Abstracts

Identification of the location and extent of epileptogenic brain tissue is essential for successful surgical resection. ECoG is currently widely used to define and localize epileptogenic zone. However, the ECoG recordings are usually visually inspected for epileptiform activities to locate their generators. The aim of the present study is to develop and evaluate a novel method which can quantitatively map the cortical activation during epileptiform discharges, and to localize its sites of initiation. The successful establishment of such novel methodology may have a significant impact on improving the success rate of surgical treatment of medically refractory epilepsy., The activation time of local cortical tissue is estimated from the time course of interictal ECoG. The activation map represents the pattern of propagation of epileptiform activity, and is coregistered with a cortex model derived from patients[apos] MRI. For each interictal spike, only one activation map is obtained, thus representing data reduction compared with ECoG maps. To evaluate the performance of this novel method, interictal ECoG recordings were analyzed for 8 pediatric epilepsy patients. The sites of initiation of the epileptiform propagation were compared with ictal onset zones in the same patients, as identified from ECoGs during seizures., The sites of initiation of epileptiform propagation were found to be overlapped with the seizure onset zones determined from ictal ECoG recordings in 7 out of 8 pediatric epilepsy patients. Fig. 1 illustrates a typical cortical activation map (a) and the ictal onset zone identified from ictal ECoG (b). Blue color (a) shows initiation of epileptiform propagation, and pink color (b) shows the ictal onset zone in the same patient. For patients with multiple seizure foci, each focus were revealed by analyzing interictal spikes with different spatial patterns., The time difference between spike peaks of the interictal events in the leading channel and other channels can be effectively defined as the local cortical activation time. The present cortical activation mapping based on this time latency can be used to predict the seizure onset zones in pediatric epilepsy patients. Full establishment of this novel technology may have a major impact to surgical planning for pediatric epilepsy patients.[figure1], (Supported by NIH EB00178 and NSF BES-0411898 (B.H.).)