A tensor based morphometry study of patients with cognitive impairment and dementia in parkinson's disease

prefrontal, orbitofrontal, parietal, temporal, anterior cingulate and posterior cingulate/precuneus values divided by the cerebellar cortical PiB retention for each subject, with equal weighting of the individual values in computing the summary measure. Hippocampal volumes were analyzed as adjusted W-scores for head size, age and gender. Results: The global cortical PiB retention in DLB patients was on average lower than AD, but higher than cognitively normal subjects. Similarly, hippocampal Wscores of DLB patients were on average higher than AD, but lower than cognitively normal subjects. Three of the five (60%) DLB patients were ‘‘PiB positive’’ (global cortical PiB retention summary measure 1.5), and one subject was ‘‘borderline’’ (1.49). Hippocampal W-scores were lower than zero in three of the five (60%) DLB patients. Only one DLB patient had both hippocampal atrophy and ‘‘positive PiB.’’ Plotting hippocampal W-scores against global cortical PiB retention completely separated the DLB and AD subjects (Figure). Conclusions: MRI and PiB PET are complementary in distinguishing patients with DLB and AD, and provide insight into the pathological mechanisms underlying dementia in DLB patients. A majority of the DLB patients had PiB retention and/or hippocampal atrophy, in agreement with pathology studies showing that patients with clinically diagnosed DLB may often have some degree of additional AD pathology.