Abstracts

Rationale: To investigate the utility of magnetic source imaging (MSI) and single photon emission computed tomography (SPECT) in localizing the epileptogenic zone (EZ) and predicting epilepsy surgery outcome in patients with non-lesional neocortical partial epilepsy. Both modalities were compared with intracranial EEG (ICEEG).Methods: Data from 14 patients with non-lesional neocortical epilepsy who underwent presurgical evaluation including non-invasive and intracranial video-Electroencephalography (EEG)-monitoring, MSI, and ictal and interictal SPECT were studied. All of them had epilepsy surgery with follow-up for at least 6 months, the postoperative seizure outcome was graded as either seizure-free or not. ICEEG, MSI, and SPECT results were classified using a sublobar classification. Results: Of 14 patients 5 (35.7%) had neocortical temporal lobe epilepsy, 5 (35.7%) frontal lobe epilepsy, and 4 (28.6%) parietal lobe epilepsy. Of all patients 6 (42.9%) became seizure-free after surgery. Sublobar ICEEG has the highest sensitivity (88.3%) for localizing the EZ based on the epilepsy surgery outcome. Concordance of ICEEG and MSI results on a sublobar level has the highest specificity, positive predictive value (PPV), and odds ratio (OR) for localizing the EZ (specificity 87.5%; PPV 80%, OR 14); complete resection of both foci significantly increases the chance of a seizure-free outcome after epilepsy surgery (p = 0.033). Sublobar concordance of ICEEG and MSI is superior to concordant ICEEG and SPECT results (specificity 75%; PPV 66.7; OR 6) or any single test alone. Conclusions: This study shows conclusively that concordance with ICEEG as the current gold standard is of utmost importance for both MSI and SPECT to localize the epileptogenic zone and to determine the extent of surgical resection in non-lesional neocortical epilepsy patients. When sublobar concordant with ICEEG, MSI is more advantageous compared to SPECT in predicting seizure-free epilepsy surgery outcome.