Uncovered primary seizure foci in Lennox-Gastaut syndrome after corpus callosotomy

Purpose: Corpus callosotomy (CC) is a palliative surgical procedure to control atonic, tonic, or generalized tonic-clonic seizure in Lennox-Gastaut syndrome (LGS). Here, we report patients with LGS who underwent resective surgery, following CC better delineating the presumed seizure foci localized in one hemisphere. Methods: We retrospectively reviewed seven patients with LGS who underwent CC and subsequent cortical resection. The median follow-up duration after lobectomy was 20. months (range, 15-54. months) and three patients had follow-up periods over 24. months. The findings of video electroencephalography (EEG) monitoring, structural and functional neuroimagings were compared between pre- and post-CC. Results: Four patients had Engel class I and one patient had Engel class II outcomes following cortical resection; post-CC, compared to pre-CC, showed better localized ictal/interictal epileptiform discharges in the unilateral frontal area in two patients, in the unilateral parieto-temporo-occipital areas in one patient and in the unilateral fronto-temporal areas in the remaining two patients. Two patients had Engel Class III outcome following cortical resection; post-CC EEG continued to show multifocal epileptiform discharges but predominantly arising from a unilateral frontal area. Following CC, positron emission tomography showed localized glucose hypometabolism of which location was concordant with post-CC EEG abnormalities in all patient. Similarly, ictal/interictal single photon emission computed tomography also showed localized abnormalities concordant with post-CC EEG abnormalities in five of the six patients. Pathological assessment revealed cortical dysplasia in six patients, whereas no pathological abnormality was found in the remaining patient, who obtained Engel Class I outcome following cortical resection. Conclusion: CC could change EEG findings, glucose metabolisms and cerebral blood flows, and it is sometimes helpful in delineating the primary seizure focus in patients with LGS.