Imaging of fibro-osseous lesions of the temporal bone Justin H. Tan, MD, Asako Miyakoshi, MD, Mahmood F. Mafee, MD, FACR  Operative Techniques in Otolaryngology-Head and Neck Surgery  Volume 25, Issue 1, Pages 96-109 (March 2014) DOI: 10.1016/j.otot.2013.11.012 Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 1 Fibrous dysplasia. (A) Coronal CT of the head demonstrates the “ground-glass” appearance of fibrous dysplasia of the left temporal bone (arrow). Note the cholesteatoma (black arrowhead) of the middle ear with absent malleus, a complication of fibrous dysplasia owing to obstruction of the external canal. (Case courtesy of M.F. Mafee, MD.) (B) Axial and (C) coronal CT of the temporal bone from another patient, a 7-year-old child, showing fibrous dysplasia of the left squamozygomatic complex (arrow). Note the marked expansile nature of the lesion (arrow heads). (Case courtesy of M.F. Mafee, MD.) (D) Coronal CT demonstrates the primary sclerotic form of fibrous dysplasia of the left tympanic bone and squama of the temporal bone in a different patient (arrow). (Case courtesy of M.F. Mafee, MD.) (E) T1W MRI and (F) enhanced T1W MRI in another patient showing diffuse enhancement of the fibrous dysplasia of the right temporal bone (arrows). (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 2 Osteoma. (A) Coronal CT scan shows osteoma (o) of the right external auditory canal (arrow). The nonmineralized portions of the osteoma are isodense to ear wax (arrow head). (Case courtesy of M.F. Mafee, MD.) Exostosis. (B) Axial CT scan shows an exostosis (arrow heads) narrowing the right external auditory canal. (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 3 Presumed osteoblastoma in a patient who has been asymptomatic for 4 years. (A) Axial CT, (B) axial T1W MRI, (C) axial T2W MRI, and (D) enhanced T1W MRI demonstrate an enhancing lesion in the right temporal bone and mastoid (white arrows). (E) Tc-99 methylene diphosphaonate bone scan demonstrates increased activity (black arrow), making it difficult to distinguish from malginancy. (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 4 Osteoblastoma. (A) Coronal and (B) axial CT demonstrates an aggressive osteoblastoma of the left temporal bone (arrows). The puntate hyperdensities along the medial margin are sutures from surgical biopsy (arrow heads). (Case courtesy of M.F. Mafee, MD.) Axial (C) T1W MRI, (D) T2W MRI, and (E) enhanced T1W MRI in the same patient demonstrate marked enhancement (arrows). (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 5 Chondroblastoma. (A) Axial CT, (B) T1W MRI, and (C) T2W MRI show a chondroblastoma in the squamous portion of the right temporal bone (arrow). Note the fluid in the mastoid air cells. (D) Axial enhanced T1W MRI is actually an image of an enhancing giant cell tumor in another patient (arrow). They can look very similar to chondroblastomas. It may be difficult to differentiate these 2 entities from each other on imaging. (Figure 5A-C—case courtesy of Tony Peduto, MD, Westmead, Australia, and 5D—case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 6 Chondroblastoma. (A) Axial and (B) coronal unenhanced CT scans show a chondroblastoma involving the petrous apex. (C) Axial gadolinium-enhanced T1W MRI demonstrates enhancement of the tumor in the internal auditory canal. (Case courtesy of G. Lee, MD, Kansas City, MO.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 7 Giant cell tumor. Coronal CTs of 3 different patients (a, b, and c) demonstrating giant cell tumors of the left (A), right (B), and left (C) temporal bones. Note the expansile and destructive nature of these lesions. (D) A histologic slide from a giant cell tumor. (Figure 7B—courtesy of the Armed Forces Institute of Pathology [AFIP]). (Case courtesy of M.F. Mafee, MD.) (Color version of figure is available online.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 8 Giant cell tumor. (A) Coronal CT, (B) axial unenhanced T1W MRI, (C) axial T2W MRI, and (D) axial gadolinium-enhanced T1W MRI show the typical imaging appearance of a giant cell tumor. These include bony expansion and destruction. Heterogeneous internal signal on both T1W and T2W MRI and avid contrast enhancement. (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 9 Osteosarcoma. (A) Axial CT of the right mastoid bone in soft tissue window and (B) bone window demonstrating an osteogenic sarcoma. Note the irregular periosteal reaction with soft tissue tumor invasion. (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 10 Chondrosarcoma of the condylar fossa. (A) Axial, (B) CT unenhanced T1W MRI, (C) T2W MRI, and (D) gadolinium-enhanced T1W MRI and (E) coronal CT and (F) gadolinium-enhanced T1W MRI demonstrating a low-grade chondrosarcoma of the right temporal bone involving the right temporomandibular joint (M). Note the soft tissue extention into the infratemporal fossa (arrowheads). (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 11 Chondrosarcoma. (A) Clockwise sagittal T1W MRI, (B) axial T2W MRI, (C) axial gradient-echo MRI, and (D) axial gadolinium-enhanced T1W MRI of a chondrosarcoma of the right petrous apex (white arrows). (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 12 Otospongiosis. (A) Axial CTs of the temporal bone in a patient with otospongiosis and (B) a normal patient for comparison. Note the demineralization at the level of the fissula ante fenestram (arrows) in (A) and (B) points to the cochleariform process. The demineralized otospongiotic focus at the fissula ante fenestram is seen just posterior to the cochleariform process. There is also thickening of the stapes footplate along the oval window just posteriorly. Note the singular canal (black arrowhead) in (B) for the singular nerve. (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 13 Otospongiosis. Two axial CT scans from the same study show bilateral diffuse otospongiosis with marked obliteration of the round and oval windows niches owing to expansion of otospongiosis (arrows). The top image is slightly superior to the lower image. (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 14 18-micron micro-CT of a specimen of a normal temporal bone. Note how the bone of the otic capsule (OC) is markedly denser compared with the rest of the bone. (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 15 Gadolinium-enhanced axial T1W MRI of otospongiosis. There is enhancement at the level of the fissula ante fenstrum (white arrow head) and the choclear capsule (long arrow). There is fat in the petrous apex (black arrowhead) which is intrinsically bright on T1W MRI. (Case courtesy of M.F. Mafee, MD.) Operative Techniques in Otolaryngology-Head and Neck Surgery 2014 25, 96-109DOI: (10.1016/j.otot.2013.11.012) Copyright © 2014 Elsevier Inc. Terms and Conditions