Electrical stimulation of the anterior nucleus of thalamus for treatment of refractory epilepsy

Epicranial focal cortex stimulation for minimally invasive neuromodulation of the epileptogenic region: A review

Epicranial focal cortex stimulation (FCS) is a new type of neurostimulation for pharmacoresistant focal epilepsy, which has recently been CE-certified for treatment of European patients. Stimulation is performed via an epicranially placed five-contact electrode array, which applies high frequency stimulation and DC-like cathodal stimulation to the individual epileptogenic brain region. Stimulation at appropriate intensities is not perceived by patients, and first evidence from two prospective unblinded clinical trials suggests excellent tolerability of both, subgaleal implantation and transcranial stimulation. In epilepsies arising from the dorsolateral brain convexity, FCS resulted in a median seizure reduction of >50 % after 6 months which further increased to >60 % after 2 years. This compares favorably to more invasive neurostimulation approaches.

Pre-ictal causal connectivity reveals the epileptic network characteristics for deep brain stimulation

Deep brain stimulation of anterior nucleus of the thalamus (ANT-DBS) is an effective clinical treatment for drug-resistant focal epilepsy. However, the complex epileptic network characteristics underlying ANT-stimulation effectiveness remain unknown, owing to currently unclear connectivity between ANT and seizure-related cortex in pre-ictal periods. Here, we developed a novel individualized pre-ictal ANT-cortical tripartite connectivity network (PANT-CTCNet), aiming to reveal epileptic network characteristics using intracranial stereo-electroencephalography (sEEG) recordings in five patients with focal epilepsy for 90 trials. Each trial represented a pre-ictal or post-stimulus sEEG duration, which was used to construct the epileptic network. By employing conditional Granger causality, we constructed individualized ANT-cortical connectivity networks and found a common epileptic network centred on ANT closely connected with seizure-related cortex in pre-ictal periods. After ANT stimulation for clinical validation, strengthened pre-ictal connectivity between ANT and epileptogenic zones led to significant decline in the causal intensity of epileptic networks. The PANT-CTCNet can give a quantitative reference for clinical preoperative evaluation of patient suitability for ANT-DBS treatment. These findings regarding epileptic network characteristics provide theoretical basis in the selection of optimal surgical candidates for personalized ANT-DBS.

Thalamic neural activity and epileptic network analysis using stereoelectroencephalography: a prospective study protocol

INTRODUCTION

Epilepsy is a prevalent chronic neurological disorder, with approximately one-third of patients experiencing intractable epilepsy, often necessitating surgical intervention. Deep brain stimulation (DBS) of the thalamus has been introduced as a palliative surgical option for seizure control; however, its precise mechanisms remain largely unclear. The thalamus plays a crucial role in coordinating neural networks, both in normal brain function and the propagation of epileptic activity. This study aims to investigate the involvement of the thalamus in epilepsy networks using stereoelectroencephalography (SEEG) to monitor thalamic activity during epileptic seizures in patients with drug-resistant epilepsy.

METHODS AND ANALYSIS

This single-arm, non-randomised, prospective, exploratory study will be conducted at Nagoya University Hospital, involving 10 patients undergoing SEEG for presurgical evaluation of drug-resistant epilepsy. Participants must be 18 years or older, have normal cognitive function and provide informed consent. Between 7 and 14 SEEG electrodes, including 2 in the bilateral thalamus, will be implanted in key thalamic nuclei (anterior, dorsomedial, centromedian and pulvinar) using a robotic system. The primary outcome focuses on electroencephalographic findings from the thalamus, emphasising waveform and frequency changes around seizures. Secondary outcomes include postoperative seizure frequency, changes in cognitive function and neuroimaging results. SEEG data will be recorded continuously for 1-2 weeks to capture both ictal and interictal activity. Data analysis will employ t-tests to compare ictal and interictal periods, with p values <0.05 deemed statistically significant. This study seeks to characterise thalamic spectral and connectivity changes during seizures, identify the thalamic subnuclei involved in seizure propagation and explore their association with seizure outcomes, potentially contributing to future DBS candidate selection. By advancing our understanding of the thalamus in epilepsy networks, this research aims to improve DBS interventions, ultimately enhancing seizure control in patients with intractable epilepsy.

ETHICS AND DISSEMINATION

This study was approved by the ethics committee of the Nagoya University Graduate School of Medicine (Approval No. 2024-0044). All participants will provide written informed consent prior to enrolment. The results of this study will be disseminated through publication in a peer-reviewed journal and presentations at academic conferences.

TRIAL REGISTRATION NUMBER

jRCT1042240024.

Rest-activity rhythm phenotypes in adults with epilepsy and intellectual disability

OBJECTIVE

Rest-activity rhythms (RARs) are perturbed in many forms of neuropsychiatric illness. In this study, we applied wrist actigraphy to describe RAR perturbations in intellectually disabled adults with epilepsy ("E + ID"), using a cross-sectional case-control design. We examined whether RAR phenotypes correlated with epilepsy severity, deficits in adaptive function, and/or comorbid psychopathology.

METHODS

Caregivers of E + ID subjects provided informed consent during routine ambulatory clinic visits and were asked to complete standardized surveys of overall epilepsy severity (GASE, Global Assessment of Severity of Epilepsy), adaptive function (ABAS-3, Adaptive Behavior Assessment System-3) and psychopathology (ABCL, Adult Behavior Checklist). Caregivers were also asked to ensure that subjects wore an Actiwatch-2 device continuously for at least ten days. From actograms, we calculated RAR amplitude, acrophase, robustness, intradaily variability (IV), interdaily stability (IS), and estimates of sleep quantity and timing. We compared these RAR metrics against those from (i) a previously published cohort of adults with epilepsy without ID (E-ID), and (ii) a historical control cohort of age- and sex-matched intellectually able subjects from the Study of Latinos (SOL).

RESULTS

46 E + ID subjects (median age 26, 47% female) provided a median recording duration of 11 days. Surveys reflected low to extremely low levels of adaptive function and low/subclinical levels of psychopathology. Compared with E-ID and SOL cohorts, E + ID subjects displayed significantly lower measures of RAR amplitude, robustness, and IS, with significantly higher IV and total daily sleep. K-means clustering of E + ID subjects recognized a cluster with pronounced hypoactivity, hypersomnia, and elevated rhythm fragmentation (cluster A), an intermediate group with metrics similar to E-ID, and cluster "C" subjects that featured hyper-robust and high amplitude RARs. All three clusters were similar in age, body mass index, antiseizure medication (ASM) polytherapy, ABAS3, and ABCL scores.

SIGNIFICANCE

Adults with epilepsy and intellectual disability display a wide spectrum of RAR phenotypes that do not neatly correlate with measures of adaptive function or epilepsy severity. Prospective studies are necessary to determine whether continuous actigraphic monitoring can sensitively capture changes in chronobiological health that may arise with disease progression, ASM side effects, or other acute health deteriorations.

PLAIN LANGUAGE SUMMARY

Rest-activity rhythms (RARs) can be measured using continuously worn wrist activity monitors. We show that compared to controls, adults with epilepsy and intellectual disability (E + ID) display RARs that are more fragmented, weaker in amplitude, and unstable across days. Within our E + ID cohort, we observed a wide spectrum of RAR phenotypes that we clustered into three subtypes, which were similar in overall average measures of adaptive functioning and psychiatric symptoms.

Deep brain stimulation for epilepsy: A systematic review and meta-analysis of randomized and non-randomized studies of thalamic targeting

INTRODUCTION

Deep Brain Stimulation (DBS) of the thalamus for drug-resistant epilepsy (DRE) is an emerging treatment modality. This systematic review and meta-analysis sought to evaluate the efficacy of stimulating different targets within the thalamus.

METHODS

A systematic search of four databases was conducted. Rates for overall seizure reduction (SR), responder rate (RR ≥50 % SR), and seizure freedom (SF) were evaluated at a minimum time point of 12 months post-stimulation commencement in the anterior (ANT) and centro-median (CMN) thalamic nuclei. Subgroup analyses for a minimum 24 months follow up, sensitivity analyses, and funnel plots to assess for publication bias were also performed. Risk of bias was assessed using the ROBINS-I tool.

RESULTS

Fourty-nine articles met the inclusion criteria. The mean seizure reduction (SR) across 21 studies was 62.31 % (95 % CI: 55.99-68.62, p < 0.01). Specifically, SR was 64.28 % for ANT (95 % CI: 57.55-71.01, p < 0.01) and 69.11 % for CMN (95 % CI: 58.14-80.09, p < 0.01). Meta-analyses of 41 ANT studies and 12 CMN studies reported a response rate (RR) of 61.51 % (95 % CI: 54.11-68.9, p < 0.01) and 69.09 % (95 % CI: 54.01-84.16, p < 0.01), respectively. Overall seizure freedom (SF) was 3.57 % % for ANT (95 % CI: 1.86-5.28, p = 0.45) and 1.32 % for CMN(95 % CI: 0-4.45, p = 0.81). For ANT, RR was 67.63 % (95 % CI: 61.04-74.23) for follow-up periods longer than 24 months, and 44.05 % (95 % CI: 26.73-61.38) for periods shorter than 24 months. The SF rate for ANT was 3 % (95 % CI: 1-4 %) for follow-up under 12 months. For CMN, RR was 70 % (95 % CI: 53-87 %) for periods over 24 months, and 68 % (95 % CI: 31-100 %) for periods under 24 months. The SF rate for CMN was 1 % (95 % CI: 0-4 %) for periods under 12 months. There was no strong evidence of publication bias based on funnel plot analysis, and results were consistent across sensitivity analyses. Insufficient data precluded meta-analysis for other nuclei.

