Can post-mortem MRI be used as a proxy for in vivo? A case study

Abstract

<i>Post-mortem</i> <i>in situ</i> MRI has been used as an intermediate between brain histo(patho)logy and <i>in vivo</i> imaging. However, it is not known how comparable <i>post-mortem</i> <i>in situ</i> is to <i>ante-mortem</i> imaging. We report the unique situation of a patient with familial early-onset Alzheimer's disease due to a <i>PSEN1</i> mutation, who underwent <i>ante-mortem</i> brain MRI and <i>post-mortem</i> <i>in situ</i> imaging only 4 days apart. T1-weighted and diffusion MRI was performed at 3-Tesla at both time points. Visual atrophy rating scales, brain volume, cortical thickness and diffusion measures were derived from both scans and compared. <i>Post-mortem</i> visual atrophy scores decreased 0.5-1 point compared with <i>ante-mortem</i>, indicating an increase in brain volume. This was confirmed by quantitative analysis; showing a 27% decrease of ventricular and 7% increase of whole-brain volume. This increase was more pronounced in the cerebellum and supratentorial white matter than in grey matter. Furthermore, axial and radial diffusivity decreased up to 60% <i>post-mortem</i> whereas average fractional anisotropy of white matter increased approximately 10%. This unique case study shows that the process of dying affects several imaging markers. These changes need to be taken into account when interpreting <i>post-mortem</i> MRI to make inferences on the <i>in vivo</i> situation.