Bilateral anterior capsulotomy for intractable depression

Ventral targeted anterior capsulotomy for treatment-resistant depression and obsessive-compulsive disorder: A treatment method with cases

BACKGROUND

Ablative surgery using bilateral anterior capsulotomy (BAC) is an option for treatment resistant depression (TRD) and obsessive-compulsive disorder (TROCD). The location and extent of the lesion within anterior limb of the internal capsule (ALIC) remains uncertain. Accumulating evidence has suggested that the lesion should be located ventrally while limiting the dorsal extent. Our center is now targeting specific fiber tracts within the lower half of the ALIC.

METHOD

Presurgical diffusion tensor Magnetic Resonance Imaging (MRI) was used to identify individual fibre tracts within the ventral aspect of the ALIC in the last two patients who underwent BAC at our center. One patient had TRD and the other had both TROCD and TRD. Radiofrequency-induced thermal lesions were created in the identified targets with lesion volumes between 20 and 229 mm3 (average 95 mm3).

FINDINGS

Both patients were responders with neither experiencing significant side effects including compromised executive functions.

LIMITATIONS

The generalizability of our findings is limited because the outcome is based on two subjects.

CONCLUSION

This work suggests that BAC can be individually tailored and more limited to the ventral aspect of the ALIC and is effective and safe for TRD and TROCD. Accumulating data also suggests that to be clinically effective the length of the capsulotomy should be about 10mm. BAC's use may increase with the growing utilization and mastery of magnetic resonance guided focused ultrasound.

Noninvasive Capsulotomy for Refractory Depression by Frameless Stereotactic Radiosurgery

PURPOSE

Effective treatment options for refractory depression are needed. Recent advancements permit both precise ablative radiation and functional neurologic connectome analysis using standard MRI. We combined these innovations to perform stereotactic radiosurgical capsulotomy for the treatment of medically refractory major depressive disorder and study connectome response using a novel tractography-based approach.

METHODS AND MATERIALS

Patients with medically refractory depression were enrolled on a prospective pilot single-arm observational trial from 2020 to 2021 at a single academic tertiary referral center. Bilateral ablation of the anterior limb of the internal capsule was accomplished by mask-based linear accelerator stereotactic radiosurgery. Beck's Depression Inventory measured efficacy. Montreal Cognitive Assessment evaluated cognition.

RESULTS

Three patients were enrolled. Depression burden was improved by 88% at 12 month follow-up and by 55% at 18 month follow-up for patient 1 and 2, respectively. Patient 1 discontinued ketamine therapy, and patient 2 discontinued electroconvulsive therapy. Patient 3 reported global improvement in symptoms and function at 3 months. All 3 patients had reduction or resolution of suicidal ideation. No patient experienced cognitive decline or neurologic toxicity, and MoCA score, as well as subjective patient-reported evaluations of concentration and attention, were superior after treatment. Tractography confirmed intended disruption of the cortico-striatal-thalamo-cortical loop with structural reorganization in the connectome. Connectome change was consistent between patients. Observed increases in caudate and putamen connectivity and decreases in thalamic connectivity may explain improved concentration, attention, and depression. The diversity and magnitude of connectome change may correlate with degree of clinical response.

CONCLUSIONS

In three patients with refractory depression, radiosurgical capsulotomy significantly reduced the burden of depression. Functional connectome reorganization offers neurobiological evidence to support further investigations of the role of radiosurgery in depression.

