Statistical parametric mapping of regional glucose metabolism in mesial temporal lobe epilepsy

We investigated statistical parametric mapping (SPM) use for positron emiss ion tomography (PET) with [F-18]fluorodeoxyglucose (FDG) data analysis in m esial temporal lobe epilepsy. The study involved 14 patients with temporal lobe epilepsy ultimately treated by anterior temporal lobectomy. Surgical o utcome in terms of seizure control was favorable in 12 patients. Two differ ent SPM approaches were designed to analyze each FDG-PET scan: a direct com parison with a control group (n = 27) and a search for significant interhem ispheric asymmetry considering the asymmetry existing in the control group. Statistical inference was performed, first, without correction for multipl e comparisons (making the hypothesis of temporal hypometabolism) and, secon d, after correction for multiple comparisons. Search for temporal interhemi spheric asymmetry under the hypothesis of temporal hypometabolism was the m ost reliable SPM approach: hypometabolism was identified on the side chosen for resection in most cases (sensitivity, 71%; specificity, 100%) and was predictive of favorable postsurgical outcome in 90% of the patients, There was no false-positive result within the control group using this approach. After correction for multiple comparisons, SPM also identified in some pati ents temporal hypermetabolic areas as well as extratemporal cortical and su bcortical hypometabolic areas on the side of resection but also on the cont ralateral side. In a further step, SPM was used for a group analysis of pat ients with favorable outcome after reversing scans when needed to set an id entical lateralization in all patients. This analysis identified multiple i psilateral temporal and extratemporal hypometabolic regions; when temporal metabolic changes were specifically assessed, the contralateral mesiotempor al region was found hypermetabolic, possibly as a manifestation of compensa tory mechanisms in the presence of a unilateral epileptogenic lesion. (C) 2 000 Academic Press.