Progress in defining the premotor phase of Parkinson's disease

Studies on the premotor phase of PD are important for our understanding of when and where does PD start and how it evolves in these initial stages. Several ongoing studies combine clinical, genetic and neuroimaging investigations to study the premotor phase in subjects at high risk for developing such as hyposmic individuals (PARS study) or nonmanifesting carriers of LRRK2 mutations (ASAP Study). The diagnosis of premotor PD remains still elusive but the information becoming available on premotor PD should guide the search for predictive biomarkers and the identification of risk or protective factors for PD.