Pulsatile Brain Motion as a Marker of Brain Aging and Dementia: Insights from 3D q-aMRI.

Heart-brain interactions, including cardiac-induced brain pulsatility, are thought to support brain homeostasis, yet their alteration with aging and neurodegeneration remains poorly understood. Here, we used three-dimensional quantitative amplified MRI (q-aMRI) to visualize and quantify cardiac-induced pulsatile brain motion across healthy individuals and those on the Alzheimer's and Lewy body disease spectra. Expert evaluations revealed consistent distinctions between normal and abnormal motion patterns, which were further characterized using strain-based biomechanical features. Principal component analysis identified interpretable signatures of abnormal motion that emerged predominantly after midlife and were closely linked to chronological age. Even after accounting for age, these biomechanical features differentiated individuals with clinical and biomarker evidence of neurodegenerative disease. Together, these findings suggest that q-aMRI-derived measures of cardiac-gated pulsatile brain motion may serve as imaging biomarkers of normal brain aging and dementia.