SPECT und PET bei nichtläsioneller Epilepsie

Abstract

AbstractBackgroundPositron emission tomography (PET) and single-photon emission computed tomography (SPECT) are applied in epilepsy mostly during presurgical assessment. Nonlesional focal epilepsy is very challenging for presurgical evaluation in cases of refractory epilepsy.ObjectivesWe aimed to investigate the contribution of PET and SPECT to focus localization in nonlesional epilepsy.MethodsThe basic principles of SPECT and PET including different tracers were reviewed. The literature and the most recent publications are discussed in view of findings in nonlesional epilepsy.ResultsIctal SPECT shows a high sensitivity of over 80% for ictal onset zone in nonlesional epilepsy. Postprocessing with subtraction ictal SPECT co-registered with MRI (SISCOM) or statistical parametric mapping are the gold standard. Histopathological findings in nonlesional epilepsies with concordant ictal SPECT imaging show focal cortical dysplasia in up to 75% of cases. Ictal injection is unsuccessful in approximately 20% of cases and the procedure is very time consuming and labor intensive. Fluorodeoxyglucose (FDG)-PET in nonlesional epilepsy shows variable sensitivity of 46–76%. As with ictal SPECT, it benefits from postprocessing of co-registration with magnetic resonance imaging (MRI) or even statistical parametric mapping. Hybrid PET/magnetic resonance imaging (MRI) scanners provide additional benefits for identifying lesions. Other PET tracers (11C‑Flumazenil (FMZ), α-11C‑methyl-L-tryptophane (AMT)) are clinically applied in special cases only. Both procedures contribute complementary information in multimodal imaging diagnostics.ConclusionsIctal SPECT and PET are optional diagnostic tools for presurgical assessment in nonlesional epilepsies. They may reverse nonlesional to lesional epilepsy status and identify nonlesional epileptic foci with a fair chance of seizure freedom after epilepsy surgery.