Brain apparent diffusion coefficient evaluation in pediatric patients with neurofibromatosis type 1.

OBJECTIVE: The most frequent intracranial appearance in children with neurofibromatosis type 1 (NF1) is represented by the presence of hyperintense lesions on T2-weighted images, the so-called "unidentified bright objects" (UBOs). Di Paolo demonstrated that these lesions represent foci of myelin vacuolization with increased water content. The aim of this study was to investigate the isotropic apparent diffusion coefficient (ADC) values within the UBOs and normal-appearing brain and at the regressed UBO sites.
METHODS: Fifteen consecutive children with NF1 underwent magnetic resonance diffusion evaluation of the brain. Fifteen healthy age- and sex-matched children constituted the control group. Apparent diffusion coefficient maps were obtained, and regions of interest were placed bilaterally in 8 different areas. Two cortical areas were evaluated using single-pixel analysis. Apparent diffusion coefficient values within the UBOs were calculated by using irregular regions of interest. Regressed UBO sites were investigated by using circular regions of interest. Apparent diffusion coefficient values within the different areas were compared using a t test.
RESULTS: Compared with the controls, NF1 patients showed higher ADC values (P < 0.001) in all locations. In the NF1 group, the mean ADC value in the UBOs was higher than in other locations (P < 0.001). The mean ADC value within the regressed UBO sites was higher than in the normal-appearing locations (P < 0.001).
CONCLUSIONS: The higher ADC values in children with NF1 suggest an increase in water content of the normal-appearing brain. The UBOs are the areas with the highest water content. The regressed UBOs sites show higher water content than the normal-appearing areas.