Measuring electroencephalographic seizure adequacy during electroconvulsive therapy: a comparison of 2 definitions

The second edition of The ECT Handbook of the Royal College of Psychiatrists gives importance to the pattern of electroencephalographic (EEG) seizure rather than to the duration for measuring seizure adequacy. We examined the potential effect of this change in definition by estimating the restimulation rates in electroconvulsive therapy. The new definition of EEG seizure was applied to 102 computerized EEG recordings obtained during electroconvulsive therapy sessions in an academic institute in India. The EEGs were read by 2 independent researchers blind to each other's ratings and blind to the motor seizure status. All 41 seizures considered "adequate" by the old definition also satisfied the new definition. Only 1 (2%) of the 58 "inadequate" seizures by the old definition was found to be adequate by the new definition. We had a very good interrater agreement on this reclassification (kappa = 0.86). In this sample, a seizure with polyspikes and a 3-Hz activity (new definition) tended to last longer than 25 seconds (old definition), satisfying both definitions. An estimated 2% of the patients with adequate seizures could have been restimulated during the study period.