A taxonomy of the brain's white matter: twenty-one major tracts for the 21st century

The functional and computational properties of brain areas are determined, in large part, by their connectivity profiles. Advances in neuroimaging and network neuroscience allow us to characterize the human brain noninvasively, but a comprehensive understanding of the human brain demands an account of the anatomy of brain connections. Long-range anatomical connections are instantiated by white matter, which itself is organized into tracts. These tracts are often disrupted by central nervous system disorders, and they can be targeted by neuromodulatory interventions, such as deep brain stimulation. Here, we characterized the connections, morphology, traversal, and functions of the major white matter tracts in the brain. There are major discrepancies across different accounts of white matter tract anatomy, hindering our attempts to accurately map the connectivity of the human brain. However, we are often able to clarify the source(s) of these discrepancies through careful consideration of both histological tract-tracing and diffusion-weighted tractography studies. In combination, the advantages and disadvantages of each method permit novel insights into brain connectivity. Ultimately, our synthesis provides an essential reference for neuroscientists and clinicians interested in brain connectivity and anatomy, allowing for the study of the association of white matter's properties with behavior, development, and disorders.

[Contemporary methods of non-drug therapy for depression]

The review presents information on the most effective current non-drug methods of treatment of depression used in practice. A review of publications in PubMed and PsycINFO and Cochrane Library over the past 10 years was conducted. Non-drug biological therapies demonstrate high efficacy in the reduction of depressive symptoms in patients with recurrent depressive disorder. The use of non-drug therapy does not preclude the continuation of pharmacological therapy. In order to choose an optimal method of treatment, the psychophysical state of a patient, severity of depressive symptoms, response to drug therapy, and possibility of prescribing pharmacological therapy should be taken into account, and the principles of evidence-based medicine should be taken into consideration when making a decision.

Examining cognitive change in magnetic resonance-guided focused ultrasound capsulotomy for psychiatric illness

Magnetic resonance-guided focused ultrasound (MRgFUS) anterior capsulotomy is a novel treatment option for patients with refractory obsessive compulsive disorder (OCD) or major depressive disorder (MDD). However, there is concern that lesional psychiatric surgery procedures may have adverse effects on cognition. In this study, we examined whether MRgFUS capsulotomy causes cognitive decline in patients with psychiatric illness. Ten patients with refractory OCD (n = 5) or MDD (n = 5) underwent MRgFUS capsulotomy. Cognitive functioning was measured at baseline as well as 6 months and 12 months postoperatively, with a battery of neuropsychological tests assessing domains of executive function, memory, and processing speed. Scores were analyzed at the individual-level, and changes ≥2 standard deviations were considered clinically significant. We also examined whether changes in clinical symptoms were associated with changes in cognitive performance. At baseline intellectual functioning was in the average to high-average range for the group. Following MRgFUS capsulotomy, there were no deteriorations in cognition that reached ≥2 standard deviations at 6 or 12 months. Eight out of ten patients demonstrated a ≥2 standard deviation improvement in at least one cognitive score at 6 or 12 months postoperatively. Improvements in clinical symptoms correlated significantly with self-reported improvements in frontal lobe function (p < 0.05), but not with objective measures of cognitive functioning. To summarize, MRgFUS capsulotomy did not result in cognitive decline in this cohort of patients with refractory OCD or MDD, suggesting that this procedure can be offered to patients with a very low risk of cognitive side effects.

Magnetic resonance-guided focused ultrasound capsulotomy for refractory obsessive compulsive disorder and major depressive disorder: clinical and imaging results from two phase I trials

Obsessive compulsive disorder (OCD) and major depressive disorder (MDD) are common, often refractory, neuropsychiatric conditions for which new treatment approaches are urgently needed. Magnetic resonance-guided focused ultrasound (MRgFUS) is a novel surgical technique permitting incisionless ablative neurosurgery. We examined the safety profile, clinical response, and imaging correlates of MRgFUS bilateral anterior capsulotomy in patients with refractory obsessive compulsive disorder (OCD, N = 6) and major depressive disorder (MDD, n = 6). There were no serious adverse events. Nonserious adverse events included headaches and pin-site swelling in 7/12 patients. The response rate was 4/6 and 2/6 in the OCD and MDD cohorts respectively. To delineate the white-matter tracts impacted by capsulotomy, a normative diffusion MRI-based structural connectome was used, revealing tracts terminating primarily in the frontal pole, medial thalamus, striatum, and medial-temporal lobe. Positron emission tomography (PET) analysis (nine subjects) revealed widespread decreases in metabolism bilaterally in the cerebral hemispheres at 6 months post treatment, as well as in the right hippocampus, amygdala, and putamen. A pretreatment seed-to-voxel resting-state functional magnetic resonance imaging (rs-fMRI) analysis (12 subjects) revealed three voxel clusters significantly associated with eventual clinical response. MRgFUS capsulotomy appears to be safe, well tolerated, and according to these initial results, may be an important treatment option for patients with refractory OCD and MDD. MRgFUS capsulotomy results in both targeted and widespread changes in neural activity, and neuroimaging may hold potential for the prediction of outcome.