CONCLUSION

These findings demonstrate efficacy of ANT and CMN DBS for patients with DRE, defined by responder rate and seizure reduction. Further research is required to optimize patient selection, predict individual response, and assess non-seizure related outcomes.

Refining centromedian nucleus stimulation for generalized epilepsy with targeting and mechanistic insights from intraoperative electrophysiology

Epilepsy affects 65 million people worldwide, with 30% suffering from drug-resistant epilepsy. While surgical resection is the primary treatment, its application is limited in generalized epilepsy. Centromedian nucleus neurostimulation offers a promising alternative, yet its mechanisms remain unclear, limiting target optimization. We present a multimodal approach integrating intraoperative thalamic and sub-scalp electroencephalogram recordings with post-implant reconstructions to define neural targets affected by centromedian nucleus stimulation. We find that stimulating low-activity regions near the centromedian nucleus, particularly the white matter of internal medullary lamina, induces significant cortical delta power increases greater than stimulation within high-activity areas inside the nucleus. Implantation in these low-activity targets results in greater than 50% seizure reduction in all three subjects. These findings suggest that seizure control primarily involves stimulating white matter regions such as the internal medullary lamina rather than the centromedian nucleus itself. A personalized, electrophysiology-guided implantation approach may enhance neurostimulation efficacy in drug-resistant epilepsy.

Temporal lobectomy in bilateral temporal lobe epilepsy: A relook at factors in selection, invasive evaluation and seizure outcome

OBJECTIVES

We sought retrospectively to assess outcomes in bilateral temporal lobe epilepsy (BTLE) patients undergoing resective temporal lobe surgery following invasive EEG lateralization in comparison to unilateral TLE (UTLE).

METHODS

Patients undergoing surgical intervention for TLE (the vast majority being mesial temporal lobe epilepsy) during a 7-year period were retrospectively categorized as suspected BTLE (sBTLE) or UTLE. Temporal lobectomy was performed in the sBTLE group on the side of maximum number of intracranial EEG seizure onsets. EEG, MRI, laterality of iEEG ictal onset (in sBTLE), seizure outcome and drug tapering data were retrospectively analyzed.

RESULTS

Of 148 adult patients undergoing temporal lobe epilepsy surgery, 24 (16.2 %) fit the criteria of sBTLE, amongst whom iEEG ictal onset proved to be unilateral in 14 (uBTLE, 58.3 %) and bilateral in 10 (dBTLE, 41.7 %). Of operated patients in the dBTLE group, the first seizure onset was ipsilateral to the resection in 4 patients (57.1 %) and contralateral in 3 (42.9 %). In the UTLE group, seizure freedom (Engel 1) was achieved in 87.8 % at mean follow-up of 59.2 ± 27.9 months. Seizure freedom was achieved in 92.9 % of uBTLE patients at 52.8 ± 36.6 months. Seven of 10 dBTLE patients underwent resection on the side of maximum number of iEEG seizure onset, and 6 (85.7 %) remained seizure-free at 40.14 ± 25 months. There was no statistically significant difference in seizure-free outcome between UTLE and sBTLE (Pearson Chi-Square test, p-value = 0.67).

CONCLUSION

High seizure freedom rates were observed in both unilateral and bilateral disease following standard temporal lobectomy. However, the study lacks pre- and post-resection neuropsychological data to conclude on the cognitive sequelae of resective surgery in established bilateral mesiotemporal epilepsy.

Enhancing seizure control in ultra-refractory postencephalitic epilepsies using multinodal network neuromodulation

This case series reports the formidable challenge posed by postencephalitic epilepsies, characterized by frequent drug-resistant seizures and neuropsychiatric and cognitive comorbidities. Polypharmacy is frequently required, and surgical resection may not be feasible due to multifocality. Neuromodulation therapies, including Deep Brain Stimulation (DBS) and Responsive Neurostimulation (RNS), offer a potential lifeline. In this case series, we shed light on the intricate landscape of seizure management and neuropsychiatric comorbidities in five individuals with frequent seizures (often weekly) and ultra-refractory epilepsy (defined as resistance to more than six different antiseizure medications, including failed epilepsy surgery) following catastrophic encephalitis. Four out of five patients achieved at least 50% reduction in seizure frequency following multimodal neuromodulation interventions. Moreover, we underscore the pivotal role of RNS electrocorticography (ECoG) in monitoring the epileptiform burden to guide therapy. Postencephalitic patients often present with a complex interplay of epileptic and nonepileptic (including neuropsychiatric) events, necessitating distinct therapeutic approaches. RNS ECoG emerges as a critical tool for differentiation and tailored therapy. While our findings highlight the potential effectiveness of neuromodulation in managing postencephalitic epilepsy, further research is needed to identify predictors of treatment response and explore the application of these therapies in chronic epilepsy caused by encephalitis. Overall, neuromodulation offers hope for improving these patients' quality of life.

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.

Nanoengineered, ultrasmall and catalytic potassium calcium hexacyanoferrate for neuroprotection and temporal lobe epilepsy treatment

Hippocampal sclerosis, characterized by significant hippocampal neuronal loss, oxidative stress, glial cell proliferation, and inflammatory responses, constitutes a pivotal component in the pathogenesis of temporal lobe epilepsy (TLE). Traditional treatment strategies, mainly involving anti-epileptic drugs, face challenges including ineffectiveness, drug tolerance, and adverse reactions, complicating management of the condition. Herein, we design and engineer ultrasmall potassium calcium hexacyanoferrate (III) nanoparticles, designated as KCaHNPs, which feature a broad spectrum of enzymatic activities analogous to superoxide dismutase, catalase, peroxidase, and glutathione peroxidase. KCaHNPs efficiently neutralize excessive reactive oxygen species, mitigate mitochondrial dysfunction, maintain neuronal integrity, and prevent apoptosis. Importantly, KCaHNPs significantly reduce neuronal damage, apoptosis, ferroptosis, and glial cells activation in TLE-afflicted rats, thereby improving spatial and short-term memory, and diminishing epileptic hyperexcitability. Prophylactic deployment of KCaHNPs markedly decreases the frequency and duration of seizures, extends the latency period before the onset of initial seizures, and enhances neural functions within the hippocampal CA3 area. Collectively, these findings underscore the potent therapeutic and prophylactic efficacy of KCaHNPs in mitigating TLE by bolstering cellular defense mechanisms against oxidative stress and inflammation. This innovative approach holds promise as a comprehensive and efficacious strategy for managing temporal lobe epilepsy and potentially other complex neurological disorders.

Optimizing stimulation parameters for anterior thalamic nuclei deep brain stimulation in epilepsy: A randomized crossover trial

OBJECTIVE

The effects of brain stimulation for diseases like epilepsy are delayed, making stimulation optimization difficult. The parameters for anterior thalamic nuclei (ANT) deep brain stimulation (DBS) for focal drug-resistant epilepsy management are often restricted to those used in the SANTE landmark trial. There is little evidence regarding effective alternatives, and low-frequency stimulation is typically neglected. We prospectively compare a widely differing stimulation parameter set to typical settings.

METHODS

This randomized, modified crossover, open trial compares the efficacy and safety of an alternative set of parameters using continuous low-frequency stimulation (cLFS) with a longer pulse width (7 Hz, 200 μs, continuous) compared to SANTE's intermittent high-frequency stimulation (iHFS) with a short pulse width (145 Hz, 90 μs, cycling 1 min on/5 min off). After 3 months on a randomly assigned first set, patients are switched to the other settings, unless seizure-free. Patients are re-evaluated after 3 more months, which marks the completion of the trial. After that, they can either remain on the same settings or switch back.

RESULTS

Sixteen patients with a median baseline seizure frequency of 13.8 seizures/month (interquartile range [IQR] = 2.7-22.8) were included in the analysis. At trial completion (median follow-up = 30 weeks, IQR = 26-35), ANT-DBS significantly reduced median seizure frequency (62%, IQR = 18-81, Wilcoxon test statistic [W] = 99, p = .008). Both iHFS (33%, IQR = 0-65, W = 81, p = .02) and cLFS (73%, IQR = 30-79, W = 105, p = .001) significantly reduced median seizure frequency. cLFS showed improved median seizure frequency reduction compared to iHFS (W = 63, p = .03) and was not associated with any moderate or severe adverse effects.

