|Year : 2019 | Volume
| Issue : 3 | Page : 140-145
Correlation between high-resolution computed tomography temporal bone findings and surgical findings in patients with inflammatory diseases of the middle ear
Jeslean Jose1, Uttam B George2, Ashish Varghese3, Shubhra Rathore2
1 Department of Radio Diagnosis, St. John's National Academy of Health Sciences, Bengaluru, Karnataka, India
2 Department of Radiodiagnosis, Christian Medical College, Ludhiana, Punjab, India
3 Department of ENT, Christian Medical College, Ludhiana, Punjab, India
|Date of Submission||10-Dec-2018|
|Date of Decision||20-Jan-2019|
|Date of Acceptance||22-Apr-2019|
|Date of Web Publication||13-Aug-2019|
Department of Radiodiagnosis, Christian Medical College, Ludhiana - 141 008, Punjab
Source of Support: None, Conflict of Interest: None
Background: With the advent of high-resolution computed tomography (HRCT), more information can be obtained about the anatomy of the middle ear, soft tissue pathologies, and the complications of middle ear disease process as compared to the conventional diagnostic methods. Aims: This study aims to study the spectrum of HRCT temporal bone findings in inflammatory middle ear diseases as well as correlate computed tomography (CT) with intraoperative findings. Settings and Design: This is a cross-sectional study including all consecutive patients presenting to the ear, nose, and throat department with a provisional diagnosis of inflammatory middle ear disease requiring surgical management and referred to department of radiodiagnosis for HRCT temporal bone. Materials and Methods: The HRCT findings of 58 such patients were compared with the intraoperative findings. Statistical Analysis Used: Interrater agreement Kappa was used to find agreement between CT and surgical findings. Diagnostic test was used to find out sensitivity, specificity, negative predictive value, and positive predictive value of CT taking surgery as gold standard. P < 0.05 was considered as statistically significant. Results: HRCT had high sensitivity for delineating the disease at most of the sites except for the facial canal and integrity of stapes. Correlative accuracy was highest in the region of the incus, labyrinth, scutum, sinus plate, inner ear, and jugular bulb. Conclusions: Our study showed moderate to very good correlation between HRCT temporal bone and operative findings. It also allowed early identification of complications enabling a better surgical approach and treatment plan.
Keywords: Cholesteatoma, high-resolution computed tomography, inflammatory middle ear diseases
|How to cite this article:|
Jose J, George UB, Varghese A, Rathore S. Correlation between high-resolution computed tomography temporal bone findings and surgical findings in patients with inflammatory diseases of the middle ear. CHRISMED J Health Res 2019;6:140-5
|How to cite this URL:|
Jose J, George UB, Varghese A, Rathore S. Correlation between high-resolution computed tomography temporal bone findings and surgical findings in patients with inflammatory diseases of the middle ear. CHRISMED J Health Res [serial online] 2019 [cited 2020 Sep 21];6:140-5. Available from: http://www.cjhr.org/text.asp?2019/6/3/140/264379
| Introduction|| |
Middle ear diseases are defined as diseases restricted to the middle ear cleft which includes the middle ear cavity, mastoid, and the eustachian tube. Chronic otitis media may be further classified into  mucosal disease (active/inactive), squamous disease (active/inactive), and healed chronic otitis media. The diagnosis of this disease is usually a combination of clinical findings including history, otoscopic examination, and pure-tone audiometry as well as radiological findings.
Radiological assessment of the inflammatory diseases of the middle ear is challenging and involves deep understanding of anatomy. High-resolution computed tomography (HRCT) excels in the evaluation of middle ear disease process and adjacent bone, and its advent has significantly altered the contribution of radiological imaging in the preoperative diagnosis of middle ear disease. Of the middle ear structures, HRCT is most valuable for the detection of early erosive changes in the ossicles, as well as in the detection of nondependant soft tissue opacification suggestive of cholesteatoma.
