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Round Window Obliteration by Osteoma of the Middle Ear

At presentation, a 16-year-old girl had a 2-year history of progressive left-sided hearing loss. She reported no tinnitus, vertigo, or otorrhea. She had had frequent otitis media as a child but denied previous otologic surgery. Examination showed a well-aerated middle ear space with a circumscribed white mass visible in the posterior mesotympanum. This mass appeared to abut the manubrium of the malleus. By Weber testing, a 512-Hz tuning fork lateralized to the left ear. Bone conduction was greater than air conduction by Rinne examination of the left ear. An audiogram revealed a normal bone conduction threshold, with a 15-dB air-bone gap on the left and a speech reception threshold of 40 dB. CT scan revealed a bone density mass in the mesotympanum of the left ear with no evidence of bony erosion or soft tissue mass to suggest cholesteatoma (Fig 1). The patient underwent middle ear exploration, which revealed a bony mass filling the inferior portion of the mesotympanum, abutting the malleus handle as well as the incus and stapes. The round window was obliterated by this mass. Most of the mass was removed from the promontory as a single specimen with a curette, freeing the ossicular chain. However, the round window remained obstructed by residual osteoma. Pathologic analysis was consistent with benign osteoma. Three months after surgery, the patient noted a mild improvement in hearing in the operative ear. A postoperative audiogram confirmed that the speech reception threshold in the left ear improved only slightly to 30 dB.