|Year : 2022 | Volume
| Issue : 2 | Page : 144-148
Correlation of eustachian tube dimension and chronic otitis media
Sherin Varghese1, MK Goutham1, Marina Saldanha1, Rajeshwary Aroor1, Raghuraj Uppoor2, Vadisha Srinivas Bhat1
1 Department of ENT, K S Hegde Medical Academy, Mangalore, Karnataka, India
2 Department of Radiology, K S Hegde Medical Academy, Mangalore, Karnataka, India
|Date of Submission||22-Feb-2021|
|Date of Decision||04-Apr-2021|
|Date of Acceptance||28-Apr-2021|
|Date of Web Publication||21-Sep-2022|
Dr. M K Goutham
Department of ENT, K S Hegde Medical Academy, Deralakatte, Mangalore - 575 018, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Eustachian tube (ET) is a dynamically intricate and poorly accessible structure connecting the nose and the middle ear. Although chronic otitis media (COM) is multifactorial disease, ET dysfunction is an important but overlooked predisposing factor. With newer evidence into the dynamics and prognostic factor in outcome of middle ear surgeries, it has become a focus of research. Our study aims to evaluate the various ET parameters using high-resolution computed tomography (HRCT) scan with multiplanar reconstruction technique. These parameters were compared between the diseased and normal ears to evaluate any association between the ET parameters and middle ear disease. Materials and Methods: It is a retrospective study of 66 HRCTs, with 47 HRCTs of COM and rest were controls. ET parameters including (a) ET-angle, (b) length, (c) pretympanic diameter, and (d) diameter at isthmus are measured accurately using HRCT temporal bone. Results: ET angle was significantly obtuse in COM group (154.81° ± 6.33°) when compared with the controls (149.99° ± 6.24°) with P < 0.001. Similar observation in ET angle was noted in diseased ear (154.54° ± 5.79°) in unilateral COM when compared with contralateral ear (149.56° ± 6.87°) (P = 0.001). ET was longer in COM group (3.44 ± 0.31) when compared with controls (3.4 ± 0.35). Pretympanic diameter and diameter at isthmus were greater in control group. Conclusion: The obtuse ET angle and narrow pretympanic diameter may contribute to the pathogenesis of COM. These measurements may be useful in the assessment of ET function preoperatively and might help in determining the surgical outcome. HRCT of temporal bone with multiplanar reconstruction is an effective tool to measure ET dimensions accurately.
Keywords: Chronic otitis media, eustachian tube, high-resolution computed tomography, temporal bone
|How to cite this article:|
Varghese S, Goutham M K, Saldanha M, Aroor R, Uppoor R, Bhat VS. Correlation of eustachian tube dimension and chronic otitis media. Indian J Otol 2022;28:144-8
|How to cite this URL:|
Varghese S, Goutham M K, Saldanha M, Aroor R, Uppoor R, Bhat VS. Correlation of eustachian tube dimension and chronic otitis media. Indian J Otol [serial online] 2022 [cited 2022 Sep 25];28:144-8. Available from: https://www.indianjotol.org/text.asp?2022/28/2/144/356452
| Introduction|| |
The Eustachian tube More Details (ET) is a narrow structure of 32–38 mm in length that connects the middle ear to the nasopharynx. It is composed of a bony part opening into the anterior wall of the middle ear and a cartilaginous part opening on the lateral wall of the nasopharynx, with a narrow isthmus at the junction between the two. Ventilation, equalization of pressure, and drainage of secretions from the middle ear to the nasopharynx are the main functions of the ET.
Chronic otitis media (COM) is a multifactorial disease with major predisposing factor being ET dysfunction (ETD). Studies show that 70% of patients undergoing tympanoplasty for COM show ETD., The overall prevalence of chronic obstructive ETD is around 1% in adults.
Although ET is a significant factor determining the outcome of ear surgery, surgeons often overlook ET while studying the high-resolution computed tomography (HRCT) of temporal bones preoperatively. ET anatomy, histopathology, dynamics, and its role in the development of COM are still a focus of research and have gained recent momentum with newer procedures such as balloon eustachian tuboplasty (BET). The aim of our study is to evaluate the various ET parameters and analyze these anatomical variations in ET between normal and COM ears. HRCT scan with multiplanar reconstruction technique was used in measuring various ET dimensions including angles and diameters.,
| Materials and Methods|| |
It is a retrospective case-based study done between July 2017 and April 2020 in the otolaryngology department in our institution. After obtaining ethical clearance from Institutional Ethical Cell, all the HRCT scans of temporal bone done during the study period were studied. No consent was required as it was a retrospective study involving computed tomography (CT) scans.