The anterior limb of the internal capsule: Anatomy, function, and dysfunction

The last two decades have seen a re-emergence of neurosurgery for severe, refractory psychiatric diseases, largely due to the advent of more precise and safe operative techniques. Nevertheless, the optimal targets for these surgeries remain a matter of debate, and are often grandfathered from experiences in the late 20th century. To better explore the rationale for one target in particular - the anterior limb of the internal capsule (ALIC) - we comprehensively reviewed all available literature on its role in the pathophysiology and treatment of mental illness. We first provide an overview of its functional anatomy, followed by a discussion on its role in several prevalent psychiatric diseases. Given its structural integration into the limbic system and involvement in a number of cognitive and emotional processes, the ALIC is a robust target for surgical treatment of refractory psychiatric diseases. The advent of novel neuroimaging techniques, coupled with image-guided therapeutics and neuromodulatory treatments, will continue to enable study on the ALIC in mental illness.

Tractographic description of major subcortical projection pathways passing the anterior limb of the internal capsule. Corticopetal organization of networks relevant for psychiatric disorders

BACKGROUND

Major depression (MD) and obsessive-compulsive disorder (OCD) are psychiatric diseases with a huge impact on individual well-being. Despite optimal treatment regiments a subgroup of patients remains treatment resistant and stereotactic surgery (stereotactic lesion surgery, SLS or Deep Brain Stimulation, DBS) might be an option. Recent research has described four networks related to MD and OCD (affect, reward, cognitive control, default network) but only on a cortical and the adjacent sub-cortical level. Despite the enormous impact of comparative neuroanatomy, animal science and stereotactic approaches a holistic theory of subcortical and cortical network interactions is elusive. Because of the dominant hierarchical rank of the neocortex, corticofugal approaches have been used to identify connections in subcortical anatomy without anatomical priors and in part confusing results. We here propose a different corticopetal approach by identifying subcortical networks and search for neocortical convergences thereby following the principle of phylogenetic and ontogenetic network development.

MATERIAL AND METHODS

This work used a diffusion tensor imaging data from a normative cohort (Human Connectome Project, HCP; n = 200) to describe eight subcortical fiber projection pathways (PPs) from subthalamic nucleus (STN), substantia nigra (SNR), red nucleus (RN), ventral tegmental area (VTA), ventrolateral thalamus (VLT) and mediodorsal thalamus (MDT) in a normative space (MNI). Subcortical and cortical convergences were described including an assignment of the specific pathways to MD/OCD-related networks. Volumes of activated tissue for different stereotactic stimulation sites and procedures were simulated to understand the role of the distinct networks, with respect to symptoms and treatment of OCD and MD.

RESULTS

The detailed course of eight subcortical PPs (stnPP, snrPP, rnPP, vlATR, vlATRc, mdATR, mdATRc, vtaPP/slMFB) were described together with their subcortical and cortical convergences. The anterior limb of the internal capsule can be subdivided with respect to network occurrences in ventral-dorsal and medio-lateral gradients. Simulation of stereotactic procedures for OCD and MD showed dominant involvement of mdATR/mdATRc (affect network) and vtaPP/slMFB (reward network).

