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Feasibility of Round Window Exposure via External Auditory Canal: Classification and Predictive Landmarks
Jiayu Sun1,2,3, Haoyue Tan1,2,3, Jianqing Chen1,2,3
1Department of Otolaryngology Head and Neck Surgery Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine Shanghai China.
Laryngoscope Investigative Otolaryngology
|March 25, 2025
Summary
This study found that 54% of the round window membrane (RWM) is visible through the ear canal without bone removal. Anatomical measurements can predict RWM visibility for future inner ear treatments.
Area of Science:
- Otolaryngology
- Surgical Anatomy
- Endoscopic Ear Surgery
Background:
- The round window membrane (RWM) is a critical structure for inner ear interventions.
- Direct visualization of the RWM via the external auditory canal (EAC) without bony removal is challenging.
- Understanding the anatomical feasibility is crucial for minimally invasive otologic procedures.
Purpose of the Study:
- To assess the feasibility and anatomical factors associated with exposing the RWM through the EAC.
- To identify pre-operative predictors for successful RWM visualization during endoscopic tympanoplasty.
Main Methods:
- Retrospective analysis of surgical videos and CT scans from 50 adult patients undergoing endoscopic tympanoplasty type I.
- Classification of round window niche (RWN) and RWM exposure based on surgical visualization.
- Measurement of anatomical parameters including RWM-tympanic annulus distance and scala tympani dimensions using specialized coordinate systems.
Main Results:
- Round window niche (RWN) exposure was achieved in 60% of cases.
- Complete or partial visualization of the round window membrane (RWM) occurred in 54% of patients.
- Longer RWM-tympanic annulus distances and narrower scala tympani widths were significantly associated with better RWM exposure.
- External auditory canal (EAC) dimensions in axial and coronal planes were reliable predictors of RWM visibility.
Conclusions:
- Partial visualization of the RWM is feasible in a majority of adults via the EAC without bone removal.
- Pre-operative anatomical measurements of the EAC and middle ear structures can reliably predict RWM exposure.
- These findings support the potential for minimally invasive inner ear therapies targeting the RWM.
