Abstracts

Rationale:  Past studies have suggested that primary generalized seizures are not truly “generalized” and are seen to involve selective regions of cortex such as medial frontal and orbital frontal regions. This present study expands upon this work to understand the source activation of inter-ictal discharges in medically refractory primary generalized epilepsy using improved source localization methods. Such methods may provide more precise techniques to aid in generalized epilepsy evaluations.  Methods: Five adult patients (30-46yo) with primary generalized epilepsy underwent high-density EEG (HD-EEG). For each patient, 256 channel HD-EEG was recorded for one hour. The data was reviewed by an experienced epileptologist to identify inter-ictal spike discharges. Inter-ictal spikes were identified in three of the five records. Identified inter-ictal discharges were grouped and averaged for each patient based on topography. Atlas source reconstruction was applied to each unique spike group. sLORETA with a regularization of 10^-2 was employed in the localization process. Spatial temporal dynamics analysis was applied to the averages at three time points of each spike population ­­­­(spike onset, spike peak, and slow wave) (Table 1) and was observed on a voxel atlas model and an x-y-z planar slice representation (Figure 1). Results:  Source reconstruction of the averaged complexes revealed spatial temporal dynamics of the spike populations that demonstrate propagation of activation from the onset of the spike to its peak and to the peak of the following slow wave. At the onset of the spike, two of the patients showed unilateral temporal onset sources that then propagated to their unique peak activation sources. The third showed onset activation in the left dorsal and medial frontal cortex which remained stable from the onset of the spike to its peak. Peak activation localization of the spike itself for each patient was reflective of their individual spike topography. With this, two patients showed lateralized activity of the left dorsal frontal cortex which included slight activation of the dorso-medial frontal cortex, while the other showed anterior temporal pole activation. Of these three patients, all showed propagation of activity from their peak sources to the temporal lobes at maximal activation of the slow wave. Conclusions:  Two hundred fifty-six-channel HD-EEG Atlas voxel source reconstruction using spatial temporal dynamics analysis confirms the previous findings that selective regions of cortex play a role in primary generalized epileptic activity and such regions can be identified specifically with enhanced EEG and localization methods. The present data set confirms the identification and involvement of regions such as the medial frontal cortex and also reveals lateralized focal sources with an emphasis of activation in the temporal lobes. Source reconstruction with individual head models would be an ideal future direction of this project as to track the exact cortical dipole sources of the identified complexes. Funding: None