Differentiating corticobasal degeneration and Alzheimer disease by longitudinal clinical and cognitive features

Corticobasal degeneration (CBD) has a heterogeneous presentation, contributing to diagnostic delay and inaccuracy. Despite recent advances in clinical characterization, little is known concerning the longitudinal measures that distinguish patients with progressive cognitive impairment due to CBD from those with more common causes of dementia, including Alzheimer disease (AD). To address this issue, we compared the clinical features and psychometric performance of individuals with autopsy-proven CBD and AD who presented with cognitive complaints. Clinical features and psychometric performance (adjusted for age, gender, education and illness severity) were compared between 17 individuals with autopsy-proven CBD and 16 with AD. Participants were assessed in the longitudinal Memory and Aging Project at the Knight Alzheimer Disease Research Center or the affiliated Memory Diagnostic Center outpatient clinic. Progressive memory impairment (47%), difficulties with judgement and problem solving (35%), language dysfunction (29%) and behavioral/personality changes (24%) were the most common initial complaints among participants with CBD. Of these, only problems with judgement and problem solving were reported more frequently by participants with CBD (p=.02). At the time of first assessment, no differences were observed between participants with CBD or AD concerning the duration of symptoms (2.6±1.6 years, p=.79) or illness severity (CDR-Sum of Boxes; 4±2.7, p=.70). Participants with CBD were, however, distinguished by superior performance on logical memory tests (p=.006), and greater impairment on the Boston Naming Test (p=.03). Across follow-up, participants with CBD experienced significantly greater declines in logical memory, verbal fluency and illness severity, compared to participants with AD. The emergence of asymmetric motor/sensory dysfunction (p