Responsive neurostimulation as a treatment for super-refractory focal status epilepticus: a systematic review and case series

OBJECTIVE

Super-refractory status epilepticus (SRSE) has high rates of morbidity and mortality. Few published studies have investigated neurostimulation treatment options in the setting of SRSE. This systematic literature review and series of 10 cases investigated the safety and efficacy of implanting and activating the responsive neurostimulation (RNS) system acutely during SRSE and discusses the rationale for lead placement and selection of stimulation parameters.

METHODS

Through a literature search (of databases and American Epilepsy Society abstracts that were last searched on March 1, 2023) and direct contact with the manufacturer of the RNS system, 10 total cases were identified that utilized RNS acutely during SE (9 SRSE cases and 1 case of refractory SE [RSE]). Nine centers obtained IRB approval for retrospective chart review and completed data collection forms. A tenth case had published data from a case report that were referenced in this study. Data from the collection forms and the published case report were compiled in Excel.

RESULTS

All 10 cases presented with focal SE: 9 with SRSE and 1 with RSE. Etiology varied from known lesion (focal cortical dysplasia in 7 cases and recurrent meningioma in 1) to unknown (2 cases, with 1 presenting with new-onset refractory focal SE [NORSE]). Seven of 10 cases exited SRSE after RNS placement and activation, with a time frame ranging from 1 to 27 days. Two patients died of complications due to ongoing SRSE. Another patient's SE never resolved but was subclinical. One of 10 cases had a device-related significant adverse event (trace hemorrhage), which did not require intervention. There was 1 reported recurrence of SE after discharge among the cases in which SRSE resolved up to the defined endpoint.

CONCLUSIONS

This case series offers preliminary evidence that RNS is a safe and potentially effective treatment option for SRSE in patients with 1-2 well-defined seizure-onset zone(s) who meet the eligibility criteria for RNS. The unique features of RNS offer multiple benefits in the SRSE setting, including real-time electrocorticography to supplement scalp EEG for monitoring SRSE progress and response to treatment, as well as numerous stimulation options. Further research is indicated to investigate the optimal stimulation settings in this unique clinical scenario.

A Method of Intraoperative Registration Verification to Prevent Accuracy Errors in Robot-Assisted Stereotactic Electroencephalography Electrode Placement

BACKGROUND

Robotic-assisted stereotactic electroencephalography (sEEG) electrode placement is increasingly common at specialized epilepsy centers. High accuracy and low complication rates are essential to realizing the benefits of sEEG surgery. The aim of this study was to describe for the first time in the literature a method for a stereotactic registration checkpoint to verify intraoperative accuracy during robotic-assisted sEEG and to report our institutional experience with this technique.

METHODS

All cases performed with this technique since the adoption of robotic-assisted sEEG at our institution were retrospectively reviewed.

RESULTS

In 4 of 111 consecutive sEEG operations, use of the checkpoint detected an intraoperative registration error, which was addressed before completion of sEEG electrode placement.

CONCLUSIONS

The use of a registration checkpoint in robotic-assisted sEEG surgery is a simple technique that can prevent electrode misplacement and improve the safety profile of this procedure.

Electrocorticography Analysis in Patients With Dual Neurostimulators Supports Desynchronization as a Mechanism of Action for Acute Vagal Nerve Stimulator Stimulation

PURPOSE

Both vagal nerve stimulation (VNS) and responsive neurostimulation (RNS System) are treatment options for medically refractory focal epilepsy. The mechanism of action of both devices remains poorly understood. Limited prior evidence suggests that acute VNS stimulation may reduce epileptiform activity and cause EEG desynchronization on electrocorticography (ECoG). Our study aims to isolate effects of VNS on ECoG as recorded by RNS System in patients who have both devices, by comparing ECoG samples with and without acute VNS stimulation.

METHODS

Ten 60-second ECoGs each from 22 individuals at 3 epilepsy centers were obtained-5 ECoGs with VNS "off" and 5 ECoGs with VNS "on." Electrocorticograps containing seizures or loss of telemetry connection artifact were excluded from analysis (total of 169 ECoGs were included). Electrocorticographs were analyzed for differences in spectral content by generating average spectrograms for "on" and "off" states and using a linear mixed-effects model to isolate effects of VNS stimulation.

RESULTS

Acute VNS stimulation reduced average power in the theta band by 4.9%, beta band by 3.8%, and alpha band by 2.5%. The reduction in theta power reached statistical significance with a P value of <0.05.

CONCLUSIONS

Our results provide evidence that acute VNS stimulation results in desynchronization of specific frequency bands (salient decrease in theta and beta bands, smaller decrease in alpha band) in ECoGs recorded by the RNS device in patients with dual (VNS and RNS) neurostimulators. This finding offers support for desynchronization as a theorized mechanism of action of VNS. Further research may lead to future improved neurostimulator efficacy by informing optimal stimulation programming parameters.

Let's Talk About Sex: Integrating Sex as a Biological Variable Into Epilepsy Research

There is a long history of underrepresentation of women and female animals being studied in scientific research, which has resulted in gaps in knowledge and at times, inaccurate clinical recommendations. There is a gradual shift in the mindset of the scientific community on this issue, in part related to policy changes enacted by the National Institute of Health (NIH). Sex must now be accounted for as a biological variable in both basic and clinical research. This review discusses the history of evolving policies on inclusion of sex-informed data in scientific research, and the ways in which epilepsy researchers can approach future studies in a manner that takes sex as a biological variable into account.

Recent advances in epilepsy management

PURPOSE OF REVIEW

Recent advances in our understanding of seizure generation have resulted in modified recommendations for when seizure treatment should be initiated, revisions to our definition of status epilepticus, and new pharmacological and neuromodulatory therapies. The goal of this review is to provide the anesthesiologist with an overview of the advancements they are most likely to encounter while providing clinical care.

RECENT FINDINGS

There have been recent modifications to seizure definitions and treatment recommendations. These include the idea that treatment with antiepileptic therapy should be initiated after the first unprovoked seizure in individuals who are at high risk for another seizure, and that the idea that status epilepticus should be thought of as a two-phase process, related to an initial phase after which intervention should be started, and a second phase after which time risk of long-term sequelae is increased. Additionally, several new therapies have become available that have novel mechanisms of action, which are more efficacious and have fewer side-effects.

SUMMARY

As knowledge about mechanisms of seizure generation has improved, there has been a concurrent evolution in our thinking about seizure-related definitions, and indications for initiation of treatment. Several next generation drug therapies with more specific targets have also become available. Taken together, there have been significant improvements in care options.