SIGNIFICANCE

Results support cLFS for ANT-DBS as a safe and effective alternative to typical iHFS parameters. Stimulation with widely differing parameter sets may be as effective as or, in some situations, more effective than typical stimulation parameters.

Inter-seizure variability in thalamic recruitment and its implications for precision thalamic neuromodulation

BACKGROUND

Thalamic stimulation is a promising approach to controlling seizures in patients with intractable epilepsy. It does not, however, provide good control for everyone. A big issue is that the role of the thalamus in seizure organization and propagation is unclear. When using responsive stimulation devices, they must detect seizure activity before sending stimulation. So, it's important to know which parts of the thalamus are involved in different seizures.

METHODS

To better choose thalamic targets for stimulation, we studied how different seizures spread to each stimulation target. Expert reviews and automated tools were used to identify seizure spread recorded from invasive recordings. We categorized seizures based on how they start and spread, and determined whether seizures reached thalamic areas early or late. We used generalized linear models (GLM) to evaluate which seizure properties are predictive of time of spread to the thalamus, testing effect significance using Wald tests.

RESULTS

We show that seizures with <2 Hz synchronized-spiking patterns do not spread early to the thalamus, while seizures starting with faster activity (<20 Hz) spread early to all thalamic areas. Most importantly, seizures that begin broadly across the brain quickly recruit the centromedian and pulvinar areas, suggesting these may be better stimulation targets in such cases. Alternatively, seizures that start deep in the temporal lobe tend to involve the anterior part of the thalamus, meaning the centromedian might not be the best choice for those seizures.

CONCLUSIONS

Our results suggest that by analyzing electrical activity during seizures, we can better predict which parts of the thalamus are involved. This could lead to more effective stimulation treatments for people with epilepsy.

Two-year outcomes of epicranial focal cortex stimulation in pharmacoresistant focal epilepsy

OBJECTIVE

This study was undertaken to report on the long-term safety and efficacy of epicranial focal cortex stimulation (FCS) using the EASEE device as adjunctive neuromodulatory therapy in improving seizure control in adults with pharmacoresistant epilepsy originating from one predominant epileptogenic zone.

METHODS

Prospective open-label follow-up of patients from the EASEE II and PIMIDES I clinical trials was done for a period of 2 years after the epicranial implantation of the EASEE electrode and stimulator device.

RESULTS

Thirty-three patients underwent device implantation, and stimulation was activated in 32 patients. Of these, 26 patients continued stimulation up to 2-year follow-up and provided seizure diary data for efficacy analysis. The 50% responder rate at 2-year follow-up was 65.4% (95% confidence interval = 44.3-82.8), corresponding to a median seizure frequency reduction of 68%. Patients reported improved health-related quality of life. Tolerability was excellent, and there were no severe adverse events considered to be related to implantation or stimulation, nor were adverse effects on mood or cognition reported.

SIGNIFICANCE

Results of the 2-year follow-up show that epicranial FCS is well tolerated by patients while providing improved seizure control in the long term. It thus offers a minimally invasive treatment option for patients with a predominant epileptic focus.

Comparison of structural connectomes for modeling deep brain stimulation pathway activation

INTRODUCTION

Structural connectivity models of the brain are commonly employed to identify pathways that are directly activated during deep brain stimulation (DBS). However, various connectomes differ in the technical parameters, parcellation schemes, and methodological approaches used in their construction.

OBJECTIVE

The goal of this study was to compare and quantify variability in DBS pathway activation predictions when using different structural connectomes, while using identical electrode placements and stimulation volumes in the brain.

APPROACH

We analyzed four example structural connectomes: 1) Horn normative connectome (whole brain), 2) Yeh population-averaged tract-to-region pathway atlas (whole brain), 3) Petersen histology-based pathway atlas (subthalamic focused), and 4) Majtanik histology-based pathway atlas (anterior thalamus focused). DBS simulations were performed with each connectome, at four generalized locations for DBS electrode placement: 1) subthalamic nucleus, 2) anterior nucleus of thalamus, 3) ventral capsule, and 4) ventral intermediate nucleus of thalamus.

RESULTS

The choice of connectome used in the simulations resulted in notably distinct pathway activation predictions, and quantitative analysis indicated little congruence in the predicted patterns of brain network connectivity. The Horn and Yeh tractography-based connectomes provided estimates of DBS connectivity for any stimulation location in the brain, but have limitations in their anatomical validity. The Petersen and Majtanik histology-based connectomes are more anatomically realistic, but are only applicable to specific DBS targets because of their limited representation of pathways.

SIGNIFICANCE

The widely varying and inconsistent inferences of DBS network connectivity raises substantial concern regarding the general reliability of connectomic DBS studies, especially those that lack anatomical and/or electrophysiological validation in their analyses.

Neurostimulation in Childhood Epilepsy

Epilepsy is a common and debilitating neurological disorder in children, and approximately a third of them have ongoing seizures despite adequate trial of antiseizure medications. Neurostimulation approaches may be an option for those with drug resistant epilepsy. Several invasive and non-invasive devices have been trialled and found to be effective in reducing seizure burden in drug resistant epilepsy. These techniques appear to be safe and well tolerated. We review the available evidence for the use of these devices, including vagus nerve stimulation, deep brain stimulation, responsive neurostimulation, chronic subthreshold cortical stimulation, transcranial magnetic stimulation and transcranial direct current stimulation. The results of trials are promising but there are fewer studies in children. Apart from vagus nerve stimulation, none of the other neurostimulation techniques are currently approved for use in children and their use is off-label or in clinical trials. Further well-designed trials are needed, especially in children, to identify the most effective neurostimulation options and optimal parameters for improvement of seizure burden and quality of life. Neurostimulation techniques are also being trialled for treatment of refractory status epilepticus, but lack of robust evidence (mainly case studies or case series reports) makes it difficult to predict therapeutic benefit at present.

Multi-Parameter MRI for Evaluating Glymphatic Impairment and White-Matter Abnormalities and Discriminating Refractory Epilepsy in Children

OBJECTIVE

To explore glymphatic impairment in pediatric refractory epilepsy (RE) using multi-parameter magnetic resonance imaging (MRI), assess its relationship with white-matter (WM) abnormalities and clinical indicators, and preliminarily evaluate the performance of multi-parameter MRI in discriminating RE from drug-sensitive epilepsy (DSE).

MATERIALS AND METHODS

We retrospectively included 70 patients with DSE (mean age, 9.7 ± 3.5 years; male:female, 37:33) and 26 patients with RE (9.0 ± 2.9 years; male:female, 12:14). The diffusion tensor imaging analysis along the perivascular space (DTI-ALPS) index as well as fractional anisotropy (FA), mean diffusivity (MD), and nodal efficiency values were measured and compared between patients with RE and DSE. With sex and age as covariables, differences in the FA and MD values were analyzed using tract-based spatial statistics, and nodal efficiency was analyzed using a linear model. Pearson's partial correlation was analyzed. Receiver operating characteristic (ROC) curves were used to evaluate the discrimination performance of the MRI-based machine-learning models through five-fold cross-validation.

RESULTS

In the RE group, FA decreased and MD increased in comparison with the corresponding values in the DSE group, and these differences mainly involved the callosum, right and left corona radiata, inferior and superior longitudinal fasciculus, and posterior thalamic radiation (threshold-free cluster enhancement, P < 0.05). The RE group also showed reduced nodal efficiency, which mainly involved the limbic system, default mode network, and visual network (false discovery rate, P < 0.05), and significantly lower DTI-ALPS index (F = 2.0, P = 0.049). The DTI-ALPS index was positively correlated with FA (0.25 ≤ r ≤ 0.32) and nodal efficiency (0.22 ≤ r ≤ 0.37), and was negatively correlated with the MD (-0.24 ≤ r ≤ -0.34) and seizure frequency (r = -0.47). A machine-learning model combining DTI-ALPS, FA, MD, and nodal efficiency achieved a cross-validated ROC curve area of 0.83 (sensitivity, 78.2%; specificity, 84.8%).

CONCLUSION

Pediatric patients with RE showed impaired glymphatic function in comparison with patients with DSE, which was correlated with WM abnormalities and seizure frequency. Multi-parameter MRI may be feasible for distinguishing RE from DSE.

Adenosine Kinase: An Epigenetic Modulator and Drug Target

Adenosine kinase (ADK, EC: 2.7.1.20) is an evolutionarily ancient ribokinase, which acts as a metabolic regulator by transferring a phosphoryl group to adenosine to form AMP. The enzyme is of interest as a therapeutic target because its inhibition is one of the most effective means to raise the levels of adenosine and hence adenosine receptor activation. For these reasons, ADK has received significant attention in drug discovery efforts in the early 2000s for indications such as epilepsy, chronic pain, and inflammation; however, the report of adverse events regarding cardiovascular and hepatic function as well as instances of microhemorrhage in the brain of preclinical models prevented further development efforts. Recent findings emphasize the importance of compartmentalization of the adenosine system reflected by two distinct isoforms of the enzyme, ADK-S and ADK-L, expressed in the cytoplasm and the cell nucleus, respectively. Newly identified adenosine receptor independent functions of adenosine as a regulator of biochemical transmethylation reactions, which include DNA and histone methylation, identify ADK-L as a distinct therapeutic target for the regulation of the nuclear methylome. This newly recognized role of ADK-L as an epigenetic regulator points toward the potential disease-modifying properties of the next generation of ADK inhibitors. Continued efforts to develop therapeutic strategies to separate nuclear from extracellular functions of adenosine would enable the development of targeted therapeutics with reduced adverse event potential. This review will summarize recent advances in the discovery of novel ADK inhibitors and discuss their potential therapeutic use in conditions ranging from epilepsy to cancer.

