Cerebrospinal fluid biomarkers of Parkinson's disease: an update

Investigation of disease-specific biomarkers has the potential to advance the understanding of what causes Parkinson's disease (PD) and can lead to discovery of better treatments. Although PD's clinical features can be unmistakable, current laboratory methods have not enhanced its recognition. Over several decades, many attempts have sought out potential neurochemical indicators of PD diagnosis and progression. A logical starting point for this search has been cerebrospinal fluid (CSF), a biospecimen contiguous with the brain sites of pathology in this disorder. Guiding the search for biomarkers has been an understanding that neurons undergoing degeneration manifest distinct physiological changes such as abnormal protein aggregation, altered mitochondrial function, and a decline in neurotransmitter output. Beyond targeted searches for PD biomarkers, some studies have taken an exploratory approach by profiling large numbers of CSF constituents in the hopes of a successful discovery. This chapter will review the highlights of several decades of investigation into CSF PD biomarkers.