Hippocampal intracerebral evoked potentials as a marker of its functionality in drug-resistant epilepsy

Afiliação

(1)    Aix Marseille Univ, INSERM, INS, Inst Neurosci Syst, Marseille, France; University Hospital Professor Edgard Santos (HUPES), Clinical Neurophysiology, Brazil.

(2)    AP-HM, Hôpital de la Timone, Service de Neurophysiologie Clinique, Marseille, France.

(3)    Aix Marseille Univ, INSERM, INS, Inst Neurosci Syst, Marseille, France; AP-HM, Timone Hospital, Stereotactic and Functional Neurosurgery, France.

(4)    Aix Marseille Univ, INSERM, INS, Inst Neurosci Syst, Marseille, France.

(5)    Aix Marseille Univ, INSERM, INS, Inst Neurosci Syst, Marseille, France; AP-HM, Hôpital de la Timone, Service de Neurophysiologie Clinique, Marseille, France.

(6)    Aix Marseille Univ, INSERM, INS, Inst Neurosci Syst, Marseille, France; AP-HM, Hôpital de la Timone, Service de Neurophysiologie Clinique, Marseille, France.

Resumo

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.