This study demonstrates that detecting in vivo amyloid plaques by molecular imaging is considerably frequent in most of the dementia syndromes and shows that there are frequent discordance between molecular diagnosis and clinical assumption.

Two patients with mild cognitive impairment underwent C-PiB and F-FDG brain PET. Both patients had previously gone through a contrast-enhanced MRI scan that revealed extra-axial tumors next to the sphenoid wing, suggestive of meningiomas. C-PiB PET images showed a highly increased uptake by the extra-axial masses. These 2 cases represent 1.2% of our C-PiB population (n = 163). No meningioma was found with negative C-PiB uptake. The F-FDG concentration was not increased within the lesions. C-PiB could be used as a meningioma marker.