Abstracts

Rationale: Animal studies and clinical observations suggest that epilepsy is associated with inflammation. Translocator protein 18 kDa (TSPO) is a marker of inflammation and can be measured in the living human brain with positron emission tomography (PET) and the radioligand 11C-PBR28. In this study, we sought to determine if TSPO expression is increased ipsilateral to the seizure focus in patients with temporal lobe epilepsy. Methods: Ten patients with unilateral temporal lobe epilepsy and seven healthy subjects were studied with 11C-PBR28 PET and magnetic resonance imaging (MRI). Uptake of radioactivity after injection of 11C-PBR28 was measured from regions of interest drawn bilaterally onto MR images. Brain uptake from ipsilateral and contralateral hemispheres was compared using a paired samples t-test. Results: Brain uptake was 10% higher ipsilateral to the seizure focus in the hippocampus, but not in other brain regions. This asymmetry was more pronounced in patients with hippocampal sclerosis than in those without. Both in healthy subjects and in patients with epilepsy, we noted small foci of higher uptake within the hippocampi; in these foci, uptake was 22% higher ipsilateral to the seizure focus in the patients. In healthy subjects, no hemispheric asymmetry in brain uptake was seen either in whole hippocampus or in foci of higher uptake. Conclusions: We found evidence for increased expression of TSPO in ipsilateral hippocampus of patients with temporal lobe epilepsy. Our results suggest that inflammatory processes may play a role in the pathophysiology of temporal lobe epilepsy.