YBOCS and MADRS response. In contrast to prior reports, however, tracts connected to STN were not reliably correlated with response. Thus, patient-specific imaging and a guideline-adherent analysis were unable to identify a tractographic target with sufficient effect size to drive clinical decision-making or predict individual outcomes. These findings suggest caution in interpreting the results of normative connectome studies.

Deep brain stimulation for obsessive-compulsive disorder: A systematic review of worldwide experience after 20 years

BACKGROUNDTwenty years after its first use in a patient with obsessive-compulsive disorder (OCD), the results confirm that deep brain stimulation (DBS) is a promising therapy for patients with severe and resistant forms of the disorder. Nevertheless, many unknowns remain, including the optimal anatomical targets, the best stimulation parameters, the long-term (LT) effects of the therapy, and the clinical or biological factors associated with response. This systematic review of the articles published to date on DBS for OCD assesses the short and LT efficacy of the therapy and seeks to identify predictors of response.AIMTo summarize the existing knowledge on the efficacy and tolerability of DBS in treatment-resistant OCD.METHODSA comprehensive search was conducted in the PubMed, Cochrane, Scopus, and ClinicalTrials.gov databases from inception to December 31, 2020, using the following strategy: “(Obsessive-compulsive disorder OR OCD) AND (deep brain stimulation OR DBS).” Clinical trials and observational studies published in English and evaluating the effectiveness of DBS for OCD in humans were included and screened for relevant information using a standardized collection tool. The inclusion criteria were as follows: a main diagnosis of OCD, DBS conducted for therapeutic purposes and variation in symptoms of OCD measured by the Yale-Brown Obsessive-Compulsive scale (Y-BOCS) as primary outcome. Data were analyzed with descriptive statistics.RESULTSForty articles identified by the search strategy met the eligibility criteria. Applying a follow-up threshold of 36 mo, 29 studies (with 230 patients) provided information on short-term (ST) response to DBS in, while 11 (with 155 patients) reported results on LT response. Mean follow-up period was 18.5 ± 8.0 mo for the ST studies and 63.7 ± 20.7 mo for the LT studies. Overall, the percentage of reduction in Y-BOCS scores was similar in ST (47.4%) and LT responses (47.2%) to DBS, but more patients in the LT reports met the criteria for response (defined as a reduction in Y-BOCS scores > 35%: ST, 60.6% vs LT, 70.7%). According to the results, the response in the first year predicts the extent to which an OCD patient will benefit from DBS, since the maximum symptom reduction was achieved in most responders in the first 12-14 mo after implantation. Reports indicate a consistent tendency for this early improvement to be maintained to the mid-term for most patients; but it is still controversial whether this improvement persists, increases or decreases in the long term. Three different patterns of LT response emerged from the analysis: 49.5% of patients had good and sustained response to DBS, 26.6% were non responders, and 22.5% were partial responders, who might improve at some point but experience relapses during follow-up. A significant improvement in depressive symptoms and global functionality was observed in most studies, usually (although not always) in parallel with an improvement in obsessive symptoms. Most adverse effects of DBS were mild and transient and improved after adjusting stimulation parameters; however, some severe adverse events including intracranial hemorrhages and infections were also described. Hypomania was the most frequently reported psychiatric side effect. The relationship between DBS and suicide risk is still controversial and requires further study. Finally, to date, no clear clinical or biological predictors of response can be established, probably because of the differences between studies in terms of the neuroanatomical targets and stimulation protocols assessed.CONCLUSIONThe present review confirms that DBS is a promising therapy for patients with severe resistant OCD, providing both ST and LT evidence of efficacy.