Differences between Pick disease and Alzheimer disease in clinical appearance and rate of cognitive decline

Objectives: To define the cognitive characteristics of Pick disease (PcD), and to determine which features distinguish PcD from Alzheimer disease (AD) , in a cross-sectional and longitudinal study. Methods: The participants were 44 patients with PcD (10 pathologically veri fied), 121 patients with AD (14 pathologically verified), and 60 normal con trol subjects. We obtained information regarding the initial symptom of dem entia from each patient's caregiver, estimated global dementia severity by the Blessed Dementia Scale and the Activities of Daily Living Scale, and as sessed specific cognitive domains by administering 10 tests of memory, lang uage, visuospatial, and reasoning abilities and selective attention. Results: Among initial symptoms reported by caregivers, personality change and language impairment were significantly more common in PcD than AD; defi cits in memory were common in both groups but more prevalent in AD (P<.001) . At initial cognitive testing, the scores of patients with PcD were inferi or to those of normal controls on all tests, except on a measure of visuosp atial function; the scores of patients with AD were inferior to those of co ntrols on all tests. Patients with PcD were superior to patients with AD on measures of explicit memory (P<.001) and visuospatial function (P = .001) but had greater impairments on the Activities of Daily Living Scale (P<.05) . During the course of illness, patients with PcD declined significantly fa ster than those with AD on language tests and on global measures of dementi a severity (P<.05), whereas measures of explicit memory and visuospatial an d reasoning abilities worsened equally in both patient groups. Conclusions: There is a characteristic cognitive profile and course of deme ntia in PcD. Nonetheless, cognitive test performance does not clearly disti nguish PcD from AD.