Diagnosis depends on the presence of two or more cardinal motor features such as rest tremor, bradykinesia, or rigidity [Hughes et al., 1992]. Functional neuroimaging holds the promise of improved diagnosis and allows assessment in early disease [Piccini and Whone, 2004]. Two studies draw attention to the di±culties in the diagnosis of the disease in the early stages [Tolosa et al., 2006]. In a prospective clinicopathological study, Rajput [Rajput et al., 1991] showed that initial clinical diagnosis within 5 years from the disease onset was correct in 65% of the cases. After a mean duration of 12 years, the ¯nal diagnosis of PD by the clinician was confirmed with autopsy in 76% of cases.