Radiologic Assessment of the Round Window Anatomy in Pediatric Patients Relevant to Gene Therapy and Inner Ear Drug Delivery.

Objective: To investigate the anatomical diversity of the round window (RW) in the pediatric population, focusing on its transcanal trajectory and anatomical angles. The study aims to provide insights into how RW accessibility changes with age, which may impact surgical planning and drug delivery approaches.

Study design: Retrospective radiologic review of pediatric patients who underwent high-resolution CT scans of the temporal bone.

Setting: Tertiary care center.

Patients: Ninety-one pediatric ears from 50 patients with normal anatomy between the ages of 0 and 15 years were analyzed.

Interventions: Radiologic measurements: Using OsiriX MD, scans were reformatted to measure RW access angles, depth, and volume. Using 3D Slicer for 3D reconstruction, RW niche segmentation and volumetric analysis were performed.

Main outcome measures: Main outcome measures included evaluation of transcanal angle to the RW membrane, depth and opening angle of the RW, volume and shape variability, and its three-dimensional localization relative to the umbo.

Results: The results demonstrated that the mean transcanal angle to the RW membrane was 98.8° ± 7°. The transcanal angle to the RW increased significantly with age, with the ≥24-month age group demonstrating a mean increase of 6.2° compared to the younger cohort (p < 0.0001). Additionally, the RW position was found to shift inferiorly as age increased, with a mean difference of 0.47 mm (p = 0.01).

Conclusions: This study provides valuable anatomical insights into changing pediatric RW morphology. These results may have implications for future surgical approaches, particularly for transcanal drug delivery and gene therapy in pediatric patients.