Background and purpose:
We report a patient with abnormal diffusion tensor imaging (DTI) and tractography of the corticospinal tract caused by mass effect from adjacent enlarged Virchow-Robin spaces.
Methods:
DTI was performed using 25 noncollinear directions. Fractional anisotropy (FA) and mean diffusivity (MD) maps were generated. Region-of-interest measurements of the corticospinal tracts were organized in histograms, and comparisons were made between sides. Statistical analysis consisted of a Wilcoxon rank-sum nonparametric test and a two-sample test of proportions to compare the relative percentage of voxels >.8.
Results:
The patient had no signs or symptoms of motor weakness. The corticospinal tract adjacent to the enlarged Virchow-Robin spaces showed significant changes in the proportion of FA > .8, distribution of FA and distribution of MD (P < .001).
Conclusions:
Diffusion tensor changes may be caused by enlarged Virchow-Robin spaces in the absence of clinical signs or symptoms. We hypothesize that the DTI changes are due to alterations in the extravascular extracellular space. Tensor changes should be interpreted with caution in patients with space occupying mass lesions such as brain tumors.