Clinical value and predictors of subclinical seizures in patients with temporal lobe epilepsy undergoing scalp video-EEG monitoring

The aim of this study was to determine the clinical importance and predictors of SCSs in a large population of patients with temporal epilepsy (TLE) undergoing video electroencephalographic (VEEG) monitoring. We reviewed the VEEG data of 327 consecutive patients with TLE admitted to our epilepsy center between August 2012 and January 2017. Demographic, electro-clinical, and neuroimaging data were recorded and re-analyzed. To our knowledge, this is the first study assessing SCSs recorded by long-term VEEG monitoring in patients with TLE. Twenty-seven of 327 (8.3%) patients exhibited SCSs during VEEG monitoring. Of these patients, 24 had both SCSs and clinical seizures. The mean duration of the SCSs was 23.18 s (range: 5–1307 s). Of the 27 patients with SCSs, 24 (88.9%) showed localizing value during the diagnostic process. Seventeen patients exhibited colocalization with clinical seizures, 4 showed useless localization related to clinical seizures, and 3 did not have clinical seizures. Sixteen patients (59.3%) experienced their first SCSs within the first 24 h of monitoring and one had the first SCSs within 20 min. Multivariate logistic regression analysis showed that age <18 years at VEEG monitoring (OR = 3.272, 95% CI = 1.283–8.343, p = 0.013) and bilateral IEDs (OR = 4.558, 95% CI = 1.982–10.477, p < 0.001) were independently associated with the presence of SCSs. Thus, SCSs are not uncommon in patients with TLE, particularly those with age <18 years or bilateral IEDs, and should be considered of significant clinical relevance during the diagnostic process.