Diagnosis of Parkinson's disease: progress and future prospects

This review focuses on methods for diagnosing Parkinson's disease (PD), highlighting clinical, pathological, and biomarker-driven approaches. For each of these diagnostic approaches, the past, present, and future prospects of diagnosing PD will be explored. Our understanding of PD-its pathogenesis and clinical spectrum-is ever changing. PD is now recognized as a complex multisystem disorder with motor and nonmotor features, including those preceding the onset of classic motor features as well as different phenotypes, often associated with different genetic mutations. Theories regarding the pathophysiology of PD and the role of alpha-synuclein, its deposition outside of the central nervous system, and possible progression or propagation are discussed. It has been almost 200 years since James Parkinson first described this disorder, and since then, our understanding of the disease process has evolved and become more sophisticated. However, the clinical diagnostic criteria used have remained fairly static for decades. Proposals for redefining PD's diagnostic criteria incorporate clinical, pathological, and biomarker-driven elements, individually and/or collectively, and may need to consider whether individualized risk and personalized profiles could be ascertained.