Restricted diffusion in vanishing white matter.

OBJECTIVE To investigate the occurrence of restricted diffusion in vanishing white matter, the affected structures,the time of occurrence in the disease course, and the histopathologic correlate. DESIGN Retrospective observational study. PATIENTS Forty-six patients with vanishing white matter. SETTING VU University Medical Center. MAIN OUTCOME MEASURES We evaluated all available diffusion-weighted imaging studies in our database and recorded the areas that displayed restricted diffusion in 1 or more patients. We measured the mean apparent diffusion coefficients of these areas in all patients and used the putamen for internal quality control. We recorded age and disease duration during magnetic resonance imaging, and we obtained a magnetic resonance image of a postmortem vanishing white matter brain slice and subsequently performed histopathologic stainings. RESULTS Areas with decreased apparent diffusion coefficient values were found in the U fibers (n=21 patients), cerebellar white matter (n=18), middle cerebellar peduncle(n=8), pyramids (n=8), genu (n=8) or splenium (n=9) of the corpus callosum, and posterior limb of the internal capsule(n=10). Overall, patients showing restricted diffusion(n=32)were younger and had shorter disease duration. Histopathologic analysis of the brain slice revealed that regions with restricted diffusion had a higher cell density. CONCLUSION In vanishing white matter, restricted diffusion can be found in relatively spared regions with high cellularity particularly in young patients with short disease duration.