Evidence of white matter tract disruption in MRI hyperintensities

Background: Diffusion tensor imaging (DTI) of brain tissue measures the apparent diffusion coefficient (ADC), or isotropic diffusion, and anisotropy, or diffusion as influenced by tissue structure. We hypothesized that hyperintensities, when compared with normal tissue by DTI, would show evidence of damage through an increased ADC and decreased anisotropy. We also hypothesized that DTI changes in hyperintensities would be similar between depressed subjects and control subjects. Methods: Fourteen depressed geriatric patients and nineteen control subjects received DTI. The ADC and anisotropy of normal tissue from standard regions were compared with hyperintensities from these regions. The Students' t test compared individual regions and averaged white matter results. Results: Hyperintensities showed higher ADC and lower anisotropy than normal regions. Gray matter exhibited similar trends. There was no significant difference in diffusion characteristics of hyperintensities between subjects and control subjects. Conclusions: Hyperintensities damage the structure Of brain tissue, and do so comparably in depressed subjects and control subjects. (C) 2001 Society of Biological Psychiatry.