|Year : 2015 | Volume
| Issue : 2 | Page : 103-106
Role of high-resolution computed tomography scan in the evaluation of cholesteatoma: A correlation of high-resolution computed tomography with intra-operative findings
Sandeep Sreedhar, Kailesh Pujary, Ashish Chandra Agarwal, R Balakrishnan
Department of ENT, Kasturba Medical College, Manipal University, Manipal, Karnataka, India
|Date of Web Publication||20-Apr-2015|
Dr. Ashish Chandra Agarwal
Department of ENT, Kasturba Medical College, Manipal University, Manipal - 576 104, Karnataka
Source of Support: None, Conflict of Interest: None
Context: Correlation of the extent of disease on a high-resolution computed tomography (HRCT) temporal bone with intraoperative findings. Aim: This study was done to find the correlation between the preoperative HRCT scan and intra-operative findings in patients diagnosed with chronic suppurative otitis media (CSOM) attico-antral type of disease. Settings and Design: The study was done at a tertiary care hospital, and a cross-sectional study design was employed. Subjects and Methods: The findings of HRCT scan of 25 patients clinically diagnosed to have CSOM attico-antral type of disease were compared with the intraoperative findings. The commonly affected structural parameters were compared. Statistical Analysis Used: Statistical analysis was performed using Statistical Package for Social Sciences (SPSS) version 11.5 (SPSS: An IBM company). For the current study, kappa, frequency and percentage were considered. Results: HRCT scan was found to have a high sensitivity for identification of the disease at most of the sites within the temporal bone except for the sinus tympani and the stapes region. Conclusion: A HRCT scan acts a good preoperative imaging modality for the otologist to predict disease during the surgery and to explain the possible outcomes to the patient.
Keywords: Cholesteatoma, High-resolution computed tomography scan, Mastoidectomy
|How to cite this article:|
Sreedhar S, Pujary K, Agarwal AC, Balakrishnan R. Role of high-resolution computed tomography scan in the evaluation of cholesteatoma: A correlation of high-resolution computed tomography with intra-operative findings. Indian J Otol 2015;21:103-6
|How to cite this URL:|
Sreedhar S, Pujary K, Agarwal AC, Balakrishnan R. Role of high-resolution computed tomography scan in the evaluation of cholesteatoma: A correlation of high-resolution computed tomography with intra-operative findings. Indian J Otol [serial online] 2015 [cited 2020 Sep 25];21:103-6. Available from: http://www.indianjotol.org/text.asp?2015/21/2/103/155294
| Introduction|| |
Acquired cholesteatoma often arises from a postero-superior retraction pocket of the tympanic membrane or as an attic cholesteatoma. Due to expansion, it starts eroding the surrounding structures such as the scutum and the ossicular chain. This occurs probably due to the release of substances by mononuclear inflammatory cells and osteoclasts.  An expanding cholesteatoma can invade the antrum and the mastoid space, eroding additional structures such as the bony facial canal, the tegmen and the lateral semi-circular canal (LSSC).
The role of X-rays in the assessment of a cholesteatoma is very limited. Many views have been described, such as the Schuller's, Stenver's, Towne's, Owen's, and Law's. However, these are only helpful in demonstrating a large cholesteatoma cavity. Subtle changes like ossicular erosion, involvement of hidden areas and erosion of the facial canal and the LSSC are extremely difficult to assess using an X-ray.
High-resolution computed tomography (HRCT) scan of the temporal bone is one of the imaging modalities used to evaluate the extent of a cholesteatoma prior to surgery. A HRCT scan can show the subtle details of a small cholesteatoma.  The sinus tympani and facial recess, known as the hidden areas of middle ear, can be identified in a HRCT temporal bone. Information regarding the status of ossicular chain erosion and erosion of the LSSC and the fallopian canal can also be appreciated by this scan. Studies evaluating the inner and middle ear pathology employ a high-resolution thin-section CT scanning with a slice thickness of 1 mm. The recent refinements of CT scan permit spatial resolution of l.1:0.1 mm. The displayed picture element or pixel has been reduced to 0.25 mm × 0.25 mm × 1.5 mm. The problem with a CT, at present, is, only axial and coronal sections can be obtained.  Sagittal and oblique sections are obtained by reconstruction of the data collected in the horizontal plane using computer software. However, these images are not as good as the direct images. Their quality will improve in the future as the technology evolves.
| Subjects and Methods|| |
This prospective study was conducted in the Department of Otolaryngology and the Department of Radiology of a tertiary care hospital between April 2011 and October 2012. A total of 25 patients who were clinically diagnosed with attico-antral type of chronic suppurative otitis media (CSOM) were included. The exclusion criteria were a chronic co-morbid condition like granulomatous diseases and a history of ear surgery.
The diagnosis of CSOM attico-antral disease was made after a detailed clinical examination of the ear. A preoperative HRCT scan of the temporal bone-axial and coronal sections, using Philips 64 slice Multiplanar CT scanner, was done in all the cases. The findings of HRCT were noted and tabulated. All the scans were evaluated by a single radiologist. These patients then underwent surgery that is, either an inside out or an outside in canal wall down mastoidectomy, depending on the extent of disease and pneumatization of mastoid. All the cases were operated/assessed by the same senior otologist. The intraoperative findings were compared with HRCT scan findings.