DISCUSSION

Corticofugal search strategies for the evaluation of stereotactic approaches without anatomical priors often lead to confusing results which do not allow for a clear assignment of a procedure to an involved network. According to our simulation of stereotactic procedures in the treatment of OCD and MD, most of the target regions directly involve the reward (and affect) networks, while side-effects can in part be explained with a co-modulation of the control network.

CONCLUSION

The here proposed corticopetal approach of a hierarchical description of 8 subcortical PPs with subcortical and cortical convergences represents a new systematics of networks found in all different evolutionary and distinct parts of the human brain.

Hypoactivity in the Paraterminal Gyrus Following Bilateral Anterior Capsulotomy

OBJECTIVE

Bilateral anterior capsulotomy (BAC) is one of the ablative neurosurgical procedures used to treat major depressive disorder or obsessive-compulsive disorder when all other therapies fail. Tristolysis, a reduction in sadness, is the most striking clinical effect of BAC and is seen in the first 1 to 2 weeks after surgery. This retrospective study measured regional cerebral blood flow (rCBF) following surgery to identify which cortical regions were impacted and could account for this clinical effect.

METHODS

All patients had their capsulotomies done in Vancouver by the same team. Pre- and postoperative single-photon emission computed tomography perfusion scans were analyzed for 10 patients with major depressive disorder and 3 with obsessive-compulsive disorder. rCBF was measured semiquantitatively by calculating the ratio between an identified region of interest and a whole brain reference area.

RESULTS

Decreased rCBF was found in the paraterminal gyri. Increased rCBF was found in the dorsolateral prefrontal cortices and in the left lateral temporal lobe.

CONCLUSIONS

BAC causes hypoactivity in the paraterminal gyri and is the most likely explanation for its tristolytic effect, suggesting that the paraterminal gyrus is the limbic cortical locus for the emotion of sadness. Increased activity in the dorsolateral prefrontal cortices may be occurring via connectional diaschisis, and suppression by overactive paraterminal gyri during depression may account for some of the neurocognitive deficits observed during depressive episodes.

Evolution of gamma knife capsulotomy for intractable obsessive-compulsive disorder

For more than half a century, stereotactic neurosurgical procedures have been available to treat patients with severe, debilitating symptoms of obsessive-compulsive disorder (OCD) that have proven refractory to extensive, appropriate pharmacological, and psychological treatment. Although reliable predictors of outcome remain elusive, the establishment of narrower selection criteria for neurosurgical candidacy, together with a better understanding of the functional neuroanatomy implicated in OCD, has resulted in improved clinical efficacy for an array of ablative and non-ablative intervention techniques targeting the cingulum, internal capsule, and other limbic regions. It was against this backdrop that gamma knife capsulotomy (GKC) for OCD was developed. In this paper, we review the history of this stereotactic radiosurgical procedure, from its inception to recent advances. We perform a systematic review of the existing literature and also provide a narrative account of the evolution of the procedure, detailing how the procedure has changed over time, and has been shaped by forces of evidence and innovation. As the procedure has evolved and adverse events have decreased considerably, favorable response rates have remained attainable for approximately one-half to two-thirds of individuals treated at experienced centers. A reduction in obsessive-compulsive symptom severity may result not only from direct modulation of OCD neural pathways but also from enhanced efficacy of pharmacological and psychological therapies working in a synergistic fashion with GKC. Possible complications include frontal lobe edema and even the rare formation of delayed radionecrotic cysts. These adverse events have become much less common with new radiation dose and targeting strategies. Detailed neuropsychological assessments from recent studies suggest that cognitive function is not impaired, and in some domains may even improve following treatment. We conclude this review with discussions covering topics essential for further progress of this therapy, including suggestions for future trial design given the unique features of GKC therapy, considerations for optimizing stereotactic targeting and dose planning using biophysical models, and the use of advanced imaging techniques to understand circuitry and predict response. GKC, and in particular its modern variant, gamma ventral capsulotomy, continues to be a reliable treatment option for selected cases of otherwise highly refractory OCD.

