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Neuroradiology Case of the Week

Case 83

Terry Chun, MD and P-L Westesson, MD, PhD, DDS

Clinical Presentation: The patient is a 6-year-old male with multiple café au lait spots and a history of pulmonary stenosis.

Radiological Findings:  A multi-lobulated mass is present along the right carotid sheath from the level of the T2 vertebral body into the thoracic inlet. This mass demonstrates hyperintense T2 signal, isointense T1 signal, and no significant enhancement. Splaying of the right internal carotid artery and right internal jugular vein are seen. There is no evidence for hemodynamically significant stenosis or occlusion of these vessels.

Diagnosis: Watson’s syndrome with a neurofibroma

Discussion: Watson’s syndrome is characterized by congenital pulmonary valvular stenosis, café au lait spots, dull intelligence, and short stature [1-3]. Approximately one-third of patients have neurofibromas [1]. It is a rare disease with an autosomal dominant inheritance pattern [1]. Symptoms often overlap with that of neurofibromatosis type 1, but certain characteristics are more common. The following table indicates the incidence of some clinical findings [1].

     Neurofibromas are unencapsulated masses that occur in subcutaneous tissue or nerve [4-5]. These tumors usually affect spinal roots and, rarely, cranial nerves. Histologically, neurofibromas are a mixture of Schwann cells, fibroblasts, reticulin, and collagen [4]. Plexiform neurofibromas, which appear multi-lobulated, are pathognomonic for neurofibromatosis type 1 [5]. Approximately 2-12% of plexiform neurofibromas degenerate into malignant peripheral nerve sheath tumors [5].
     Neurofibromas are best characterized by MRI. Typical findings are a mass that is sometimes multi-lobulated (plexiform) with isointense T1 and hyperintense T2 signals. Moderate enhancement is often seen.
     Definitive treatment is surgical resection. However, plexiform neurofibromas have a high recurrence rate [5].

References:

1. Allanson JE, Upadhyaya M, Watson GH, et al. Watson syndrome: is it a subtype of type 1 neurofibromatosis? J Med Genet 1991; 28:752-756.
2. Friedman JM, Arbiser J, Epstein JA, et al. Cardiovascular disease in neurofibromatosis 1: Report of the NF1 Cardiovascular Task Force. Genet in Med 2002; 4(3):105-111.
3. Lin AE, Birch PH, Korf BR, et al. Cardiovascular malformations and other cardiovascular abnormalities in neurofibromatosis 1. Am J Med Genet 2000; 95:108-117.
4. Osborn AG. Diagnostic Neuroradiology. Mosby, St. Louis, 1994.
5. Osborn AG, Blaser SI, Salzman KL. Pocket Radiologist, Brain, Top 100 Diagnoses. Amirsys, Salt Lake City, 2002.