Morphometry of the external auditory canal: Radiological study



: External auditory canal, Temporal bone, Morphometry, Computed tomography


Aim: Morphometry of the external auditory canal was not previously studied among the normal population in the literature. In this study we aimed to indicate normal values and age, gender, and side related changes of the external auditory canal of healthy individuals.Methods: Computed Tomography (CT) images of 379 patients were evaluated in this cross-sectional study. Two diameters at three points were measured on sagittal images for each side: First point was at the level of the tympanic membrane where chorda tympani leaves the bony canal. The height (1a) and width (1b) were measured from the ground where the cylindrical view of EAC was most prominent. The second point was at isthmus level, where height (2a) and width (2b) were measured. The third point was the most lateral site of external auditory canal (EAC) at the level of the tympanomastoid suture where height (3a) and width (3b) were measured. Age, gender, and side related changes for each measurement were statistically analyzed.Results: The diameter of each point in each direction was similar between the left and right sides. The median diameter of left 1a was 9.4 mm in males and 9.2 mm in females, which was significantly different. The “a” diameter of each point was higher in males than females for both sides. There was no significant difference between males and females in terms of b diameters. Diameter 1b was higher on the left side compared to the right side for females, while left-right side comparisons for other measurements were similar. None of the diameters differed between the left and right sides for males.Conclusion: Normal measurements of EAC diameters and its age, sex and side related changes are important for surgeons, radiologists, and anatomists. Proper evaluation of EAC is critical for transcanal endoscopic ear surgery and early diagnosis of a pathology impairing the anatomy of EAC on radiologic images.


Download data is not yet available.


Standring S. Gray’s anatomy: the anatomical basis of clinical practice, Churchill Livingstone Spain: Elsevier; 2008. p.420.

Moore KL, Agur MRA, Dalley AF. Clinically Oriented Anatomy. Philadelphia: Lippincott Williams&Wilkins; 2014.p 967.

Al-Hussaini A, Owens D, Tomkinson A. Assessing the accuracy of tympanometric evaluation of external auditory canal volume: a scientific study using an ear canal model. Eur Arch Otorhinolaryngol. 2011;268(12):1721–5. doi: 10.1007/s00405-011-1555-5.

Shahnaz N, Davies D. Standard and multifrequency tympanometric norms for Caucasian and Chinese young adults. Ear Hear. 2006;27(1):75-90.

EgoIf DP, Nelson DK, Howell HC, Larson VD. Quantifying ear-canal geometry with multiple computer-assisted tomographic scans. J Acoust Soc Am. 1993;93(5):2809-19.

Shanks JE, Lilly DJ. An evaluation of tympanometric estimates of ear canal volume. J Speech Hear Res. 1981;24(4):557-66.

Yu JF, Tsai GL, Fan CC, Chen C, Cheng CC, Chen CC. Non-invasive technique for in vivo human ear canal volume measurement. J Mech Med Biol. 2012;12(4). doi: 10.1142/S0219519412500649.

Magliulo G. Acquired atresia of the external auditory canal: recurrence and long-term results. Ann Otol Rhinol Laryngol. 2009;118(5):345-9.

Sanna M, Russo A, Khrais T, Jain Y, Augurio AM .Canalplasty for severe external auditory meatus exostoses. J Laryngol Otol. 2004;118(8):607-11.

Cole RR, Jahrsdoerfer RA. The risk of cholesteatoma in congenital aural stenosis. Laryngoscope. 1990;100(6):576-8. doi:10.1288/00005537-199006000-00004.

Altmann F, Waltner JG. Cholesteatoma of the external auditory meatus. Arch Otolaryngol. 1943;38(3):236-40. doi:10.1001/archotol.1943.00670040249005.

Ayache S, Beltran M, Guevara N. Endoscopic classification of the external auditory canal for transcanal endoscopic ear surgery. Eur Ann Otorhinolaryngol Head Neck Dis. 2019;136(4):247-50. doi: 10.1016/j.anorl.2019.03.005.

Yu JF, Lee KC, Wang RH, Chen YS, Fan CC, Peng YC, et al. Anthropometry of external auditory canal by non-contactable measurement. Appl Ergon. 2015;50:50-5. doi: 10.1016/j.apergo.2015.01.008.

Zemplenyi J, Gilman S, Dirks D. Optical method for measurement of ear canal length. J Acoust Soc Am. 1985;78(6):2146-8.

Djupesland G, Zwislocki JJ. Sound pressure distribution in the outer ear. Acta Otolaryngol. 1973 Apr;75(4):350-2. doi:10.3109/00016487309139744.

Man SC, Nunez DA. Tympanoplasty—conchal cavum approach. J Otolaryngol Head Neck Surg. 2016;6(45):1. doi: 10.1186/s40463-015-0113-3.

Zhao S, Han D, Wang D, Li J, Dai H, Yu Z. The formation of sinus in congenital stenosis of external auditory canal with cholesteatoma. Acta Otolaryngol. 2008;128(8):866-70. doi: 10.1080/00016480701784940.

Mostafa BE, El Fiky L. Congenital cholesteatoma: the silent pathology. ORL J Otorhinolaryngol Relat Spec. 2018;80(2):108-16. doi: 10.1159/000490255.

Walker D, Shinners MJ. Congenital Cholesteatoma. Pediatr Ann. 2016;45(5):e167-70. doi: 10.3928/00904481-20160401-01.






Research Article

How to Cite

Çalışkan S, Çetin H, Akkaşoğlu S. Morphometry of the external auditory canal: Radiological study. J Surg Med [Internet]. 2020 Jan. 2 [cited 2022 Dec. 7];4(1):76-9. Available from: