Diagnosis of Ictal Hyperperfusion Using Subtraction Image of Ictal and Interictal Brain Perfusion SPECT / 대한핵의학회잡지

A robust algorithm to disclose and display the difference of ictal and interictal perfusion may facilitate the detection of ictal hyperfusion foci. Diagnostic performance of localizing epileptogenic zones with subtracted SPECT images was compared with the visual diagnosis using ictal and interictal SPECT, MR, or PET. Ictal and interictal Tc-99m-HMPAO cerebral perfusion SPECT images of 48 patients(pts) were processed to get parametric subtracted images. Epileptogenic foci of all pts were diagnosed by seizure free state after resection of epileptogenic zones. In subtraction SPECT, we used normalized difference ratio of pixel counts((ictal-interictal)/interictalx100%) after correcting coordinates of ictal and interictal SPECT in semi-automatized 3-dimensional fashion. We found epileptogenic zones in subtraction SPECT and compared the performance with visual diagnosis of ictal and interictal SPECT, MR and PET using post-surgical diagnosis as gold standard. The concordance of subtraction SPECT and ictal-interictal SPECT was moderately good(kappa=0.49). The sensitivity of ictal-interictal SPECT was 73% and that of subtraction SPECT 58%. Positive predictive value of ictal-interictal SPECT was 76% and that of subtraction SPECT was 64%. There was no statistical difference between sensitivity or positive predictive values of subtraction SPECT and ictal-interictal SPECT, MR or PET. Such was also the case when we divided patients into temporal lobe epilepsy and neocortical epilepsy. We conclude that subtraction SPECT we produced had equivalent diagnostic performance compared with ictal-interictal SPECT in localizing epileptogenic zones. Additional value of these subtraction SPECT in clinical interpretation of ictal and interictal SPECT should be further evaluated.

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.