(1009) Congenital Ossicular Chain Anomalies: A Systematic Review and Meta-analysis on Surgical Findings and Audiological Outcomes

Introduction: Congenital ossicular chain anomalies are rare and challenging to diagnose prior to surgical exploration. Our aim was to review the literature for the reported prevalence and audiological outcomes of various anomalies in patients with an intact external ear undergoing middle ear exploration for congenital conductive hearing loss, to better guide surgeons on potential surgical findings and outcomes.

Methods: A systematic search strategy was performed in accordance with the PRISMA checklist. Articles were obtained from PubMed, Web of Science and Cochrane databases from their inception to March 2023. Studies included patients with congenital conductive hearing loss and ossicular chain anomalies without additional underlying pathology such as familial hearing loss, otosclerosis, or other middle ear disease. A total of 101 studies were reviewed for full-text screening, of which, 27 studies met eligibility for inclusion. Data was collected on patient demographics, type of ossicular chain anomaly, surgical interventions, complications, and audiologic results.

Results: A total of 1,438 ears (ages 2-75 years; 50.7% male) were reviewed. Anomalies were subdivided using the Teunissen and Cremers classification system: 353 ears (26%) were categorized as class I, isolated stapes ankylosis; 224 ears (17%) as class II, stapes ankylosis with other ossicular chain anomalies; 667 ears (49%) as class III, ossicular chain anomalies with mobile stapes footplate; and 106 ears (8%) as class IV, oval window aplasia. Unclassifiable ears were excluded from analysis. Hearing outcomes were measured as differences in pure tone audiometry (PTA) or closure of the air bone gap (ABG) and were compared across classes. The average change in PTA for all classes was 21.15 dB, 95% CI [17.91, 24.39] and ABG was 19.9 dB, 95% CI [15.64, 24.15]. There was no statistically significant difference in audiological results between classes.

Conclusions: Thus, class III anomalies comprised the majority of congenital ossicular anomalies and successful hearing outcomes are possible regardless of the anomaly.