Osseous dysplasias of the temporal bone, which include fibrous dysplasia, osteopetrosis, Paget disease, and osteogenesis imperfecta, lead to bone remodeling that can lead to temporal bone deformation, external auditory canal (EAC) stenosis, conductive and sensorineural hearing loss, and cholesteatoma development. High-resolution computed tomography (CT) imaging of the temporal bone aids in establishing a differential diagnosis.
ESSENTIALS OF DIAGNOSIS
Pain, headache, hearing loss.
Otitis externa, middle ear effusions, cholesteatoma.
Ground-glass appearance on CT imaging.
Fibrous dysplasia (FD) is the most common benign osseous dysplasia. While it most commonly occurs in the trunk, limbs, and skull, the temporal bone is involved in 18% to 70% of those cases with skull involvement (Figure 66–1). The 3 recognized forms of the disease are: monostotic (MFD), nonsyndromic polyostotic (PFD), and McCune-Albright syndrome (MAS). MFD is generally considered the most common form, occurring in 11% to 85% of cases. PFD consists of multisite involvement, whereas MAS is defined by 2 of the following 3 features: PFD, unilateral café au lait spots, and/or excessive autonomous hormone production, usually manifesting as precocious puberty. In the largest study to date, describing a multicenter experience in managing 66 patients with temporal bone FD, the average age at diagnosis was 24.8 years, 59% were women, and 89% were diagnosed with PFD, 24% of whom had MAS. However, other authors have reported that temporal bone involvement occurs twice as frequently in men as it does in women.
An example of left-sided fibrous dysplasia with a pagetoid and cystic components, the pagetoid component demonstrating the ground-glass appearance.
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With an approximate prevalence of 1 to 2 individuals per 30,000 people, FD is a disorder of abnormal bone metabolism, the result of activating mutations of the alpha-subunit of the stimulatory G protein, leading to increased proliferation and inappropriate differentiation of the osteoblastic cells. While FD is generally considered a spontaneous mutation, Pardo-Maza et al. report the case of a 16-year-old girl who developed FD in a canal wall down mastoid cavity, theorizing that her prior radical mastoidectomy 9 years previously led to the development of her FD. In the initial description of FD in the temporal bone, Schlumberger postulated that “it could be caused by a disturbance of the normal reparative processes ...