Prevalence and predictors of subclinical seizures during scalp video-EEG monitoring in patients with epilepsy

Abstract

Objective: This study first aimed to establish the prevalence and predictors of subclinical seizures in patients with epilepsy undergoing video electroencephalographic monitoring, then to evaluate the relationship of sleep/wake and circadian pattern with subclinical seizures. Methods: We retrospectively reviewed the charts of 742 consecutive patients admitted to our epilepsy center between July 2012 and October 2014. Demographic, electro-clinical data and neuroimage were collected. Results: A total of 148 subclinical seizures were detected in 39 patients (5.3%) during video electroencephalographic monitoring. The mean duration of subclinical seizures was 47.18 s (range, 5–311). Pharmacoresistant epilepsy, abnormal MRI and the presence of interictal epileptiform discharges were independently associated with subclinical seizures in multivariate logistic regression analysis. Subclinical seizures helped localizing the presumed epileptogenic zone in 24 (61.5%) patients, and suggested multifocal epilepsy in five (12.8%). In addition, subclinical seizures occurred more frequently in sleep and night than wakefulness and daytime, respectively, and they were more likely seen between 21:00–03:00 h, and less likely seen between 09:00–12:00 h. Thirty patients (76.9%) had their first subclinical seizures within the first 24 h of monitoring while only 7.7% of patients had their first subclinical seizures detected within 20 min. Conclusion: Subclinical seizures are not uncommon in patients with epilepsy, particularly in those with pharmacoresistant epilepsy, abnormal MRI or interictal epileptiform discharges. Subclinical seizures occur in specific circadian patterns and in specific sleep/wake distributions. A 20-min VEEG monitoring might not be long enough to allow for their detection.

KEYWORDS:

• subclinical seizure
• epilepsy
• video electroencephalographic monitoring

Acknowledgements

The authors are grateful to Yelei Tang for his help in EEG reading.

Declaration of Interest

The authors declare that they have no conflict of interest.

This project was supported by grants from the National Natural Science Foundation of China [grant number 81171227], [grant number 81271435], [grant number 91332202].

Supplementary material

Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/00207454.2016.1220946.

Additional information

Funding

The National Natural Science Foundation of China