Introduction: Papez proposed the memory and emotion associated network, which is termed limbic network. However, in vivo human limbic network has not been established. We investigate the connectivity of human limbic system using cortico-cortical evoked potential (CCEP), which reveals the brain networks.
Methods: This retrospective analysis included 28 patients with medically intractable focal epilepsy who underwent stereoelectroencephalogram electrode implantation and CCEP. Alternating 1 Hz electrical stimuli were delivered to the parts of limbic system (amygdala, anterior and posterior hippocampus, anterior and posterior cingulate gyrus, parahippocampal gyrus, lateral and medial orbitofrimtal cortex). A total of 40-60 stimuli were averaged in each trial to obtain CCEP responses. CCEP distributions were evaluated by calculating the root mean square of CCEP responses.
Results: The anterior hippocampal stimulation elicited prominent CCEP responses in the ipsilateral posterior hippocampus, medial orbitofrontal cortex, parahippocampal gyrus, insula, fronto-parietal operculum and lateral temporal cortex. The posterior hippocampal stimulation induced CCEP responses in the ipsilateral anterior hippocampus, parahippocampal gyrus, posterior cingulate gyrus and lateral temporal cortex. Furthermore, the present findings revealed the connections from the anterior cingulate cortex to the ipsilateral medial frontal and parietal areas. Posterior cingulate cortex received the connections from the bilateral precuneus, cuneus, posterior cingulate gyrus, posterior hippocampus and lateral temporo-parietal areas. The parahippocampal gyrus, lateral and medial orbitofrontal cortex received the connections from the adjacent cortices. Amygdala projected to the broad areas including the ipsilateral anterior and posterior hippocampus, medial and lateral orbitofrontal cortex, parahippocampal gyrus, insula, lateral temporal cortex, anterior and posterior cingulate gyrus, pre-supplementary motor area, premotor area and inferior parietal lobule.
Conclusions: This finding supports the assertion that the limbic system has anatomical connectivity including intrinsic reverberating circuits and extrinsic output. Differences in network activation will determine differences in surgical strategies, likely improving long-term seizure freedom outcome.
Patient Care: This study elucidates the limbic network and improves surgical strategies in patients with limbic epilepsy.
Learning Objectives: By the conclusion of this session, participants should be able to: 1)Describe the connection patterns of limbic network, 2)Improve surgical strategies to obtain the long-term seizure freedom outcome, 3)Identify the usefulness of cortico-cortical evoked potentials in SEEG operated patients