Brainstem Associated Somatosensory Evoked Potentials and Response to Vagus Nerve Stimulation: An Investigation of the Vagus Afferent Network.

Hrishikesh Suresh,Han Yan,Mike Vandenberk,Ayako Ochi,Samuel Strantzas,Christina Go,Ivanna Yau,Roy Sharma,George M Ibrahim,Puneet Jain,Elizabeth Kerr,O Carter Snead,Karim Mithani,Karanbir Brar,Elizabeth Donner,Elizabeth Pang,Hiroshi Otsubo

doi:10.3389/fneur.2021.768539

Abstract

Despite decades of clinical usage, selection of patients with drug resistant epilepsy who are most likely to benefit from vagus nerve stimulation (VNS) remains a challenge. The mechanism of action of VNS is dependent upon afferent brainstem circuitry, which comprises a critical component of the Vagus Afferent Network (VagAN). To evaluate the association between brainstem afferent circuitry and seizure response, we retrospectively collected intraoperative data from sub-cortical recordings of somatosensory evoked potentials (SSEP) in 7 children with focal drug resistant epilepsy who had failed epilepsy surgery and subsequently underwent VNS. Using multivariate linear regression, we demonstrate a robust negative association between SSEP amplitude (p < 0.01), and seizure reduction. There was no association between SSEP latency and seizure outcomes. Our findings provide novel insights into the mechanism of VNS and inform our understanding of the importance of brainstem afferent circuitry within the VagAN for seizure responsiveness following VNS.

Highlights

Epilepsy is amongst the most common and debilitating neurological disorders in children, affecting 1–2% of the pediatric population [1]
Diffusion tensor imaging (DTI) and magnetoencephalography (MEG) investigations have revealed that increased structural and functional connectivity within the vagus afferent network (VagAN)—a complex neuronal network that appears to be engaged during stimulation of the vagus nerve—portends Vagus nerve stimulation (VNS) response [5, 6, 8]
We explore the association between characteristics of the subcortically recorded component of the somatosensory evoked potential (SSEP) related to brainstem function and their association with VNS response

Summary

Introduction

Epilepsy is amongst the most common and debilitating neurological disorders in children, affecting 1–2% of the pediatric population [1]. Vagus nerve stimulation (VNS) is a safe and well-tolerated treatment option for drug-resistant epilepsy (DRE) that involves electrical stimulation of the vagus nerve at the level of the neck using an implantable device. Recent advances in connectomics have identified a number of structural and functional biomarkers associated with VNS response [6, 7]. Diffusion tensor imaging (DTI) and magnetoencephalography (MEG) investigations have revealed that increased structural and functional connectivity within the vagus afferent network (VagAN)—a complex neuronal network that appears to be engaged during stimulation of the vagus nerve—portends VNS response [5, 6, 8]. VNS responders demonstrate greater engagement of VagAN circuitry with stimulation of the median nerve, which shares overlapping afferent neuronal circuitry with the vagus nerve [8]

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