Abstracts

Rationale: Previous positron emission tomography (PET) studies have shown reduced serotonin (5HT1A) receptor binding in depression and epilepsy, suggesting that altered serotonergic neurotransmission is present. In patients with depression, some studies have shown altered 5HT transport (5HTT). Methods: We used [11C]-3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)- benzonitrile (DASB) to image 5HTT and to image 5HT1A receptors in a preliminary study of 5HT transport in 4 patients with localization-related epilepsy and 4 healthy controls. [18F]-WAY 100635 (FCWAY) was used in 3 patients, and compared with a group of 16 healthy controls studied previously. PET was performed on the GE advance scanner in 3-D mode (full-width at half-maximum 6-7 mm). Each PET volume was registered to T1-weighted MR images. For DASB data, the co-registered PET and MR images were spatially normalized to a template brain. A reference region method (Cannon et al Biological Psychiatry 2007. 2007;62:870-877) was used to compute DASB binding. For FCWAY data, MR-based partial volume correction (PVC) was performed and the gray matter segmented mask applied to original and PVC-corrected PET parametric images to sample only gray matter pixels. 3-D ROIs were manually drawn on MR volumes. The ROIs were transferred to the masked PET images and the average regional values were computed. Results: In controls, DASB binding values were comparable to previously reported studies. We found that DASB binding was 6-28% lower in patients than controls, with the greatest differences in bilateral striatum, thalamus, amygdala and raphe. The difference was present in remote and contralateral regions, as well as in the epileptogenic zone itself. FCWAY binding was 16-34% lower than in controls. There was no clear relationship between FCWAY and DASB binding. Conclusions: Reduction in serotonin transport provides evidence additional to reduced 5HT1A binding in suggesting impaired serontonergic neurotransmission in localization-related epilepsy.