title: Late lateralizing and localizing EEG features of scalp-recorded temporal lobe seizures.
abstract: The authors studied the lateralizing value for temporal epileptogenesis of focal or hemispheric EEG ictal features that first appear > or = 5 seconds after hemispheric or diffuse EEG changes or after an artifact-obscured onset, by correlation with side of lobectomy abolishing or producing > or = 90% improvement of complex partial seizures (CPS). One hundred forty-eight seizures in 39 patients rendered seizure-free (SF) by lobectomy lacked early localizing features of which 91 (61%) seizures in 37 (95%) patients had late lateralizing or localizing phenomena. Eighty-seven (96%) of 91 late localizing or lateralizing seizures occurred ipsilateral to lobectomy, involving 35 (95%) of 37 patients. Late contralateral and shifting phenomena occurred in a total of 4 seizures of 2 patients. Among 17 non-SF but > or = 90% improved patients, 30 (48%) of 63 seizures lacking early localizing features showed late localizing or lateralizing phenomena. Of these, twenty (67%) involving 12 (71%) patients occurred ipsilateral to lobectomy. Among the remaining 5 (29%) patients, a total of 5 seizures (17%) were contralateral while 5 (17%) exhibited shifting laterality. These data indicate that seizures with late (> or = 5 seconds) localizing or lateralizing features cannot be discounted when assessing laterality of temporal epileptogenesis but cannot be used as the sole electrographic criterion.
authors.affiliation: University Hospital, Epilepsy Unit, The University of Western Ontario, London, Canada.
authors.forename: W T
authors.initials: WT
authors.lastname: Blume
authors.forename: J
authors.initials: J
authors.lastname: Ravindran
authors.forename: N J
authors.initials: NJ
authors.lastname: Lowry
mesh_terms: D000293:Adolescent; D000328:Adult; D004569:Electroencephalography / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D011612:Psychosurgery; D013997:Time Factors