Serial MRI scans of 30 patients (mean age, 12 years) with neurofibromatosis Type 1 (NF-1) showed the evolution of high-signal brain lesions in a prospective study at the University of Connecticut Health Center, Farmington, and Children’s Medical Center, Hartford, CT. At initial examination, 19 patients had brain lesions identified by MRI, located in the hemisperes in 19, the brainstem in 10, and cerebellum in 10. Over a mean follow-up interval of 2 to 3 years, a decrease in total number and size of lesions in the hemispheres and cerebellum was noted, whereas brainstem lesions increased in number and size. Mass effect was associated with lesions in the brainstem, thalamus and cerebellar peduncles. Surgery or radiotherapy was required for mass lesions in 3 patients. 
COMMENT. High-signal MRI lesions in NF-1 evolve over time. They either increase or decrease in size or number, dependent on the location. Brainstem lesions are likely to increase whereas hemisphere and cerebellar lesions may regress. Correlations between T2-weighted hyperintensities (UBOs) and lower IQs in children with NF-1 have been reported by Denckla MB and others. (See PPN III, 1997;pp 291-294).