Objective: To define the evolution of identified high-signal brain parenchymal lesions on magnetic resonance imaging (MRI) studies in patients with neurofibromatosis type 1 (NF-1).
Design: A cohort of patients with NF-1 who underwent MRI were identified prospectively and their imaging studies analyzed.
Patients: All referred patients with NF-1 (as defined by National Institutes of Health consensus criteria), who had undergone imaging with MRI were eligible. Of 123 patients with NF-1 whose conditions were evaluated, 30 patients had undergone 59 MRIs. There were 22 males and 8 females, aged 1 to 53 years with mean age of 12.5 years. Two groups of patients were identified, those with brain lesions (WBL) and those with no brain lesions. All initial and subsequently obtained MRIs from the WBL group were analyzed and tallied for number, size, and location of lesions over serial studies.
Results: Of the 19 patients with WBL, lesions were in hemispheres in 19 patients, and in the brainstem and the cerebellum in 10 patients each, respectively. Lesions were located in the cerebellum and globus pallidus most often (87 of 129 lesions). Of the patients with WBL having serial studies, a total of 97 lesions equaling 197 units (mean, 2.03 units per lesion) were identified at initial study. Follow-up evaluation (interval, 0.5-4.5 years; mean, 2.3 years), showed a decrease in both total number of lesions (68 [-29%]) and size (132 units; mean, 1.86 units per lesion [-33%]). Importantly, brainstem lesions increased in both number (+36%) and size (+6.4%) over the same intervals in 7 of 13 patients with WBL studied serially, whereas hemispheric and cerebellar lesions were more evanescent.
Conclusions: High-signal T2 lesions on MRI in patients with NF-1 evolve over time. The evolution of the NF-1 lesion is region specific and may relate to preferential region-specific effects of the NF-1 gene product.