Brainstem triggers absence seizures in human generalized epilepsy

Simultaneous analysis of brainstem auditory evoked potentials (BAEPs) with reference to electroencephalography (EEG) was designed to examine the brainstem function corresponding to the EEG event. With this method, we investigated the brainstem function pre- and during the paroxysmal discharge in human absence seizures classified as primary generalized epilepsy (PGE). Two types of functional change in the lower brainstem were revealed as parameters of wave-III components (amplitude and area) of BAEPs without significant change in the upper brainstem. One was long-range biphasic fluctuation (acceleration followed by abrupt deceleration with the maximum -6.4 +/- 3.2 s before the seizure onset), and the other was rhythmic oscillation with 3 Hz. The latter, synchronized with the cortical spike-and-wave complex, imposed on the descending slope of the former. One important point is that both preceded the onset of cortical paroxysmal discharge. The results reappraise the classical hypothesis of "centrencephalic system" on seizure generating mechanism in human PGE. The results prove the primary triggering role of the lower brainstem that is independent of sleep-related synchronizations. The method is applicable to other types of EEG event for the investigation of brainstem involvement. (C) 1999 Elsevier Science B.V. All rights reserved.