Biomarkers of Parkinson's disease: recent insights, current challenges, and future prospects

Abstract

A biomarker represents a tool possibly helping physicians in predicting onset, diagnosis, and progression of a disease as well as evaluating the response to disease-modifying treatments. Currently, there is no biomarker fulfilling all such ideal criteria for Parkinson's disease (PD). In this article, we have critically reviewed the literature searching for the most reliable and reproducible clinical, biochemical, and imaging biomarkers for prodromal phase, diagnosis, and progression of PD. Different comprehensive batteries of biomarkers have been proposed as a sensitive approach to predict the onset of PD during the prodromal phase. There is a discussion about the redefinition of the clinical diagnosis of PD, including clinical biomarkers as non-motor symptoms; however, on the other hand, we have also observed that imaging biomarkers support the differential diagnosis from other causes of parkinsonism. Various clinical (eg, freezing of gait or cognitive impairment), biochemical (eg, epidermal growth factor, insulin-like growth factor 1, uric acid, etc), and imaging (eg, functional mag- netic resonance imaging, voxel-based morphometry, etc) biomarkers may help envisaging disease progression of PD. To conclude, given the lack of a single biomarker that could track the entire course of the disease, our challenge is to find the best combinations of biomarkers for the different stages of the disease.