Authors :
Shan Wang; Cong Chen, School of Medicine, Zhejiang University; Andreas Alexopoulos, Epilepsy Center, Neurological Institute, Cleveland Clinic; Aung Thandar, Cleveland Clinic; Bo Jin, School of Medicine, Zhejiang University; Imad M. Najm, Cleveland Clinic
Rationale: Nonclinical seizures (NCS) are frequently recorded in pre-surgical evaluation of patients with focal epilepsy. The localization value of NCS was examined in a few previous studies but the included patients did not all have surgery or postoperative seizure outcomes. In this study, we aimed to address these limitations by evaluating the characteristics and prognostic significance of NCS in a cohort of epilepsy patients who underwent surgery and had postoperative seizure outcomes at 1 year. Methods: We included a total of 127 consecutive patients (age>2 years) who had both NCS and clinical seizures (CS) during their pre-surgical scalp video EEG recording from Cleveland Clinic Epilepsy Center (from January 2008 to December 2016
,110 patients
) and the Second Affiliated Hospital of Zhejiang University Epilepsy Center
(from September 2012 to April 2017, 17 patients). All patients had subsequent epilepsy surgery and at least one-year follow up. Concordance between NCS and CS were categorized as: concordant, partially concordant or discordant. Resection analysis was performed as compared to resection site based on post-operative MRI/CT, for NCS and CS separately; results were categorized as included, partially include, or not included. Patient demographics, electroclinical, neuroimaging, and seizure outcome data were also examined. Results: Among the 127 patients included in the study, 77 patients (60.6%, 77/127) had Engel’s Class I outcome (72 Ia and 5 Ib) at one year of follow-up. In 71 patients (55.9%, 71/127), localization of NCS and CS were concordant, including 37 patients with temporal lobe epilepsy. Multivariate logistic analysis showed partial / no concordance between CS and NCS (P=0.045, 95% CI=1.017-4.455), and daily seizure frequency (P=0.047, 95% CI=1.011-4.957) were independently associated with seizure recurrence. In the seizure-free group of 77 patients (1 patient without postsurgical MRI/CT), the NCS region was included in the resection in 37 patients (48.7%, 37/76), partially included in 21 patients (27.6%, 21/76) and not included in 18 patients (23.7%, 18/76); CS region was included in the resection in 39 patients (51.3%, 39/76), partially included in 19 patients (25%, 19/76) and not included in 18 patients (23.7%, 18/76). Conclusions: NCS on scalp video-EEG monitoring contain useful localization for presurgical evaluation and therefore should not be ignored. Partial or no concordance between CS and NCS as well as daily seizures are both negative prognostic factors for seizure-free outcome. Funding: None