Bold temporal dynamics in absence seizures: An EEG-fMRI coregistration study

Recent studies have demonstrated BOLD signal changes related to interictal generalized spike-wave discharge discharges in idiopathic generalized epilepsy (IGE) describing a cortical-subcortical network. Our objective is to describe BOLD dynamics and its temporal variations during absence seizures in patients with IGE. Method: We studied two patients with IGE and Juvenile Absence Epilepsy. Scalp EEG was recorded by means of a 32 channels MRI-compatible EEG recording system. Functional data were acquired with a 3T Philips Achieva MR system. Event-related analysis was performed using absence seizures as regressors convolved with seven standard hemodynamic response function (HRF) starting at: -9, -6, -3 second before EEG onset of absence seizures, time 0 (onset),and +3, +6, +9 second after it. Results: Temporal analysis showed pre-ictal activations in frontal and parieto-occipital cortex. At seizure onset, activations were evident in thalamus, basal ganglia and mesial temporal regions. Deactivations were observed in precuneus from 6 sec before to 9 sec after the seizure onset, and in brainstem, caudate nuclei, anterior cingulate until 6 sec after it. Conclusion: Temporal analysis of absence seizures showed pre-ictal involvement of cortical regions (frontal cortex and precuneus). Then we observed an extended cortical-subcortical network including thalamus,basal ganglia, temporal mesial regions and brainstem. The involvement of these regions started at seizure onset and persisted many seconds after its end.