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Steven Y. Ng, MBBS; Victor L. Villemagne, MD; Colin L. Masters, MD; Christopher C. Rowe, MD

Arch Neurol. 2007;64(8):1140-1144.

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 β amyloid (Aβ) as measured by carbon 11–labeled Pittsburgh Compound B (¹¹C-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 ¹¹C-PiB positron emission tomographic studies. Retention of ¹¹C-PiB was compared between different groups using statistical parametric mapping.

Main Outcome Measure  The topography of cortical ¹¹C-PiB binding in atypical vs typical Alzheimer disease.

Results  Cortical ¹¹C-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 ¹¹C-PiB binding pattern to Alzheimer disease although ¹¹C-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 ¹¹C-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 β amyloid reduction.

Author Affiliations: Department of Nuclear Medicine, Centre for Positron Emission Tomography, Austin Health, Melbourne, Australia (Drs Ng, Villemagne, and Rowe); Department of Pathology, University of Melbourne, Melbourne (Drs Villemagne and Masters); and Mental Health Research Institute of Victoria, Melbourne (Drs Villemagne and Masters).