AJR:199, July 2012 W99 On MRI, localized neurofibroma lesions usually show nonspecific signal intensity and variable contrast enhancement. The classic target sign appearance, which is less com- mon but nearly pathognomonic, is seen on T2-weighted images with high-signal-inten- sity myxoid material peripherally and a rela- tively low-signal-intensity fibrous component centrally (Fig. 2). The “reverse target” sign may be present on T1-weighted images after IV gadolinium administration; it is charac- terized by enhancement of the central fibrous component and a relative lack of enhance- ment of the surrounding myxoid component. Diffuse Neurofibromas Like localized neurofibromas, most diffuse neurofibromas encountered in clinical prac- tice are solitary and are seen in patients with- out NF1; approximately 10% are seen in pa- tients with NF1. Diffuse neurofibromas tend to occur primarily in children and young adults [4]. The term “diffuse neurofibroma” refers to the infiltrative nature of the tumor and does not indicate multifocality. Diffuse neurofibro- mas involve the skin and subcutaneous tissues, often extending to the underlying fascia, and enhance after IV gadolinium administration. Two growth patterns exist: infiltrative with a reticulated branching pattern and plaquelike with elevation of the skin and thickening of the underlying dermis [5] (Fig. 3). Plexiform Neurofibromas Plexiform neurofibromas, unlike localized and diffuse neurofibromas, are essentially pathognomonic of NF1, occurring in up to 40% of patients with NF1. Usually starting early in childhood, plexiform neurofibromas represent Musculoskeletal Manifestations of Neurofibromatosis Type 1 Neel B. Patel 1 Gregory Scott Stacy Patel NB, Stacy GS 1 Both authors: Department of Radiology, University of Chicago, 5841 S Maryland Ave, MC 2026, Chicago, IL 60637. Address correspondence to N. B. Patel ([email protected]). Musculoskeletal Imaging • Pictorial Essay WEB This is a Web exclusive article. AJR 2012; 199:W99–W106 0361–803X/12/1991–W99 © American Roentgen Ray Society N eurofibromatosis type 1 (NF1), also known as von Recklinghau- sen disease, is one of the most common genetic diseases, affect- ing 1 in 3000 individuals. It is an autosomal- dominant disorder due to a mutation or dele- tion of the NF1 gene on chromosome 17. Neurofibromin, the gene product, acts as a tu- mor suppressor [1] and is important in skeletal development and growth [2]. NF1 is the most common type of neurofibromatosis and the most common of the phakomatoses, a group of congenital neurocutaneous disorders. The diagnosis is based on a variety of clinical fea- tures [3] (Table 1). NF1 is characterized by the formation of neurofibromas and abnor- malities related to mesodermal dysplasia. It affects multiple organ systems, with skeletal abnormalities seen in up to 50% of patients. Neurofibromas The neurofibroma, a type of benign pe- ripheral nerve sheath tumor, is the hallmark of NF1. Three varieties of neurofibromas ex- ist: localized, diffuse, and plexiform. Localized Neurofibromas Most localized neurofibromas encountered in clinical practice are solitary and are seen in patients without NF1 [4]; however, in pa- tients with NF1, localized neurofibromas rep- resent the most common variety of neurofi- broma. They usually arise during childhood and adolescence, are multiple, and tend to in- volve larger and deeper nerves than do neuro- fibromas seen in patients without NF1. Local- ized neurofibromas often have an elongated or fusiform shape and the affected nerve may be seen entering or exiting the mass (Fig. 1). Keywords: conventional radiography, MRI, musculoskeletal system, neurofibromatosis type 1 DOI:10.2214/AJR.11.7811 Received August 30, 2011; accepted after revision September 24, 2011. Presented at the 2011 annual meeting of the American Roentgen Ray Society, Chicago, IL. Winner of Certificate of Merit. OBJECTIVE. We will describe and illustrate various musculoskeletal manifestations of neurofibromatosis type 1 (NF1) encountered on imaging studies. CONCLUSION. Because NF1 is one of the most common genetic disorders, radiolo- gists should be familiar with its imaging manifestations. Patel and Stacy Musculoskeletal Manifestations of NF1 Musculoskeletal Imaging Pictorial Essay Downloaded from www.ajronline.org by 171.243.67.90 on 05/30/23 from IP address 171.243.67.90. Copyright ARRS. For personal use only; all rights reserved
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