MR imaging of abdominopelvic involvement in neurofibromatosis type 1: a review of 43 patients

Background: Plexiform neurofibromas are a frequent complication of neurofibromatosis type 1. This article discusses MR imaging findings and distribution of plexiform neurofibromas in the abdomen and pelvis. Objective: To define the most prevalent patterns of involvement and MR imaging findings in abdominopelvic neurofibromatosis type 1. Materials and methods: We reviewed the MR appearance of abdominopelvic lesions in 23 male and 20 female patients (median age: 16 years) with type 1 neurofibromatosis. The patients were part of a multi-institutional study of 300 patients. Imaging included coronal or sagittal, and axial short tau inversion recovery images. Results: The most common abdominopelvic involvement was in the abdominopelvic wall (n=28, 65%) and lumbosacral plexus (n=27, 63%). Retroperitoneal involvement was frequent (n=15, 35%). Lesions were less often intraperitoneal (21%) (P=0.001). Pelvic disease (n=27, 63%), neural canal involvement (n=18, 42%), and hydronephrosis (n=4, 9%) were also noted. Target-like appearance of plexiform lesions was noted in more than half the patients. Conclusion: Abdominopelvic involvement in neurofibromatosis type 1 is primarily extraperitoneal. Although lesions are most prevalent in the abdominopelvic wall and lumbosacral plexus, retroperitoneal and pelvic involvement is common and usually affects important organs. MR imaging added information in the initial and follow-up clinical evaluation of these patients.