Correlation between PET and SISCOM in temporal lobe epilepsy.

The subtraction of interictal from ictal SPECT coregistered to 3-dimensional (3D) MRI (SISCOM) and (18)F-FDG PET are 2 techniques that are involved in the definition of the epileptogenic zone in refractory partial temporal lobe epilepsy (TLE). The aim of this study was compare, region by region, the functional patterns obtained by both strategies, SISCOM and PET, in patients with unilateral TLE. METHODS: Perfusion data using SISCOM and metabolic data using (18)F-FDG PET scans were acquired from 17 patients with unilateral TLE. The functional metabolism and perfusion maps were overlaid onto a 3D rendering of the patient's anatomic MRI scans. RESULTS: The functional patterns that were observed with PET and SISCOM were found mainly in the ipsilateral and contralateral temporal lobes, in the orbitofrontal and insular cortices. Despite the high rate of concordance, in some cases discrepancies could be observed between PET and SISCOM abnormalities: In the mesial regions, as in the anterior neocortex, PET abnormalities were found more frequently than SISCOM changes. SISCOM abnormalities were found more frequently in the posterior temporal neocortex. In the extratemporal cortex, SISCOM abnormalities were more widespread. CONCLUSION: The marked rate of concordance between PET and SISCOM abnormalities observed in relatively extensive regions shows that, in TLE, seizures were generated and spread in metabolically abnormal regions.