Current-Source Dipole of Anterior Temporal Spikes: Clinical Significance of Orientation

ABSTRACT

BACKGROUND: The voltage topography of temporal spikes has two distinct patterns, designated type I and type II; the orientation of the current-dipole source (O-CDS) of type I spikes tends to be oblique, while that of type II spikes tends to be horizontal. The purpose of this study was to identify the effects of the O-CDS of anterior temporal spikes on clinical factors including onset age, seizure frequency, secondary generalization, disease duration, intractability, polytherapy, febrile seizure, hippocampal sclerosis, and neocortical-temporal aura. METHODS: We examined the scalp electroencephalograms of 24 patients with temporal lobe epilepsy (TLE) and anterior temporal spikes. A spatiotemporal dipole model was applied to determine the O-CDS of the averaged spikes in each patient. We performed current-source analysis of multiple spatiotemporal dipole models using Brain Electrical Source Analysis software. The patients were divided into two subgroups according to their O-CDS pattern: oblique and horizontal. Clinical factors were compared between the two groups. RESULTS: Sixteen patients were classified into the oblique group, and 8 patients into the horizontal group. A neocortical-temporal aura was more commonly observed in the horizontal group (p<0.05), while drug-resistance tendencies were more commonly observed in the oblique group (p<0.1). CONCLUSIONS: The horizontal O-CDS of anterior temporal spikes may be more frequently associated with a neocortical-temporal aura than the oblique O-CDS in TLE. In addition, the oblique O-CDS pattern suggests a tendency toward drug resistance. The findings of this study imply that the oblique O-CDS pattern of anterior temporal spikes may provide additional electrophysiologic information regarding drug-resistant mesial TLE.