Background and Objectives The purpose of this study was to assess the likelihood of capturing a patient's typical event in question on ambulatory video-EEG monitoring (AVEM) based on certain baseline patient or event characteristics.

Methods We retrospectively reviewed 300 studies that resulted between June 2021 and August 2022 ordered by adult epileptologists. Patients were included in event analysis if the study was ordered for the purpose of capturing an event (and excluded for all other purposes).

Results A total of 149 studies were included in event analysis. Sixty-eight patients (46%) had their typical events captured on AVEM. Diagnosis was an epileptic seizure in 17 patients (25%), psychogenic nonepileptic seizure in 7 (10%), and other nonepileptic events in 44 (65%). Regarding event frequency, for patients who on average had daily events, 84% had events captured, which corresponds to a significantly increased odds ratio (OR 17.90, 95% CI 7.55–42.44, p < 0.001). For those who had events <1 per week to ≥1 per month, only 9% had events captured (OR 0.06, 95% CI 0.02–0.19, p < 0.001). No patients who had events less frequently than once per month had a diagnostic AVEM. Regarding the number of antiseizure medications (ASMs), the odds ratio was increased for those not on ASMs (OR 2.65, 95% CI 1.17 –6.03, p = 0.02) and decreased for those on 1 ASM (OR 0.28, 95% CI 0.13 –0.60, p = 0.001). There was no statistical significance based on event type (motor vs nonmotor), prior seizure diagnosis, history of psychiatric comorbidity, or presence of a focal brain lesion.

Discussion Certain baseline characteristics can increase or decrease the pretest probability of capturing a typical event on AVEM, particularly the frequency of events and number of ASMs. This can be useful information for clinicians before ordering a study so that resources can be properly allocated.