A Scoping Review of Responsive Neurostimulation in Focal Cortical Dysplasia-Related Epilepsy

OBJECTIVE

Responsive Neurostimulation (RNS) is a closed-loop neuromodulation therapy approved for treating drug resistant epilepsy (DRE) with 1 or 2 seizure foci, but its potential utility for treating complex seizure networks, such as in focal cortical dysplasia (FCD), remains uncertain. This review and commentary discuss the current practice of RNS use in focal cortical dysplasia-related drug-resistant epilepsy(FCD-DRE), and the potential of individualized approaches.

METHODS

Our scoping review followed a search to identify relevant studies on epilepsy and RNS across MEDLINE, Embase, and Web of Science, yielding 674, 1,255, and 579 results, respectively followed by abstract and full text review to include FCD-DRE. Data on history, imaging, intracranial EEG, RNS implantation and programming strategies were recorded.

RESULTS

78 patients with FCD-DRE across 25 studies were included. The most common lead configuration was two depth electrodes in 53 % (19/36). The median seizure reduction was 85 % [IQR = 66, 96] with a median follow up of 17 months., including 6 patients (7.6 %) achieving seizure freedom for a median 15 months. In 17 patients with resections and RNS implantation, median seizure frequency reduction was 87 % (N = 15), not significantly different from the group with RNS only. 8 patients with cortical and thalamic leads had median seizure frequency reduction of 87 % [IQR = 51, 92]. RNS was effective when used in refractory status epilepticus associated with FCDs.

SIGNIFICANCE

RNS is a flexible therapy that effectively reduces seizures in FCD-DRE. Electrographic and imaging signatures can potentially be leveraged. Hybrid resection with RNS approaches and the role in refractory status epilepticus associated with FCD is highlighted. Future studies are necessary to optimize RNS therapy in FCD-DRE.

Impact of Vagus Nerve Stimulation for the Treatment of Drug-resistant Epilepsy on Patterns of Use and Cost of Healthcare Services and Pharmacotherapy Among Medicare Enrollees: Findings From Analyses of Healthcare Claims From the Centers of Medicare and Medicaid Services

PURPOSE

To examine the expected impact of vagus nerve stimulation (VNS) on patterns of utilization and cost of healthcare services and prescription pharmacotherapies among Medicare enrollees with drug-resistant epilepsy (DRE) versus continued use of antiseizure medications (ASMs) alone.

METHODS

This was a retrospective, observational, cohort study that used healthcare claims data from the US Centers for Medicare and Medicaid Services. All Medicare enrollees who underwent VNS implantation between January 1, 2011 and December 31, 2020 were selected. Individuals without at least 24 months of continuous enrollment before implantation (index date) and at least 1 month of enrollment immediately thereafter were excluded. Patients without a diagnosis of epilepsy on the index date, and those without ASM claims during the 1-year period before that date, were also excluded. Observed patterns of utilization and cost of healthcare services and pharmacotherapies during the 2-year period prior to VNS were used to develop regression models to predict these outcomes during the 2-year period following the index date. Predicted monthly outcomes from these models during each month of the 24-month follow-up period were compared with corresponding outcomes observed in the database, with differences (observed minus expected) attributed to VNS implantation.

FINDINGS

A total of 16,223 Medicare enrollees had a procedure code for VNS between January 1, 2011, and December 31, 2020, of whom 19.4% (n = 3155) met all other selection criteria. Expected composite rates of hospitalizations and emergency department (ED) visits were higher than observed for all-cause (38.95 events per 100 person-months [PMs] vs 23.15 per 100 PMs) and epilepsy-related (33.46 per 100 PMs vs 15.97 per 100 PMs) events (P < 0.001 for both comparisons). Following the index month, mean monthly observed all-cause costs were $1286 lower than expected; epilepsy-related costs were $1351 lower. Differences between predicted and observed all-cause costs (including costs related to implantation) did not differ significantly by month 20, indicating an expectation that VNS "breaks even" within 2 years of implantation.

IMPLICATIONS

VNS implantation was associated with 41% and 52% reductions in all-cause and epilepsy-related hospitalizations and ED visits, respectively (both vs expected), for Medicare patients with DRE, and its implantation may be cost-neutral within 2 years of the procedure. These results are similar in direction and magnitude to those observed in a previous study of commercially insured patients with DRE. Additional research is needed to better understand the impacts of neuromodulator implantation on other important outcomes, such as health-related quality of life.

One-hertz low-frequency stimulation of anterior substantia nigra pars reticulata attenuates seizure via biased disinhibitory circuits

OBJECTIVE

Low-frequency stimulation (LFS) targeting key seizure nodes holds promising potential for the treatment of epilepsy. The substantia nigra pars reticulata (SNr) plays an important role in seizure control yet has structural heterogeneity. This study aims to explore the therapeutic potential of LFS across different subregions of the SNr.

METHODS

Different types of seizure models, including kainic acid-induced hippocampal and neocortical seizure models and a pentetrazol-induced seizure model, were used to address the therapeutic potential of LFS in different subregions of SNr. Fiber photometry, specific cell ablation, and viral tracing were used to measure the release of different neurotransmitters and heterogeneous circuit organizations of subregions of SNr.

RESULTS

We found that 1-Hz LFS in the anterior SNr (a-SNr), but not in the posterior SNr (p-SNr), generally alleviated seizure severity in all three mouse seizure models. Notably, the antiseizure effects were frequency-dependent, with 100-Hz high-frequency stimulation being less effective and 20-Hz stimulation having hardly any impact. Regarding the mechanism of the discrepancy, fiber photometry showed that 1-Hz, rather than 20- or 100-Hz, stimulation in the a-SNr significantly increased γ-aminobutyric acid release from exogenous inputs compared with stimulation in the p-SNr, which was further supported by their biased brain-wide disinhibitory inputs.

SIGNIFICANCE

These results demonstrate that 1-Hz LFS in the a-SNr may be of therapeutic significance in various types of seizures, highlighting the necessity to precisely target the a-SNr at low frequency for seizure treatment.

Dataset of long-term multi-site LFP activity with spontaneous chronic seizures in temporal lobe epilepsy rats

The characteristics of refractory epilepsy change with disease progression. However, relevant studies are scarce due to the difficulty in obtaining long-term multi-site data from patients with epilepsy. This work aimed to provide a long-term brain electrophysiological dataset of 15 pilocarpine-treated rats with temporal lobe epilepsy (TLE). The dataset was constituted by multi-site local field potential (LFP) signal recorded from 12 sites in the Papez circuit in TLE, including spontaneous seizures and interictal fragments in the chronic period. The LFP data were saved in MATLAB, stored in the Neurodata Without Borders format, and published on the DANDI Archive. We validated the dataset technically through specific signal analysis. In addition, we provided MATLAB codes for basic analyses of this dataset, including power spectral analysis, seizure onset pattern identification, and interictal spike detection. This dataset could reveal how the electrophysiological and epileptic network properties of the brain of rats with chronic TLE changed during epilepsy development, thus help inform the design of adaptive neuromodulation for epilepsy.

Deep Brain Stimulation for Post-Hypoxic Myoclonus: A Case Correlating Local Field Potentials to Clinical Outcome

Background

Post-hypoxic myoclonus (PHM) is characterized by generalized myoclonus after hypoxic brain injury. PHM is often functionally impairing and refractory to medical therapies. There are a handful of reports utilizing deep brain stimulation (DBS) to treat medically refractory PHM.

Case Report

A 56-year-old woman developed PHM following an anoxic brain injury. Utilizing a stimulating and sensing DBS system, we show clinical improvement in myoclonus at 6 months and correlate it to local field potential (LFP) activity.

Discussion

We present the first case to utilize DBS sensing to correlate LFP activity to myoclonus improvement. Our case contributes to the growing evidence of DBS for PHM.

