Cholinergic neuronal loss in the basal forebrain and mesopontine tegmentum of progressive supranuclear palsy and corticobasal degeneration

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are clinically characterized by atypical parkinsonism and cognitive disorders and classified in the same histopathological category showing neuronal and glial neurofibrillary tangles (NFTs). To characterize the vulnerability of the forebrain and midbrain cholinergic systems in PSP and CBD, we performed a comparative study of cholinergic neuronal changes in the nucleus basalis of Meynert (NBM) and the laterodorsal tegmental and pedunculopontine tegmental nuclei (LdtgN and PptgN) of brains obtained at autopsy (three cases of PSP, one case of CBD and six cases without neurological diseases) by immunohistochemistry for choline acetyltransferase (ChAT) and Gallyas-Braak staining. In the NBM, the number of neurons and the ChAT-positivity rate of remaining neurons were decreased more in CBD than PSP. On the other hand, in the PptgN and LdtgN neurons were reduced much more, and more NFTs were observed in PSP than CBD. PSP showed a severe decrease of neurons and the ChAT-immunopositive neurons in the LdtgN but less in the PptgN. In CBD, there was a mild deletion of the ChAT-immunostained neurons in the PptgN, but not in the LdtgN. In PSP, cholinergic neurons in the LdtgN are likely to be more vulnerable than PptgN and NBM.