Cortical activation in generalized seizures.

OBJECTIVE

Patients with generalized epilepsy exhibit different epileptiform events including asymptomatic interictal spikes (IS), absence seizures with spike-wave discharges (SWDs), and myoclonic seizures (MS). Our objective was to determine the spatiotemporal patterns of cortical activation in SWDs, IS, and MS in the Gabra1 juvenile myoclonic epilepsy mouse.

METHODS

We fabricated affordable, flexible high-density electroencephalography (HdEEG) arrays and recorded spontaneous SWD, IS, and MS with video/HdEEG. We determined differences among the events in amplitude spectral density (ASD) in the δ/θ/α/β/γ frequency bands at baseline (3.5-4.0 seconds before the first spike time, t ) and the prespike period (0.1-0.5 seconds before t ), and we elucidated the spatiotemporal activation during the t spike.

RESULTS

All three events had an increase in ASD between baseline and prespike in at least one frequency band. During prespike, MS had the largest δ-band ASD, but SWD had the greatest α/β/γ band ASD. For all three events, the ASD was largest in the anterior regions. The t spike voltage was also greatest in the anterior regions for all three events and IS and MS had larger voltages than SWD. From 7.5 to 17.5 msec after t , MS had greater voltage than IS and SWD, and maximal voltage was in the posterior parietal region.

SIGNIFICANCE

Changes in spectral density from baseline to prespike indicate that none of these generalized events are instantaneous or entirely unpredictable. Prominent engagement of anterior cortical regions during prespike and at t suggest that common anterior neural circuits participate in each event. Differences in prespike ASD signify that although the events may engage similar brain regions, they may arise from distinct proictal states with different neuronal activity or connectivity. Prolonged activation of the posterior parietal area in MS suggests that posterior circuits contribute to the myoclonic jerk. Together, these findings identify brain regions and processes that could be specifically targeted for further recording and modulation.