Functional Segmentation of the Anterior Limb of the Internal Capsule: Linking White Matter Abnormalities to Specific Connections

The anterior limb of the internal capsule (ALIC) carries thalamic and brainstem fibers from prefrontal cortical regions that are associated with different aspects of emotion, motivation, cognition processing, and decision-making. This large fiber bundle is abnormal in several psychiatric illnesses and a major target for deep brain stimulation. Yet, we have very little information about where specific prefrontal fibers travel within the bundle. Using a combination of tracing studies and diffusion MRI in male nonhuman primates, as well as diffusion MRI in male and female human subjects, we segmented the human ALIC into five regions based on the positions of axons from different cortical regions within the capsule. Fractional anisotropy (FA) abnormalities in patients with bipolar disorder were detected when FA was averaged in the ALIC segment that carries ventrolateral prefrontal cortical connections. Together, the results set the stage for linking abnormalities within the ALIC to specific connections and demonstrate the utility of applying connectivity profiles of large white matter bundles based on animal anatomic studies to human connections and associating disease abnormalities in those pathways with specific connections. The ability to functionally segment large white matter bundles into their components begins a new era of refining how we think about white matter organization and use that information in understanding abnormalities.SIGNIFICANCE STATEMENT The anterior limb of the internal capsule (ALIC) connects prefrontal cortex with the thalamus and brainstem and is abnormal in psychiatric illnesses. However, we know little about the location of specific prefrontal fibers within the bundle. Using a combination of animal tracing studies and diffusion MRI in animals and human subjects, we segmented the human ALIC into five regions based on the positions of axons from different cortical regions. We then demonstrated that differences in FA values between bipolar disorder patients and healthy control subjects were specific to a given segment. Together, the results set the stage for linking abnormalities within the ALIC to specific connections and for refining how we think about white matter organization in general.

Current and emerging brain applications of MR-guided focused ultrasound

MRI guided focused ultrasound is an emerging technique that uses acoustic energy to noninvasively treat intracranial disorders. At high frequencies, it can be used to raise tissue temperatures and ablate discrete brain targets with sub-millimeter accuracy. This application is currently under investigation for a broad range of clinical applications, including brain tumors, movement disorders, and psychiatric conditions. At low frequencies MRI guided focused ultrasound can be used to modulate neuronal activity and in conjunction with injected microbubbles, can open the blood-brain barrier to enhance the delivery of therapeutic compounds. The last decade has seen dramatic advances in the science of MRI guided focused ultrasound, helping elucidate both its mechanisms and potential in pre-clinical models, and its translational promise across myriad clinical applications. This review provides an update of current and emerging MRI guided focused ultrasound applications for intracranial disorders and describes future directions and challenges for the field.

The History and Future of Ablative Neurosurgery for Major Depressive Disorder

BACKGROUND

There is an urgent need to develop safe and effective treatments for patients with treatment-resistant depression (TRD). Several neurosurgical procedures have been developed to treat the dysfunctional brain circuits implicated in major depression.

OBJECTIVES

This review describes the most common ablative procedures used to treat major depressive disorder: anterior cingulotomy, subcaudate tractotomy, limbic leucotomy, and anterior capsulotomy. The efficacy and safety of each are discussed and compared with other current and emerging modalities, including deep brain stimulation (DBS) and MR-guided focused ultrasound (MRgFUS).

METHODS

The PubMed and MEDLINE electronic databases were used in this study, through July 2016. Keywords, including "treatment resistant depression," and "ablative neurosurgery," etc. were used to generate reference hits.

RESULTS

Approximately a third to half of patients who underwent ablative procedures achieved a treatment response and/or remission. The efficacy and safety profiles corresponding to both ablative procedures and DBS were very similar.

