Intracranial Ictal Electroencephalographic Patterns in Parietal Lobe Epileptic Seizures : Correlation with Surgical Outcome

BACKGROUNDS: Parietal lobe epilepsy is uncommon and its intracranial ictal EEG findings have not been well elucidated. We investigated the ictal EEG patterns of epilepsy originating from the parietal lobe and its adjacent areas recorded by intracranial subdural electrode arrays. METHODS: The following intracranial ictal EEG patterns from twenty patients who underwent epilepsy surgery for medically intractable parietal lobe epilepsy were studied: 1) Anatomical ictal onset area [pure parietal (PP), combined parietal and extraparietal, such as fronto-parietal, temporo-parietal, etc. (EP)], 2) localization within the parietal lobe, 3) extent of the ictal onset zone, 4) the number of ictal onset zones, 5) frequency and waveform of ictal onset rhythms, and 6) type of spreading. RESULTS: Twelve patients (60%) were seizure-free (5 from PP, 7 from EP) and 8 were with persistent seizures (3 from PP, 5 from EP). Eight patients (40%) had ictal onset from PP and 12 were from EP. There were! Significant correlations with surgical outcome (p<0.05) in two variables: extent of ictal onset zone and type of spread. Patients with focal onset zones (n=9) showed better outcomes (eight are seizure-free) than those with wide ictal onset zones (4 out of 7 are seizure-free). Patients with slow spreading patterns showed better outcomes (12 from 16 are seizure-free) than those with fast spreading outcomes (all of them had persistent seizures). CONCLUSIONS: The extent of ictal onset zones correlates with surgical outcomes. The patterns of intracranial ictal EEG are helpful in predicting the surgical outcomes for parietal lobe epilepsy. (J Korean Neurol Assoc 19(5):478~484, 2001)

Epileptogenic Zones in Intractable Epilepsy Patients with Dysembryoplastic neuroepithelial tumor

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.