Acute Disruption of Cortical Epileptiform Discharges With Thalamic Stimulation

SUMMARY

Thalamic neuromodulation has emerged as a promising treatment for drug-resistant epilepsy, with deep brain stimulation of the anterior nucleus of the thalamus currently Food and Drug Administration approved for this purpose. The Stimulation of the Anterior Nucleus of Thalamus for Epilepsy trial demonstrated that chronic anterior nucleus of the thalamus stimulation can significantly reduce seizure burden. In addition, the centromedian nucleus is gaining interest as a potential neuromodulation target among epilepsy experts, though its use remains off-label. Effective selection of neuromodulation targets requires reliable biomarkers, ideally with real-time feedback, yet studies on the acute effects of thalamic stimulation on epileptiform activity remain limited. Our cases provide novel evidence of acute suppression of epileptiform activity in the cerebral cortex-specifically, the cingulate and insular cortices-after anterior nucleus of the thalamus and centromedian nucleus stimulation, respectively, through stereoelectroencephalography electrodes. This finding enhances our understanding of cortical responses to thalamic stimulation and supports its therapeutic potential in both chronic and acute settings. Emerging research suggests that other thalamic nuclei may also play a role in managing epilepsy originating from different brain regions. We emphasize that routine stereoelectroencephalography implantation in thalamic nuclei may provide valuable clinical insights and aid in selecting the optimal target for stimulation. This case mini-series contributes to the growing evidence supporting the therapeutic potential of thalamic neuromodulation in epilepsy treatment.

Stimulation of the anterior thalamus modulates behavior in multiple cognitive domains

BACKGROUND

Deep Brain Stimulation (DBS) of the ATN (Anterior Thalamic Nuclei) has been used to treat refractory epilepsy. Despite the fact that the ATN plays a crucial role in various cognitive functions, including emotional processing, memory, and spatial navigation, there is limited understanding of the effects of ATN-DBS across multiple cognitive domains.

OBJECTIVE

In order to gain insight into the variability in the cognitive outcome of DBS across tasks and individuals, we investigated effects of ATN-DBS on multiple cognitive functions within the same patients and stimulation parameters.

METHODS

Eleven patients with refractory epilepsy performed four cognitive behavioral tasks: Emotional Attention Network, Emotional Face Categorization, Word Recognition, and Head Direction. In each task, reaction time, emotional response, or accuracy was measured under on- and off-DBS conditions. Volumes of tissue activated (VTA) were also estimated to investigate target-specific effects on cognition.

RESULTS

ATN-DBS facilitated attention following the presentation of a negative visual stimulus and increased the inclination to perceive a face as expressing an emotion. Furthermore, ATN-DBS disrupted the precision of head direction in the absence of visual cues. Although overall word recognition memory appeared unaffected by ATN-DBS, individual performance changes depended on the location of VTAs. Interestingly, modulation in one cognitive domain did not consistently result in changes in other domains.

CONCLUSIONS

ATN-DBS can influence human behavior across multiple cognitive domains, but with varying degrees of individual difference across tasks. The findings emphasize the complexity of the ATN in its involvement in human cognition and provide novel insight into individualized methods for neuromodulation.

Optogenetic stimulation of the dorsal striatum bidirectionally controls seizures

Despite a century of development of antiseizure medications, up to a third of people with epilepsy do not achieve seizure freedom with drug therapy. Deep brain stimulation is of growing use, but just as with pharmacotherapy, is not universally effective. Identifying new targets for deep brain stimulation-and in particular sites that are effective against a range of seizure types-may close this gap. Engagement of the basal ganglia experimental seizures was first observed almost 75 y ago. However, the role of the basal ganglia's input nucleus, the striatum, in seizure control is relatively understudied. To address this gap, we used an optogenetic approach to activate and inactivate neurons in the dorsal striatum of rats submitted to the gamma-butyrolactone (GBL) model of absence epilepsy, amygdala kindling model of temporal lobe epilepsy, and pilocarpine-induced Status Epilepticus (SE). Open-loop (continuous light delivery) optogenetic activation of dorsal striatal neurons robustly suppressed seizures in all models. By contrast, open-loop optogenetic silencing increased absence seizure expression and facilitated SE onset but had no effect on kindled seizures. In the GBL model, we also tested the effects of closed-loop modulation (light delivery in response to seizure detection). Closed-loop activation reduced duration of spike-wave discharges (SWDs), while closed-loop inhibition increased SWD duration. These results demonstrated previously unrecognized antiabsence effects associated with striatal neuromodulation. These findings demonstrate a robust, bidirectional role of the dorsal striatum in the control of multiple seizure types, suggesting that the striatum is a site that can exert broad-spectrum control of seizures.

Modulating limbic circuits in temporal lobe epilepsy: impacts on seizures, memory, mood and sleep

Temporal lobe epilepsy is a common neurological disease characterized by recurrent seizures that often originate within limbic networks involving amygdala and hippocampus. The limbic network is involved in crucial physiologic functions involving memory, emotion and sleep. Temporal lobe epilepsy is frequently drug-resistant, and people often experience comorbidities related to memory, mood and sleep. Deep brain stimulation targeting the anterior nucleus of the thalamus (ANT-DBS) is an established therapy for temporal lobe epilepsy. However, the optimal stimulation parameters and their impact on memory, mood and sleep comorbidities remain unclear. We used an investigational brain sensing-stimulation implanted device to accurately track seizures, interictal epileptiform spikes (IES), and memory, mood and sleep comorbidities in five ambulatory subjects. Wireless streaming of limbic network local field potentials (LFPs) and subject behaviour were captured on a mobile device integrated with a cloud environment. Automated algorithms applied to the continuous LFPs were used to accurately cataloged seizures, IES and sleep-wake brain state. Memory and mood assessments were remotely administered to densely sample cognitive and behavioural response during ANT-DBS in ambulatory subjects living in their natural home environment. We evaluated the effect of continuous low-frequency and duty cycle high-frequency ANT-DBS on epileptiform activity and memory, mood and sleep comorbidities. Both low-frequency and high-frequency ANT-DBS paradigms reduced seizures. However, continuous low-frequency ANT-DBS showed greater reductions in IES, electrographic seizures and better sleep and memory outcomes. These results highlight the potential of synchronized brain sensing and dense behavioural tracking during ANT-DBS for optimizing neuromodulation therapy. While studies with larger patient numbers are needed to validate the benefits of low-frequency ANT-DBS, these findings are potentially translatable to individuals currently implanted with ANT-DBS systems.

Remote Regulation of Molecular Diffusion in Extracellular Space of Parkinson's Disease Rat Model by Subthalamic Nucleus Deep Brain Stimulation

Subthalamic nucleus deep brain stimulation (STN-DBS) is an effective therapy for Parkinson's disease (PD). However, the therapeutic mechanisms remain incompletely understood, particularly regarding the extracellular space (ECS), a critical microenvironment where molecular diffusion and interstitial fluid (ISF) dynamics are essential for neural function. This study aims to explore the regulatory mechanisms of the ECS in the substantia nigra (SN) of PD rats following STN-DBS. To evaluate whether STN-DBS can modulate ECS diffusion and drainage, we conducted quantitative measurements using a tracer-based magnetic resonance imaging. Our findings indicated that, compared to the PD group, STN-DBS treatment resulted in a decreased diffusion coefficient (D*), shorted half-life (T 1/2), and increased clearance coefficient (k') in the SN. To investigate the mechanisms underlying these changes in molecular diffusion, we employed enzyme-linked immunosorbent assay (ELISA), Western blotting (WB), and microdialysis techniques. The results revealed that STN-DBS led to an increase in hyaluronic acid content, elevated expression of excitatory amino acid transporter 2 (EAAT2), and a reduction in extracellular glutamate concentration. Additionally, to further elucidate the mechanisms influencing ISF drainage, we employed immunofluorescence and immunohistochemical techniques for staining aquaporin-4 (AQP-4) and α-synuclein. The results demonstrated that STN-DBS restored the expression of AQP-4 while decreasing the expression of α-synuclein. In conclusion, our findings suggest that STN-DBS improves PD symptoms by modifying the ECS and enhancing ISF drainage in the SN regions. These results offer new insights into the mechanisms and long-term outcomes of DBS in ECS, paving the way for precision therapies.

Electrical Coordinated Reset stimulation induces network desynchronization in an in vivo model of status epilepticus

Epilepsy, a neurological disorder characterized by recurrent seizures, profoundly impacts individuals worldwide. Various electrical stimulation protocols have been investigated to mitigate epileptic seizures, among which Coordinated Reset (CR) stimulation may have potential for inducing long-lasting neural desynchronization. This study explores the acute effects of CR stimulation on synchronization dynamics during Status Epilepticus (SE) in an in vivo animal model. An electrographically sustained seizure-state was induced via 4-aminopyridine (4AP) administration to CA3. Custom-designed electrode probes were implanted to facilitate simultaneous recording and electrical stimulation. Analytical univariate and bivariate features were constructed from the LFP time-series recording. Feature metrics focused on spike synchronization metrics and continuous signal analysis of amplitude, spectral power and phase synchronization across electrode pairs and frequency bands. Significance of modulation was assessed through permutation testing of the observed differences between the CR-stimulated group (N = 5) compared to the control (no stimulation) group (N = 3) during SE. Results showed overall decrease in amplitude and power univariate features, and a significant modulation of bivariate synchronization and connectivity measures across the spectrum between the CR stimulation and control group. Our findings underscore the potential effectiveness of CR stimulation in attenuating excessive neural synchronization, paving the way for further exploration of CR stimulation as a viable intervention for network desynchronization of epileptiform activity and subsequently treatment of seizures.

