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Evaluation of Growth and Development of the External Auditory Canal Using 624 Temporal Bone Computed Tomography Scans
Kazuki Matsuura1, Hidekane Yoshimura1, Yoshinori Tsukahara2
1Department of Otorhinolaryngology - Head and Neck Surgery.
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.
Insights
Pediatric external auditory canal (EAC) anatomy significantly changes in the first year of life. For cochlear gene therapy in infants under one, a transmastoid approach is recommended over transcanal due to narrow EAC dimensions.
Area of Science:
- Otolaryngology
- Pediatric Surgery
- Medical Imaging
Background:
- Cochlear gene therapy for autosomal recessive deafness 9 utilizes transcanal and transmastoid approaches.
- Transcanal endoscopic approaches may be limited in young children due to small external auditory canal (EAC) size.
- Evaluating pediatric EAC anatomy is crucial for surgical planning.
Purpose of the Study:
- To assess pediatric external auditory canal (EAC) anatomy using temporal bone computed tomography (CT).
- To determine the feasibility of transcanal endoscopic approaches in pediatric patients.
- To inform surgical approach selection for cochlear gene therapy in children.
Main Methods:
- Retrospective analysis of 624 temporal bone CT scans from children aged 0-18 years.
- Detailed measurements of EAC dimensions, including lengths, angles, and diameters.
- Standardized assessment method applied to all CT scans.
Main Results:
- Significant increases in EAC length and diameter observed between 0 and 1 year of age.
- Annual increases in key measurements: 2.21 mm (inferior wall length), 8.59 mm (bony wall length), 33.0 degrees (angle), and 1.43 mm (narrowest diameter).
- Tympanic membrane diameter remained constant throughout childhood.
Conclusions:
- Transcanal endoscopic ear surgery feasibility is dependent on EAC narrowest point diameter and bony length.
- A transmastoid microscopic approach is recommended for patients under 1 year of age.
- Findings guide surgical approach selection for pediatric cochlear gene therapy.
