Impedance Characteristics of Stimulation Contacts in Deep Brain Stimulation of the Anterior Nucleus of the Thalamus and Its Relationship to Seizure Outcome in Patients With Refractory Epilepsy

Long-term seizure reduction in generalized epilepsy after anterior nucleus of the thalamus stimulation

INTRODUCTION

In 2018 the FDA approved the use of anterior nucleus of the thalamus (ANT) deep brain stimulation (DBS) for focal epilepsy in response to the results of the Stimulation of the Anterior Nucleus of Thalamus for Epilepsy (SANTÉ) double-blind randomized controlled trial. While generalized epilepsy (GE) was never assessed in this trial, subsequent follow up clarified that focal to bilateral tonic-clonic seizures were reduced in these subjects. In rare cases ANT DBS has nonetheless been pursued for patients with GE.

METHODS

We report a 27-year-old male with idiopathic GE who was successfully treated with ANT DBS. Prior to DBS, the patient typically had three or four generalized tonic-clonic seizures (GTCS) per week, amongst other seizures, and was refractory to both medication and vagal nerve stimulation (VNS). We also systematically reviewed the literature to understand the extent to which ANT DBS has been used in GE, under what circumstances, and with what results.

RESULTS

Five years since the introduction of ANT DBS, the patient has remained free of GTCS. Over this time, other seizures were also markedly reduced. For the systematic review, a comprehensive literature search using PubMed, Cochrane, and Google Scholar identified 23 GE patients treated with ANT DBS across 13 publications. 13 patients had patient-specific seizure outcomes reported. Clinical findings, seizure characteristics, and outcomes were summarized, demonstrating that ANT DBS surgery typically occurred after failed VNS and was usually effective, including 3 patients who became free of GTCS.

CONCLUSION

This anecdotal evidence of effectiveness suggests that some GE networks can be modulated by high-frequency stimulation at the ANT node. When established therapies have failed, ANT DBS is a therapeutic option, but the treatment requires further structured research in treating GE.

Advancing thalamic neuromodulation in epilepsy: Bridging adult data to pediatric care

Thalamic neuromodulation has emerged as a treatment option for drug-resistant epilepsy (DRE) with widespread and/or undefined epileptogenic networks. While deep brain stimulation (DBS) and responsive neurostimulation (RNS) depth electrodes offer means for electrical stimulation of the thalamus in adult patients with DRE, the application of thalamic neuromodulation in pediatric epilepsy remains limited. To address this gap, the Neuromodulation Expert Collaborative was established within the Pediatric Epilepsy Research Consortium (PERC) Epilepsy Surgery Special Interest Group. In this expert review, existing evidence and recommendations for thalamic neuromodulation modalities using DBS and RNS are summarized, with a focus on the anterior (ANT), centromedian(CMN), and pulvinar nuclei of the thalamus. To-date, only DBS of the ANT is FDA approved for treatment of DRE in adult patients based on the results of the pivotal SANTE (Stimulation of the Anterior Nucleus of Thalamus for Epilepsy) study. Evidence for other thalamic neurmodulation indications and targets is less abundant. Despite the lack of evidence, positive responses to thalamic stimulation in adults with DRE have led to its off-label use in pediatric patients. Although caution is warranted due to differences between pediatric and adult epilepsy, the efficacy and safety of pediatric neuromodulation appear comparable to that in adults. Indeed, CMN stimulation is increasingly accepted for generalized and diffuse onset epilepsies, with recent completion of one randomized trial. There is also growing interest in using pulvinar stimulation for temporal plus and posterior quadrant epilepsies with one ongoing clinical trial in Europe. The future of thalamic neuromodulation holds promise for revolutionizing the treatment landscape of childhood epilepsy. Ongoing research, technological advancements, and collaborative efforts are poised to refine and improve thalamic neuromodulation strategies, ultimately enhancing the quality of life for children with DRE.

Functional network dynamics between the anterior thalamus and the cortex in deep brain stimulation for epilepsy

