PET of Brain Amyloid and Tau in Mild Cognitive Impairment

Amyloid senile plaques and tau neurofibrillary tangles are neuropathological hallmarks of Alzheimer's disease that accumulate in the cortical regions of the brain in persons with mild cognitive impairment who are at risk for Alzheimer's disease. Noninvasive methods to detect these abnormal proteins are potentially useful in developing surrogate markers for drug discovery and diagnostics.

We enrolled 83 volunteers with self-reported memory problems who had undergone neurologic and psychiatric evaluation and positron-emission tomography (PET). On the basis of cognitive testing, 25 volunteers were classified as having Alzheimer's disease, 28 as having mild cognitive impairment, and 30 as having no cognitive impairment (healthy controls). PET was performed after injection of 2-(1-{6-[(2-[F-18]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile (FDDNP), a molecule that binds to plaques and tangles in vitro. All subjects also underwent 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) PET, and 72 underwent magnetic resonance imaging (MRI).