LRRK2 and Parkinson disease: 21Brain imaging research in non-manifesting carriers of LRRK2 mutations and individuals at the prodromal stage of sporadic PD has identified presynaptic deficits and dopamine release defects before the appearance of motor symptoms.87,88 Collectively, these findings suggest that gaining a deeper understanding of synaptic dysfunctions of dopamine neurons may present a window of opportunity for therapeutic interventions.