The Role of Ictal Brain Single Photon-Emission Tomography in Refractory Epilepsy Complementary to Magnetic Resonance Imaging and Electroencephalogram – Our Experience

Abstract

Background: Correct identification of the epileptogenic zone (EZ) is essential for surgical success for focal epilepsy. There are multiple modalities which are available for detecting the anatomical and the functional abnormalities. The purpose of this study was to determine the complementary role of ictal brain single photon-emission tomography (SPECT) in delineating the EZ in addition to electroencephalogram (EEG) and magnetic resonance imaging (MRI). Methodology: Clinical and diagnostic data from patients with refractory epilepsy undergoing ictal brain SPECT (IEBS), EEG, MRI between 2014 and 2019 were analyzed retrospectively. Tc99m-ethyl cysteinate dimer was administered intravenously during or within 30 s of onset of seizure activity. Results: Eighty-nine patients aged: Four months-32 years (median age: Eight years) were studied. The concordance of IEBS with MRI and EEG were studied. Among them, EEG was normal in 22 and abnormal in 67 (multifocal: 40, unifocal: 8, generalized: 19). MRI was normal in 36, abnormal in 26, nonspecific in 24 and not done in three patients. Of the 80 patients showing tracer uptake in IEBS, 14-multifocal uptake and 66-unifocal uptake (EEG and MRI were not showing any abnormality in 15 and 27 patients, respectively). Unifocal uptake in IEBS was concordant with EEG in 11 (16.67%) and MRI in 15 (27.72%). The concordance and nonconcordance of the results among the two imaging modalities or EEG assuming surgical site as the gold standard was noted. Twenty-two had undergone surgical removal of the EZ, 15 was conformable with MRI or IEBS. Conclusion: In patients with noncontributory EEG and MRI, IEBS could detect the epileptogenic focus. Therefore, depending entirely on EEG and MRI may limit its diagnosis. IEBS, MRI and EEG are complementary to each other in the detecting the epileptogenic focus.