Deep learning on brief interictal intracranial recordings can accurately characterize seizure onset zones

Abstract

Objective: Epilepsy is a debilitating disorder affecting more than 50 million people worldwide, and one third of patients continue to have seizures despite maximal medical management. If patients' seizures localize to a discrete brain region, termed a seizure onset zone, resection may be curative. Localization is often confirmed with stereotactic electroencephalography; however, this may require patients to stay in the hospital for weeks to capture spontaneous seizures. Automated localization of seizure onset zones could therefore improve presurgical evaluation and decrease morbidity.

Methods: Using more than 1 000 000 interictal stereotactic electroencephalography segments collected from 78 patients, we performed five-fold cross-validation and testing on a multichannel, multiscale, one-dimensional convolutional neural network to classify seizure onset zones.

Results: Across held-out test sets, our models achieved a seizure onset zone classification sensitivity of .702 (95% confidence interval [CI] = .549-.805), specificity of .741 (95% CI = .652-.835), and accuracy of .738 (95% CI = .687-.795), which was significantly better than models trained on random labels. The models performed well across the entire brain, with top five region performance demonstrating accuracies between 70.0% and 88.4%. When split by outcomes, the models performed significantly better on patients with favorable Engel outcomes after resection or who were responsive neurostimulation responders. Finally, SHAP (Shapley Additive Explanation) value analysis on median-normalized input data assigned consistently high feature importance to interictal spikes and large deflections, whereas similar analyses on histogram-equalized data revealed differences in feature importance assignments to low-amplitude segments.

Significance: This work serves as evidence that deep learning on brief interictal intracranial data can classify seizure onset zones across the brain. Furthermore, our findings corroborate current understandings of interictal epileptiform discharges and may help uncover novel interictal morphologies. Clinical application of our models may reduce dependence on recorded seizures for localization and shorten presurgical evaluation time for drug-resistant epilepsy patients, reducing patient morbidity and hospital costs.

Keywords: SHAP analysis; convolutional neural network; presurgical evaluation; seizure onset zone localization.