The relevance of interictal rCBF brain SPECT in temporal lobe epilepsy. Diagnostical value and effects of spatial resolution

This study retrospectively evaluates interictal rCBF-SPECT using Tc-99m-HMPAO to localize an epileptogenic area of epilepsy patients in comparison to the results of MRI. In 55 patients the complete data set could be obtained retrospectively, 36 of them being evaluated using SPECT systems with relatively low spatial resolution and 19 pt. being evaluated using moderate- to high-resolution SPECT systems. Overall sensitivity of the interictal rCBF-SPECT was 75%, with 69% for low-resolution systems and 84% for high-resolution systems. Overall sensitivity of MRI was 60%. The overall positive predictive value (PPV) was 87% for the interictal rCBF-SPECT and 87% for MRI. False lateralization using rCBF-SPECT occurred in 5 pt.(9%), however in 3 pt. the area of hypoperfusion correlated with a detectable MRI pathology, yet EEG/ECoG revealed the epileptogenic focus to be elsewhere. The interictal rCBF-SPECT revealed reasonable sensitivity and PPV in pt. suffering from focal temporal lobe epilepsy and modern SPECT systems showed significantly improved results. The interictal SPECT could add significant information prior to the application of ECoG. This specially appeared to be useful in patients with a normal MRI scan. In patients presenting with a clear pathology on MRI and a corresponding EEG focus, ECoG could be avoided if the interictal rCBF-SPECT additionally showed localized and singular involvement of the affected temporal lobe. ECoG was mainly applied in those patients with relatively wide-spread hypoperfusion additionally involving frontal or parietal cortical areas. (S.Y.)