NEUROFIBROMATOSIS TYPE-1 - THE EVOLUTION OF DEEP GRAY AND WHITE-MATTER MR ABNORMALITIES

PURPOSE: To investigate the evolution of deeply located high-signal-in tensity abnormalities of the brain on T2-weighted MR images of patient s with neurofibromatosis type 1 (NF-1). METHODS: The study consists of two patient groups: 1) retrospective evaluation of MR scans of 24 sym ptomatic NF-1 patients, 10 of whom were sequentially studied, and 2) p rospective MR evaluations of 20 asymptomatic NF-1 subjects from 14 fam ilies; 2 of these families were sequentially studied. RESULTS: Deeply located, high-signal-intensity abnormalities on T2-weighted images wer e noted in 34 of 44 NF-1 subjects (77%). If NF-1 patients are grouped according to age, 28 of 30 subjects (93%) younger than 15 years had th e lesions, whereas 4 of 7 subjects (57%) between 16 and 30 years, and 2 of 7 subjects (29%) older than 31 years had lesions. High-signal les ions in basal ganglia and brain stem were demonstrated in all decades with relatively high frequency. Lesions in the cerebellar white matter and dentate nuclei were mainly found in the patients younger than 10 years, and never found after the third decade. In 13 sequential studie s (mean interval, 24 months), lesions appeared to increase in size in 3, remain unchanged in size in 2, and decrease in size in 7. One subje ct showed a mixed pattern of lesion size change. CONCLUSIONS: Deeply l ocated high-signal-intensity lesions on T2-weighted MR images are more evident in young NF-1 patients. The underlying brain abnormality, whi le pathologically unproved, is probably transient.