The importance of methodological context in pediatric vagus nerve stimulation outcome reporting

We read with genuine interest the recent work of Bansal and colleagues, describing pediatric vagus nerve stimulation (VNS) outcomes from a single high-volume center.1 The authors are to be acknowledged for compiling an extensive dataset and for sharing insights spanning nearly two decades of clinical practice. Because pediatric VNS studies with long-term follow-up remain relatively uncommon, this contribution is an important addition to the literature. At the same time, several methodological considerations may help contextualize the findings and guide interpretation. The reported 90.5% responder rate and 20.5% seizure-freedom rate are notably higher than those consistently observed in prospective multicenter studies and meta-analyses.2, 3 When efficacy estimates substantially exceed those in the broader literature—particularly in retrospective studies—clarity around outcome definitions becomes especially important. Although seizure severity is described as contributing to baseline burden, no operational definition or structured assessment tool is provided. Baseline seizure frequency was categorized, but not incorporated as a covariate in any subsequent analysis. Moreover, the inclusion of a “sporadic” (less than monthly) seizure frequency category suggests that a subset of participants may have had relatively low baseline seizure burden, limiting interpretability of disease severity at study entry. Seizure outcome assessments also relied on multiple data sources. Although some encounters incorporated long-term electroencephalography (EEG) evaluation, others relied primarily on caregiver reporting, with seizure diaries available only intermittently. Prior prospective pediatric VNS work, including from our own group, has demonstrated meaningful discrepancies between caregiver- and clinician-reported seizure frequency even when standardized tools are used.4 Greater clarification regarding how objective and subjective measures were integrated would strengthen interpretability. The quality of life (QoL) findings likewise merit additional context. The study reports exceptionally high rates of subjective QoL improvement, yet these were derived solely from caregiver narratives without validated instruments, predefined scales, or clinician corroboration. By contrast, a recent prospective multi-center North American cohort study found that 37.1% of children achieve meaningful improvements in QoL, defined as exceeding the minimal clinically-important difference on a validated instrument.5 Subjective benefit rates approaching 90% are difficult to contextualize in the absence of standardized QoL measures and may reflect expectancy or reporting effects in addition to true functional change. Combined with an outcome scale that does not capture seizure worsening and with no accounting for anti-seizure medication (ASM) changes—both of which can substantially influence seizures and QoL—the risk of overestimating treatment benefit becomes substantial. Several associations highlighted in the manuscript, including early implantation and ultra-rapid duty cycling, did not retain statistical significance after Bonferroni correction. Presenting these results as exploratory would help avoid overinterpretation. This distinction is particularly relevant in light of population-level analyses demonstrating a non-linear, inverted U-shaped relationship between VNS dosing parameters and clinical response.6 Prior work suggests optimal population-level output current near 1.6 mA, with higher stimulation settings not necessarily conferring additional benefit.6 Interpretation is further complicated by differences in stimulation exposure in open- vs closed-loop (auto-stimulation) device models. Finally, in the absence of a matched control group, longitudinal improvements likely reflect the combined effects of multiple concurrent interventions. Patients managed in a quaternary epilepsy care environment may also benefit from iterative ASM optimization, dietary therapies, management of comorbidities such as obstructive sleep apnea, caregiver education, or subsequent surgical interventions. Consideration of these co-interventions would further clarify the degree to which observed outcome trajectories can be attributed to VNS programming. Additional context regarding device inactivation generator depletion, and the distinction between point-prevalent and sustained seizure freedom would also be informative. Taken together, these considerations suggest that although the study adds real-world experience, interpretation of the main findings should be approached cautiously. Most importantly, careful framing will help ensure that the reported outcomes are interpreted in proportion to the methodological design, thereby supporting informed decision-making for clinicians and families navigating pediatric VNS therapy. We gratefully acknowledge the support of the University of Toronto Libraries' Open Access Agreements & APC Discounts program, which helped cover the article processing charges for this publication. G.M.I. has received consulting fees from LivaNova, Synergia, and Medtronic and serves on the advisory boards of Synergia Medical and the Pediatric Epilepsy Surgery Alliance. T.F.D. and K.M. declare no conflicts of interest related to the present study. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines. Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.