Evaluation of Growth and Development of the External Auditory Canal Using 624 Temporal Bone Computed Tomography Scans for Appropriate Cochlear Gene Delivery.

OBJECTIVE

Clinical trials on cochlear gene therapy for patients with autosomal recessive deafness 9 through transcanal and transmastoid approaches were reported in 2024. While both are clinically feasible in older patients, the small size of the external auditory canal (EAC) in younger patients may limit the applicability of transcanal endoscopic approaches. Therefore, we aimed to evaluate pediatric EAC anatomy by using temporal bone computed tomography (CT).

STUDY

DESIGN

Retrospective study.

SETTING

Tertiary center.

PATIENTS: Children aged 0 to 18 years.

INTERVENTIONS: We analyzed 624 temporal bone CT scans obtained between 2017 and 2024.

MAIN OUTCOME MEASURES: Measurements included the full, bony, and cartilaginous lengths of the posterior and inferior EAC walls, angle between the inferior EAC wall and tympanic membrane, diameter at the narrowest point of the EAC, and tympanic membrane diameter, all assessed using a standardized method.

RESULTS

The full and bony lengths of the inferior EAC wall, the angle between the inferior EAC wall and tympanic membrane, and the diameter at its narrowest point increased dramatically between 0 and 1 year of age. During this period, the annual increases in these measurements were 2.21 mm, 8.59 mm, 33.0 degrees, and 1.43 mm, respectively. In contrast, the tympanic membrane diameter remained unchanged throughout childhood.

CONCLUSIONS

The feasibility of transcanal endoscopic ear surgery depends on the diameter at the narrowest point of the EAC, the endoscope and surgical instrument dimensions, and the length of the bony part of the EAC needed to elevate a tympanomeatal flap. Based on our findings, a transmastoid microscopic approach should be considered instead of transcanal approach in patients under 1 year of age.