Usefulness of corregistration and post-processing of MR and interictal SPECT images for localization of epileptogenic focus in children – preliminary report

BACKGROUND Children with focal epilepsy unresponsive to anticonvulsant therapy may become surgical candidates. Inter-ictal SPECT (SPECT-IN) studies demonstrate an area of hypoperfusion within the seizure focus in up to 50% of patients. The goal of this study was to evaluate the usefulness of corregistration of MR and SPECT-IN images for localization of the epileptogenic focus. MATERIAL/METHODS Brain MRI and SPECT-IN were performed in 20 children (mean age 9.5). We found multifocal (3-6 perfusion deficits in 10 patients) or diffuse perfusion deficits (lobar) in all patients. In fused MR and SPECT images we evaluated average activity in volumes-of-interest (VOIs) outlined in each gray matter region with deficits. Average VOI activity below average total brain activity with at least 15% difference to the mirror VOI in the brain cortex on the opposite side of was considered as "true" perfusion deficit (TPD). RESULTS In all children from our group, MRI and SPECT-IN image fusion and evaluation of TPD allowed to verify most of multifocal or diffuse deficits: in each of 12 patients we found 1 TPD, in each of 6 patients 2 TPD and in each of 2 patients 3 TPD. In 8 patients with 2 or 3 TPD we used scalp EEG or ictal SPECT for identification of one probable location of epileptogenic focus. CONCLUSIONS In children with refractory focal epilepsy, image fusion of MRI and SPECT-IN with evaluation of TPD has potential clinical utility in localization of epileptogenic focus.