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Thirty Years of Global Deep Brain Stimulation: "Plus ça change, plus c'est la même chose"?

The advent of deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson's disease 30 years ago has ushered a global breakthrough of DBS as a universal method for therapy and research in wide areas of neurology and psychiatry. The literature of the last three decades has described numerous concepts and practices of DBS, often branded as novelties or discoveries. However, reading the contemporary publications often elicits a sense of déjà vu in relation to several methods, attributes, and practices of DBS. Here, we review various applications and techniques of the modern-era DBS and compare them with practices of the past. Compared with modern literature, publications of the old-era functional stereotactic neurosurgery, including old-era DBS, show that from the very beginning multidisciplinarity and teamwork were often prevalent and insisted upon, ethical concerns were recognized, brain circuitries and rational for brain targets were discussed, surgical indications were similar, closed-loop stimulation was attempted, evaluations of surgical results were debated, and controversies were common. Thus, it appears that virtually everything done today in the field of DBS bears resemblance to old-time practices, or has been done before, albeit with partly other tools and techniques. Movement disorders remain the main indications for modern DBS as was the case for lesional surgery and old-era DBS. The novelties today consist of the STN as the dominant target for DBS, the tremendous advances in computerized brain imaging, the sophistication and versatility of implantable DBS hardware, and the large potential for research. Many aspects of contemporary DBS bear strong resemblance to practices of the past. The dominant clinical indications remain movement disorders with virtually the same brain targets as in the past, with one exception: the STN. Other novel brain targets - that are so far subject to DBS trials - are the pedunculopontine nucleus for gait freezing, the anteromedial internal pallidum for Gilles de la Tourette and the fornix for Alzheimer's disease. The major innovations and novelties compared to the past concern mainly the unmatched level of research activity, its high degree of sponsorship, and the outstanding advances in technology that have enabled multimodal brain imaging and the miniaturization, versatility, and sophistication of implantable hardware. The greatest benefit for patients today, compared to the past, is the higher level of precision and safety of DBS, and of all functional stereotactic neurosurgery.

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Stereotactic Staged Asymmetric Bilateral Radiofrequency Lesioning for Parkinson's Disease.

Parkinson's disease (PD) is one of the most common neurodegenerative progressive disorders. Despite the dominance of neurostimulation technology, stereotactic lesioning operations play a significant role in the treatment of PD. The aim of the study was to evaluate the effectiveness and safety of staged bilateral asymmetric radiofrequency (RF) stereotactic lesioning in a highly selected group of PD patients. A retrospective review of 418 consecutive patients undergoing stereotactic ablation for advanced PD at our institution revealed 28 patients who underwent staged asymmetric bilateral ablation. In this subset, after initial RF thalamotomy, contralateral pallidotomy was performed in 16 (57.1%) patients (group Vim-GPi), and contralateral lesion of the subthalamic nucleus (STN) was performed in 12 (32.9%) patients (group Vim-STN). The mean duration of disease before the first surgery was 9.9 ± 0.8 years. The mean interval between the two operations was 3.5 ± 0.4 years (range, 1-10 years); in the Vim-GPi group, it was 3.1 ± 0.4 years; and in the Vim-STN group, it was 4.3 ± 0.1 years. After the second operation, the long-term follow-up lasted from 1 to 8 years (mean 4.8 ± 0.5 years). All patients were evaluated 1 year after the second operation. One year after staged bilateral lesioning, the mean tremor score improved from baseline, prior to the first operation, from 19.8 to 3.8 (improvement of 81%), the overall mean rigidity score improved from 11.0 to 3.7 (improvement of 66%), and hypokinesia improved from 14.8 to 8.9 (improvement of 40%). One year after staged bilateral lesioning, the total UPDRS score improved in the Vim-GPi group by 47% in the OFF and 45.9% in the ON states. In the Vim-STN group, the total UPDRS score improved from baseline, prior to the first operation, by 44.8% in the OFF and 51.6% in the ON states. Overall, levodopa dose was reduced by 43.4%. Neurological complications were observed in 4 (14.3%) cases; among them, 1 (3.6%) patient had permanent events related to local ischemia after pallidotomy. Staged asymmetric bilateral stereotactic RF lesioning can be a safe and effective method in highly selected patients with advanced PD, particularly where deep brain stimulation is not available or desirable. Careful identification and selection of patients for ablative surgery allow achieving optimal results in the treatment of PD with bilateral symptoms.

