PREDICTORS OF OUTCOME AFTER ANTERIOR TEMPORAL LOBECTOMY - POSITRON EMISSION TOMOGRAPHY

We assessed the relationship between temporal lobe metabolism measured quantitatively and qualitatively with PET using [F-18]-fluorodeoxyglu cose (FDG) and postoperative seizure frequency after anterior temporal lobectomy. Forty-three patients with refractory partial epilepsy had anterior temporal lobectomy and preoperative assessment with PET-FDG. Qualitative PET analysis was performed visually by two blinded observe rs, and quantitative PET analysis was performed using an anatomic temp late for six control and six temporal lobe subregions, deriving an asy mmetry index for each region. Seizure outcome was assessed 1 year afte r surgery; patients were classified as being seizure-free or as having persistent seizures. Qualitative data were analyzed using Fisher's ex act test and the t test, and quantitative data were analyzed using a r epeated-measures ANOVA. Thirty-two patients (74%) were seizure-free at follow-up, and 11 had persistent seizures, although most improved. Tw enty-nine of 35 patients (83%) with restricted temporal lobe hypometab olism by visual analysis were seizure-free, compared with three of eig ht patients (37.5%) with normal scans or multilobar hypometabolism. Qu antitative analysis revealed that an asymmetry of mesial temporal lobe glucose consumption (uncal region) correlated with improved surgical outcome (p < 0.02). We developed a logistic regression model to predic t individual outcome based on the asymmetry in uncal metabolism. Later al temporal metabolism did not correlate with outcome. We conclude tha t both visual PET analysis and quantitative PET analysis predict outco me after temporal lobectomy, although quantitative measures offer more precise information.