Accurate prediction of postoperative outcome in mesial temporal lobe epilepsy - A study using positron emission tomography with (18)fluorodeoxyglucose

Background: Recent studies suggest that positron emission tomography may be a reliable predictive indicator of clinical outcome following surgical tre atment for epilepsy. Objective: We calculated 30 patients with documented medial temporal lobe e pilepsy to determine if prediction of postoperative outcome is improved wit h the use of positron emission tomography with (18)fluorodeoxyglucose. Patients and Methods: We performed a discriminant analysis to determine the combination of metabolic asymmetry indexes in temporal and extratemporal r egions defined by magnetic resonance imaging that best predicted the postop erative outcome. Seizure outcome was assessed at least 2 years after surger y: patients were classified as seizure free (n=14, group A), mostly improve d (n=10, group B), or as having persistent seizures (n=6, group C). Results: Discriminant analysis was first performed in groups A and C. The t emporal pole seemed to be the only temporal region for which metabolism was a significant predictor of the postoperative outcome (F-1,F-18=10.19; P=.0 05). The predictive value of positron emission tomography with (18)fluorode oxyglucose was considerably improved by the multivariate analysis (F-4,F-15 =7.21; P=.002), which correctly predicted the 2-year prognosis in 100% of t he patients using 4 regions: the temporal pole, the medial temporal region, the anterior part of the lateral temporal neocortex, and the basofrontal r egion. As a validation, we performed this 4-region analysis in the patients in group B. The difference among the 3 groups was highly significant (F=15 .5, P<.001). Conclusion: These findings suggest that the interictal metabolic pattern re liably predicts the 2-year prognosis after surgery in patients with medial temporal lobe epilepsy.