Subclinical seizures: The demographic data and scalp video-EEG findings, concordance with the epilepsy type and prognosis

Abstract

BackgroundSubclinical seizures(SCSs) are overlooked in clinical practice. This study aims to investigate clinical, electrophysiological features of SCSs detected during video-electroencephalography(EEG) monitorization(VEM), concordance of the epilepsy type and SCSs, and predictors of the concordance. MethodsThe data of drug-resistant epilepsy patients who had undergone video-EEG between 2010 and 2020 were investigated. Ictal activities showing temporospatial evolution lasted ≥ 10 s, without any behavioural changes were considered SCSs. Findings were re-evaluated for ictal localization, lateralization, ictal discharge type, vigilance status, and duration of SCSs to the accompaniment of clinical findings. Additionally, the concordance of epilepsy type and SCSs were analyzed. ResultsFifty-five SCSs were obtained in 24 of 804 patients (2,9 %) who were followed in the VEM unit; the epilepsy type of the patients was temporal in 26 and extratemporal lobe epilepsy in 29 SCSs. Among 55 SCSs recordings, 30 originated from the temporal lobe and 24 from the extratemporal lobe, and seizure localization could not be determined in one. The patients were younger, age at seizure onset was earlier, habitual seizures were more frequent, multiple anti-seizure drug use was higher, seizures more frequently occurred during sleep, cranial MR tended to be abnormal, patients were more likely to have a history of perinatal injury/head trauma, and the concordance of discharge patterns was lower in extratemporal SCSs.The concordance of epilepsy type with localization and lateralization of SCSs was not statistically significant. ConclusionsSCSs originating from the temporal and extratemporal lobes might show similar characteristics with the epilepsy type, and SCSs might have clinical importance apart from epilepsy surgery.