Time interval providing highest yield for initial EEG in patients with new onset seizures

Timing providing highest yield of initial electroencephalogram (EEG) after new onset unprovoked seizures, is an important and practical issue both in diagnosis and patient care. Current guidelines suggest routine EEG is the standard of care in work-up. However, yield of the initial EEG and exact timeframe in which to perform remain unclear and standardization in both adult and pediatric populations is still lacking. Our objective was to determine a concrete timeframe to perform initial EEG in patients with new onset unprovoked seizures and provide greater yield of EEG benefits in patient management.

This is a retrospective chart review study of both pediatric and adult patients identified from EEG Database over 1999-2014 located at Kaleida Health at Buffalo using keyword "new onset seizure".

The percentage of EEGs revealing epileptiform discharges is much higher if EEGs are performed within 12hours after the seizure onset compared to studies done beyond this timeframe (53.1% versus 23.9%). There was no significant difference in the presence of epileptiform discharges if the study is done 12hours after the seizure onset. Odds ratio was 3.599 (the presence of epileptiform discharges) with a Confidence Interval of 1.691-7.660 (p=0.001) within first 12hours of initial event.

This study demonstrated statistical significance in yield of epileptiform discharges by performing EEG within the first 12hours of seizure onset, in both adult and pediatric populations, which should be considered for clinical practice and patient care.