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Neuroradiology Case of the Week
Case 381
February 2009
Virendra Kumar, MD and P-L Westesson MD, PhD, DDS
Clinical
Presentation: A 24-year-old male presented with history of fall down the stairs with loss of consciousness.
Imaging Findings: The floor and lateral wall of the right orbit shows expansion with ground-glass haziness. It shows sclerosis and lucency, with the lucent part being more than sclerotic area.
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| Figure 1. Cystic/lucent area in the lateral and medial part of the expanded right maxillary antrum.
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Figure 2. Sagittal reformat with expanded inferior part/floor of right orbit.
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Diagnosis: Fibrous dysplasia with predominant lucent area (cystic variety)
Discussion: Fibrous dysplasia was first reliably recognized in 1891 by von Recklinghausen in a report in which he describes patients with a disorder of bone characterized by fibrotic changes and deformity. However, Lichtenstein and Jaffe [1] proposed the term “fibrous dysplasia” as the preferred nomenclature for this characteristic disorder of bone.
Fibrous dysplasia is a benign but slowly progressive bone disorder of unknown origin in which normal cancellous bone is replaced by immature woven bone and fibrous tissue. It is a relatively uncommon, nonfamilial congenital disorder of bone that is usually manifested before the third decade of life.
There is no sex preference. Fibrous dysplasia comprises approximately 2.5% of all bone
tumors and nearly 7.5% of benign bone neoplasms. It may be isolated in its monostotic form (representing 70% of cases and most commonly affecting the ribs and femur), or it may involve multiple foci including the longbones, skull, and cranial base.
Craniofacial involvement is present in 50-100% of cases of polystotic and 10% of monostotic form. There is a predilection for involvement of the frontal, sphenoid, ethmoid, and maxillary bone complexes. Various terms have been applied to fibrous dysplasia with craniofacial involvement, including craniomaxillofacial, cranioorbital, frontoorbital, orbital, and complex fibrous dysplasia.
Fibrous dysplasia exhibits distinctive radiological characteristics. There have been three imaging-categorized forms of fibrous dysplasia: sclerotic, cystic (lytic), and mixed varieties. The mixed-type fibrous dysplasia is most common, representing 40% of cases. The sclerotic form comprises 35% of cases and typically involves the cranial base. Cystic fibrous dysplasia is least common.
Differentials to be considered are aneurysmal bone cyst, unicameral cyst, nonossifying fibroma, osteochondroma, giant cell and eosinophilic granulomas.
References:
- Lichtenstein L, Jaffe HL. Fibrous dysplasia of bone. Arch Path 1942; 33: 777-816.
- Firat D, Stutzman L. Fibrous dysplasia of the bone. Review of twenty-four cases. Am J Med. 1968 Mar;44(3):421-9. [PubMed]
- Daffner RH, Kirks DR, Gehweiler JA Jr, Heaston DK. Computed tomography of fibrous dysplasia. AJR Am J Roentgenol. 1982 Nov;139(5):943-8. [PubMed]
- Riley GM, Greenspan A, Poirier VC. Fibrous dysplasia of a parietal bone. J Comput Assist Tomogr. 1997 Jan-Feb;21(1):41-3. [PubMed]
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