Temporal lobe asymmetry in FDG-PET uptake predicts neuropsychological and seizure outcomes after temporal lobectomy.

OBJECTIVE: The objective of this study was to determine whether preoperative [18 F]fludeoxyglucose (FDG)-positron emission tomography (PET) asymmetry in temporal lobe metabolism predicts neuropsychological and seizure outcomes after temporal lobectomy (TL).

METHODS: An archival sample of 47 adults with unilateral temporal lobe epilepsy who underwent TL of their language-dominant (29 left, 1 right) or nondominant (17 right) hemisphere were administered neuropsychological measures pre- and postoperatively. Post-TL seizure outcomes were measured at 1year. Regional FDG uptake values were defined by an automated technique, and a quantitative asymmetry index (AI) was calculated to represent the relative difference in the FDG uptake in the epileptic relative to the nonepileptic temporal lobe for four regions of interest: medial anterior temporal (MAT), lateral anterior temporal (LAT), medial posterior temporal (MPT), and lateral posterior temporal (LPT) cortices.

RESULTS: In language-dominant TL, naming outcomes were predicted by FDG uptake asymmetry in the MAT (r=-0.38) and LPT (r=-0.45) regions. For all patients, visual search and motor speed outcomes were predicted by FDG uptake asymmetry in all temporal regions (MPT, r=0.42; MAT, r=0.34; LPT, r=0.47; LAT, r=0.51). Seizure outcomes were predicted by FDG uptake asymmetry in the MAT (r=0.36) and MPT (r=0.30) regions. In all of these significant associations, greater hypometabolism in regions of the epileptic temporal lobe was associated with better postoperative outcomes.

CONCLUSIONS: Our results support the conclusion that FDG uptake asymmetry is a useful clinical tool in assessing risk for cognitive changes in patients being considered for TL.