Ambulatory video EEG extended to 10 days: A retrospective review of a large database of ictal events

•The referring clinical question was not answered entirely by the first seizure in 29.56% of studies.•Diagnostic and classification indications required a minimum of 7 days for at least 99% of studies to be answered.•Ambulatory video EEG monitoring time needed to capture events is significantly higher in patients with focal compared with generalized epilepsies. This work aims to determine the ambulatory video electroencephalography monitoring (AVEM) duration and number of captured seizures required to resolve different clinical questions, using a retrospective review of ictal recordings. Patients who underwent home-based AVEM had event data analyzed retrospectively. Studies were grouped by clinical indication: differential diagnosis, seizure type classification, or treatment assessment. The proportion of studies where the conclusion was changed after the first seizure was determined, as was the AVEM duration needed for at least 99% of studies to reach a diagnostic conclusion. The referring clinical question was not answered entirely by the first event in 29.6% (n = 227) of studies. Diagnostic and classification indications required a minimum of 7 days for at least 99% of studies to be answered, whilst treatment-assessment required at least 6 days. At least 7 days of monitoring, and potentially multiple events, are required to adequately answer these clinical questions in at least 99% of patients. The widely applied 72 h or single event recording cut-offs may be inadequate to adequately answer these three indications in a substantial proportion of patients. Extended duration of monitoring and capturing multiple events should be considered when attempting to capture seizures on video-EEG.