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Figure 4. A woman with history of right total hearing loss after radical mastoidectomy who developed a mild hearing loss in her left, only hearing, ear. She also had a temporary left facial weakness, initially attributed to a Bell's palsy. CT scans confirmed the otoscopically apparent cholesteatoma, with (a) erosion of the scutum and malleus head (arrow). (b) Despite lack of vertigo there is a fistula of the lateral semicircular canal (arrow) and attenuated tegmen. Exposure of the fistula at surgery risked a profound bilateral sensorineural hearing loss in the only functioning ear, so the keratin matrix was preserved. (c) CT of the contralateral ear demonstrates the open mastoid cavity but also the unsuspected fistula of this lateral canal that had resulted in destruction of cochlear function at operation. This defect compares with (d) the intact dome of the semi-circular canal in another, similar, mastoid cavity.
