Optimal duration of video-electroencephalographic monitoring to capture seizures

• Video-EEGs performed over 5 years were analysed to evaluation the optimal duration of monitoring.
• The highest yield occurs on the first day of monitoring.
• Five days of monitoring is probably sufficient to diagnose 99% of positive cases in a 7 day program.

We aimed to find the optimal duration of long-term video-electroencephalographic monitoring (VEM) to capture seizures in patients with epileptic seizures (ES) and psychogenic non-epileptic seizures (PNES) by evaluating the time to first clinical event and the diagnostic yield of clinical events and positive cases in each day of VEM. Patients aged ⩾18 years who underwent VEM from May 2009 to June 2014 were studied retrospectively. Demographic, clinical and VEM data (including total monitoring length, type and time to first event, total number of ES/PNES) were collected. The difference in time to the first event between ES and PNES was analysed with Mann–Whitney U test. Of 207 VEM studies performed during the 5 year period, 108 recordings captured seizures (ES and PNES) (52.2%). Median times to the first ES and PNES were 19.7 and 23.4 hours, respectively (p = 0.99). A small majority (53.7%) of event-positive patients had their first event on the first day of monitoring. By the end of the fifth day, 98% of all clinical events were captured and 99% of all positive cases were diagnosed. In conclusion, in a patient monitoring program where a diagnosis is reached by capturing seizures, 5 days is probably sufficient to capture the greatest number of events and diagnose 99% of those patients.