Loss of cholinergic neurons in the pedunculopontine nucleus in Parkinson's disease is related to disability of the patients.

We investigated neuronal number and size in the pars compacta of the pedunculopontine nucleus (PPN) in Parkinson's disease (PD). In PD, the number of Luxol fast blue (LFB) neurons was reduced by 27% from the mean control value (p=0.04) and the cholinergic (choline acetyltransferase, ChAT-positive) neuron number was reduced by 36% (p=0.03). In addition to neuronal loss, the remaining neurons in the PPN in PD were smaller than in controls. The profile area of LFB neurons was reduced by 14% (p=0.009) and that of ChAT-positive neurons by 26% (p=0.001). There was more severe loss of ChAT-positive neurons with a more severe stage of the disease, evaluated by the modified Hoehn and Yahr scale (r=-0.66, p=0.03). The neuron number decreased much more than could be expected on the basis of decrease in cell size alone.