In the early and incidental cases of Parkinson's disease, alpha-synuclein accumulation was observed in various areas of the nervous system, including the brain and peripheral autonomic nervous system, suggesting that these may have occurred multicentrally. In progressive supranuclear palsy, the distribution/density of tau-positive structures were consistent with the manifesting clinical features. Furthermore, the distribution/laterality of tau-positive structures suggested the possibility of lesion extension along fiber connections. Tissue clearing and three-dimensional analysis enabled high-resolution imaging of tau-positive structures in progressive supranuclear palsy and provided important insights into the pathomechanism of lesion formation in this disease.