Abstract Details

Title Propagation of Epileptiform Discharge along the Papez Circuit Demonstrated with Stereotactic EEG in a Patient with Temporal Lobe Epilepsy

Topic Epilepsy/Clinical Neurophysiology (EEG)

Presentation(s) P7 - Poster Session 7 (8:00 AM-9:00 AM)

Poster/Presentation
Number 10-002

Objective To describe the propagation pathway of epileptiform discharges through the Papez circuit recorded by intracranial stereotactic electroencephalography (SEEG) in a patient with intractable temporal lobe epilepsy.

Background The Papez circuit denotes a closed-loop pathway within the modern limbic system that is integral in memory function, emotive processes, and behavior. The circuit travels from the hippocampus through the fornix to the mamillary bodies, projecting through the mammillothalamic tract to synapse in the anterior thalamic nucleus. It continues to the cingulum via the anterior thalamic radiation, coursing around the corpus callosum and retrosplenial area to end in the entorhinal cortex within the parahippocampal gyrus. A final re-entrant projection to the hippocampus completes the circuit.

Design/Methods Case report.

Results A 27-year-old male with pharmacoresistant right temporal lobe epilepsy was admitted for SEEG monitoring to determine candidacy for epilepsy surgery. Depth electrodes were placed targeting the right anterior amygdala (RAM), right anterior hippocampus (RAH), right posterior hippocampus (RPH), right basal temporal region (RBT), right lingula (RLIN), right retrosplenium (RRS), right posterior cingulate (RPC), right middle cingulate (RMC), and left anterior hippocampus (LAH). Observation of interictal epileptiform discharges revealed that spike onsets seen first in RAH were closely followed by RPH and consistently seen 170-190 ms later over RRS, RPC, and RMC. The latter sequence was consistent with antidromic propagation in the Papez circuit, initiating in the hippocampal head, propagating through the fornix into the cingulate bundle, and presumably into the anterior thalamus thereafter.

Conclusions Hippocampal evoked potentials have been observed in response to stimulation of the anterior nucleus of the thalamus in deep-brain stimulation (DBS) studies (REF - Osorio et. al.). This SEEG patient had sampling of multiple limbic structures and demonstrated the reciprocal effect of endogenous epileptiform potentials originating in the hippocampus propagating retrogradely in the Papez circuit toward the thalamus via the fornix and cingulum.

Authors/Disclosures
Brian J. Coffey, MD PRESENTER	Dr. Coffey has nothing to disclose.
Giridhar P. Kalamangalam, MD, PhD (University of Florida)	Dr. Kalamangalam has nothing to disclose.
Maria J. Bruzzone, MD, FAAN (University of Florida)	Dr. Bruzzone has nothing to disclose.

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