Abstracts

RATIONALE: Frontal lobe seizures are usually classified in Prefrontal, Premotor and Central seizures. We recently hypothesized that the underlying organization of pre-frontal lobe seizures (PFLS) is represented by specific neural networks according to the differential involvement of each of two cytoarchitectonically functional systems: the latero-ventral system and the medio-dorsal system (Pandia & Yeterian, 1996). In this study, we explored this hypothesis using non -linear regression analysis of stereo- encephalographic (seeg) signals during prefrontal seizures. METHODS: Twelve seizures in six patients with drug-resistant PFLS, diagnosed from ictal SEEG recordings obtained during pre-surgical evaluation, were studied. Intracerebrally implanted depth electrodes with multiple leads according to Talairach's method were used to sample frontal lobe regions. According to Pijn et al (1993) we used a non-linear correlation coefficient (h2) as a measure of the degree and the direction of coupling on SEEG signal pairs from adjacent leads located either in lateroventral prefrontal areas (orbito frontal region, inferior frontal gyrus and the opercular region), medioventral prefrontal areas (cingulate anterior gyrus, frontal superior gyrus ) as well as the premotor regions or the temporal lobe. RESULTS: Three distinct generic types of PFLS were identified : (1)Lateroventral PFLS, characterized by high ictal h2 values observed between different areas of lateroventral systems; (2) Mediodorsal PFLS , characterized by high ictal h2 values between different areas of mediodorsal systems and (3) Overlapping PFLS ,characterized by high ictal h2 values between the lateroventral and mediodorsal systems. CONCLUSIONS: These results demonstrate that distinct functional relationships take place between the two prefrontal system in PFLS. Such finding could have important implications to better understand the complex organization and the symptoms of PFLS.