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Neuroradiology Case of the Week
Case 369
December 2008
Trushar Sarang, MD
Clinical
Presentation: A 68-year-old male with known brain cancer was evaluated with MR for a recurrent mass lesion.
Imaging Findings: Diffuse innumerable skin nodules covering the scalp.
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| Figure 1: Axial CT demonstrates innumerable soft tissue densities in the superficial scalp soft tissue. |
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Figure 2:
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Figure 3:
Figures 2 and 3. Axial MRI T1 +/- contrast images demonstrate diffuse enhancement of the innumerable superficial skin lesions. There is a more well defined nodule in the posterior left scalp with mildly heterogeneous signal.
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Figure 4: Axial T2 MRI demonstrates a rounded lesion in the posterior left scalp with a central area of low signal. This may represent the classic 'target' appearance as a result of a central area of collagen.
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| Figure 5: Coronal T1 + contrast image demonstrates enhancement of innumerable skin nodules. |
Diagnosis: Cutaneous manifestation of Neurofibromatosis Type 1
Discussion: Neurofibromatosis type 1 is one of the phacomytosis (neurocutaneous) disorders caused by an autosomal dominant gene mutation on chromosome 17. The incidence is 1 in 2500 live births, making this disease the most commonly inherited tumor syndrome.
The features of NF1 on brain imaging are many and include optic nerve glioma (15-20% of patients), increased incidence of astrocytomas (occurring in 1-3% of cases), and cutaneous nodules. There is also an increased incidence of anaplastic astrocytomas, glioblastoma multiforme, brainstem gliomas, medulloblastoma, and ependymomas. This case demonstrates a patient with a severe cutaneous manifestation of NF1. There are innumerable enhancing skin neurofibromas on T1 contrast enhanced images. On T2 images there is a rounded posterior left scalp lesion with a central area of low signal. This lesion may represent the typical 'target' appearance of a cutaneous neurofibroma. The center of the 'target' is a small focus of collagen.
The classic imaging appearance of NF1 are focal areas of abnormal signal intensity (FASI) in white and gray matter without mass effect. Common locations include the globus pallidi, thalami, white matter tracts, hippocampus, and brainstem. A plexiform neurofibroma can involve the orbit, scalp, skull base, and anywhere along the spine.
References:
- Osborn AG, Blaser SI, Salzman KL, et al. Diagnostic Imaging: Brain, 1st ed. Altona: Amirsys Inc, 2004.
- Grossman R. Yousem D. Neuroradiology, The Requisites. 2nd Ed. Philadelphia: Mosby, 2003.
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