Clinical markers of early nigrostriatal neurodegeneration in idiopathic rapid eye movement sleep behavior disorder

Background: Rapid eye movement sleep behavior disorder (RBD) is an early feature in a synucleinopathies and may precede other clinical manifestations of disease for several years. Olfactory dysfunction and mild motor abnormalities (MMAs) are highly prevalent in prodromal a synucleinopathies such as RBD and are suspected to be predictive neurodegenerative markers. Because both markers also are highly prevalent in the healthy elderly population, the discriminative value to detect an early neurodegenerative process is unclear. Methods: We examined 28 patients with idiopathic RBD (iRBD) without manifest neurodegenerative disease to determine diagnostic accuracy of MMAs and olfactory dysfunction in identifying patients with early nigrostriatal degeneration in transcranial sonography (TCS) and 123 I-2b-carbomethoxy-3b-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane single-photon emission computed tomography ( 123