ENT - September 2020 - 532

Clinical Study

A Retrospective Study to Identify
the Relationship Between the Dimension
of Osseous External Auditory Canal
and Chronic Otitis Media

Ear, Nose & Throat Journal
2020, Vol. 99(8) 532-536
ª The Author(s) 2019
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DOI: 10.1177/0145561319840884
journals.sagepub.com/home/ear

Yi-Fang Lee, MD1,2, Pei-Yin Wei, MD1,2, Chia-Huei Chu, MD, MPH1,2,
Wen-Huei Liao, MD, PhD1,2, An-Suey Shiao, MD1,2,
and Mao-Che Wang, MD, PhD1,2

Abstract
Whether the dimension of the osseous external auditory canal (OEAC) is related to chronic otitis media (COM) remains an
important but unresolved issue. In the literature, routine canaloplasty has been suggested to help elucidate this problem. In this study,
we intended to investigate the relationship between the diameter or shape of OEAC and COM. We retrospectively reviewed the
high-resolution computed tomography (HRCT) images of the temporal bones of 62 patients with unilateral COM who underwent
tympanoplasty from January 1, 2011, to December 31, 2013. For comparison, the HRCT images of another 62 patients with normal
ears were collected to be the control group. The shape of OEAC was categorized into 5 groups according to Mahboubi's classification, and the dimension of each patient's OEAC was measured at 2 defined sections (annular section and isthmus/midcanal
section). The most prevalent shape of OEAC for the lesion sides of the ears was cylindrical, followed by conical, and hourglass in
both the COM and the control groups. As to the dimension of OEAC, there were no significant differences between lesion ears and
normal ears among patients in the COM group as well as between lesion ears in the COM group and normal ears in the control
group. We concluded that the bony dimension of the external ear canal was not related to COM. This suggested that chronic
inflammation or infection of middle ear may not cause bony thickening of OEAC, despite the kind of OEAC shape involved.

Introduction

Patients and Methods

Canal stenosis is defined as narrowing of the dimension of the
external auditory canal (EAC), with a cause that can be either
congenital or acquired. Multiple etiological factors of acquired
canal stenosis have been published to date, including persistent
otitis externa,1 trauma (surgical or nonsurgical), malignancy2,
or irradiation.3 In 1999, Kimberley et al suggested that chronic
otitis media (COM) could cause acquired canal stenosis; therefore, routine canaloplasty is necessary when performing tympanoplasty.4 Based on our clinical observations and daily
practice, there seems to be a tendency for most patients with
COM to have a smaller dimension of the EAC. However, the
relationship between COM and acquired canal stenosis has
rarely been mentioned in the literature in the last 15 years.1,5
The human EAC is composed of 2 portions-the cartilaginous and the osseous part. In most otolaryngology texts, the
osseous external auditory canal (OEAC) is described as located
in the medial two-thirds of EAC, and its anatomic feature can
be evaluated clearly by high-resolution computed tomography
(HRCT).6-7 In 2012, Mahboubi introduced a standard and
objective method to determine the anatomic dimension of
OEAC.5 In this study, we try to figure out whether the dimension of OEAC or the shape of OEAC was related to COM.

Patients
We conducted a retrospective analysis of high-resolution temporal bone computed tomography (CT) images of 2 cohorts of
adult patients. The first cohort (COM group) consisted of all
patients with unilateral COM who underwent tympanoplasty
from January 2011 to December 2013 by the same surgeon.
Ears with exostoses, canal atresia, congenital canal stenosis,
history of temporal bone fracture, otologic surgery, bilateral
COM, cholesteatoma, or tumor were excluded from this study.
In addition, HRCT images of temporal bone taken from other

1

Department of Otolaryngology-Head and Neck Surgery, Taipei Veterans
General Hospital
2
School of Medicine, National Yang-Ming University, Taipei
Received: September 25, 2017; revised: November 21, 2017; accepted:
November 30, 2017
Corresponding Author:
Mao-Che Wang, MD, PhD, Department of Otolaryngology-Head and Neck
Surgery, Taipei Veterans General Hospital, Postal address: No. 201, Shi-Pai
Road, Sec. 2, Beitou, Taipei 11217.
Email: wangmc@vghtpe.gov.tw
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ENT - September 2020

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