Intracranial ictal onset zone in nonlesional lateral temporal lobe epilepsy on scalp ictal EEG.
OBJECTIVE
To determine the ictal focus and the role of seizure characteristics, fluorodeoxyglucose (FDG) PET, and subtraction ictal SPECT in patients diagnosed as having nonlesional lateral temporal lobe epilepsy by long-term scalp video-EEG monitoring.


METHODS
The authors studied 33 consecutive patients with nonlesional neocortical epilepsy who had a scalp ictal onset zone localized in the temporal lobe and good surgical outcome after focal neocortical resection. All patients were evaluated using intracranial recordings prior to resection. Semiology, FDG-PET, and ictal-interictal subtraction SPECT were used to verify the diagnostic role of these methods in the localization of epileptic foci.


RESULTS
The ictal onset zones, confirmed by intracranial study, were the lateral temporal (22 patients), parietal (5), frontal (3), temporoparietal (2), and occipital (1) areas. FDG-PET analyzed by statistical parametric mapping correctly localized the epileptogenic lobe in 18 of 33 patients and subtraction ictal SPECT correctly localized it in 13 of 25 patients. However, in patients with extratemporal ictal onset zones, FDG-PET and ictal SPECT in combination correctly localized the epileptogenic lobe in only 3 of 11 cases.


CONCLUSIONS
An extratemporal ictal onset zone was encountered in patients with nonlesional lateral temporal lobe seizures based on scalp video-EEG monitoring. FDG-PET and subtraction SPECT had localizing value in no more than half of patients.
D000328:Adult; D038481:Anterior Temporal Lobectomy; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D017034:Epilepsy, Frontal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D004833:Epilepsy, Temporal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D019788:Fluorodeoxyglucose F18; D005625:Frontal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009778:Occipital Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology; D010296:Parietal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology; D016037:Single-Blind Method; D013382:Subtraction Technique; D013702:Temporal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon; D016896:Treatment Outcome; D014741:Video Recording
D019788:Fluorodeoxyglucose F18