Endoscopic classification of the external auditory canal: a prerequisite for transcanal endoscopic ear surgery at Yaoundé Central Hospital

Abstract

Introduction: Full visualization of the tympanic membrane, which depends on the anatomy of the external auditory canal (EAC), is the ideal in endoscopic ear surgery. Our study aimed to evaluate the endoscopic classes of the EAC in healthy Cameroonians and to analyze the influence of demographic factors on these morphological variations.

Material and methods: This was a cross-sectional study conducted on 387 healthy volunteers (774 EACs). Each EAC was examined using a 0° rigid endoscope. EACs were classified as CES 0 or CES 1 depending on whether the eardrum was fully or partially visible, in accordance with the Canal Endoscopic Scale (CES). The CES 1 class was subdivided based on the location of the obstruction (anterior, posterior, superior, inferior, circumferential). Data were analyzed with a significance threshold of p < 0.05.

Results: The sample consisted of 236 (61%) women and 151 (39%) men with a mean age of 46.1 ± 19.1 years. The eardrum was fully visible in 718 (92.7%) CAEs and partially visible in 56 (7.23%) EACs. The CES 1a type predominated, accounting for 48.2% of type 1 cases. There were no significant differences between CES classes and gender or age.

Conclusion: The anatomy of the EAC provided optimal access for endoscopy in more than 92% of cases. Visibility limitations, primarily related to the anterior wall, were independent of age and sex. These results confirm the viability of the exclusive transcanal approach as an anatomically appropriate standard