1

Introduction

Chronic Otitis Media (COM) is a multifactorial disease with a complex nature of occurrence. Upper airway infections, recurrent otitis media, dysfunction of the Eustachian tube (ET) and nasopharynx, ciliary dysfunction, and allergy are among the investigated probable risk factors . COM is defined as the chronic infection and inflammation of the middle ear and mastoid cavity lasting more than 3 months and causing ear discharge, hearing loss and tympanic membrane perforation .

The Eustachian Tube (ET), involves a critical role in development of COM . Pressure equalization, mucociliary clearance and protection of the middle ear are the three main functions of the ET . The ET is composed of fibrocartilaginous and bony segments. The bony segment is completely located in the petrous portion of the temporal bone and it lies on the anterior wall of the middle ear . In healthy individuals, the bony segment is always open but the fibrocartilaginous portion is closed at rest and opens during swallowing, yawning, sneezing or by Valsalva Maneuver . The bony and fibrocartilaginous segments meet by an irregular bony structure .

The current medical literature supports the evidence that anatomic and functional problems of ET may play a role in COM pathogenesis . Doyle reported an animal study that concludes failure of the ET to open causes an inflammation and leads to mucosal disturbances similar to that of otitis media with effusion (OME). He also concluded that the duration of the obstruction is correlated with the severity of the disease. Also in some patients who have structural anomalies of ET, like Down Syndrome or craniofacial anomalies, there is an increased risk of development of middle ear disease .

The ET anatomy, physiology and function need to be clarified to understand the pathogenesis of COM. In this retrospective research we measured the bony segment diameter of the ET bilaterally with Temporal Bone Computed Tomography (CT) right at the connection between bony and fibrocartilaginous segments in patients with unilateral COM. Only unilateral COM patients were included to our study because our aim was to evaluate the effect of ET diameter on COM.

2

Material and method

The study was reviewed and approved by the institutional review board at the GOP Taksim Education and Research Hospital (32/10.08.2016). Our data is obtained from the Ear Nose and Throat and Radiology Departments of Haseki Education and Research Hospital, in between June 2015 and January 2016. The patients who were both clinically and radiologically diagnosed with unilateral COM (tympanic membrane perforation with or without purulent discharge) and had undergone Tympanoplasty with or without Mastoidectomy were enrolled in this study. The Temporal bone CT’s of patients who had soft tissue inflammation or infection at middle ear and/or mastoid cavities were included to study. The patients with bilateral disease, tympanic membrane perforation without mastoid or middle ear inflammation, craniofacial anomalies and ET obstruction were excluded. The junction between bony and fibrocartilaginous segments of the ET were measured bilaterally and diseased and healthy sides were compared for the statistical analysis.

2

Material and method

The study was reviewed and approved by the institutional review board at the GOP Taksim Education and Research Hospital (32/10.08.2016). Our data is obtained from the Ear Nose and Throat and Radiology Departments of Haseki Education and Research Hospital, in between June 2015 and January 2016. The patients who were both clinically and radiologically diagnosed with unilateral COM (tympanic membrane perforation with or without purulent discharge) and had undergone Tympanoplasty with or without Mastoidectomy were enrolled in this study. The Temporal bone CT’s of patients who had soft tissue inflammation or infection at middle ear and/or mastoid cavities were included to study. The patients with bilateral disease, tympanic membrane perforation without mastoid or middle ear inflammation, craniofacial anomalies and ET obstruction were excluded. The junction between bony and fibrocartilaginous segments of the ET were measured bilaterally and diseased and healthy sides were compared for the statistical analysis.

3

Measurement

The measurements are collected by only one radiologist for excluding person to person variation. A multidetector CT system (Brilliance 64, Philips Medical System Cleveland Ohio) was used for CT imaging. Imaging parameters included a slice thickness and reconstruction interval of 0.5 mm, a pitch of 0.652, and a field of view of 25 × 25 cm. Images were transferred to an offline Picture Archiving and Communication System (PACS). ET bony diameters were measured on axial plane images. The connection between fibrocartilaginous and osseous segments of the ET which is the most irregular and narrowest portion on axial CT images was defined and the diameter of this segment is measured ( Fig. 1 , Fig. 2 ). The measurements were carried out bilaterally.

Arrow head showing the narrowest portion of the bony Eustachian tube.

Right diseased and left healthy ears ET diameter measurement.

4

Statistical analysis

Normalisation control is undergone by drawing graphics with single-sample Kolmogorov Smirnov test, histogram, Q-Q plot and box plot. The data are given as standard deviation, minimum, maximum, frequency and percentage. The differences between the healthy and diseases ET diameters are evaluated by paired t -test. Significance interval is taken with p < 0.05 and bidirectionally. NCSS 10 program is used for analysis.