Leonardo Iaccarino, Renaud La Joie, Lauren Edwards, Amelia Strom, Daniel R Schonhaut, Rik Ossenkoppele, Julie Pham, Taylor Mellinger, Mustafa Janabi, Suzanne L Baker, David Soleimani-Meigooni, Howard J Rosen, Bruce L Miller, William J Jagust, Gil D Rabinovici
Cerebral Cortex, https://doi.org/10.1093/cercor/bhaa184
Publication year: 2020

A deeper understanding of the spatial relationships of β-amyloid (Aβ), tau, and neurodegeneration in Alzheimer’s disease (AD) could provide insight into pathogenesis and clinical trial design. We included 81 amyloid-positive patients (age 64.4 ± 9.5) diagnosed with AD dementia or mild cognitive impairment due to AD and available 11C-PiB (PIB), 18F-Flortaucipir (FTP),18F-FDG-PET, and 3T-MRI, and 31 amyloid-positive, cognitively normal participants (age 77.3 ± 6.5, no FDG-PET). W-score voxel-wise deviation maps were created and binarized for each imaging-modality (W > 1.64, P < 0.05) adjusting for age, sex, and total intracranial volume (sMRI-only) using amyloid-negative cognitively normal adults. For symptomatic patients, FDG-PET and atrophy W-maps were combined into neurodegeneration maps (ND). Aβ-pathology showed the greatest proportion of cortical gray matter suprathreshold voxels (spatial extent) for both symptomatic and asymptomatic participants (median 94–55%, respectively), followed by tau (79–11%) and neurodegeneration (41–3%). Amyloid > tau > neurodegeneration was the most frequent hierarchy for both groups (79–77%, respectively), followed by tau > amyloid > neurodegeneration (13–10%) and amyloid > neurodegeneration > tau (6–13%). For symptomatic participants, most abnormal voxels were PIB+/FTP+/ND− (median 35%), and the great majority of ND+ voxels (91%) colocalized with molecular pathology. Amyloid spatially exceeded tau and neurodegeneration, with individual heterogeneities. Molecular pathology and neurodegeneration showed a progressive overlap along AD course, indicating shared vulnerabilities or synergistic toxic mechanisms.