Cognitive and behavioral features discriminate between Alzheimer's and Parkinson's disease

Objective: To compare the cognitive and behavioral profiles of Alzheimer's disease (AD) and cognitively impaired patients with Parkinson's disease (PD) and to determine the individual measures that best discriminate the two patient groups. Background: Neuropsychologic studies of patients with AD and PD have generated debate over the distinction between "cortical" and "subcortical" dementias, with some studies showing significant differences and others showing little difference in the cognitive profiles of these groups. Studies evaluating behavioral differences between the patient groups have been somewhat more successful in adequately discriminating these syndromes. To address this issue, we examined cognitive and behavioral profiles of patients with AD and cognitively impaired patients with PD on two frequently used assessment instruments. Method: Patients were diagnosed according to published and accepted criteria for AD and PD. Eighteen patients with AD and 18 patients with PD, matched on age and education, were administered the Mattis Dementia Rating Scale and Frontal Systems Behavior Scale (formally Frontal Lobe Personality Scale). Results: The two groups did not differ on overall Dementia Rating Scale score or total Frontal Systems Behaviour Scale score. However, examination of subscale score revealed that the patients with AD performed significantly worse than the patients with PD on the Memory subscale of the Dementia Rating Scale, and patient with PD were rated as being more apathetic than the patients with AD on the Frontal Systems Behavior Scale. When these two variables were entered into a discriminant function analysis, an overall classification accuracy of 6% was demonstrated, with 89% of the AD group and 83% of the PD group correctly classified. Conclusions: These findings suggest that even though global cognitive dysfunction and behavioral disturbance may appear similar in patients with AD and cognitively impaired patients with PD, specific measures of these functions that are sensitive to the underlying neuropathology of each disease do differ significantly.