Neuromodulation in pediatric drug-resistant epilepsy

This is a summary of the three commercially available neuromodulation devices for refractory epilepsy, highlighting their use in children. The article offers a high-level review of the proposed mechanisms of vagus nerve stimulation, responsive neurostimulation, and deep brain stimulation, the pivotal trials leading to their approval for use in the United States, as well as their efficacy and associated adverse effects.

Neurosurgical Breakthroughs of the Last 50 Years: A Historical Journey Through the Past and Present

This article presented the author's historical perspective on 25 of the most significant neurosurgical breakthrough events of the last 50 years. These breakthroughs have advanced neurosurgical patient care and management. They have improved the management of aneurysms, arteriovenous malformations, tumors, stroke, traumatic brain injury, movement disorders, epilepsy, hydrocephalus, and spine pathologies. Neurosurgery has evolved through research, innovation, and technology. Several neurosurgical breakthroughs were achieved using neuroendoscopy, neuronavigation, radiosurgery, endovascular techniques, and refinements in computer technology. With these breakthroughs, neurosurgery did not change; it just progressed. Neurosurgery should continue its progress through research to obtain new knowledge for the benefit of our patients.

Systematic Review of Experimental Deep Brain Stimulation in Rodent Models of Epilepsy

OBJECTIVES

Deep brain stimulation (DBS) is an established neuromodulatory technique for treating drug-resistant epilepsy. Despite its widespread use in carefully selected patients, the mechanisms underlying the antiseizure effects of DBS remain unclear. Herein, we provide a detailed overview of the current literature pertaining to experimental DBS in rodent models of epilepsy and identify relevant trends in this field.

MATERIALS AND METHODS

A systematic review was conducted using the PubMed MEDLINE database, following PRISMA guidelines. Data extraction focused on study characteristics, including stimulation protocol, seizure and behavioral outcomes, and reported mechanisms of action.

RESULTS

Of the 1788 resultant articles, 164 were included. The number of published articles has grown exponentially in recent decades. Most studies used chemically or electrically induced models of epilepsy. DBS targeting the anterior nucleus of the thalamus, hippocampal formation, or amygdala was most extensively studied. Effective stimulation parameters were identified, and novel stimulation designs were explored, such as closed-loop and unstructured stimulation approaches. Common mechanisms included synaptic modulation through the depression of excitatory neurotransmission and inhibitory release of GABA. At the network level, antiseizure effects were associated with the desynchronization of neural networks, characterized by decreased low-frequency oscillations.

CONCLUSIONS

Rodent models have significantly advanced the understanding of disease pathophysiology and the development of novel therapies. However, fundamental questions remain regarding DBS mechanisms, optimal targets, and parameters. Further research is necessary to improve DBS therapy and tailor treatment to individual patient circumstances.

Invasive Neurostimulation for the Treatment of Epilepsy

Although electricity has been used in medicine for thousands of years, bioelectronic medicine for treating epilepsy has become increasingly common in recent years. Invasive neurostimulation centers primarily around three approaches: vagus nerve stimulation (VNS), responsive neurostimulation (RNS), and deep brain stimulation (DBS). These approaches differ by target (e.g., cranial nerve, cortex, or thalamus) and stimulation parameters (e.g., triggered stimulation or continuous stimulation). Although typically noncurative, these approaches can dramatically reduce the seizure burden and offer patients new treatment options. There remains much to be understood about optimal targets and individualized stimulation protocols. Objective markers of seizure burden and biomarkers that quickly quantify neural excitability are still needed. In the future, bioelectronic medicine could become a curative approach that remodels neural networks to reduce pathological activity.

Mechanistic insights into the interaction between epilepsy and sleep

Epidemiological evidence has demonstrated associations between sleep and epilepsy, but we lack a mechanistic understanding of these associations. If sleep affects the pathophysiology of epilepsy and the risk of seizures, as suggested by correlative evidence, then understanding these effects could provide crucial insight into the basic mechanisms that underlie the development of epilepsy and the generation of seizures. In this Review, we provide in-depth discussion of the associations between epilepsy and sleep at the cellular, network and system levels and consider the mechanistic underpinnings of these associations. We also discuss the clinical relevance of these associations, highlighting how they could contribute to improvements in the management of epilepsy. A better understanding of the mechanisms that govern the interactions between epilepsy and sleep could guide further research and the development of novel approaches to the management of epilepsy.

Exploring Patient Perspectives: A Structured Interview Study on Deep Brain Stimulation as a Novel Treatment Approach for Mild Cognitive Impairment

INTRODUCTION

Limited treatments for Mild Cognitive Impairment (MCI) highlight the need to explore innovations including Deep Brain Stimulation (DBS), with patient perspectives key to ethical protocol development.

METHODS

Seven MCI patients and four care partners were interviewed (Feb 2023-Jan 2024) about daily MCI challenges, desired treatment outcomes, and views on DBS. Thematic analysis following COREQ guidelines identified key themes.

RESULTS

DBS was a novel concept for all (7/7), and most expressed interest (6/7) despite concerns about invasiveness (6/7) and preference to exhaust medications first (4/7). Care partners (4/4) shared concerns about invasiveness and emphasized proven efficacy. Key deciding factors included the involved procedural risk (6/7), desired significant outcomes (6/7), and prior testing for MCI (7/7). Most participants (6/7) were hesitant to be the first to try DBS, while one was willing.

CONCLUSION

Patient and care partner insights on DBS for MCI are crucial for balancing innovation with ethical, patient-centered research.

Efficacy of neuromodulation of the pulvinar nucleus for drug-resistant epilepsy

OBJECTIVE

The pulvinar nucleus of the thalamus has extensive cortical connections with the temporal, parietal, and occipital lobes. Deep brain stimulation (DBS) targeting the pulvinar nucleus, therefore, carries the potential for therapeutic benefit in patients with drug-resistant posterior quadrant epilepsy (PQE) and neocortical temporal lobe epilepsy (TLE). Here, we present a single-center experience of patients managed via bilateral DBS of the pulvinar nucleus.

METHODS

A single-institution retrospective review of five patients who underwent bilateral pulvinar DBS for drug-resistant TLE or PQE was performed. Stimulation parameters were adjusted monthly as needed, and side effects were monitored. The primary outcome was the percentage reduction in patient-reported seizure frequency in comparison to the preimplant baseline. The location of the active electrode contacts in relation to pulvinar thalami that produced the best seizure outcome was identified. Chronic sensing of the pulvinar local field potentials (LFPs) and circadian pattern of modulation of the LFP amplitudes were analyzed.

RESULTS

Four patients (80%) experienced a >70% reduction in seizure frequency, whereas one patient had >50% reduction in seizure. Mean seizure reduction was 79% at a median follow-up of 13 months (range = 9-21 months). No significant side effects were noted. Of all the pulvinar subnuclei, stimulation of the medial pulvinar nucleus (MPN) produced the best seizure outcome in all patients except for two, in whom active contacts in the MPN but also in more lateral and inferior locations resulted in the most significant reduction in seizures. Chronic timeline data identified changes in LFP amplitude associated with stimulation and seizure occurrences.

SIGNIFICANCE

In this first ever report on a series of patients undergoing bilateral pulvinar DBS for drug-resistant epilepsy, we demonstrate that stimulation of the pulvinar and in particular the MPN is a safe and viable option for patients with nonlesional PQE or TLE. The optimal target for stimulation and relative merits of open versus closed loop stimulation should be delineated in future studies.

Fabrication of micro-wire stent electrode as a minimally invasive endovascular neural interface for vascular electrocorticography using laser ablation method

Objective. Minimally invasive endovascular stent electrode is a currently emerging technology in neural engineering with minimal damage to the neural tissue. However, the typical stent electrode still requires resistive welding and is relatively large, limiting its application mainly on the large animal or thick vessels. In this study, we investigated the feasibility of laser ablation of micro-wire stent electrode with a diameter as small as 25μmand verified it in the superior sagittal sinus (SSS) of a rat.Approach. We have developed a laser ablation technology to expose the electrode sites of the micro-wire on both sides without damaging the wire itself. During laser ablation, we applied a new method to fix and realign the micro-wires. The micro-wire stent electrode was fabricated by carefully assemble the micro-wire and stent. We tested the electrochemical performances of the electrodes as a neural interface. Finally, we deployed the stent electrode in a rat to verified the feasibility.Main result. Based on the proposed micro-wire stent electrode, we demonstrated that the stent electrode could be successfully deployed in a rat. With the benefit of the smaller design and laser fabrication technology, it can be fitted into a catheter with an inner diameter of 0.6mm. The vascular electrocorticography can be detected during the acute recording, making it promising in the application of small animals and thin vessels.Significance. The method we proposed combines the advantages of endovascular micro-wire electrode and stent, helping make the electrodes smaller. This study provided an alternative method for deploying micro-wire electrodes into thinner vessels as an endovascular neural interface.