Treatment of diseases like squamous chronic otitis media includes mandatory surgical treatment because of the risk for labyrinthine or cerebromeningeal complications. The primary objective of any surgery in inflammatory middle ear disease is to obtain a dry ear and second objective is to restore the functional capacity of the ear, and both of these are better facilitated by the aid of a radiological preoperative assessment. The disease extent often determines the aggressiveness of the surgical approach.,
One among the numerous advantages of HRCT is the timely detection of pathologies including early cholesteatoma with subtle bony erosion or ossicular displacement. This early detection by HRCT scan with the use of a simple minimally invasive surgical technique (atticotomy) will solve the problem and preserve hearing. The various associated complications such as facial nerve paralysis and labyrinthine fistula are well-recognized preoperatively by careful interpretation of the HRCT scan. Despite these advantages, viewpoints remain varied on the utility of preoperative radiological assessment. A correlative study of HRCT in atticoantral disease concluded that the high levels of false positives and negatives prevent wholesome reliability on HRCT. Results from other studies failed to demonstrate the usefulness of computed tomography (CT) scan in simple chronic otitis media but its application proved valuable in cases of cholesteatoma or revision surgery. Another correlative study by Vlastarakos et al. suggested very strong agreement between HRCT and surgical findings in the mastoid air cell complex and sigmoid sinus while there was no correlation in the areas of scutum, attic wall, and oval window.
This study is being undertaken to further assess the clinical correlation and utility of HRCT before surgical intervention in patients with inflammatory middle ear diseases with two major objectives.
| Materials and Methods|| |
This cross-sectional study was conducted in a tertiary care hospital in North India, in the Department of Radiodiagnosis from January 1, 2014 to June 30, 2015. Informed consent was obtained from all patients (adults and children more than 7 years) who were a part of the study.
From a finite population, with 88% sensitivity and 95% confidence interval and with alpha = 0.05, the minimum required sample size was calculated to be 41.
Following Institutional Research Committee approval, all consecutive patients referred to the Department of Radiodiagnosis from the ear, nose, and throat (ENT) outpatient department with a provisional clinical diagnosis of inflammatory middle ear disease posted for surgery were included in the study. Diseases included were squamous and mucosal diseases not responding to medical management.
Patients with previous history of ear surgery, implants as well as noninflammatory middle ear disease.
Patients were subjected to HRCT evaluation using Philips Ingenuity 128 slice CT scanner, and HRCT of the temporal bone was performed with serial 0.67 mm thin sections and 0.33 mm increments.
After obtaining an informed consent for participation in the study, short clinical history and relevant clinical examination findings were noted on a standard pro forma before radiological evaluation.
The HRCT findings were recorded on a standard pro forma which included various bony and soft tissue structures seen within the middle ear cleft. Following surgery, these parameters were individually compared with surgical findings.
Categorical variables were presented in number and percentage (%), and continuous variables were presented as mean ± standard deviation and median. Normality of data was tested by Kolmogorov–Smirnov test. If the normality was rejected, then non parametric test was used.
Statistical tests were applied as follows: interrater agreement Kappa was used to find agreement between CT and surgical findings. Diagnostic test was used to find sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of CT taking surgery as gold standard.
P < 0.05 was considered as statistically significant. Data analysis was done using Statistical Package for Social Sciences version 21.0. (IBM, Chicago, USA).
| Results|| |
A total of 58 patients were included in the study. Of these, majority (55%) fell into the 21 years to 40 years age group. Correlation between HRCT findings and surgical findings was evaluated on the basis of the sensitivity, specificity, and levels of agreement with respect to 18 set parameters based on the kappa value.
Highest level of agreement between the CT and surgical findings in the area of the labyrinth with 100% sensitivity and specificity. All 8 cases of labyrinthine erosion on CT were found to be eroded intraoperatively with no false positives/false negatives [Table 1] and [Figure 1]. Very good agreement was noted in the Incus [Table 2] – this was also the highest recorded among the three ossicles with κ = 0.86. A high sensitivity of 92.86% in detecting incus erosions and specificity of 95.24% in detecting no erosions were observed with the use of HRCT temporal bone. Furthermore, the incus was the most commonly eroded ossicle in our study being present in 73.21% of patients who underwent surgery [Figure 2]. There was good agreement between the HRCT and surgical findings of the malleus with statistically significant value of <0.0005 [Table 2]. CT had 87.10% sensitivity in detecting malleus erosions and 81.48% specificity in detecting no erosions. Of a total of 32 cases in which CT revealed malleus erosions, 27 of these revealed intraoperative erosions. However, 5 of these were false positives, which is the highest number among the three ossicles. The poorest agreement among the ossicles was in the region of stapes with kappa of 0.569. Sensitivity was also the lowest among the 3 ossicles of approximately 70.9%. Of the 25 cases of stapedial erosion reported on CT, 22 of these had erosions intraoperatively while 3 of these were false positives. In nine cases, no erosions were reported on CT while surgery revealed erosions giving us the highest number of false negatives in the region of the stapes.
