Frequency-dependent Characteristics In Neuromagnetic Activity Related To Termination In Childhood Absence Epilepsy

Objective:Childhood absence epilepsy(CAE)is characterized by bilateral synchronous symmetric 3Hz spike-wave discharges(SWDs)with an abrupt onset and offset recorded on electroencephalography(EEG)accompanied by unresponsive consciousness.Previous studies on CAE were mostly focused on the pre-ictal and onset periods,but few on the seizure termination.The aim of this study was to quantify the neuromagnetic activities related to the termination of absence seizures by analyzing neuromagnetic signals using magnetoencephalography(MEG)in multifrequency bands.Method:MEG data were recorded from 12 drug-naive patients with CAE.Accumulated source imaging(ASI)was used to analyze the MEG data in seven frequency ranges(1-4Hz,4-8Hz,8-12 Hz,12-30 Hz,30-80 Hz,80-250 Hz,and 250-500Hz).Four segments with a duration of 3s each were used to represent the different ictal periods during absence seizures.Segments with durations longer than 30 s from ictal periods of at least 10 s were considered interictal intervals.Two adjacent periods were compared with each other to investigate the changes in neuromagnatic signals during absence seizures.Results:the frequency-dependent changes in cortical neuromagnetic locations related to seizure termination were predominantly localized to the frontal cortex(FC),the parieto-occipito-temporal cortex(POT),and the precuneus(PC).A decrease in neuromagnetic activity in the FC in the 12-30 Hz and 30-80 Hz frequency bands wasthe earliest change related to the termination of absence seizures.The source strength in 30-80 Hz begined to decrease from the seizure onset to the middle of the seizure,which is the decrease in source strength during ictal periods.the strength of neuromagnetic activity at 30-80 Hz was correlated with the duration of epilepsy and decreased after seizure onset.Conclusion:Our results suggest that the frequency-dependent activities in the FC may play an important role in the termination of absence seizures.An earlier decrease in 30-80 Hz may result in the transition from the ictal period to seizure termination.