Anterior nucleus of thalamus deep brain stimulation for medication refractory epilepsy modulates theta and low-frequency gamma activity: a case study

A 35-year-old gentleman with a traumatic brain injury was diagnosed with refractory epilepsy with electroencephalogram and imaging findings supporting a broad seizure onset pattern in bilateral frontotemporal regions. He therefore received a Medtronic Percept PC Deep Brain Stimulator (DBS) placed bilaterally in the anterior nucleus of the thalamus (ANT). While most refractory epilepsy patients' stimulation parameters use the SANTE trial standard clinical settings of 145 Hz, 90 μs, with cycling 1-min stimulation on and 5 min stimulation off, this participant underwent 7 different stimulation parameter tests at home following testing in the clinic of 24 different stimulation parameters across 12 neurologist visits. This device allows for simultaneous stimulation of the ANT while recording the ANT local field potential (LFP) response under different stimulation parameters. Slepian multitaper analysis, modified Fitting Oscillations, and One Over F method for detrending the aperiodic component were performed to analyze neural oscillations in the frequency domain captured in the clinic. This participant was participating in a clinical study examining the effectiveness of nonstandard DBS settings to minimize broadband neural activity in the ANT. Statistically significant neuromodulatory suppression of gamma oscillations was observed in the clinic under multiple stimulation settings. We compared the ability of these research stimulation parameters to suppress at-home ANT neural activity against the standard clinical settings and examined the effects of both sets of parameters on LFP power nonstationarity. At home, theta/alpha LFP power suppression was statistically significantly reduced under the 125 Hz, 50 μs setting as opposed to the clinical setting of 145 Hz, 90 μs. The participant has achieved greater than 50% seizure reduction for over 1 year since the last neurology visit. Suppression of gamma in the clinic in the right hemisphere and suppression of theta at home in the left hemisphere show promise as quantitative feedback biomarkers for ANT-DBS. Understanding the local and network relationships of theta and slow gamma oscillations in the thalamus would further explain how these modulated oscillations may relate to the onset and propagation of seizures.

Human pulvinar stimulation engages select cortical pathways in epilepsy

The pulvinar has been proposed as an effective neuromodulation target for patients with posterior quadrant and temporal epilepsies. However, the pulvinar has a large tissue volume, multiple subnuclei, and widespread cortical connections. It remains unknown whether electrical stimulation of distinct pulvinar subregions affects the temporal, occipital, and parietal areas differently. To address this gap, we delivered single-pulse electrical stimulation to the pulvinar and measured the resulting brain stimulation evoked potentials in twelve patients undergoing stereotactic EEG for drug-resistant epilepsy. Brain stimulation evoked potentials were parameterized across the occipital, temporal and parietal cortex. Stimulation of the lateral pulvinar elicited significant brain stimulation evoked potentials in striate and extrastriate areas that diminish as stimulation shifts towards the medial pulvinar. Conversely, stimulation of the ventral aspect of the medial pulvinar produced significant lateral temporal evoked potentials, which diminish with lateral pulvinar stimulation. We also found that stimulation of the dorsomedial pulvinar evoked significant parietal responses with limited striate/extrastriate and lateral temporal responses. These results demonstrate that electrical stimulation of specific pulvinar subregions influences distinct occipital, parietal and lateral temporal areas. Selective targeting of pulvinar subregions to maximize seizure network engagement may be essential for individualized treatment of posterior quadrant and temporal epilepsies.

A Posterior Approach for Combined Targeting of the Centromedian Nucleus and Pulvinar for Responsive Neurostimulation

BACKGROUND AND OBJECTIVES

Neuromodulation for the treatment of epilepsy is a growing field, and several thalamic nuclei (including the anterior nucleus, centromedian nucleus [CM], and pulvinar) have been implicated and targeted. Although an anterior trajectory approach to the CM is conventionally used, we report on a novel posterior trajectory which can be useful when the conventional anterior approach is surgically challenging, or where dual CM and pulvinar coverage is desired.

METHODS

Clinical and imaging data were retrospectively collected from 7 patients with at least 1 posterior trajectory CM lead and 4 patients with at least 1 anterior trajectory CM lead.

RESULTS

Patients in the anterior and posterior trajectory groups had a mean of 48.1% and 65.2% seizure reduction, respectively, and were not significantly different (P = .53). Patients in the posterior trajectory group had contacts within the CM and/or pulvinar. There were no pulvinar contacts in the anterior trajectory group. Analysis of structural connectivity in 1 patient from each group revealed temporal- and occipital-projecting tracts for electrodes within the anterior and medial pulvinar nuclei. Stimulated thalamic nuclei from the anterior trajectory lead did not show any temporal- or occipital-projecting tracts.

CONCLUSION

We demonstrate that a posterior trajectory approach to the CM is feasible, safe, and effective in drug-resistant epilepsy. This provides an alternative option when the conventional anterior approach is surgically infeasible or when dual CM/pulvinar coverage is desired.

Deep brain stimulation of the anterior nucleus of the thalamus reduces the risk for status epilepticus in focal drug-resistant epilepsy

OBJECTIVE

Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is a third-line treatment option for patients with refractory focal epilepsy. However, the effect on recurrent episodes of status epilepticus (SE) after ANT-DBS implantation has not been systematically investigated. Here, we set out to determine whether ANT-DBS has a preventive clinical effect on the risk of SE in difficult-to-treat epilepsies.

METHODS

We performed a retrospective, monocentric analysis in a cohort of patients with refractory epilepsy who received bilateral DBS implantation in the ANT (n = 24). Medical records were reviewed to compare the total number of SE in each patient before and after surgery.

RESULTS

Out of 24 patients, 11 (46 %) had 20 episodes of SE preoperatively, 17 of which were unprovoked. Postoperatively, only 2 patients developed SE, one of which was provoked. The relative annual risk of SE in this cohort was reduced from 28.8 % (per patient year) preoperatively to 1.9 % postoperatively, demonstrating a statistically significant reduction in SE incidence with ANT-DBS (p < 0.005). Survival analysis confirmed significantly longer status-free survival postoperatively.

CONCLUSION

ANT-DBS may be beneficial as a preventive intervention in patients with refractory epilepsy at high risk for recurrent SE.

The thalamus: Structure, function, and neurotherapeutics

The complexity and expansive nature of thalamic research has led to numerous interventions for varied disease states. At the same time, this complexity along with siloed areas of study can hinder a comprehensive understanding. The goal of this paper is to give the reader a broader and more detailed perspective on the thalamus. In order to accomplish this goal, the paper begins with a summary of the function, electrophysiology, and anatomy of the normal thalamus. With this foundation, thalamic involvement in neurological diseases is discussed with a focus on epilepsy. Therapeutic interventions in the thalamus for epilepsy as well as movement disorders, psychiatric conditions and disorders of consciousness are described. Lastly limitations in the field and future models of data sharing and cooperation are explored.

MRgFUS disconnection surgery for hypothalamic hamartoma-related epilepsy: case report and literature review

BACKGROUND

Drug-resistant epilepsy (DRE) secondary to hypothalamic hamartoma (HH) often requires surgical resection or stereotactic radiosurgery, which frequently fail to provide satisfactory outcomes and are associated with severe side effects. Magnetic resonance-guided focused ultrasound (MRgFUS) may represent a minimally invasive surgical approach to HH by offering precise thermal ablation of sub-millimetric brain targets while sparing surrounding structures.

METHODS

We present the case of a 19-year-old man with HH-associated DRE, who was successfully treated with MRgFUS. The procedure resulted in effective ablation of the hypothalamic interface of the HH, disconnecting the epileptogenic lesion from the surrounding brain tissue. We also reviewed the literature on MRgFUS for DRE.

RESULTS

The patient experienced a complete resolution of seizures and significant improvements in social and occupational functioning over an 18-month follow-up period. No neurological, cognitive, or endocrinological adverse effects were observed.

CONCLUSION

Our case report and literature review suggest that MRgFUS may achieve adequate seizure control in DRE associated with HH without adverse effects. While MRgFUS shows promise for other forms of DRE, data remain preliminary, and some safety concerns persist. Further studies with long-term follow-up are warranted to better support the use of MRgFUS in DRE.

Interictal paroxysmal fast activity and functional connectivity in steroid responsive and non-responsive Lennox-Gastaut syndrome

OBJECTIVE

The aim of this study was to investigate the changes in interictal paroxysmal fast activity and functional connectivity before and after steroid pulse therapy in patients with Lennox-Gastaut syndrome (LGS).

METHODS

The medical records of patients who visited the pediatric neurology clinics with LGS as their primary complaint and completed intravenous methylprednisolone therapy were reviewed. Effects of steroid therapy on clinical seizures and scalp EEG were analyzed. Generalized paroxysmal fast activity (GPFA) burden were detected and compared before and after treatment. As a measure of global functional connectivity, we calculated mutual information (MI) between all channels, which was then used to assess network topology.

RESULTS

Steroid pulse therapy improved seizure control in 20 (27 %) patients. Fourteen (18.9 %) children became complete seizure-free, but 8 patients experienced relapses subsequently. The later age of disease onset, shorter duration of epilepsy, and definite cerebral structural etiology were found to advantageous for hormone response. A significant correlation was observed between GPFA burden and diary seizure number. Patients with higher GPFA burdens and higher MI values exhibited a poor response to steroid treatment. Patients who respond positively to steroids therapy demonstrated longer characteristic path length, higher modularity and lower global efficiency in high beta and gamma bands.