|Figure 1: Sagittal (a and b) and coronal (c) computed tomography sections show soft tissue attenuation contents in the middle ear. Erosions are also noted along the tegmen tympani (arrows in a and b) and tympanic part of temporal bone (arrow in c)|
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|Figure 2: Axial, coronal, and sagittal computed tomography sections (a, b, and c, respectively) show automastoidectomy with associated soft tissue attenuation (arrows in a and c) and absent ossicles (*in a and b)|
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Very good radiologic–surgical correlation (i.e., κ = 0.80–1.00) was observed in the protympanum, antrum, and aditus with respect to the presence/absence of soft tissue attenuation [Table 3] and [Figure 3]. Both the mastoid antrum and aditus ad antrum were locations in the middle ear cleft with the least number of false positives and false negatives. Good agreement (κ = 0.60–0.80) was further noted in the external auditory canal as well as the absence/presence of soft tissue attenuation in the mesotympanum, hypotympanum, as well as the epitympanum [Table 3].
|Figure 3: Axial computed tomography sections show tympanic membrane perforation (arrow in a). b and c show erosions involving labyrnth and lenticular process of incus, respectively|
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There was good agreement between CT and surgical findings in terms of blunting or erosion of the scutum which forms the lateral wall of the attic and is frequently involved in cholesteatoma. There was a sensitivity of 71.43% for CT in detecting along with a higher specificity of 94.74% in ruling out a scutum erosion [Table 1]. There was good agreement in the area of the inner ear including cochlea with a κ = 0.658 [Table 1]. CT had a sensitivity of 50% in detecting erosions of the promontory. However, the one case of involvement given on CT was confirmed intraoperatively with no false positives and a specificity of 100%. There was moderate agreement between the CT and surgical findings in the region of the sinus plate having a κ = 0.472 [Table 1]. The 2 cases of confirmed erosion during surgery were both detected on CT with a 100% sensitivity. CT had a specificity of 92.73% in ruling out erosion of the sinus plate. However, of the 6 cases reported to be eroded on CT, only two were confirmed surgically while 4 cases were deemed false positives.
Fair agreement (kappa of 0.268) was observed in the tegmen tympani. However, CT had a 100% sensitivity in detecting tegmen tympani erosions with all 3 cases of erosion found during surgery being detected on HRCT. CT had a specificity of 77.36% in ruling out erosion of the tegmen [Table 1]. The highest number of false positives in the study was seen in this area with 15 cases being reported as abnormal on CT and only 3 of them being confirmed surgically with the rest 12 being false positives. Poorest correlation was seen in the region of the fallopian canal with a κ = 0.104 and a P = 0.378 [Table 4]. Furthermore, the sensitivity of HRCT in detecting facial canal erosions was the lowest among all the studied variables being a mere 56.1%. Similar low specificity of 58.3% was seen in the ability of HRCT in detecting an intact facial canal in patients without facial canal erosion. Of the 28 cases of reported facial canal dehiscence or erosion, 23 cases were confirmed intraoperatively with 5 false-positive cases. A total of 40 cases of 54 were found to have facial canal erosion intraoperatively, of which CT was able to detect 22 cases with the rest, i.e., 18 cases being false negatives. Majority of the cases with facial canal erosions were found to have squamous disease intraoperatively with few isolated cases of mucosal disease demonstrating facial canal dehiscence.
| Discussion|| |
The maximum incidence of middle ear inflammatory diseases was found in the 21–30 age group with a mean age of 32.66 years. A slight male preponderance was also found being 53.4% of the studied patients.
The most common finding in the study was soft tissue attenuation in the mastoid with loss of its aeration being found a vast majority, i.e., 94.5% of patients. Soft tissue attenuation or sclerosis of the mastoid air cells is almost always coexistent with inflammatory diseases of the middle ear due to the proximity of the mastoid air cells to the middle ear.
