In patients with epilepsy who achieve seizure freedom, an attempt at discontinuing antiseizure medications (ASMs) is often considered. The decision to withdraw ASMs is complex, and physicians frequently utilize EEG as a tool to guide medication discontinuation; however, routine EEG is brief and may provide only a limited amount of clinically meaningful information. This study investigates the utility of prolonged 24-hour video EEG (VEEG) monitoring in detecting epileptiform discharges (EDs) in seizure-free patients before discontinuing ASMs.

For inclusion in this study, we selected seizure-free patients with epilepsy who had a normal last routine EEG, and who underwent VEEG in preparation for potential ASM withdrawal. We evaluated the yield and latency of EDs in the VEEG recordings, and we compared the rate of ED detection during the first 60 minutes versus later in the recording.

We identified 27 patients who fit the inclusion criteria; 10 (37%) exhibited EDs on VEEG. Nine (90%) of these 10 patients showed their EDs beyond 60 minutes, with the mean latency to the first ED being 230 minutes. The number needed to treat (NNT) to detect additional EDs with VEEG compared to the first hour was 3, with an absolute increase in yield of 34.6% and a relative increase of 90%. Younger age and the presence of EDs on a previous EEG were predictive of detecting EDs on VEEG (p = 0.040 and 0.039 respectively).

Our results suggest that 24-hour VEEG is more sensitive in detecting EDs than routine EEG in seizure-free patients, and thus may be superior to routine EEG in individualized risk assessments for seizure recurrence. Younger patients and those with EDs on prior EEG may especially benefit from prolonged monitoring.