CONCLUSION

Add-on steroid therapy can be considered as an optional adjunct for LGS. GPFA could be utilized as a parameter to predict treatment effects and prognosis for LGS. The group that responded to steroids showed a high level of local clustering and low long-range network connectivity. This study provides real-world evidence regarding the effectiveness of steroid in refractory LGS.

MORE Than Meets the Eye: The Evolving Landscape of DBS in Epilepsy

Long-Term Evaluation of Anterior Thalamic Deep Brain Stimulation for Epilepsy in the European MORE Registry Kaufmann E, Peltola J, Colon AJ, Lehtimäki K, Majtanik M, Mai JK, Bóné B, Bentes C, Coenen V, Gil-Nagel A, Goncalves-Ferreira AJ, Ryvlin P, Taylor R, Brionne TC, Gielen F, Song S, Boon P; MORE study group. Epilepsia. 2024;65(8):2438-2458. doi: 10.1111/epi.18003 Objective: Short-term outcomes of deep brain stimulation of the anterior nucleus of the thalamus (ANT-DBS) were reported for people with drug-resistant focal epilepsy (PwE). Because long-term data are still scarce, the Medtronic Registry for Epilepsy (MORE) evaluated clinical routine application of ANT-DBS. Methods: In this multicenter registry, PwE with ANT-DBS were followed up for safety, efficacy, and battery longevity. Follow up ended after 5 years or upon study closure. Clinical characteristics and stimulation settings were compared between PwE with no benefit, improvers, and responders, that is, PwE with average monthly seizure frequency reduction rates of ≥50%. Results: Of 170 eligible PwE, 104, 62, and 49 completed the 3-, 4-, and 5-year follow up, respectively. Most discontinuations (68%) were due to planned study closure as follow up beyond 2 years was optional. The 5-year follow-up cohort had a median seizure frequency reduction from 16 per month at baseline to 7.9 per month at 5-year follow up (P  < .001), with most-pronounced effects on focal-to-bilateral tonic–clonic seizures (n = 15, 77% reduction, P  = .008). At last follow up (median 3.5 years), 41% (69/170) of PwE were responders. Unifocal epilepsy (P  = .035) and a negative history of epilepsy surgery (P  = .002) were associated with larger average monthly seizure frequency reductions. Stimulation settings did not differ between response groups. In 179 implanted PwE, DBS-related adverse events (AEs, n = 225) and serious AEs (n = 75) included deterioration in epilepsy or seizure frequency/severity/type (33; 14 serious), memory/cognitive impairment (29; 3 serious), and depression (13; 4 serious). Five deaths occurred (none were ANT-DBS related). Most AEs (76.3%) manifested within the first 2 years after implantation. Activa PC depletion (n = 37) occurred on average after 45 months. Significance: MORE provides further evidence for the long-term application of ANT-DBS in clinical routine practice. Although clinical benefits increased over time, side effects occurred mainly during the first 2 years. Identified outcome modifiers can help inform PwE selection and management.

Principles of Stereotactic Surgery

BACKGROUND AND OBJECTIVES

Stereotactic procedures are used to manage a diverse set of patients across a variety of clinical contexts. The stereotactic devices and software used in these procedures vary between surgeons, but the fundamental principles that constitute safe and accurate execution do not. The aim of this work is to describe these principles to equip readers with a generalizable knowledge base to execute and understand stereotactic procedures.

METHODS

A combination of a review of the literature and empirical experience from several experienced surgeons led to the creation of this work. Thus, this work is descriptive and qualitative by nature, and the literature is used to support instead of generate the ideas of this framework.

RESULTS

The principles detailed in this work are categorized based on 5 clinical domains: imaging, registration, mechanical accuracy, target planning and adjustment, and trajectory planning and adjustment. Illustrations and tables are used throughout to convey the concepts in an efficient manner.

CONCLUSION

Stereotactic procedures are complex, requiring a thorough understanding of each step of the workflow. The concepts described in this work enable functional neurosurgeons with the fundamental knowledge necessary to provide optimal patient care.

Effect of deep brain stimulation on the severity of seizures and the quality of life in patients with multifocal drug-resistant epilepsy in Iran: A pilot review of local experience

This study investigates the impact of the anterior nucleus of the thalamus deep brain stimulation (ANT-DBS) on patients with drug-resistant epilepsy (DRE) in Iran, specifically focusing on its effects on seizure metrics, severity and its influence on quality of life over time. A cohort of eight patients with DRE in Iran who underwent ANT-DBS was evaluated. Pre-operative assessments included comprehensive documentation of seizure frequency, duration, severity scores, and the Quality of Life in Epilepsy Inventory (QOLIE-13). Each patient also underwent high-resolution imaging using a 1.5 Tesla MRI, with targeted electrode placement in the anterior thalamic area. Post-operative evaluations measured changes in seizure frequency, severity scores, duration, and quality of life indicators. All subjects presented with DRE, and the mean age of participants was 24.62 years. Post-operative data revealed significantly reduced seizure frequency, duration, and severity scores. Notably, this reduction was more pronounced at the 6-month follow-up than the 3-month assessment, indicating a progressive therapeutic effect. All patients demonstrated a response to ANT-DBS, with two individuals achieving seizure freedom. Additionally, there was a marked improvement in quality of life, particularly in the domains of energy/fatigue and social functioning. ANT-DBS has been established as a promising and safe therapeutic intervention for patients with DRE. In a cohort of DRE patients in Iran, the treatment demonstrated comparable efficacy in decreasing seizure frequency and severity and enhancing self-reported quality of life, consistent with findings reported in the existing literature. The therapeutic benefits of ANT-DBS appear to augment over time.

Comparative Review of Seizure and Cognitive Outcomes in Resective, Ablative, and Neuromodulatory Temporal Lobe Epilepsy Surgery

Resective surgery for drug-resistant temporal lobe epilepsy remains underutilized in the United States. While anteromesial temporal lobectomy consistently achieves the highest rates of long-term seizure freedom, it comes with greater risks for memory and language decline. Magnetic resonance imaging-guided laser interstitial thermal therapy and neuromodulation have gained popularity due to perceived lower surgical risk and faster recovery, although they yield lower rates of sustained seizure freedom. Neuromodulation with vagus nerve, deep brain, or responsive neurostimulation provides an option for patients ineligible for resection or ablation, but overall seizure outcomes remain modest. Balancing improved seizure control with open resection against the potential cognitive advantages of less invasive treatments is complex, requiring careful patient selection. Future research must refine these approaches to optimize results. Thoughtful, individualized decision-making, guided by each patient's clinical scenario and goals, is paramount for achieving the best balance between seizure freedom, cognitive preservation, and overall patient outcome.

Thalamic stimulation induced changes in network connectivity and excitability in epilepsy

Background

The clinical effects of deep brain stimulation for neurological conditions manifest across multiple timescales, spanning seconds to months, and involve direct electrical modulation, neuroplasticity, and network reorganization. In epilepsy, the delayed effects of deep brain stimulation on seizures limit optimization. Single pulse electrical stimulation and the resulting pulse evoked potentials offer a measure network effective connectivity and excitability. This study leverages single pulse and high frequency thalamic stimulation during stereotactic electroencephalography to assess seizure network engagement, modulate network activity, and track changes in excitability and epileptiform abnormalities.

Methods

Ten individuals with drug resistant epilepsy undergoing clinical stereotactic electroencephalography were enrolled in this retrospective cohort study. Each underwent a trial of high frequency (145 Hz) thalamic stimulation. Pulse evoked potentials were acquired before and after high frequency stimulation. Baseline evoked potential root-mean-square amplitude assessed seizure network engagement, and modulation of amplitude (post high frequency stimulation versus baseline; Cohen's d effect size) assessed change in network excitability. Interictal epileptiform discharge rates were measured by an automated classifier at baseline and during high frequency stimulation. Statistical significance was determined using paired-sample t-tests (p<0.05 significance level). This study was approved by the Mayo Clinic Institutional Review Board, with informed consent obtained from all participants.

Results

Thalamic stimulation delivered for >1.5 hours significantly reduced pulse evoked potential amplitudes in connected areas compared to baseline, with the degree of modulation correlated with baseline connectivity strength. Shorter stimulation durations did not induce reliable changes. High frequency stimulation immediately suppressed interictal epileptiform discharge rates in seizure networks with strong baseline thalamocortical connectivity. Pulse evoked potentials delineated the anatomical distribution of network engagement, revealing distinct patterns across thalamic subfields.

Conclusion

Pulse evoked potentials and thalamic stimulation during stereotactic electroencephalography provide novel network biomarkers to evaluate target engagement and modulation of large-scale networks across acute and subacute timescales. This approach demonstrates potential for efficient, data-driven neuromodulation optimization, and a new paradigm for personalized deep brain stimulation in epilepsy.