The pontomesencephalotegmental cholinergic system does not degenerate in Alzheimer's disease.

The pedunculopontine and laterodorsal tegmental nuclei comprising the pontomesencephalotegmental (PMT) cholinergic system were examined for the presence of neuropathology and loss of presumed cholinergic cells in patients diagnosed with Alzheimer's disease-senile dementia of the Alzheimer type (AD-SDAT), Parkinsonian dementia, and multi-infarct dementia. Although neurofibrillary changes and plaque-like entities were observed in both nuclei in AD-SDAT and Parkinson's disease dementia, these pathologic indices were not seen consistently in control individuals or in those with multi-infarct dementia, and in none of the diagnostic categories was loss of neuronal somata found in the PMT cholinergic complex. Because appreciable degeneration of cholinergic neurons does occur in the basal forebrain in AD-SDAT, it is concluded that cholinergic phenotype alone is not a sufficient condition indicating predilection for neuronal loss in that dementing illness.