CONCLUSIONS

The longitudinal experience with ablative procedures shows that there remains an important role for accurate, discrete lesions in disrupting affective circuitry in the treatment of TRD. New modalities, such as MRgFUS, have the potential to further improve the accuracy of ablative procedures, while enhancing safety by obviating the need for open brain surgery.

Clinical improvements following bilateral anterior capsulotomy in treatment-resistant depression

BACKGROUND

The purpose of this study was to evaluate a programme of lesion surgery carried out on patients with treatment-resistant depression (TRD).

METHOD

This was a retrospective study looking at clinical and psychometric data from 45 patients with TRD who had undergone bilateral stereotactic anterior capsulotomy surgery over a period of 15 years, with the approval of the Mental Health Act Commission (37 with unipolar depression and eight with bipolar disorder). The Beck Depression Inventory (BDI) before and after surgery was used as the primary outcome measure. The Montgomery-Asberg Depression Rating Scale was administered and cognitive aspects of executive and memory functions were also examined. We carried out a paired-samples t test on the outcome measures to determine any statistically significant change in the group as a consequence of surgery.

RESULTS

Patients improved on the clinical measure of depression after surgery by -21.20 points on the BDI with a 52% change. There were no significant cognitive changes post-surgery. Six patients were followed up in 2013 by phone interview and reported a generally positive experience. No major surgical complications occurred.

CONCLUSIONS

With the limitations of an uncontrolled, observational study, our data suggest that capsulotomy can be an effective treatment for otherwise TRD. Performance on neuropsychological tests did not deteriorate.

The Co-evolution of Neuroimaging and Psychiatric Neurosurgery

The role of neuroimaging in psychiatric neurosurgery has evolved significantly throughout the field's history. Psychiatric neurosurgery initially developed without the benefit of information provided by modern imaging modalities, and thus lesion targets were selected based on contemporary theories of frontal lobe dysfunction in psychiatric disease. However, by the end of the 20th century, the availability of structural and functional magnetic resonance imaging (fMRI) allowed for the development of mechanistic theories attempting to explain the anatamofunctional basis of these disorders, as well as the efficacy of stereotactic neuromodulatory treatments. Neuroimaging now plays a central and ever-expanding role in the neurosurgical management of psychiatric disorders, by influencing the determination of surgical candidates, allowing individualized surgical targeting and planning, and identifying network-level changes in the brain following surgery. In this review, we aim to describe the coevolution of psychiatric neurosurgery and neuroimaging, including ways in which neuroimaging has proved useful in elucidating the therapeutic mechanisms of neuromodulatory procedures. We focus on ablative over stimulation-based procedures given their historical precedence and the greater opportunity they afford for post-operative re-imaging, but also discuss important contributions from the deep brain stimulation (DBS) literature. We conclude with a discussion of how neuroimaging will transition the field of psychiatric neurosurgery into the era of precision medicine.

Examining the relationship between fatigue and cognition after stroke: A systematic review

Many stroke survivors experience fatigue, which is associated with a variety of factors including cognitive impairment. A few studies have examined the relationship between fatigue and cognition and have obtained conflicting results. The aim of the current study was to review the literature on the relationship between fatigue and cognition post-stroke. The following databases were searched: EMBASE (1980-February, 2014), PsycInfo (1806-February, 2014), CINAHL (1937-February, 2014), MEDLINE (1946-February, 2014), Ethos (1600-February, 2014) and DART (1999-February, 2014). Reference lists of relevant papers were screened and the citation indices of the included papers were searched using Web of Science. Studies were considered if they were on adult stroke patients and assessed the following: fatigue with quantitative measurements (≥ 3 response categories), cognition using objective measurements, and the relationship between fatigue and cognition. Overall, 413 papers were identified, of which 11 were included. Four studies found significant correlations between fatigue and memory, attention, speed of information processing and reading speed (r = -.36 to .46) whereas seven studies did not. Most studies had limitations; quality scores ranged from 9 to 14 on the Critical Appraisal Skills Programme Checklists. There was insufficient evidence to support or refute a relationship between fatigue and cognition post-stroke. More robust studies are needed.

