A 50-year-old woman presented with a 20-year history of a progressively enlarging, firm mass over the right mastoid process and a small mass at the inferior border of the right mandible. There was no associated history of hearing loss, tinnitus, vertigo, auricular discharge, trauma or facial paralysis. Physical examination revealed a fixed, non-tender 3-cm diameter bony mass arising from the mastoid process. The skin temperature and color, otoscopic examination and a complete audiometric battery were all normal.
Coronal and axial CT scans revealed a large, smooth, bony mass arising from the mastoid cortex. Additionally seen was a small bony protuberance arising from the outer cortex of the mandible, although this was somewhat obscured by dental artifact. Both of these lesions were radiographically compatible with a diagnosis of osteoma. The middle and inner ear and facial nerve were normal. The patient underwent an upper gastrointestinal series with small bowel follow-through and a colonoscopy; both were negative for intestinal polyposis, thus ruling out Gardner's syndrome.
The patient was taken to the operating room for excision of the mastoid lesion. A standard postauricular incision was made and the periosteum was elevated off the mastoid process. The mastoid lesion was identified as a spherical bony mass approximately 3 by 2.5 cm with a narrow base attached to the underlying skull. The base of the osteoma was drilled until normal mastoid air cells were seen and the mass was freed from the surrounding bone; the resection was completed by using a chisel to separate the remaining attachment. Pathologic examination confirmed it to be an osteoma. The patient's postoperative course was uneventful.