Efficacy of a 1- to 3-day ambulatory electroencephalogram in recording epileptic seizures.

The duration of an ambulatory electroencephalogram (aEEG) necessary to record epileptic seizures was studied in neurological patients. A total of 2221 aEEG recordings were made for 2035 inpatients. Ambulatory EEG lasting 1 to 8 days (mean, 1.6 days) included seizures or typical undiagnosed symptomatic attacks in 750 recordings (34%), and 266 of them were epileptic in origin. Symptomatic attacks without simultaneous EEG discharges were exhibited in 27% of the epileptic patients. Of the total number of epileptic seizures, 81% were encountered during the first 24 hours, an additional 10% during the next 24 hours, and 7% during the third 24-hour period. Our conclusion was that, in patients exhibiting epileptic seizures during the aEEG recording, the diagnosis will be confirmed by a 2-day recording in the vast majority of the cases.