Comparison of cognitive changes in patients with Alzheimer's and Parkinson's disease
Y. Stern, M. Richards, M. Sano and R. Mayeux
Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY.
OBJECTIVE--To compare cognitive changes in the dementias of Parkinson's
disease (PD) and Alzheimer's disease (AD). DESIGN--Case series, group
comparisons. SETTING--Ambulatory care referral center.
PATIENTS--Consecutive sample of 14 patients with PD dementia and 27 with
probable AD matched for overall intellectual function using a mental status
test, as well as 14 non-demented PD and 12 mild probable AD patients,
similarly matched for overall intellectual function. All demented patients
met Diagnostic and Statistical Manual, Revised Third Edition, criteria for
dementia. MAIN OUTCOME MEASURES--Performance on a battery of
neuropsychological tests assessing verbal and nonverbal memory, verbal
fluency, and constructional ability. RESULTS--Nondemented and demented
patients with PD performed worse than their probable AD comparison groups
on verbal fluency and visuospatial tasks. Cognitive changes attributable to
dementia were similar in PD and probable AD but were not identical. The
patients with probable AD demonstrated more marked change in memory
performance with delay. CONCLUSIONS--Our findings suggest that when
dementia occurs in PD it is overlaid on cognitive changes that already
exist in nondemented patients but that the dementing process in PD involves
systems other than those responsible for cognitive change in nondemented PD
patients. We hypothesize that in most cases, dementia in PD involves
changes in a nondopaminergic neurotransmitter system but is not due to
concomitant AD.