The following parameters were compared:
- Scutum erosion
- Tegmen erosion
- Erosion of the facial canal
- Erosion of LSSC
- Ossicular destruction
- Involvement of the facial recess and sinus tympani
- Eustachian tube (ET) involvement
- Soft tissue density in the mesotympanum, attic, aditus and antrum.
The kappa test was used as a measure of reliability to study the correlation between HRCT scan and intraoperative findings.
Based on the kappa value, the level of agreement can be categorized into:
- Poor agreement = Less than 0.20
- Fair agreement = 0.20-0.40
- Moderate agreement = 0.40-0.60
- Good agreement = 0.60-0.80
- Very good agreement = 0.80-1.00.
| Results|| |
In our study, there were a total of 25 patients, 18 males and 7 females. On examination, 19 patients had a postero-superior quadrant retraction pocket with cholesteatoma flakes, and six patients had attic cholesteatoma with pars flaccida perforation.
The results of this study are tabulated in [Table 1]. The sensitivity and specificity of HRCT are shown in [Graph 1].
| Discussion|| |
High-resolution computed tomography scan is better than conventional modalities of radiological imaging in the preoperative diagnosis and assessment of a cholesteatoma. It provides a detailed anatomical picture of the temporal bone and the possible variations in its anatomy. In a preoperative HRCT scan, the presence of a soft tissue density mass in the attic, aditus, antrum or mesotympanum aided diagnosis with a sensitivity of 90-94% and a specificity of 60-70% in studies done by Sirigiri and Dwaraknath,  Mafee et al.,  O'Reilly et al.  and Shaffer et al.  Jackler et al.  and Garber and Dort  though, found it to be less sensitive and specific. In our study, HRCT had a 100% sensitivity value for identifying cholesteatoma in mesotympanum, aditus, mastoid antrum and ET area, and 95.2% sensitivity in the attic region.
A HRCT scan is less sensitive in differentiating a cholesteatoma mass from granulation tissue. Most authors are in agreement with this finding. ,, Mafee et al.  believed that it was possible to identify cholesteatoma by the low attenuation value. Johnson et al.  found that the presence of a well differentiated edge in the mass was a sure indication of cholesteatoma. Bony erosion, an additional sign for the presence of cholesteatoma, was identified in the studies by Jackler et al.  and O'Donoghue.  They found cholesteatoma to be present in 80% of the cases with bony erosion that were explored. Using the same criteria, O'Reilly et al.  detected 23 out of 29 cases of cholesteatoma. We found CT scan having a high sensitivity in detecting the ossicular destruction, except for the stapes. This is in agreement with the studies by Mafee et al.,  Garber and Dort  Jackler et al.  and Swartz.  Using a HRCT, Mafee et al.  were able to define the state of the ossicular chain in 89% of cases and Jackler et al.  in 83% of their cases. In contrast, O'Reilly et al.  could predict an ossicular involvement in only 50% of the cases by a CT scan. In our study, HRCT detected malleus erosion correctly. It was less sensitive for identifying incus and stapes involvement (sensitivity value of 95.5% and 83.3%). The presence of a soft tissue density around the stapes made it difficult in identifying the erosion of this bone. Sirigiri and Dwaraknath,  O'Reilly et al.,  Jackler et al.  and Garber and Dort  were able to diagnose dehiscence in the horizontal part of the facial canal with a 60% sensitivity and 90% specificity. Our study had a sensitivity and specificity of 100% and 91% respectively for this site. The dilemma occurs due to the soft tissue density over the fallopian canal.
Lateral semi-circular canal fistulae were seen in about 10% of cases of unsafe CSOM by Sheehy et al.  Their preoperative recognition may reduce the chances of a dead ear. Bates et al.  and O'Donoghue.  had detected four out of five LSSC fistulae using HRCT scan. In our study, erosion of the LSCC was accurately diagnosed in two cases, and there were two false positive reports. These findings of sensitivity 100% and specificity 91% are comparable to the study of Sirigiri and Dwaraknath.  HRCT had a sensitivity of 100% and specificity of 91% with regards to the detection of tegmen erosion in our study. This finding was similar to a study done by Jackler et al. 
As revision surgeries were not taken into consideration in this study, we had no cases of residual or recurrent cholesteatoma. Magnetic resonance imaging (MRI) scan is superior to HRCT in the detection of residual/recurrent disease. , Postcontrast T1-weighted MRI has been advocated as an effective technique for distinguishing granulation tissue from residual cholesteatoma. Cholesteatomas are avascular and do not enhance following contrast administration, whereas granulation tissue is poorly vascularized and does enhance on delayed images.  Over the past several years, data have been published advocating diffusion-weighted imaging (DWI) for evaluation of residual or recurrent cholesteatoma following the mastoidectomy.  The DWI technique adds a preparation period before the image acquisition that enhances magnetic resonance signal intensity attenuation in response to the diffusion and other spin motion occurring during this period. Although not well understood, cholesteatomas are hyperintense on DWI images compared with cerebrospinal fluid and brain parenchyma. This attribute can also be helpful in a situation when the ear canal is filled with a polyp, making further clinical evaluation difficult.
| Conclusion|| |
The experience of the surgeon and his surgical acumen are the deciding factors in predicting the outcome of an intervention. Yet, a HRCT scan can be a good preoperative tool as it can pick up disease in most of the sites within the middle ear cleft. The identification of stapes erosion and sinus tympani involvement, though, is not predictable on a HRCT. The HRCT acts as a preoperative diagnostic tool for assessment of extent of the disease. It can predict the outcome of the surgery and also helps in discussing these possibilities with the patient.
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