The locus ceruleus and dementia in Parkinson's disease.

We compared numbers of neuronal profiles in the locus ceruleus (LC) from sections of brainstem in 13 patients with Parkinson's disease (PD) without concurrent Alzheimer's disease (AD) with counts from age-matched controls and from patients with PD and concurrent AD. We also evaluated the relationships between presence of dementia or LC neuronal loss and additional pathologic measures related to dementia in PD. Among patients with PD without concurrent AD, the presence of dementia was associated with significantly lower LC neuronal counts (at all anatomic levels); greater neuronal loss within the ventral tegmental area, nucleus basalis of Meynert, and possibly the medial (but not the lateral) substantia nigra pars compacta; and more Lewy bodies in the anterior cingulate gyrus. Correlations between lower LC neuronal counts and these other pathologic measures were generally positive and often significant. We conclude that dementia in PD is associated with pathologic involvement of multiple extranigral neuronal populations.