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Distinct Biomarkers of ANT Stimulation and Seizure Freedom in an Epilepsy Patient with Ambulatory Hippocampal Electrocorticography

Introduction: Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) and responsive neurostimulation (RNS) of the hippocampus are the predominant approaches to brain stimulation for treating mesial temporal lobe epilepsy (MTLE). Both are similarly effective at reducing seizures in drug-resistant patients, but the underlying mechanisms are poorly understood. In rare cases where it is clinically indicated to use RNS and DBS simultaneously, ambulatory electrophysiology from RNS may provide the opportunity to measure the effects of ANT DBS in the putative seizure onset zone and identify biomarkers associated with clinical improvement. Here, one such patient became seizure free, allowing us to identify and compare the changes in hippocampal electrophysiology associated with ANT stimulation and seizure freedom. Methods: Ambulatory electrocorticography and clinical history were retrospectively analyzed for a patient treated with RNS and DBS for MTLE. DBS artifacts were used to identify ANT stimulation periods on RNS recordings and measure peri-stimulus electrographic changes. Clinical history was used to determine the chronic electrographic changes associated with seizure freedom. Results: ANT stimulation acutely suppressed hippocampal gamma (25–90Hz) power, with minimal theta (4–8Hz) suppression and without clear effects on seizure frequency. Eventually, the patient became seizure free alongside the emergence of chronic gamma increase and theta suppression, which started at the same time as clobazam was introduced. Both seizure freedom and the associated electrophysiology persisted after inadvertent DBS discontinuation, further implicating the clobazam relationship. Unexpectedly, RNS detections and long episodes increased, although they were not considered to be electrographic seizures, and the patient remained clinically seizure free. Conclusion: ANT stimulation and seizure freedom were associated with distinct, dissimilar spectral changes in RNS-derived electrophysiology. The time course of these changes supported a new medication as the most likely cause of clinical improvement. Broadly, this work showcases the use of RNS recordings to interpret the effects of multimodal therapy. Specifically, it lends additional credence to hippocampal theta suppression as a biomarker previously associated with seizure reduction in RNS patients.

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Hemorrhagic Safety of Magnetic Resonance-Guided Focused Ultrasound Thalamotomy for Tremor without Interruption of Antiplatelet or Anticoagulant Therapy

Introduction: Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy is an incision-less ablative technique used to treat medically refractory tremor. Although intracerebral hemorrhage has not been reported with MRgFUS thalamotomy for the treatment of movement disorders, clinicians commonly interrupt active blood thinning medications prior to the procedure or offer gamma knife radiosurgery instead. However, MRgFUS uses focal thermoablation, and bleeding risk is likely minimal. This study aimed to evaluate the safety of MRgFUS thalamotomy in patients with essential tremor (ET) and tremor-dominant Parkinson’s disease (PD) without interrupting anticoagulant or antiplatelet therapies. Methods: This was a single-center retrospective case series of all patients with ET or PD undergoing MRgFUS from February 2019 through December 2022 (n = 96). Demographic variables and medications taken at the time of surgery were obtained. Our primary outcome was the type and frequency of hemorrhagic complications noted on the operative report or postoperative imaging. Results: The mean age of patients was 74.2 years, and 26% were female. Forty patients were taking ≥1 antiplatelet or anticoagulant medications. No patient actively taking anticoagulant or antiplatelet therapies had a hemorrhagic complication during or <48 h after the procedure. Conclusion: The frequency of intra- or postoperative complications from MRgFUS was not higher in patients actively taking anticoagulant or antiplatelet therapies relative to those who were not. Our findings suggest that MRgFUS thalamotomy does not necessitate interrupting anticoagulant or antiplatelet therapies. However, given the limited number of patients actively taking these therapies in our cohort (n = 40), additional testing in large, prospective studies should be conducted to further establish safety.

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Deep Brain Stimulation for Pediatric Dystonia: Clinicians’ Perspectives on the Most Pressing Ethical Challenges

Introduction: Pediatric deep brain stimulation (pDBS) is commonly used to manage treatment-resistant primary dystonias with favorable results and more frequently used for secondary dystonia to improve quality of life. There has been little systematic empirical neuroethics research to identify ethical challenges and potential solutions to ensure responsible use of DBS in pediatric populations. Methods: Clinicians (n = 29) who care for minors with treatment-resistant dystonia were interviewed for their perspectives on the most pressing ethical issues in pDBS. Results: Using thematic content analysis to explore salient themes, clinicians identified four pressing concerns: (1) uncertainty about risks and benefits of pDBS (22/29; 72%) that poses a challenge to informed decision-making; (2) ethically navigating decision-making roles (15/29; 52%), including how best to integrate perspectives from diverse stakeholders (patient, caregiver, clinician) and how to manage surrogate decisions on behalf of pediatric patients with limited capacity to make autonomous decisions; (3) information scarcity effects on informed consent and decision quality (15/29; 52%) in the context of patient and caregivers’ expectations for treatment; and (4) narrow regulatory status and access (7/29; 24%) such as the lack of FDA-approved indications that contribute to decision-making uncertainty and liability and potentially limit access to DBS among patients who may benefit from it. Conclusion: These results suggest that clinicians are primarily concerned about ethical limitations of making difficult decisions in the absence of informational, regulatory, and financial supports. We discuss two solutions already underway, including supported decision-making to address uncertainty and further data sharing to enhance clinical knowledge and discovery.

