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