Ictal SPECT and interictal PET in the localization of occipital lobe epilepsy

Purpose: To compare the localizing value of ictal single photon emission co mputed tomography (SPECT) and interictal fluorodeoxyglucose-positron emissi on tomography (FDG-PET) in refractory occipital lobe epilepsy. Methods. Six patients who underwent surgery for refractory epilepsy associa ted with pathology in the occipital lobe were retrospectively selected from records of the Austin & Repatriation Centre Comprehensive Epilepsy Program me. Interictal SPECT and PET and ictal SPECT were obtained by standard meth ods. All studies were read by a nuclear medicine expert blinded to clinical data except the diagnosis of epilepsy. Results: Ictal SPECT showed unilateral occipital hyperperfusion in five of six cases often accompanied by temporal lobe hyperperfusion. These patterns were seen in cases with or without magnetic resonance imaging (MRI) abnorm ality. Interictal SPECT was not localizing in any case, in contrast to PET, which showed occipital hypometabolism in three of five studies. Conclusions: Ictal SPECT can provide novel localizing data in MRI-negative occipital lobe epilepsy. Interictal PET can provide useful localizing infor mation, but its role in providing novel information was not demonstrated. I nterictal SPECT is useful only as a baseline to aid in interpretation of ic tal studies.