The Referential Montage Inadequately Localizes Corticocortical Evoked Potentials in Stereoelectroencephalography

• Type of Material: Article
• Authors: Adam Dickey, Emory University; Abdulrahman Alwaki, Emory University; Ammar Kheder, Emory University; Jon Willie, Emory University; Daniel Drane, Emory University; Nigel Pedersen, Emory University
• Language: English
• Date: 2022-07-01
• Publisher: LIPPINCOTT WILLIAMS & WILKINS
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2020 by the American Clinical Neurophysiology Society
• Final Published Version (URL): http://dx.doi.org/10.1097/WNP.0000000000000792
• Title of Journal or Parent Work: JOURNAL OF CLINICAL NEUROPHYSIOLOGY
• Volume: 39
• Issue: 5
• Start Page: 412
• End Page: 418
• Grant/Funding Information: This was work was supported by the T32 NS748019 (ASD), the Woodruff Foundation and K08 NS105929 (NPP), and R01 NS088748 (DLD).
• Keywords: Corticocortical evoked potentials; Laplacian montage; Single pulse electrical stimulation; Neurosciences; SITES; Neurosciences & Neurology; CONNECTIVITY; EEG; Stereoelectroencephalography; Brain connectivity; Science & Technology; Clinical Neurology; Life Sciences & Biomedicine; ELECTRICAL-STIMULATION

Abstract

Purpose:Corticocortical evoked potentials (CCEPs) resulting from single pulse electrical stimulation are increasingly used to understand seizure networks, as well as normal brain connectivity. However, we observed that when using depth electrodes, traditional measures of CCEPs amplitude using a referential montage can be falsely localizing, often to white matter.Methods:We pooled 27 linear electrode arrays targeting the amygdala, hippocampus, or cingulate cortex from eight participants. Using postoperative imaging, we classified contacts as being in gray matter, white matter, or bordering each and measured the amplitude using the root-mean-squared deviation from baseline in a referential, common average, bipolar, or Laplacian montage.Results:Of 27 electrode contacts, 25 (93%) had a significantly higher mean amplitude when in gray matter than in white matter using a Laplacian montage, which was significantly more than the 12 of 27 electrodes (44%) when using a referential montage (P = 0.0003, Fisher exact test). The area under the curve for a receiver operating characteristic classifying contacts as gray or white matter was significantly higher for either the Laplacian (0.79) or the bipolar (0.72) montage when compared with either the common average (0.56) or the referential (0.51) montage (P ≤ 0.005, bootstrap).Conclusions:Both the Laplacian and bipolar montages were superior to the common average or referential montage in localizing CCEPs to gray matter. These montages may be more appropriate for interpreting CCEPs when using depth electrodes than the referential montage, which has typically been used in prior studies of CCEPs with subdural grids.