Copyright @ 200 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.7 Imaging Case of the Month Lateral Semicircular Canal Dehiscence

Dehiscence of the superior and, more recently, pos-terior semicircular canals has been recognized as a structural cause of vertigo and hearing loss (1Y3). Mani-festations can include conductive hearing loss, sensori-neural hearing loss, sound- and pressure-induced dizziness, and vertigo and eye movement (4). The patho-genesis of these symptoms has been attributed to the presence of a third window, which provides a different path for the dissipation of acoustic energy (4). A subset of patients, however, are asymptomatic, and these pa-tients ’ conditions are diagnosed on imaging or postmor-tem analyses of temporal bones. Dehiscence of the lateral semicircular canal, on the other hand, has only been described in association with cholesteatoma or fenestration procedures (5). The cause of this bony dehiscence has been attributed to a number of different factors. Pressure from surround-ing structures, such as the jugular bulb, superior petrosal sinus, or brain, superimposed on a congenitally thin bone can result in erosion of the bone. Infectious patho-geneses, such as syphilis, can affect bone breakdown Address correspondence and reprint requests to Craig A. Buchman