Neurofibromatosis type 1 in children: MR imaging and follow-up studies of central nervous system findings.

Purpose: To determine the frequency, evolution and diagnostic impact of characteristic central nervous system MR imaging lesions in children with neurofibromatosis type 1 (NF1).

Subjects: We reviewed 89 children with established or clinically suspected disease. A final diagnosis of NF1 was made in 72 (age range, 10 months to 14 years).

Results: Hyperintense lesions on long TR images were detected in 78% of patients, principally involving the basal ganglia, cerebellum and brain stem. In 30% of the globus pallidus lesions, hyperintensity was seen on short TR images, being usually isointense on IR T1 weighted images. Globus pallidus lesions did not enhance. Eight patients presented atypical unenhanced lesions showing either edema, mass effect or hypointensity on short TR images; 2 of them were considered symptomatic brain stem gliomas. Six other children showed one or more growing enhanced cerebral lesions classified as tumors. Other child developed a growing enhanced lesion that markedly decreased in the follow-up studies. Twenty patients (28%) had optic gliomas. In two children, under 6 years old, this tumor appeared de novo. Forty-five children had several follow-up MR imaging studies (mean interval, 3 years). Regression of the basal ganglia lesions, both in size and/or intensity was noticed in 42% of cases, enlargement or new appearance of lesions in 24.5%, mixed increased/decreased in 7%, and stability in 26.5%. White matter lesions of the cerebellum and brain stem decreased in size in 40%, grew in 15.5%, showed a mixed increased/decreased pattern in 11%, and remained unchanged in 33.5% of cases. An involutional tendency of these lesions occurred in children older than 10 years, while progression was more frequent in younger children (P<0.05).

Conclusions: Hyperintense lesions are highly prevalent and characteristic in patients with NF1. MR imaging contributed to a definitive diagnosis of NF1 in 53% of suspected cases. Follow-up studies are necessary in the evaluation of suspected NF1, even if the first examination is negative.