There are only few studies comparing the phenotype of MSA-C and SAOA, and longitudinal studies focussing on the evolution of the phenotype of these disorders are completely lacking. In particular, the progression rate of SAOA compared to MSA-C has not been defined. In addition, it is unknown which factors predict the development of MSA-C vs. SAOA, and at which time after onset of ataxia, a reliable distinction between both disorders is possible.