Thalamic and basal ganglia metabolism on interictal ¹⁸F-FDG PET in temporal lobe epilepsy: an SUV-based analysis

The aim of this study was to investigate thalamic and basal ganglia (BG) metabolism in temporal lobe epilepsy (TLE) on interictal ¹⁸F-FDG PET using standardized uptake value (SUV). Retrospective review of data was undertaken for patients who were surgically treated for medically intractable TLE. All patients underwent ¹⁸F-FDG PET, MRI brain and EEG as preoperative workup, and subsequently underwent temporal lobe resection. Postoperative outcomes were analyzed as without or with residual disabling seizures. SUV_max and SUV_peak values were calculated for thalamus and BG. Subgroup comparisons were performed with non-parametric tests. Study sample consisted of 33 patients (58% female; mean age 44.7 years) and 33 age- and sex-matched controls. Mean SUV_peak for both right and left thalamus was significantly lower in TLE than controls (8.1 ± 1.9 vs. 9.7 ± 2.9 and 8.1 ± 1.9 vs. 9.8 ± 2.9, respectively, both p=0.035). Mean SUV_peak for thalamus on the epileptogenic side was overall significantly lower than the contralateral side (8.0 ± 2.0 vs. 8.3 ± 2.0, p=0.040). One (3%) patient with MRI- and EEG-congruent left TLE showed marked left thalamic hypometabolism as the only finding on PET. There was no evidence of basal ganglia hypometabolism. No correlation was noted between thalamic metabolic asymmetry and postoperative outcomes. Thalamic metabolism was significantly reduced in patients with TLE compared to controls, and on the epileptogenic compared to the contralateral side among patients. Thalamic hypometabolism can have value in seizure focus localization in patients without interictal temporal hypometabolism.