The incus was the most commonly affected ossicle in the study with an erosion prevalence of approximately 73.3% (also the most commonly eroded ossicle intraoperatively). The highest agreement between radiological and surgical findings was seen in incus with a κ = 0.818. Our study detected a high sensitivity in detecting ossicular destruction, especially in the region of malleus and incus with sensitivities of 87.1 and 92.86, respectively, which is in agreement with literature which presents similar results, with sensitivity ranging from 80% to 100%. However, we demonstrated lower sensitivity in stapes where lowest sensitivity of 70.9% was seen among the three ossicles. This is in agreement with the studies by Mafee et al., Garber and Dort, Jackler et al., and Swartz  and is likely due to the presence of a soft tissue density around the stapes making it difficult in identifying the erosion of this bone as stated by Sreedhar et al.
In the middle ear cleft, we found a 90.5% high prevalence of soft tissue attenuation density in the attic of all the areas in the middle ear further strengthening the known fact that cholesteatomas take origin from Prussak's space. The highest radiologic–surgical correlation was found in the protympanum with κ = 0.844.
The least prevalent finding in our study was dural sinus plate erosion being found in only about 3.5% of the studied patients.
The highest radiological–surgical correlation was seen in the labyrinth. In our study, we demonstrated one of the highest levels of sensitivity and specificity in the labyrinth both being 100% with a kappa value of 100%. This is a noteworthy finding as preoperative detection drastically reduces the chances of a dead ear. Labyrinthine fistula can be accurately detected most of the time with concurrent visualization of both axial and coronal images to detect erosion of the semicircular canals. Of the three semicircular canals, the most common canal affected is the lateral semicircular canal, and mere dependence on coronal sections alone may lead to a 50% false positive rate of dehiscence due to partial volume averaging artifact.,
The highest sensitivity of HRCT temporal bone was seen in the mastoid, sinus plate, tegmen tympani, protympanum, hypotympanum, jugular bulb as well as the labyrinth while the HRCT temporal bone was less sensitive for detecting facial canal dehiscence and erosions involving the promontory. Our study revealed the poorest correlation in detecting facial canal integrity with a sensitivity of 56.1% in detecting facial canal dehiscence/erosion and a similar low specificity of 58.3% in detecting an intact canal.
This level of sensitivity is comparable to the study done by Sirigiri et al. in which CT to find facial canal dehiscence had a 60% sensitivity but a much higher specificity of 90%. The low sensitivity of HRCT in our study as well as many others including Johnson et al. and Chee and Tan  occurs due to the partial volume averaging artifact such that the fallopian canal can be so thin even in nonpathological ear so as to appear dehiscent. Furthermore, surrounding soft tissue edema may be mistaken as bony dehiscence of the facial canal.
As invaluable as HRCT is, magnetic resonance (MR) provides additional information that helps further characterizing inflammatory/granulation soft tissue versus cholesteatoma. A combination of specific sequences (diffusion-weighted imaging, routine T1-weighted and T2-weighted images and delayed postcontrast sequences) have been found to be useful in detecting residual/recurrent cholesteatoma with few authors seen to advocate limited sequence MR imaging (MRI) in combination with HRCT in routine radiologic reporting of cholesteatoma.
De Foer et al. demonstrated the utility of MRI in detecting complications such as lateral semicircular canal erosion, labyrinth invasion, and middle cranial fossa involvement. Limitations however include the lack of temporal bone anatomical delineation and identification of bony including ossicular erosions on MR images.
The highest specificity of CT in our study was demonstrated in the jugular bulb, inner ear as well as the labyrinth, and the least specificity was seen in the region of the facial canal with a specificity of 58.33%. The highest PPV was seen in the inner ear and jugular bulb being 100%. The ability to rule out an abnormality, i.e., the NPV was the highest (100%) in the mastoid, jugular bulb, sinus plate, tegmen tympani, labyrinth as well as the protympanum and hypotympanum. The least PPV was seen in the tegmen tympani (20%) with HRCT temporal bone seen to overestimate tegmen tympani erosions.
| Conclusion|| |
This study concludes that HRCT temporal bone along with the clinical examination is a powerful diagnostic tool in the diagnosis of inflammatory diseases of the middle ear. It also provides sufficient information to the ENT surgeon regarding the extent of disease process, the complications, and anatomical variants which may be encountered intraoperatively.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]