Histopathology of diffusion imaging abnormalities in cerebral amyloid angiopathy

Objective: we sought to determine the underlying mechanism for altered white matter diffusion tensor imaging (DTI) measures at the histopathologic level in patients with cerebral amyloid angiopathy (CAA). Methods: formalin-fixed intact hemispheres from nine CAA cases and two elderly controls were scanned at 3 tesla MRI, including a diffusion-weighted sequence. DTI measures (i.e. fractional anisotropy (FA) and mean diffusivity (MD)) and histopathology measures were obtained from two tracts: the anterior thalamic radiation (ATR) and inferior longitudinal fasciculus (ILF).
Results: FA was reduced in both tracts and MD was increased in CAA cases compared to controls. Regional FA was significantly correlated with tissue rarefaction, myelin density, axonal density, and white matter microinfarcts. MD correlated significantly with tissue rarefaction, myelin density, and white matter microinfarcts, but not axonal density. FA and MD did not correlate with oligodendrocytes, astrocytes, or gliosis...