Images below require Macromedia's Flash Player to view

Neuroradiology Case of the Week

Case 190

Waseem Khan, CC3, Ajay Malhotra, MD
and Per-Lennart Westesson, MD, PhD, DDS

Clinical Presentation: The patient is a 15-year-old female presenting with right facial swelling.

Radiological Findings: There is an expansile bony lesion with “ground-glass opacification” in the right maxillary sinus. There is expansion of the cortices, but they are preserved. There is also involvement of the lateral aspect of the right superior alveolar ridge and roots of the teeth at this location.

Diagnosis: Fibrous dysplasia

Discussion: Fibrous dysplasia is a developmental disorder of mesenchyme, resulting in progressive replacement of normal cancellous bone by a mixture of immature woven bone and fibrous tissue. This results from sporadic gene mutation, and all cells descended from the mutated cell line can manifest features fibrous dysplasia. Malignant transformation is rare, and fibrous dysplasia is generally not fatal.
     Any bone may be affected, but this discussion will focus on the craniofacial form. Typically, patients less than 30 years old are affected, with a 2:1 female predominance. There are three possible presentations: monostotic, polyostotic, and McCune-Albright Syndrome. Seventy percent of cases are monostotic, affecting one of the following in order of decreasing incidence: maxilla (especially zygomatic process) or mandible, frontal bone, ethmoid, sphenoid, or temporal bone. This form has a good prognosis, with cessation of progression after the early 20’s. Polyostotic cases involve more than one bone; both the facial bones and skull base can be involved. Polyostotic disease may progress to the 30’s. McCune-Albright Syndrome is a rare disorder defined by a triad of polyostotic fibrous dysplasia, endocrine dysfunction (including precocious puberty), and café au lait spots.
     Signs and symptoms of fibrous dysplasia depend on the location of the lesion. Patients may complain of headache. Orbital lesions may cause optic neuropathy. Sinonasal roof lesions can lead to mucoceles. Extensive facial bone involvement may lead to lion-like facies. Temporal bone fibrous dysplasia may cause conductive hearing loss and facial nerve compression.
     Radiographic features on CT include “ground glass matrix” in an expansile bone lesion. This may be accompanied by areas of sclerosis or lucency. MRI shows an expansile mass with low T1 and T2 signal in ossified and/or fibrous portions of the lesion. In the active phase of the disease, T2 images may show a heterogeneous signal pattern.
     Treatment may include surgical intervention when symptomatic, though aggressive surgical management is not recommended in most cases. Radiation therapy should be avoided, as it can promote malignant transformation.
     Differential diagnoses include Paget’s disease, intraosseous meningioma, giant cell tumor and ossifying fibroma.

References:

1. Anand, MKN. Fibrous Dysplasia, emedicine. http://www.emedicine.com/RADIO/topic284.htm
2. Goetz CG. Textbook of Clinical Neurology, 2nd. ed., W.B. Saunders. 2003:590-592.
3. Kumar V, Fausto N, Abbas A. Robbins & Kotran Pathological Basis of Disease, 7th ed., W.B. Saunders. 2005:1300-1301.
4. Harnsberger R. Diagnostic Imaging: Head and Neck. Amirsys 2004: I-3-66 to I-3-69.