Non-syndromal round window atresia: an autosomal dominant genetic disorder with variable penetrance?

Abstract

Round window atresia can be seen in association with syndromal anomalies such as mandibulofacial dysostosis, Mondini type anomalies or cretinism, or with extensive otosclerosis. Non-syndromal round window atresia is extremely rare and until today there is no proof whether non-syndromal round window atresia can be inherited. We present two family members with non-syndromal round window atresia. Based on this case and on an extensive literature review, we discuss the possible ways of sound transmission with round window occlusion as well as the possibility of an autosomal dominant inheritance pattern of these two non-syndromal cases. Evaluating the hearing test results, the effect of round window atresia in non-syndromal cases cannot be thoroughly explained by current theories of sound transmission. In general, full occlusion of the round window should result in a complete air-bone-gap and a surgical procedure to open the window, e.g. a cochlear fenestration which creates a new pressure outlet for the inner ear fluids, should result in normalizing the hearing levels. Astonishingly, patients with non-syndromal round window atresia, show hearing tests similar to those in patients with otosclerosis. In contrast to otosclerosis, complete closure of the air-bone-gap by surgery in patients with round window atresia does not seem to be possible according to currently reported cases. Therefore, routine examination of the round window in stapes surgery should be part of every stapes surgery and a high resolution CT scan should be considered in particular prior to revision of unsuccessful stapes surgery. As a genetic inheritance pattern can be assumed, specific emphasis should also be laid on the patient's family history.

Superior Canal Dehiscence Syndrome: Lessons from the First 20 Years

“…Furthermore, occlusion of the round window is thought to induce a hearing loss (108, 109). In the series by Silverstein et al, hearing loss was the only subjective survey measure that did not improve after round window reinforcement (106), others have reported a conductive hearing loss (105), and additional series of patients undergoing round window reinforcement by some of the authors have shown a mild hearing loss with this surgery in the non-dehiscent ear (110, 111).…”

Effect of Cochlear Window Fixation on Air- and Bone-Conduction Thresholds

“…This factor has been studied largely by clinical observation and rarely in controlled experiments in animal models. In clinical settings, the effects of the round-window closure were unclear (17,18), ranging from no change in auditory thresholds to mild or moderate conductive hearing loss (19). The effects of ovalwindow fixation were demonstrated in patients with otosclerosis (i.e., stapedial footplate fixation), who showed a deterioration in air-conduction threshold with minimal to no change in bone conduction (18).…”

Soft tissue conduction as a possible contributor to the limited attenuation provided by hearing protection devices

“…[28] In human participants, hearing could be elicited when vibratory stimuli were applied to soft tissues such as the eye, neck, back, and thorax. [243132] These findings, as well as clinical observations showing preserved BC thresholds in the absence of two mobile windows in the inner ear,[3334] support the existence of a mechanism that is different from AC and osseous BC. [35]…”