mGluR5 PET Imaging Using 18F-FPEB in Medically Refractory Epilepsy Patients

Introduction: mGluR5 availability in medically refractory epilepsy patients compared to healthy controls (HC) using the PET agent 18F-FPEB was assessed. Methods: Five epilepsy patients (mean age: 33.6; SD: 13.04); (4F, 1M) and 8 HC (mean age: 24.4; SD of 4.8); (5 M, 3 F) were studied with a High-Resolution Research Tomography and a bolus/infusion technique. Volume of distribution corrected for plasma free fraction values (VT/fp) was determined from equilibrium data in different brain regions including the seizure onset zone (SOZ), which was determined at an epilepsy surgical conference. Results: A trend towards global decreases in 18F-FPEB VT/fp was noted. Significant decreases were seen in the frontal lobes, and limbic structures: The amygdala, hippocampi, and thalami compared to HC. No significant differences were found between SOZ and a contralateral mirror region. Conclusion: 18F-FPEB human imaging of the mGluR5 system in refractory epilepsy showed significant decreases in the frontal lobes and limbic structures. glutamate system, an immediate driver of seizures. We hypothesize that there would be major changes in the mGluR5 system in epilepsy, and conjectured that it might be useful in identifying the SOZ. Materials and Methods