Epileptogenic Zones in Intractable Epilepsy Patients with Dysembryoplastic neuroepithelial tumor

Oh, Kyung Mi; Seo, Dae Won; Hong, Seung Bong; Lee, Mun Hyang; Hong, Seung Chyul; Suh, Yeon Lim; Chung, Chin Sang; Lee, Won Yong; Kim, Yong Bum; Lee, Kwang Ho

Abstract

BACKGROUNDS: A dysembryoplastic neuroepithelial tumor (DNT) is an important cause of the intractable epilepsy. The prognosis after epileptic surgery was excellent when the epileptogenic zones were completely excised. But, the exact epileptogenic zones in epilepsy patients with DNT are not well known. The purpose of this study was to investigate where the epileptogenic zones were in epilepsy patients with DNT. That results might be helpful in having good results of epileptic surgery of DNT.
METHODS
Six patients with medically determined intractable epilepsy due to DNT were studied retrospectively. They had undergone epileptic surgery after video-EEG monitoring not only with scalp electrodes but also with invasive subdural electrodes. DNTs were located in the temporal lobe and pathologically proven in all patients. We analyzed distributions of ictal onset zones and irritative zones with non-invasive and invasive Video-EEG monitoring. Also, we reviewed the clinical features, neuroimaging features, neuropsychological tests, Wada tests and pathological findings. The operative strategy included complete resection of DNT, ictal onset and irritative zones in all patients. In two patients, modified operative strategy including amygdalohippocampectomy was done due to mesial involvement. A modified Engel's classification was used to determine surgical outcomes.
RESULTS
The irritative zones (included only more than 10% of total interictal discharges during the monitoring) showed various patterns from multifocal to unobserved. Ictal onset zones were multiple in 5 patients (dual: 3 patients, triple: 2 patients). In 1 patient, contralateral hemispheric mirror focus was observed. Mesial temporal involvement was seen in 2 patients from EEG and in 1 patient from pathology. There were discrepancies between ictal onset zones and irritative zones in 4 patients. The EEG seizures without clinical events were recorded in 1 patient. Postoperatively 5 patients were free of seizure, 1 patient had rare seizures.
CONCLUSION
Not only the wide or multiple distribution of epileptogenic zones around or in the lesion but also dual pathology of hippocampus are possible in epilepsy patients with DNT. The operative strategy including the epileptogenic zones can yield a good surgical outcome.