Ablative Limbic System Surgery: Review and Future Directions

The limbic system is a network of interconnected brain regions regulating emotion, memory, and behavior. Pathology of the limbic system can manifest as psychiatric disease, including obsessive-compulsive disorder and major depressive disorder. For patients with these disorders who have not responded to standard pharmacological and cognitive behavioral therapy, ablative surgery is a neurosurgical treatment option. The major ablative limbic system procedures currently used are anterior capsulotomy, dorsal anterior cingulotomy, subcaudate tractotomy, and limbic leucotomy. In this review, we include a brief history of ablative limbic system surgery leading up to its current form. Mechanistic justification for these procedures is considered in a discussion of the pathophysiology of psychiatric disease. We then discuss therapeutic efficacy as demonstrated by recent trials. Finally, we consider future directions, including the search for predictors of treatment response, the development of more precise targeting methods, and the use of advances in neuroimaging to track treatment response.

Intracranial applications of magnetic resonance-guided focused ultrasound

The ability to focus acoustic energy through the intact skull on to targets millimeters in size represents an important milestone in the development of neurotherapeutics. Magnetic resonance-guided focused ultrasound (MRgFUS) is a novel, noninvasive method, which--under real-time imaging and thermographic guidance--can be used to generate focal intracranial thermal ablative lesions and disrupt the blood-brain barrier. An established treatment for bone metastases, uterine fibroids, and breast lesions, MRgFUS has now been proposed as an alternative to open neurosurgical procedures for a wide variety of indications. Studies investigating intracranial MRgFUS range from small animal preclinical experiments to large, late-phase randomized trials that span the clinical spectrum from movement disorders, to vascular, oncologic, and psychiatric applications. We review the principles of MRgFUS and its use for brain-based disorders, and outline future directions for this promising technology.

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

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

Effectiveness and acceptability of deep brain stimulation (DBS) of the subgenual cingulate cortex for treatment-resistant depression: a systematic review and exploratory meta-analysis

BACKGROUND

Deep brain stimulation (DBS) applied to the subgenual cingulate cortex (SCC) has been recently investigated as a potential treatment for severe and chronic treatment-resistant depression (TRD). Given its invasive and experimental nature, a comprehensive evaluation of its effectiveness and acceptability is of paramount importance. Therefore, we conducted the present systematic review and exploratory meta-analysis.

METHODS

We searched the literature for English language prospective clinical trials on DBS of the SCC for TRD from 1999 through December 2012 using MEDLINE, EMBASE, PsycINFO, CENTRAL and SCOPUS, and performed a random effects exploratory meta-analysis using Event Rates and Hedges׳ g effect sizes.

RESULTS

Data from 4 observational studies were included, totaling 66 subjects with severe and chronic TRD. Twelve-month response and remission rates following DBS treatment were 39.9% (95% CI=28.4% to 52.8%) and 26.3% (95% CI=13% to 45.9%), respectively. Also, depression scores at 12 months post-DBS were significantly reduced (i.e., pooled Hedges׳ g effect size=-1.89 [95% CI=-2.64 to -1.15, p<0.0001]). Also, there was a significant decrease in depression scores between 3 and 6 months (Hedges׳ g=-0.27, p=0.003), but no significant changes from months 6 to 12. Finally, dropout rates at 12 months were 10.8% (95% CI=4.3% to 24.4%).

LIMITATIONS

Small number of included studies (most of which were open label), and limited long-term effectiveness data.

CONCLUSIONS

DBS applied to the SCC seems to be associated with relatively large response and remission rates in the short- and medium- to long-term in patients with severe TRD. Also, its maximal antidepressant effects are mostly observed within the first 6 months after device implantation. Nevertheless, these findings are clearly preliminary and future controlled trials should include larger and more representative samples, and focus on the identification of optimal neuroanatomical sites and stimulation parameters.