title: An improved qEEG index for asymmetry detection during the Wada test.
abstract: The Wada test is commonly used to evaluate language and memory lateralization in candidates for epilepsy surgery. The spatial Brain Symmetry Index (BSI) quantifies inter-hemispheric differences in the EEG. Its application has been shown to be feasible during Wada testing. We developed a method for the quantification of EEG asymmetry that matches visual assessments of the EEG better than BSI. Fifty-three patients' EEG data, with a total of 85 injections were analyzed. In a step-wise, data-driven manner, multiple electrode and frequency band combinations were evaluated. Eventually, BSI, calculated using only the frontal electrodes F3 and F4, was combined with a temporal measure of delta power in the central electrodes, C3 and C4, into a new measure: cBSI. Using the area under the ROC curve (AUC), we showed that cBSI performs significantly better relative to BSI (median AUC 0.98 versus 0.96, p=0.0015, Wilcoxon signed rank test). Our results showed that asymmetry detection was significantly improved by combining temporal with spatial qEEG measures. In the future, our combined qEEG measure could allow for a more objective way of monitoring EEG asymmetry, thereby increasing the feasibility of using EEG as a monitoring tool during the Wada test. Future studies should, however, validate our cBSI method in real time in the operating room or radiology suite.
authors.affiliation: Department of Clinical Neurophysiology, AZM Maastricht, Netherlands. Electronic address: guybogaarts@gmail.com.
authors.forename: Guy
authors.initials: G
authors.lastname: Bogaarts
authors.affiliation: Department of Clinical Neurophysiology, AZM Maastricht, Netherlands.
authors.forename: Erik
authors.initials: E
authors.lastname: Gommer
authors.affiliation: Department of Clinical Neurophysiology, AZM Maastricht, Netherlands.
authors.forename: Danny
authors.initials: D
authors.lastname: Hilkman
authors.affiliation: Department of Clinical Neurophysiology, AZM Maastricht, Netherlands.
authors.forename: Vivianne
authors.initials: V
authors.lastname: van Kranen-Mastenbroek
authors.affiliation: Department of Clinical Neurophysiology, AZM Maastricht, Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Reulen
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D004566:Electrodes; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007802:Language; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D008991:Monitoring, Physiologic; D055815:Young Adult
keywords: Brain symmetry index; Epilepsy surgery; Intracarotid amobarbital procedure; Neuromonitoring; Quantitative electroencephalography; Wada test