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Publication Rates and Characteristics of Clinical Trials in Deep Brain and Responsive Neurostimulation

Introduction: Prompt dissemination of clinical trial results is essential for ensuring the safety and efficacy of intracranial neurostimulation treatments, including deep brain stimulation (DBS) and responsive neurostimulation (RNS). However, the frequency and completeness of results publication, and reasons for reporting delays, are unknown. Moreover, the patient populations, targeted anatomical locations, and stimulation parameters should be clearly reported for both reproducibility and to identify lacunae in trial design. Here, we examine DBS and RNS trials from 1997 to 2022, chart their characteristics, and examine rates and predictors of results reporting. Methods: Trials were identified using <ext-link ext-link-type="uri" xlink:href="http://ClinicalTrials.gov" xmlns:xlink="http://www.w3.org/1999/xlink">ClinicalTrials.gov</ext-link>. Associated publications were identified using <ext-link ext-link-type="uri" xlink:href="http://ClinicalTrials.gov" xmlns:xlink="http://www.w3.org/1999/xlink">ClinicalTrials.gov</ext-link> and <ext-link ext-link-type="uri" xlink:href="http://PubMed.gov" xmlns:xlink="http://www.w3.org/1999/xlink">PubMed.gov</ext-link>. Pearson’s χ<sup>2</sup> tests were used to assess differences in trial characteristics between published and unpublished trials. Results: Across 449 trials, representing a cumulative cohort of 42,769 patient interventions, there were 37 therapeutic indications and 44 stimulation targets. The most common indication and target were Parkinson’s disease (40.55%) and the subthalamic nucleus (35.88%), respectively. Only 0.89% of trials were in pediatric patients (11.58% were mixed pediatric and adult). Explored targets represented 75% of potential basal ganglia targets but only 29% of potential thalamic targets. Allowing a 1-year grace period after trial completion, 34/169 (20.12%) had results reported on <ext-link ext-link-type="uri" xlink:href="http://ClinicalTrials.gov" xmlns:xlink="http://www.w3.org/1999/xlink">ClinicalTrials.gov</ext-link>, and 107/169 (63.31%) were published. ∼80% of published trials included details about stimulation parameters used. Published and unpublished trials did not significantly differ by trial characteristics. Conclusion: We highlight key knowledge and performance gaps in DBS and RNS trial research. Over one-third of trials remain unpublished >1 year after completion; pediatric trials are scarce; most of the thalamus remains unexplored; about one-in-five trials fail to report stimulation parameters; and movement disorders comprise the most studied indications.

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Intracranial Bleeding in Deep Brain Stimulation Surgery: A Systematic Review and Meta-Analysis

Background: Deep brain stimulation (DBS) is a neurosurgical treatment used for the treatment of movement disorders. Surgical and perioperative complications, although infrequent, can result in clinically significant neurological impairment. Objectives: In this study, we evaluated the incidence and risk factors of intracranial bleeding in DBS surgery. Method: Medline, EMBASE, and Cochrane were screened in line with PRISMA 2020 guidelines to capture studies reporting on the incidence of hemorrhagic events in DBS. After removing duplicates, the search yielded 1,510 papers. s were evaluated by two independent reviewers for relevance. A total of 386 abstracts progressed to the full-text screen and were assessed against eligibility criteria. A total of 151 studies met the criteria and were included in the analysis. Any disagreement between the reviewers was resolved by consensus. Relevant data points were extracted and analyzed in OpenMeta [Analyst] software. Results: The incidence of intracranial bleeding was 2.5% (95% CI: 2.2–2.8%) per each patient and 1.4% (95% CI: 1.2–1.6%) per each implanted lead. There was no statistically significant difference across implantation targets and clinical indications. Patients who developed an intracranial bleed were on average 5 years older (95% CI: 1.26–13.19), but no difference was observed between the genders (p = 0.891). A nonsignificant trend was observed for a higher risk of bleeding in patients with hypertension (OR: 2.99, 95% CI: 0.97–9.19) (p = 0.056). The use of microelectrode recording did not affect the rate of bleeding (p = 0.79). Conclusions: In this review, we find that the rate of bleeding per each implanted lead was 1.4% and that older patients had a higher risk of hemorrhage.

