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Neuroradiology Case of the Week
Case 499
June 2010
Daniel Ginat, MD, MS and P-L Westesson, MD, PhD, DDS
Clinical
Presentation: Patient is an 8-year old male with history of neurofibromatosis type I.
Imaging Findings: A large, irregular mass infiltrates through the soft tissues of the neck and upper mediastinum. The mass enhances and has nodular and worm-like components that are characteristic of plexiform neurofibromas.
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Figure 1: Sagittal T2-weighted MRI of the neck reveals a large irregular lesion in the prevertebral and upper mediastinal soft tissues. The mass contains nodular components that range from isointense to the surrounding soft tissues to strongly hyperintense. The rest of the mass exhibits relatively high-signal intensity and has a consistency reminiscent of a “bunch of worms”.
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Figure 2: Axial T2-weighted MRI through the neck shows that the mass displaces the major vessels and trachea anteriorly.
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Figure 3: On the sagittal pre-contrast T1-weighted MRI with fat saturation, the mass appears heterogeneous, but essentially isointense to muscle tissue
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| Figure 4: The corresponding sagittal post-contrast T1-weighted image demonstrates avid enhancement throughout much of the plexiform neurofibroma, particularly the nodular areas. |
Diagnosis: Plexiform neurofibroma
Discussion:
Plexiform neurofibromas are virtually pathognomonic for Neurofibromatosis type I. These lesions are comprised of Schwann cells, fibroblasts, collagen, and a mucoid matrix that cause fusiform enlargement of the primary nerve. Plexiform neurofibromas can arise from nerves located in the scalp, orbit, neck, mediastinum, retroperitoneum, pelvis, and cranial nerves, especially the first division of the fifth cranial nerve. Since these tumors are unencapsulated, they have a propensity to infiltrate surrounding tissues, often in an aggressive manner. This characteristic is what makes plexiform neurofibromas rather disfiguring, sometimes leading to an appearance of elephantiasis and exopthalamos.
Imaging will reveal the poorly defined, infiltrative nature of plexiform neurofibromas as irregular, tortuous, worm-like masses that can be associated with bone erosion or deformity, such as sphernoid wing dysplasia. These tumors are often isodense to muscle on CT and T1 isointense and T2 hyperintense on MRI. Enhancement is typical on both CT and MRI.
Although benign, plexiform neurofibromas undergo degeneration into malignant peripheral sheet tumors. Consequently, regular monitoring of plexiform neurofibromas is prudent. Surgical resection is the treatment of choice for both plexiform neurofibromas and malignant peripheral nerve sheath tumors.
References:
- Grossman RI, Yousem DM. Neuroradiology: The Requisites. Philadelphia, PA: Mosby, 2003.
- Korf BR. Plexiform neurofibromas. Am J Med Genet. 1999 Mar 26;89(1):31-7. PMID: 10469434 [PubMed]
- Tucker T, Friedman JM, Friedrich RE, Wenzel R, Fünsterer C, Mautner VF. Longitudinal study of neurofibromatosis 1 associated plexiform neurofibromas. J Med Genet. 2009 Feb;46(2):81-5. PMID: 18930997 [PubMed]
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