Abstracts

Rationale: PET studies in temporal lobe epilepsy (TLE) show reduced 5HT1A receptor binding. Similar results have been reported in primary depression, and patients with epilepsy and depression may have additional binding reduction. Serotonin transport (5HTT) studies in depression have shown variable results. Methods: Fifteen healthy controls, 7 patients with generalized epilepsy, and 6 patients with unilateral TLE (3 right-sided) as established by ictal video-electroencephalography monitoring had positron emission tomography (PET) using 11C-DASB, a radioligand with high selectivity for 5-HTT, and 18F-FCWAY, a radioligand with high selectivity for the 5-HT-1A receptor. Six controls also underwent a PET scan using 18F-FCWAY. Images were processed using MEDx (Medical Numerics, Germantown, MD, USA) and co-registered to a structural MRI using statistical parametric mapping (SPM2) software (www.fil.ion.ucl.ac.uk/spm). We normalized structural MRI and PET images to a standard MNI template, and multiplied the normalized images by a gray matter mask generated for each subject. Regions of interest (ROIs) drawn on a normalized MRI from a control subject were applied to each subject’s PET images. For DASB, we calculated voxel-by-voxel non-displaceable binding potential (BPnd), and for FCWAY, free-fraction corrected volume of distribution (V/f1). Results: Subjects with TLE had decreased 11C-DASB binding in the amygdala ipsilateral to the seizure focus compared to controls (P<0.05). However, focus to contralateral asymmetry was not increased compared with control. There was a trend toward reduced midbrain DASB BPnd. Subjects with TLE, but not generalized epilepsy, had decreased 18F-FCWAY binding in the ipsilateral amygdala and hippocampus compared to controls. There were trends for an inverse correlation between DASB BPnd and FCWAY V/f1 in hippocampus and amygdala, which reached significance in right amygdala and left hippocampus (p<0.02). There was a non-significant trend for depressed TLE patients to have higher DASB BPnd, and lower FCWAY V/f1 in amygdala and hippocampus.