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

A. Tuunainen, U. Nousiainen, E. Mervaala and P. Riekkinen
Department of Clinical Neurophysiology, Vaajasalo Hospital, Kortejoki, Finland.

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.