Evaluating atypical dementia syndromes using positron emission tomography with carbon 11-labeled Pittsburgh compound B

Context: A progressive decline in episodic memory affecting activities of daily living is the usual clinical presentation of Alzheimer disease. However, patients presenting with atypical or focal clinical symptoms such as language or visuospatial dysfunction often pose a diagnostic challenge. Objective: To explore the presence and topography of beta amyloid (A beta) as measured by carbon 11-labeled Pittsburgh Compound B (C-11-PiB) in patients with atypical presentations of dementia. Design, Setting, and Participants: At a tertiary referral center for memory disorders, 15 healthy controls, 10 patients with Alzheimer disease, a patient with primary progressive aphasia (PPA), and a patient with posterior cortical atrophy (PCA) underwent C-11-PiB positron emission tomographic studies. Retention of C-11-PiB was compared between different groups using statistical parametric mapping. Main Outcome Measure: The topography of cortical C-11-PiB binding in atypical vs typical Alzheimer disease. Results: Cortical C-11-PiB binding was higher in the group with Alzheimer disease and in the patients with PPA and PCA than the controls (P<.001). Both patients with atypical dementia had a similar C-11-PiB binding pattern to Alzheimer disease although C-11-PiB retention was higher on the left cerebral hemisphere in the patient with PPA (P<.01) and higher in the occipital cortex in the patient with PCA (P<.01). Conclusions: The presence of distinctive focal C-11-PiB retention patterns was demonstrated in 2 patients with atypical onset of dementia. Pittsburgh Compound B has the potential to facilitate differential diagnosis of dementia and identify patients who could benefit from specific therapeutic strategies aimed at beta amyloid reduction.