Prolonged EEGs in adult patients with a first unprovoked seizure: a prospective pilot study

Definitions of epilepsy have changed to include a first unprovoked seizure with a high (>60%) risk of recurrence in the next 10 years. A single seizure and an epileptiform discharge on an EEG would suffice for this diagnosis. We hypothesized that an extended six-hour EEG in adult patients presenting with a first unprovoked seizure would demonstrate an increased yield of epileptiform discharges in comparison to a standard 30-minute EEG, and therefore higher rates of epilepsy diagnosis. Thirty-eight patients were recruited at Hamilton Health Sciences over six years and 36 underwent extended six-hour EEGs. Two of seven patients demonstrated epileptiform discharges on their EEG after only the first 30 minutes of recording, observed during sleep for both patients. This correlated to an overall increase of 5.56%, or a yield of 29%. A third more patients could benefit from early diagnosis with extended EEGs. The rate of epilepsy diagnosis based on EEG overall was superior to that of brain imaging (19% versus 6%). Given the limitations due to sample size in this study, a larger trial would be beneficial to confirm these findings.