A total of 66 HRCT scans were included in the study. The case files of these patients were collected from the Medical Records Department, and the clinical findings and the diagnosis were charted. Based on the diagnosis, the study group was subdivided into COM group and normal/control group. Out of the 66 HRCTs, 47 HRCTs which were diagnosed with COM were taken as cases and the rest were controls.
For the temporal CT scanning, multislice CT scan by General Electronics Brightspeed 16 slice CT was used. Images were obtained in 0.625 mm slice thickness, and multiplanar reconstruction was obtained in GE workstation.
The parameters evaluated are pretympanic diameter, diameter at the isthmus, and ET/tubotympanic angle and length. The ET angle is the angle between the line extending through the center of the longitudinal axis drawn from the bony external ear canal and the imaginary line drawn through the center of tympanic orifice of the ET along its long axis. This was measured in the axial cuts of CT scan [Figure 1].
|Figure 1: High-resolution computed tomography of temporal bone in axial cut measuring eustachian tube angle|
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The tympanic and the pharyngeal orifices were determined in axial sections of CT scan for measuring the ET length. ET length is defined as the distance between the most superior points of tympanic orifice and pharyngeal orifice [Figure 2].
|Figure 2: High-resolution computed tomography of temporal bone in axial cut measuring eustachian tube length|
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Pretympanic segment is the part of ET that is adjacent to the tympanic orifice. The anteroposterior (AP) diameter of the pretympanic segment was measured in coronal cuts [Figure 3]. Isthmus, the narrowest part of the ET, was identified in coronal cuts and diameter at the isthmus was measured using multiplanar reconstruction technique in the coronal slices of HRCT temporal bone [Figure 4].
|Figure 3: High-resolution computed tomography temporal bone axial slice showing measurement of pretympanic anteroposterior diameter|
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|Figure 4: High-resolution computed tomography temporal bone in coronal slice sowing measurement of diameter at isthmus|
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All HRCT scans of temporal bone with or without COM were done during the data collection period.
HRCT of temporal bone with craniofacial abnormalities, congenital deformity of ear, and Downs's syndrome were excluded from the study.
Sample size calculation
Using G-power software 3.1 (Heinrich Heine University, Düsseldorf, Germany), the sample size was calculated at alpha error of 5% and 80% power. A total number of 70 ears would be required to be reviewed, of which 35 would be normal and the other 35 would be diseased.
Data management and statistics
Quantitative variables such as ET angle, length, pretympanic diameter, and diameter at the isthmus were expressed in terms of mean and standard deviation. Independent t-test was used to compare the cases with controls with regard to these parameters. Data were be compiled in MS Excel and analyzed using SPSS Version 20 (IBM, Chicago, USA).
| Results|| |
In this study, maximum number of HRCTs was done in the age group of 20–30 years with 19 counts contributing to 28.7% of cases. This was followed by age group of <20 years accounting to 17 counts (25.7%). We had 42 (63.63%) males and 24 (36.36%) females in this study.
The most common clinical indication for HRCT was squamosal disease, followed by mucosal disease [Figure 5]. There were 47 cases of COM out of which 12 were bilateral and 35 were unilateral. Among the 35 unilateral cases, 35 contralateral ears were included as controls. Of the total 59 COM ears, 53 were squamosal and 6 were mucosal types [Figure 6].
|Figure 5: Indications for high-resolution computed tomography temporal bone|
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The mean ET angle was 152.14° ± 6.68° across the two groups. The average ET length was 3.41 ± 0.32 cm. The pretympanic AP diameter showed mean value of 6.59 ± 0.68 mm and the mean diameter of the ET at the isthmus was 1.13 ± 0.85 mm.
Comparison of the eustachian tube parameters between cases and controls
ET angle was more obtuse in COM group (154.81° ± 6.33°) when compared with the controls (149.99° ± 6.24°) and was statistically significant (P < 0.001). Comparison of the ET length between the two groups showed that it was slightly longer in COM group (3.44 ± 0.31 cm), than controls (3.4 ± 0.35 cm) and was not significant (P = 0.0.495). The pretympanic AP diameter was 3.86 ± 0.68 mm and 3.97 ± 0.7 mm for COM and control groups, respectively. Diameter at isthmus was also higher in controls (1.18 ± 0.81 mm) than cases (1.08 ± 0.91) [Table 1].
|Table 1: Comparison of the various eustachian tube parameters between chronic otitis media ears and normal ears|
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Comparison of various eustachian tube parameters between the diseased and contralateral ear in patients with unilateral chronic otitis media
ET the angle was greater in the diseased ear (154.54° ± 5.79°) which was statistically significant (P = 0.001) when compared to contralateral ear (149.56° ± 6.87°). The ET length and diameter at the isthmus were also more in diseased ear. However, the pretympanic AP diameter was higher in the normal ear when compared to diseased ear [Table 2].
