Abstracts

RATIONALE: The study of interactions between medial/limbic and lateral/neocortical structures in the temporal lobe has led to an electrophysiological classification of temporal lobe epilepsies seizures (TLS) in four subtypes: medial (M), medial-lateral (ML), lateral-medial (LM), Lateral (L) TLES These subtypes extend the classical dichotomy between medial and lateral TLS. The purpose of this study is to question whether clinical presentation varies according to these subtypes. METHODS: 33 patients with drug-resistant TLEs that underwent pre-surgical SEEG recording were studied. TLES subtypes were defined according to: i/ a visual inspection of SEEG traces ii/ a detailed study of coupling between lateral and medial structures at the onset of seizures thanks to the application of linear and non linear analysis methods (coherence, non linear regression analysis). Based on video-SEEG recordings of seizures, symptoms were analyzed retrospectively, as well as clinical history and neuroimaging. RESULTS: MTLS were characterized by onset of seizures in hippocampus or/and amygdala without significant coupling with the neocortical structures. MLTLS and LMTLS were characterized by a synchronized network involving both limbic/medial and neocortical/lateral structures at seizure onset. In MLTLS the medial structures drove the neocortex, while the opposite was observed in LMTLS. LTLS were characterized by a neocortical onset without initial interactions with the medial structures. In comparison with MTLS patients, those with LMTLS or MLTLS more often presented immediate or early loss of consciousness (p<0.01) and secondary generalization during the course of their disease. Classical auras (Initial epigastric sensation or/and anxiety or fear) were not encountered in LTLEs groups but were not specific of any of the other subtypes. Hippocampal sclerosis was associated more often with MTLES but was also present in patients with MLTLES. CONCLUSIONS: This preliminary study shows that preservation of contact is the main differential criterion between MTLS and the other TLS subtypes. Most of the symptomes are produced by cortico-limbic interactions.