Hippocampal Intracerebral Evoked Potentials as a Marker of Its Functionality in Drug-Resistant Epilepsy

Daniela de Andrade Morange, Virginie Laguitton, Romain Carron, Daniele Schön, Christian-George Bénar, Bernard Giusiano, Fabrice Bartolomei, and Agnès Trébuchon.
Clinical Neurophysiology, 2022, 52 (4): 323–32@HAL

Objectives: To assess hippocampal function during stereoelectroencephalography (SEEG) investigations through the study of the medial temporal lobe event-related potential (ERP) MTL-P300. Methods: We recorded the MTL-P300 during a visual oddball task, using hippocampal electrodes implanted for SEEG in 71 patients, in a preoperative epilepsy investigation. The presence of an MTL-P300 and its amplitude were correlated with hippocampal involvement during seizures and memory function. Results: Analysis using ROC curves revealed that an MTL-P300 amplitude below-46 µV, has a specificity of 93.3% in detecting the epileptogenic zone, and absence of the MTL-P300 in the left hippocampus of patients with typical language organization was associated with marked alteration of verbal memory scores. There was a significant correlation between performance in non-verbal memory tests and the amplitude of the MTL-P300 in the right hippocampus of patients with left hemispheric seizures (immediate visual recall: r=0.67, p=0.005; delayed visual recall: r=0.56, p=0.025). Using a linear regression, we confirmed that the absence of the MTL-P300 in the left hippocampus, the involvement of the left hippocampus during seizures, and the duration of epilepsy were predictors of verbal memory deficits. Conclusion: Analysis of the MTL-P300 during SEEG recording provides relevant information for the analysis of hippocampal functionality and can help to localize the epileptogenic zone.

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