Abstracts

Rationale: To study the neural connectivity between bilateral mesial temporal lobe by cortico-cortical evoked potential (CCEP) in intractable temporal lobe epilepsy. Methods: Four patients with intractable temporal lobe epilepsy were included, male: female=1:3. All patients were performed by SEEG after multiple modalities of presurgical evaluation including long-term monitored scalp EEG, high resolution MRI, PET and psychiatric evaluation. And some of the SEEG electrodes in each patients must involved the bilateral mesial temporal structures. After the intracranial EEG monitoring finished the CCEP tests were performed. Informed consents to this study were given from all patients.CCEP Recording: For CCEP recording, we conducted electrical stimulation of the intracranial electrodes using the same parameters as previously reported . Briefly, the electrical stimulation consisted of constant current square pulses of 0.3 milliseconds duration, which were delivered at a frequency of 1 Hz in alternating polarity. Two adjacent contacts were stimulated in a bipolar manner for each electrode. The current intensity was increased to 8mA which was increased stepwise by 1mA. No abnormal sensation was reported, and no clinical seizure occurred during the CCEP recordings. An evoked potential machine (Oxford ) was used for recording CCEP. During the stimulation the CCEP were recorded from all the other electrodes. An extracranial scalp electrode(contralateral mastoid) was used as the reference. 50 responses time locked to the stimulus were averaged. Each set of stimulation was repeated and reproducibility was confirmed. Peaks that were definite and reproducible on visual examination and represented a prominent response compared with the baseline were selected for evaluation. The results  were showed by positive and negative. Results: The CCEP results demonstrated that there were connectivity between bilateral mesial temporal lobe structures (including amygdala, hippocampus head, body or tail et al) but these connectivities could be bidirectional or monodirectional. Furthermore, the EEG spreading pathway during seizures only involved some of the connectivities. Conclusions: This study probably can further explain why the mesial temporal lobe discharges prefer to propagate to contralateral mesial temporal structures and there were difference between the neural connectivity and the seizure spreading pathways. It also demonstrated that CCEP can be used to study the functional connectivity of the brain. Funding: Beijing Municipal Science & Technology Commission