Brain Metabolites and Peripheral Biomarkers Associated with Neuroinflammation in Complex Regional Pain Syndrome Using [11C]-(R)-PK11195 Positron Emission Tomography and Magnetic Resonance Spectroscopy: A Pilot Study.

Abstract

The aim of this study was to find peripheral biomarkers and central metabolites affecting neuroinflammation in complex regional pain syndrome (CRPS) patients using [11C]-(R)-PK11195 positron emission tomography (PET) and magnetic resonance spectroscopy (MRS). Using MRS and PET, we measured associations between neurometabolites and neuroinflammation in 12 CRPS patients and 11 healthy controls. Also, we investigated various peripheral parameters that may affect neuroinflammation in CRPS. We found positive correlations of Lipid (Lip)13a/total creatine (tCr) and Lip09/tCr with neuroinflammation, the distribution volume ratio (DVR) of [11C]-(R)-PK11195 in the right and left insula in CRPS patients. However, these correlations were not found in controls. High hemoglobin levels correlated with decreased neuroinflammation (the DVR of [11C]-(R)-PK11195) in the right thalamus and left insula in healthy controls. We found that high levels of glucose and pH correlated with increased neuroinflammation, but high levels of CO2, basophil, and creatinine were associated with decreased neuroinflammation in the left thalamus and the right and left insula in CRPS patients. This is the first report indicating that elevated neuroinflammation levels are associated primarily with lipids in the brain and pH, glucose, CO2, basophil, and creatinine in the peripheral parameters in CRPS patients. Our results suggest that characterizing the peripheral biomarkers and central metabolites affecting neuroinflammation is essential to understanding the pathophysiology of CRPS.