Owing to its unique connectivity profile with cortical brain regions, and its suggested role in the subcortical propagation of seizures, the anterior nucleus of the thalamus (ANT) has been proposed as a key deep brain stimulation (DBS) target in drug-resistant epilepsy. However, the spatio-temporal interaction dynamics of this brain structure, and the functional mechanisms underlying ANT DBS in epilepsy remain unknown. Here, we study how the ANT interacts with the neocortex in vivo in humans and provide a detailed neurofunctional characterization of mechanisms underlying the effectiveness of ANT DBS, aiming at defining intraoperative neural biomarkers of responsiveness to therapy, assessed at 6 months post-implantation as the reduction in seizure frequency. A cohort of 15 patients with drug-resistant epilepsy (n = 6 males, age = 41.6 ± 13.79 years) underwent bilateral ANT DBS implantation. Using intraoperative cortical and ANT simultaneous electrophysiological recordings, we found that the ANT is characterized by high amplitude θ (4-8 Hz) oscillations, mostly in its superior part. The strongest functional connectivity between the ANT and the scalp EEG was also found in the θ band in ipsilateral centro-frontal regions. Upon intraoperative stimulation in the ANT, we found a decrease in higher EEG frequencies (20-70 Hz) and a generalized increase in scalp-to-scalp connectivity. Crucially, we observed that responders to ANT DBS treatment were characterized by higher EEG θ oscillations, higher θ power in the ANT, and stronger ANT-to-scalp θ connectivity, highlighting the crucial role of θ oscillations in the dynamical network characterization of these structures. Our study provides a comprehensive characterization of the interaction dynamic between the ANT and the cortex, delivering crucial information to optimize and predict clinical DBS response in patients with drug-resistant epilepsy.

Initial case series of a novel sensing deep brain stimulation device in drug-resistant epilepsy and consistent identification of alpha/beta oscillatory activity: A feasibility study

OBJECTIVE

Here, we report a retrospective, single-center experience with a novel deep brain stimulation (DBS) device capable of chronic local field potential (LFP) recording in drug-resistant epilepsy (DRE) and explore potential electrophysiological biomarkers that may aid DBS programming and outcome tracking.

METHODS

Five patients with DRE underwent thalamic DBS, targeting either the bilateral anterior (n = 3) or centromedian (n = 2) nuclei. Postoperative electrode lead localizations were visualized in Lead-DBS software. Local field potentials recorded over 12-18 months were tracked, and changes in power were associated with patient events, medication changes, and stimulation. We utilized a combination of lead localization, in-clinic broadband LFP recordings, real-time LFP response to stimulation, and chronic recordings to guide DBS programming.

RESULTS

Four patients (80%) experienced a >50% reduction in seizure frequency, whereas one patient had no significant reduction. Peaks in the alpha and/or beta frequency range were observed in the thalamic LFPs of each patient. Stimulation suppressed these LFP peaks in a dose-dependent manner. Chronic timeline data identified changes in LFP amplitude associated with stimulation, seizure occurrences, and medication changes. We also noticed a circadian pattern of LFP amplitudes in all patients. Button-presses during seizure events via a mobile application served as a digital seizure diary and were associated with elevations in LFP power.

SIGNIFICANCE

We describe an initial cohort of patients with DRE utilizing a novel sensing DBS device to characterize potential LFP biomarkers of epilepsy that may be associated with seizure control after DBS in DRE. We also present a new workflow utilizing the Percept device that may optimize DBS programming using real-time and chronic LFP recording.

Anterior thalamic deep brain stimulation in epilepsy patients refractory to vagus nerve stimulation: A single center observational study

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Patients with drug resistant epilepsy refractory to treatment with vagal nerve stimulation benefited from anterior thalamic deep brain stimulation.

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We report a combined neuromodulation approach of simultaneous vagal nerve and deep brain stimulation.

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Additional studies are needed to assess safety and efficacy of simultaneous VNS and DBS treatment.

Anterior thalamic deep brain stimulation (DBS) is a palliative treatment that may be considered in patients with drug resistant epilepsy (DRE) that fail treatment with vagus nerve stimulation (VNS). Combining VNS and DBS treatment is a therapeutic approach rarely reported. This single center observational study aims to describe response to DBS treatment in 11 epilepsy patients resistant to medications and VNS. Patients either had inactivated VNS (DBS only) or were treated with simultaneous DBS and VNS (DBS-VNS). Focal impaired awareness (FIA) and most disabling seizure rates were examined pre-DBS implantation, 3 months following implantation, and last follow up. Overall, a decrease in FIA (47.0 ± 30.7 %, p = 0.02) and most disabling seizure rate (54.8 ± 34.2 %, p = 0.03) was seen at last follow-up (average follow-up 28.5 ± 13.5 months). Eight of 11 patients were DBS responders (most disabling seizure rate reduction above 50%). No difference in seizure control was found between seven DBS only and four DBS-VNS patients. Our results argue that patients who have failed antiseizure medication and VNS therapies, could benefit from better seizure control if treated with adjunctive DBS. Larger prospective studies are needed to assess the efficacy and safety of combined neurostimulation treatments in DRE.