|Table 2: Comparison of various eustachian tube parameters between the diseased and normal ear in patients with unilateral chronic otitis media|
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Comparison of various eustachian tube parameters between the mucosal and squamosal chronic otitis media
We observed that the ET angle, pretympanic diameter, and the diameter at the isthmus were more in mucosal disease, whereas the ET was longer in squamosal disease. However, the significance of this observation cannot be commented due to limited cases in the mucosal COM.
| Discussion|| |
ET has several functions related to middle ear such as pressure equalization, drainage, mucociliary clearance, and protection from nasopharyngeal environment. ET angulation and the length prevent the nasopharyngeal reflex into the middle ear. Nasopharyngeal end of ET is physiologically closed except for a brief period during act of swallowing or yawning, further reducing the chances of reflux into it. Adequate drainage of secretions and ventilation of middle ear are possible only with the correct arrangement of the ET. Hence, ETD can result in middle ear diseases including COM and its anatomy and physiology continues to be a focus of research. Tysome and Sudhoff in their review state that there is no single tool to measure ETD, while a battery of tests involving tubomanometry, patient reported Valsalva and Toynbee, tympanometry, and objective Valsalva, summed up as the ET Score has sensitivity and specificity of 96%.
Smith et al. in their review on imaging for ET stated that radiological assessment (CT and magnetic resonance imaging [MRI]) was a noninvasive method of detecting obstructive or patulous ETD and dynamic imaging using contrast, and scintigraphy has potential to assess the function of the tube. They also described the imaging findings in obstructive ETD as reduced bony channel in the cross-sectional size in and shallow angle of the tube in diseased ears. They stated that MRI had good soft-tissue definition, which helped in analyzing opening of ET during Valsalva with real-time turbogradient echo sequences. Tsai et al. concluded in their series of ten cholesteatoma that 3D reconstruction of HRCT temporal bone is effective tool to check ET with high level of details.
Further, with the recent advance in BET, the often neglected cartilaginous ET has attained a new limelight. Using HRCT to accurately measure the dimensions in terms of length and width of cartilaginous ET in advance puts the surgeon in an advantageous position in selecting the size of the balloon and ensures accurate placement of catheter, improving the overall success of the procedure.
In our study, the average tubotympanic/ET angle in COM was significantly obtuse (154.81° ± 6.33°) when compared to normal ears (149.99° ± 6.24°). This result was similar to a study conducted by Nemade et al. where the tubotympanic angle in COM patients was 148.12° ± 3.43°, and in normal patients, it was 145.14° ± 4.34°. In our study, similar observations were also made when we compared the tubotympanic angle between the diseased and contralateral ear in unilateral COM. This obtuse tubotympanic angle observed in COM may result in spread of upper respiratory tract infection to the middle ear, hence making it a predisposing factor in otitis media.
While according to Aksoy et al., the ET angle is more obtuse in normal (147.13° ± 6.38°) when compared to COM (145.17° ± 6.36°). Tsai et al. concluded in their series of ten unilateral attic cholesteatoma that the ET angle was significantly larger in the normal ears than in the cholesteatoma ears. However, they did not find any significant difference in the size of the ET tube orifice, ET tube length between the two sides. A study by Dinç et al. on length and angle of the ET concluded that the ET was more horizontal and shorter in COM and could be a contributory factor for development of COM.
Further, on comparing the ET angle between squamosal with the mucosal cases, the angle was found to be more obtuse in ears in mucosal disease. This finding is yet to be validated due to a limited number of mucosal cases (n = 6).
We found that the average pretympanic AP diameter in COM was lesser than the controls. While in unilateral COM patients, the diameter in the diseased ear was slightly lower than the normal ears. Nemade et al. also found similar results where the pretympanic diameter was found to be significantly less in COM than normal patients. According to a study conducted by Shim et al. on the ET aeration in COM, the cross-sectional area was significantly smaller when compared to controls. Histopathologic examination from sections of pretympanic area by Sadé et al. showed a significant inflammatory reaction when compared to the normal ears. The pretympanic area of ET tube is the largest area of ET and the most affected by middle ear pathology. The inflammatory changes are more marked in pretympanic area when compared to other sections of ET. This narrowing of the pretympanic area can result in further impaired aeration of the middle ear which demands meticulous attention during middle ear surgeries.
In our study, ET parameters such as ET length, diameter at the isthmus did not show any significant difference between COM and normal ears. This finding was consistent with a study conducted by Dinç et al. The diameter at isthmus was greater in mucosal disease on comparing with the squamosal disease.
| Conclusion|| |
We conclude that the obtuse tubotympanic angle and narrow pretympanic diameter of ET may contribute to the pathogenesis of COM. These measurements may be useful in the assessment of ET function preoperatively. The HRCT scan of the temporal bone with multiplanar reconstruction is an effective and noninvasive tool to measure the ET dimensions accurately.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2]