Distinct audiometric patterns in congenital round window atresia: A comparative study with common congenital middle ear anomalies

Abstract

Objective: Little is known about the hearing characteristics in patients with congenital round window atresia (CRWA). This study aimed to investigate hearing characteristics in patients with CRWA by comparing them with two relatively common congenital middle ear anomalies: congenital stapedial fixation (CSF) and congenital ossicular discontinuity (COD).

Methods: Literature searches yielded five patients with surgically confirmed CRWA (seven ears), who were included in the CRWA group, along with one of our patients. Air and bone conduction thresholds; air-bone gap (ABG); and presence and depth of the Carhart notch were analyzed. These audiometric variables in the CRWA group were compared with those in the CSF (n = 15) and COD (n = 22) groups, comprising patients identified from our institution's medical database.

Results: Average bone and air conduction thresholds in the CRWA group were 16.4 (standard deviation [SD]: 2.9; 95 % confidence interval [CI]: 14.6-18.3) and 44.6 (SD: 3.5; 95 % CI: 42.6-47.3) dB hearing level (HL). Bone conduction thresholds at high frequencies (≥2 kHz) were higher than those at low frequencies (<2 kHz), while air conduction thresholds at high frequencies were lower than those at low frequencies: ABGs at high frequencies were significantly smaller than those at low frequencies (2 kHz vs. 0.5 kHz, p = 0.027; 2 kHz vs. 1 kHz, p = 0.041; 4 kHz vs. 0.5 kHz, p = 0.042; 4 kHz vs. 1 kHz, p = 0.027). There were no between-group differences in incidence and depth of the Carhart notch.

Conclusion: CRWA could manifest as a distinct audiometric pattern with poorer bone conduction and better air conduction at ≥2 kHz, resulting in significantly smaller ABGs at higher frequencies than that at lower frequencies. Our findings indicated that this pattern differed from that of CSF and COD. The unique beer bottle-shaped audiogram associated with CRWA might facilitate its early diagnosis in patients with congenital conductive hearing loss.

Keywords: Congenital ossicular discontinuity; Congenital stapedial fixation; Pure-tone audiogram; Round window absence; Round window aplasia; Round window atresia.