Can Alzheimer's type pathology influence the clinical phenotype of Parkinson's disease?

Patients with clinical and pathological diagnosis of Parkinson's disease (PD) may, at death, also be found to have the pathological changes of Alzheimer's disease (AD). With this study we aim to determine the influence of AD pathology on the clinical phenotype of PD.

We studied 64 patients who donated their brains to the University of Miami Brain Endowment Bank(TM) and fulfilled the clinical and pathological criteria for PD. For the evaluation of AD pathology we used the CERAD criteria. Dementia was diagnosed, in life, also using standard criteria. Case histories were abstracted and reviewed by one investigator (SP) who then made comparisons between patients.

Patients with AD pathology (PD-AD) were older both at the time of diagnosis and death. The presence of AD pathology did not seem to influence disease duration in our cohort of PD patients. As expected there was a clear relation between AD pathology and dementia but not all PD-AD patients were demented. Psychosis and depression were also found to be more prevalent in the PD-AD patients. In the comparison between demented and non-demented PD-AD patients dementia was more likely to appear in patients with PD and definite criteria for AD.

Apart from dementia AD pathology seems to be associated with a number of other clinical characteristics of PD.