title: The mismatch negativity (MMN) potential as a tool for the functional mapping of temporal lobe epilepsies.
abstract: Temporal lobe epilepsies are associated with cognitive dysfunctions in memory which are important clues currently used clinically for the lateralization of the epileptic focus in evaluations for epilepsy surgery. Because these lobes also contain the primary auditory cortex, the study of auditory evoked potentials (AEPs) is a candidate, not yet established, complementary method to characterize epilepsy-induced dysfunction. We aimed to establish the clinical usefulness of auditory evoked potentials for the study of pediatric symptomatic temporal lobe epilepsies. A group of 17 patients (ages 4-16) with symptomatic epilepsies undergoing evaluation for epilepsy surgery epilepsy was submitted to auditory evoked potentials using 35-channel scalp EEG recordings. A control group of 10 healthy volunteers was studied with the same protocol. The P100 and mismatch negativity (MMN) potential latencies and normalized amplitudes were studied. We also performed a voxel-based lesion-symptom mapping (VLSM) to determine the anatomical areas associated with changes in the AEPs. Eleven patients had temporal lobe epilepsy, three had frontal lobe epilepsy, and three had occipital lobe epilepsy. Latencies for the P100 were normal in 15/17 and in 11/17 for the MMN, with no consistent correlation with the epilepsy type. The MMN amplitude was abnormal in 7/17 patients, all with temporal lobe epilepsies (sensitivity of 64%). Of these patients, four had a decreased MMN associated with a Heschl's gyrus lesion in the VLSM, and three had an increased MMN associated with hippocampal lesion. No extratemporal epilepsy showed MMN amplitude abnormalities (specificity of 100%). The P100 amplitude was abnormal in 3/17, two with temporal and one with frontal lobe epilepsies. The auditory MMN has a high specificity but a low sensitivity for temporal lobe epilepsy in symptomatic pediatric epilepsies. Amplitude decreases of the MMN are associated with homolateral Heschl's gyrus lesions, and MMN increases with hippocampal lesions.
authors.affiliation: Faculty of Psychology and Education Sciences, University of Coimbra, Rua do Colégio Novo, Apartado 6153, 3001-802 Coimbra, Portugal. Electronic address: r.lopes@clix.pt.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Lopes
authors.affiliation: Faculty of Psychology and Education Sciences, University of Coimbra, Rua do Colégio Novo, Apartado 6153, 3001-802 Coimbra, Portugal.
authors.forename: Mário R
authors.initials: MR
authors.lastname: Simões
authors.affiliation: Instituto Universitário de Lisboa (ISCTE-IUL), Cis-IUL, Lisbon, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Ferraz
authors.affiliation: Instituto Universitário de Lisboa (ISCTE-IUL), Cis-IUL, Lisbon, Portugal; Department of Neurophysiology, Centro Hospitalar Psiquiátrico de Lisboa, Lisbon, Portugal.
authors.forename: Alberto J R
authors.initials: AJ
authors.lastname: Leal
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D001307:Auditory Perception / Q000502:physiology; D001931:Brain Mapping; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology* / Q000601:surgery; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D057234:Preoperative Period; D013702:Temporal Lobe / Q000503:physiopathology* / Q000601:surgery
keywords: Auditory evoked potentials; EEG; MMN; Pediatric epilepsy; Temporal lobe epilepsy