a wave or a group of waves reflecting an epileptic discharge on the EEG, which appear and disappear suddenly and clearly differ in frequency, morphology and amplitude from the background activity in the EEG, characterized in general by pathognomonic epileptic patterns – spike, slow spike (acute wave), spike-wave complex. The synonym electrographic epileptic discharge is more often used. This term is usually used to describe epileptiform patterns and seizure patterns.