[Clinical characteristics of congenital atresia of the oval window]

Objective: To investigate the clinical features of patients with congenital atresia of the oval window (CAOW). Methods: A retrospective analysis was conducted on 7 cases (8 ears) of surgically confirmed CAOW treated at our department from July 2018 to July 2024. Among the cases, 1 patient had bilateral CAOW, and 4 patients had unilateral CAOW combined with other types of ossicular chain malformations in the contralateral ear. We collected and analyzed the clinical data, audiological features, and temporal bone HRCT results of all patients. Results: The 7 patients were diagnosed at ages ranging from 8 to 19 years, with a mean age of (13.2±6.9) years. None of the patients exhibited significant auricular deformities. All presented with conductive hearing loss or mixed hearing loss predominantly of the conductive type, with an intact tympanic membrane. The diagnosis of CAOW was confirmed via endoscopic tympanotomy, revealing a concave oval window area on the medial wall of the tympanic cavity, sealed by a bony plate. All 8 ears exhibited additional ossicular chain deformities. Stapes absence was present in all 8 ears. Partial absence of the incus long process was observed in 3 ears, while, abnormal bony connections between the incus long process and the promontory were seen in 4 ears, 1 ear had a short malleolar handle, 1 ear had a smaller than normal malleus volume. In addition, facial nerve deformities were found in 6 ears, with 4 ears showing bifurcation of the facial nerve and 2 ears showing facial nerve obscuration of the oval window. Pure-tone audiometry revealed that 62.5% (5/8 ears) of patients had air conduction (AC) thresholds≥60 dB preoperatively, with a mean pure-tone average (PTA) of (69.0±11.8) dB HL and a mean air-bone gap (ABG) of (52.0±7.0) dB. The mean AC threshold and ABG were higher in the low-frequency (125-1 000 Hz) range compared to the high-frequency (2 000-8 000 Hz) range (both P<0.05). Preoperative HRCT showed abnormalities in all patients, with 7 ears being diagnosable as CAOW. Although the remaining 1 ear could not be diagnosed as CAOW, stapes and incus long process absence were detected. Conclusion: CAOW is rare in clinical, as the patients with non-progressive conductive hearing loss (AC≥60 dB, ABG≥50 dB) since childhood, intact tympanic membrane without malformations of auricle and external auditory canal, and thick bony plate covered the oval window of the HRCT imaging, CAOW should be highly suspected, which could be confirmed by the exploratory tympanotomy.