Abstracts

Rationale: The analysis of spike voltage topography revealed two distinct patterns of temporal spikes of type I and type II. The application of source modeling techniques revealed that the orientation of current dipoles sources (O-CDS) of type I spikes was vertical or oblique, while that of type II spikes was horizontal. The correlation of the types with clinical data and intracranial EEGs suggest that type I spikes were more associated with medial temporal lobe epilepsy (m-TLE) than type II spikes. The purpose of this study is to identify the effects of drug resistance on the O-CDS of anterior temporal spikes in the clinically defined TLE. Methods: We examined the scalp EEGs of 11 epilepsy patients who had anterior temporal spikes and complex partial seizures of temporal lobe type. We excluded the patients with brain lesions except hippocampal sclerosis. The patients who had the seizures of undetermined origin, the seizures from extratemporal origin or any epilepsy surgery were also excluded. Five of 11 patients had unilateral hippocampal sclerosis and the others had no structural lesion in brain MRI. The patients included four females and seven males, with a mean age of 27.45 ± 14.99 years (mean ± SD). We divide the patients into two subgroups according to the drug resistance. The definition of drug resistance was the failure of two appropriate antiepileptic drugs and no more than one-year seizure-free hiatus at last follow-up. Five patients were included in the group of drug resistance epilepsy (DRE) and the remaining six patients were included in the group of drug responsive epilepsy (non-DRE). We recorded the EEGs using a 32-channel digital EEG machine, and 21 electrodes placed on the scalp according to the international 10-20 system with anterior temporal electrodes (T1, T2). We averaged 20 typical spikes in each patient. We applied a spatiotemporal dipole model to determine O-CDS of the averaged spikes and compared the O-CDS between DRE with non-DRE group. Results: The current sources of the averaged spikes were explained by a single dipole in the all five patients in DRE group. Those of the averaged spikes of non-DRE patients were explained by a single dipole in five of six patients and two dipoles in the other one patient (p=0.338). In the cases of primary or single dipole, O-CDS were compared between DRE and non-DRE group. The O-CDS were oblique in all five patients in DRE group (100%). In non-DRE group, three of six patients (50%) had oblique O-CDS and the other three patients (50%) had horizontal O-CDS (p=0.182). Conclusions: In clinically defined TLE, O-CDS of anterior temporal spikes may be different according to the drug responsiveness. Between them, O-CDS may have tendency to be more intermediate in the drug resistant patients and more horizontal in the drug responsive patients. These findings may suggest that clinically defined TLE of drug resistant patients have a tendency to have more electrophysiological characteristics of m-TLE than that of drug responsive patients.