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Ambulatory Local Field Potential Recordings from the Thalamus in Epilepsy: A Feasibility Study

Introduction: Stimulation of the thalamus is gaining favor in the treatment of medically refractory multifocal and generalized epilepsy. Implanted brain stimulators capable of recording ambulatory local field potentials (LFPs) have recently been introduced, but there is little information to guide their use in thalamic stimulation for epilepsy. This study sought to assess the feasibility of chronically recording ambulatory interictal LFP from the thalamus in patients with epilepsy. Methods: In this pilot study, ambulatory LFP was recorded from patients who underwent sensing-enabled deep brain stimulation (DBS, 2 participants) or responsive neurostimulation (RNS, 3 participants) targeting the anterior nucleus of the thalamus (ANT, 2 electrodes), centromedian nucleus (CM, 7 electrodes), or medial pulvinar (PuM, 1 electrode) for multifocal or generalized epilepsy. Time-domain and frequency-domain LFP was investigated for epileptiform discharges, spectral peaks, circadian variation, and peri-ictal patterns. Results: Thalamic interictal discharges were visible on ambulatory recordings from both DBS and RNS. At-home interictal frequency-domain data could be extracted from both devices. Spectral peaks were noted at 10–15 Hz in CM, 6–11 Hz in ANT, and 19–24 Hz in PuM but varied in prominence and were not visible in all electrodes. In CM, 10–15 Hz power exhibited circadian variation and was attenuated by eye opening. Conclusion: Chronic ambulatory recording of thalamic LFP is feasible. Common spectral peaks can be observed but vary between electrodes and across neural states. DBS and RNS devices provide a wealth of complementary data that have the potential to better inform thalamic stimulation for epilepsy.

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Preoperative Frailty Predicts Worse Outcomes after Microvascular Decompression for Trigeminal Neuralgia, Hemifacial Spasm, and Glossopharyngeal Neuralgia: A Multicenter Analysis of 1,473 Patients from a Prospective Surgical Registry

Introduction: Microvascular decompression (MVD) is an efficacious neurosurgical intervention for patients with medically intractable neurovascular compression syndromes. However, MVD may occasionally cause life-threatening or altering complications, particularly in patients unfit for surgical operations. Recent literature suggests a lack of association between chronological age and surgical outcomes for MVD. The Risk Analysis Index (RAI) is a validated frailty tool for surgical populations (both clinical and large database). The present study sought to evaluate the prognostic ability of frailty, as measured by RAI, to predict outcomes for patients undergoing MVD from a large multicenter surgical registry. Methods: The American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) database (2011–2020) was queried using diagnosis/procedure codes for patients undergoing MVD procedures for trigeminal neuralgia (n = 1,211), hemifacial spasm (n = 236), or glossopharyngeal neuralgia (n = 26). The relationship between preoperative frailty (measured by RAI and 5-factor modified frailty index [mFI-5]) for primary endpoint of adverse discharge outcome (AD) was analyzed. AD was defined as discharge to a facility which was not home, hospice, or death within 30 days. Discriminatory accuracy for prediction of AD was assessed by computation of C-statistics (with 95% confidence interval) from receiver operating characteristic (ROC) curve analysis. Results: Patients undergoing MVD (N = 1,473) were stratified by RAI frailty bins: 71% with RAI 0–20, 28% with RAI 21–30, and 1.2% with RAI 31+. Compared to RAI score 19 and below, RAI 20 and above had significantly higher rates of postoperative major complications (2.8% vs. 1.1%, p = 0.01), Clavien-Dindo grade IV complications (2.8% vs. 0.7%, p = 0.001), and AD (6.1% vs. 1.0%, p < 0.001). The rate of primary endpoint was 2.4% (N = 36) and was positively associated with increasing frailty tier: 1.5% in 0–20, 5.8% in 21–30, and 11.8% in 31+. RAI score demonstrated excellent discriminatory accuracy for primary endpoint in ROC analysis (C-statistic: 0.77, 95% CI: 0.74–0.79) and demonstrated superior discrimination compared to mFI-5 (C-statistic: 0.64, 95% CI: 0.61–0.66) (DeLong pairwise test, p = 0.003). Conclusions: This was the first study to link preoperative frailty to worse surgical outcomes after MVD surgery. RAI frailty score predicts AD after MVD with excellent discrimination and holds promise for preoperative counseling and risk stratification of surgical candidates. A risk assessment tool was developed and deployed with a user-friendly calculator: <ext-link ext-link-type="uri" xlink:href="https://nsgyfrailtyoutcomeslab.shinyapps.io/microvascularDecompression" xmlns:xlink="http://www.w3.org/1999/xlink">https://nsgyfrailtyoutcomeslab.shinyapps.io/microvascularDecompression</ext-link>.

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