Unidentified bright objects in neurofibromatosis type 1: conventional MRI in the follow-up and correlation of microstructural lesions on diffusion tensor images.

PURPOSE To evaluate the evolution of unidentified bright objects (UBOs) in individuals with neurofibromatosis type 1 (NF1) by serial magnetic resonance imaging (MRI), and to relate this to regional fractional anisotropy (FA). MATERIALS AND METHODS The signal pattern of the T2-weighted sequences in the basal ganglia, thalamus, brain stem, and cerebellum for 27 NF1 individuals and a control group were analyzed by diffusion tensor imaging (DTI). The presence or absence of UBOs in 2 consecutive MRI examinations was related to FA. RESULTS We demonstrated significant differences in FA for the basal ganglia, cerebellum, and thalamus between NF1 patients and controls (P ≤ 0.05), even with a reduction or disappearance of UBOs. CONCLUSIONS MRI allows for adequate monitoring of the temporal and spatial distribution of UBOs in patients with NF1. DTI confirmed changes in FA despite the disappearance or reduction of UBOs, thereby confirming the hypothesis that microstructural damage occurs in specific brain regions of NF1 patients.