Hemispheric Surgery Outcome Prediction Scale: Development and Validation of a Seizure Freedom Prediction Tool

Background: A subset of pediatric epilepsy patients suffer from epilepsy syndromes related to multi-lobar or hemispheric epileptogenic networks and diseases. Most of these patients are refractory to anti-seizure drug treatment, resulting in persistent disabling seizures, neurocognitive delay and impaired quality of life. In well-selected patients, hemispheric surgery is associated with excellent seizure freedom rates and relatively low complication rates. Nevertheless, 30% of patients develop seizure recurrence after cerebral hemispheric surgery. The purpose of this study was to develop and validate a model to predict seizure freedom in children undergoing cerebral hemispheric surgery for the treatment of drug-resistant epilepsy. Methods: We analyzed 1237 hemispheric surgeries performed in pediatric patients across 31 centers and 12 countries to identify predictors of seizure freedom at 12 months after surgery. A multivariate logistic regression model was developed based on the entire dataset and its performance was evaluated based on cross-validation. Missing data was handled using multiple imputation techniques. Findings: Overall, 817/1237 (66%) hemispheric surgeries led to seizure freedom (median follow-up of 24 months), and 1050/1237 (85%) were seizure free at 12 months after surgery. The regression model containing age at seizure onset, presence of generalized seizure semiology, presence of contralateral 18-fluoro-2-deoxyglucose–positron emission tomography hypometabolism, etiologic substrate and previous non-hemispheric resective surgery were predictive of seizure freedom (AUC 0·72). A practical Hemispheric Surgery Outcome Prediction Scale (HOPS) score was devised based on these results that can be used to predict seizure freedom. Interpretation: Children most likely to benefit from hemispheric surgery can be selected and counselled through the implementation of a scale derived from a multiple regression model.  Importantly, children who are unlikely to experience seizure control can be spared from the complications and deficits associated with this surgery. The HOPS score is likely to help physicians in clinical decision-making. Funding Statement: The authors stated: "None." Declaration of Interests: None of the authors has any conflict of interest to disclose. None of the authors have financial relationships relevant to this article. Gary W Mathern MD is partly supported by the Davies/Crandall Endowed Chair for epilepsy Research at UCLA. Dr. Phillip Pearl receives research support from the NIH, NSF, and Boston Healthcare Associates; royalty payments from Elsevier, Springer Pubs, and UpToDate; has served as a consultant for Agilis Biotherapeutics and GLG Health Care Council; and is Associate Editor for the Journal of Child Neurology and on the editorial boards of Annals Neurology, Epilepsia, Future Neurology, Music and Medicine, and Neurology. Dr. Jeffrey Ojemann is a shareholder of Therma Neurosciences, a grant recipient of the NIH/NSF, and serves on the advisory board for the Epilepsy Foundation of the Northwest. The views expressed in this article are not the official positions of any authors’ affiliated institutions. Ethics Approval Statement: The organizing center received IRB approval for this study and each contributing center obtained research ethics approval locally.