LRRK2 and Parkinson disease: Asymptomatic LRRK2 cases had increased basal forebrain, cuneus and striatum volumes, and unchanged hippocampus and thalamus volumes compared to healthy controls.57-60 Similarly, grey matter volume increases relative to controls have been described in the striatum of asymptomatic Parkin and PINK1 mutation carriers.61 These apparent volume increases in asymptomatic genetically at risk cases of PD have often been interpreted as compensatory mechanisms in the presence of preclinical dopaminergic degeneration.