Reliability of visual review of intracranial electroencephalogram in identifying the seizure onset zone: A systematic review and implications for the accuracy of automated methods

Abstract

Visual review of intracranial electroencephalography (iEEG) is often an essential component for defining the zone of resection for epilepsy surgery. Unsupervised approaches using machine and deep learning are being employed to identify seizure onset zones (SOZs). This prompts a more comprehensive understanding of the reliability of visual review as a reference standard. We sought to summarize existing evidence on the reliability of visual review of iEEG in defining the SOZ for patients undergoing surgical workup and understand its implications for algorithm accuracy for SOZ prediction. We performed a systematic literature review on the reliability of determining the SOZ by visual inspection of iEEG in accordance with best practices. Searches included MEDLINE, Embase, Cochrane Library, and Web of Science on May 8, 2022. We included studies with a quantitative reliability assessment within or between observers. Risk of bias assessment was performed with QUADAS-2. A model was developed to estimate the effect of Cohen kappa on the maximum possible accuracy for any algorithm detecting the SOZ. Two thousand three hundred thirty-eight articles were identified and evaluated, of which one met inclusion criteria. This study assessed reliability between two reviewers for 10 patients with temporal lobe epilepsy and found a kappa of .80. These limited data were used to model the maximum accuracy of automated methods. For a hypothetical algorithm that is 100% accurate to the ground truth, the maximum accuracy modeled with a Cohen kappa of .8 ranged from .60 to .85 (F-2). The reliability of reviewing iEEG to localize the SOZ has been evaluated only in a small sample of patients with methodologic limitations. The ability of any algorithm to estimate the SOZ is notably limited by the reliability of iEEG interpretation. We acknowledge practical limitations of rigorous reliability analysis, and we propose design characteristics and study questions to further investigate reliability.

Keywords: electrocorticography; intracranial electroencephalography; reliability; seizure onset zone; stereoencephalography.

FIGURE 1

Diagram outlining included articles at each stage of the screening process, including reasons for exclusion at the full text screening stage. There were 21 articles identified through citation searching that were excluded via title and abstract screening. HFO, high‐frequency oscillation; iEEG, intracranial electroencephalography; SOZ, seizure onset zone

FIGURE 2

The expected kappa (A), and expected beta (B) for a hypothetical study assessing reliability of a seizure foci prediction algorithm that uses epileptologist‐defined seizure onset zone as the gold standard. Both are expressed as a function of the probability of true positive electrodes within the seizure onset zone (pTP) and probability of selecting true negative electrodes outside the seizure onset zone (pTN)