Frequency of Automatic Stimulations in Responsive Vagal Nerve Stimulation in Patients With Refractory Epilepsy

Vagus nerve stimulation therapy in people with drug-resistant epilepsy (CORE-VNS): rationale and design of a real-world post-market comprehensive outcomes registry

Introduction

The Vagus Nerve Stimulation Therapy System (VNS Therapy) is an adjunctive neuromodulatory therapy that can be efficacious in reducing the frequency and severity of seizures in people with drug-resistant epilepsy (DRE). CORE-VNS aims to examine the long-term safety and clinical outcomes of VNS in people with DRE.

Methods and analysis

The CORE-VNS study is an international, multicentre, prospective, observational, all-comers, post-market registry. People with DRE receiving VNS Therapy for the first time as well as people being reimplanted with VNS Therapy are eligible. Participants have a baseline visit (prior to device implant). They will be followed for a minimum of 36 months and a maximum of 60 months after implant. Analysis endpoints include seizure frequency (average number of events per month), seizure severity (individual-rated categorical outcome including very mild, mild, moderate, severe or very severe) as well as non-seizure outcomes such as adverse events, use of antiseizure medications, use of other non-pharmacological therapies, quality of life, validated measures of quality of sleep (Pittsburgh Sleep Quality Index or Children’s Sleep Habit Questionnaire) and healthcare resource utilisation. While the CORE-VNS registry was not expressly designed to test hypotheses, subgroup analyses and exploratory analysis that require hypothesis testing will be conducted across propensity score matched treatment groups, where possible based on sampling.

Ethics and dissemination

The CORE-VNS registry has already enrolled 823 participants from 61 centres across 15 countries. Once complete, CORE-VNS will represent one of the largest real-world clinical data sets to allow a more comprehensive understanding of the management of DRE with adjunctive VNS. Manuscripts derived from this database will shed important new light on the characteristics of people receiving VNS Therapy; the practical use of VNS across different countries, and factors influencing long-term response.

Trail registration number

NCT03529045.

Vagus nerve stimulation: a 20-year Australian experience

BACKGROUND

Vagus nerve stimulation (VNS) therapy was first approved in the mid-1990s in the USA, Europe and Australia, with demonstrable efficacy in paediatric populations. Benefit in seizure frequency reduction can be observed up to 2 years post-intervention; however, few studies assess outcomes beyond this period. Furthermore, paediatric cohort sizes are small, limiting generalisability of outcome assessments. We evaluate VNS insertion outcomes and complications or side-effects in a large paediatric cohort, over a 20-year period from Queensland's first VNS insertion.

METHODS

A retrospective review was conducted of all paediatric VNS insertions at the Queensland Children's Hospital (QCH) and the Mater Children's Hospital/Mater Children's Private Hospital (MCH/MCPH) Brisbane. A minimum of 1-year follow-up from 1999 to 2020 was required for inclusion. Patients were assessed on demographics, epilepsy details, seizure outcomes and complications or side-effects.

RESULTS

In this extended follow-up cohort (76 patients, 7.2 ± 5.3 years), 51.3% of patients had ≥ 50% seizure frequency reduction, while 73.7% experienced an Engel III outcome (worthwhile benefit) or better. Eleven patients (14.9%) were seizure-free at follow-up, and 81.6% retained long-term therapy. Stimulation-related side-effects are common (17.1%) but rarely result in stimulation cessation (3.9%). Cessation occurred in 14 patients (18.4%) and most commonly related to minimal benefit (13.2%). Demographics, aetiology, seizure nature and surgical factors did not influence outcomes.

CONCLUSION

Over extended treatment periods, a large proportion of patients will benefit significantly from VNS therapy. Approximately 4 of 5 patients will retain VNS therapy, and in cases of cessation, this is most commonly related to minimal benefit. Underlying demographics, aetiology or seizure nature do not influence outcomes. This 20-year Queensland assessment of VNS therapy outcomes informs long-term expectation of VNS therapy.

The relationship between duty cycle, tachycardia threshold and autostimulation delivery in cardio-responsive vagus nerve stimulation

PURPOSE

Many patients with epilepsy are unable to completely control seizures with medication alone. Vagus nerve stimulation is an effective nonpharmacologic option for treatment-resistant epilepsy. AutoStim technology is a relatively new VNS feature that provides extra stimulations in response to tachycardia, which often precedes seizures. This feature adds a currently unknown number of extra stimulations per day. This study aims to evaluate that actual stimulations' patients receive per day as a function of varying VNS settings.

METHODS

This project was a retrospective chart review. All patients with implanted VNS devices with AutoStim technology managed at Northwestern's epilepsy clinic were included in the study. Data were collected on duty cycle, tachycardia threshold, expected number of stimulations per day, normal mode stimulations per day, and AutoStims per day. Associations between all variables were evaluated.

RESULTS

Sixty-seven patients with VNS stimulators met inclusion criteria leading to 305 unique VNS interrogation results. This study demonstrated the smallest number of extra stimulations between tachycardia thresholds of 40 and 60 with absolute minimums at 35 and 45. Our results also demonstrate a trend of decreasing extra stimulations per day with increased duty cycle at each tachycardia threshold evaluated.

CONCLUSIONS

These data demonstrate the effect of duty cycle and tachycardia threshold on extra stimulations per day and demonstrated the optimal settings for reducing extra stimulations. This research provides reassurance and information to patients and providers about the actual number of stimulations patients receive with AutoStim technology.

Responsive Vagus Nerve Stimulation for Drug Resistant Epilepsy: A Review of New Features and Practical Guidance for Advanced Practice Providers

Vagus nerve stimulation (VNS) is a safe and effective therapy that has been available for over 20 years for adults and children with drug resistant epilepsy (DRE). Since U.S. Food and Drug Administration approval in 1997, VNS has been implanted in over 100,000 patients including over 30,000 children as an adjunctive therapy in reducing the frequency of seizures in patients 4 years of age and older with focal seizures that are refractory to antiseizure medications. VNS Therapy® has evolved over time and currently offers closed-loop, responsive stimulation as well as advanced features that streamline dosing and patient management. Advanced Practice Providers (APPs) such as nurse practitioners, physician assistants and clinical nurse specialists are integral in a comprehensive healthcare team, and dedicated VNS clinics have formed at comprehensive epilepsy centers across the world that are often managed by APPs. This approach improves access, education, and continuity of care for those with VNS or those considering VNS. Here we provide a review for APPs on the VNS Therapy® system focused on new features, dosing, and troubleshooting strategies with the goal to provide guidance to those managing VNS patients.