Third Windows as a Cause of Failure in Hearing Gain after Exploratory Tympanotomy

Objective. Exploratory tympanotomy (ET) can be performed selectively on patients who have air-bone gaps (ABGs) without any apparent external or middle ear abnormalities for diagnosis and treatment of their conductive hearing loss. However, surgeons cannot always find middle ear problems. It has recently been reported that pathologic third windows in inner ears can cause ABGs. Therefore, the authors conducted this study to evaluate the inner ear anatomical problems of patients who had undergone ET.

Study Design. Case series with chart review.

Setting. Tertiary center.

Subjects and Methods. The authors included 51 consecutive patients with ABGs ≥20 dB who had undergone ET at Yonsei University Severance Hospital between 2005 and 2009. In the preoperative evaluations, all 51 patients showed normal drums on otoscopy, and no abnormal middle ear problems that could cause ABGs were detected on temporal bone computed tomography (TBCT). The authors retrospectively reevaluated the hearing results and the causes of their conductive hearing loss, including the inner ear problems, through a review of their TBCT.

Results. Six of the 51 patients were found to have inner ear abnormalities with possible pathologic third windows. Four had enlarged vestibular aqueducts (EVAs), and 2 had superior semicircular canal dehiscence (SSCD). All patients with pathologic third windows failed to improve their hearing.

Conclusion. About 12% of the patients had inner ear anomalies, which could possibly cause ABGs. Inner ear conductive components might lead to frustrating results. Therefore, surgeons must take inner ear conductive components into account before attempting ET in patients with inner ear anomalies.