Preserved structural integrity of white matter adjacent to low-grade tumors

Abstract

Background and purpose: Brain tumors may dislocate, infiltrate, or disrupt the adjacent fiber tracts. We examined (1) microstructural changes of white matter (WM) adjacent to supratentorial low grade tumors in children and (2) WM tracts of the affected hemisphere using diffusion tensor imaging (DTI). We hypothesized that the structural integrity of the adjacent WM tracts would be preserved in these slow-growing tumors.

Materials and methods: DTI was performed in 11 children with low grade tumors diagnosed by magnetic resonance imaging (MRI). Regions of interest were placed in the tumor, in WM adjacent to tumor, and on the normal contralateral side. Fractional anisotropy (FA), trace, and eigenvalues were measured. Color-coded maps and tractography were used to grade the WM tracts: Grade one was normal tract size and color hue; grade two was reduced tract size but preserved color hue; and grade three was loss of color hue or failure to track on tractography. Grades one and two were subcategorized as "a" or "b," depending on the absence or presence of tract displacement.

Results: There were no significant differences in FA, trace, and eigenvalues between WM adjacent to tumor and the contralateral side. One patient had grade 1a changes, six grade 1b, and four grade 2b.

Conclusion: We found preserved microstructural integrity of WM adjacent to low grade tumors in children. Color vector maps and tractography demonstrated displacement of the WM tracts in all but one patient. Our findings could be useful for neurosurgical planning to minimize injury to the WM tracts and improve preoperative risk analysis.