Surgical strategy and outcomes for epileptic patients with focal cortical dysplasia or dysembryoplastic neuroepithelial tumor.

PURPOSE: The purpose of this study was to clarify and compare the influence of surgical strategy on relief from seizures in patients with focal cortical dysplasia (FCD) and those with dysembryoplastic neuroepithelial tumor (DNT).

METHODS: Six patients with FCD and five patients with DNT, all of whom underwent surgical resection for medically intractable epilepsy, were compared in terms of presurgical seizure types and frequency, location of lesions, magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT) with 99mTc-ECD, scalp electroencephalogram (EEG), and long-term video-EEG recording. Prolonged subdural recordings and intraoperative electrocorticograms (ECoG) were analyzed. The influences of surgical strategies on seizure outcomes were retrospectively analyzed.

RESULTS: In all the FCD patients, ictal SPECT revealed hyperperfusion in the regions where MRI showed FCD. Interictal epileptiform activity and ictal seizure onset on ECoG performed with subdural electrodes were localized on the FCD itself. In contrast, the tumors of all the DNT patients were depicted as hypoperfuse areas on interictal SPECT scans. Ictal SPECT in one DNT patient showed hyperperfusion in the area enclosing the tumor. Interictal spiking in all DNT patients and ictal seizure onset in two DNT patients were not in the lesions themselves but in an area enclosing the lesion. All but one patient with FCD who underwent total lesionectomy became seizure free. All DNT patients who underwent resection of the epileptogenic cortex associated with lesionectomy became seizure free or achieved a 90% reduction in seizures.

CONCLUSIONS: FCD has intrinsic epileptogenicity, whereas DNT is encompassed by epileptogenic cortical areas. Therefore, total lesionectomy is an essential strategy for FCD, whereas resection of the epileptic focus associated with lesionectomy of a DNT lesion is necessary to control seizures.