الفهرس 
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Abstract
Cholesteatoma arises from squamous epithelium in the ME or mastoid cavity, which erodes the structures of the middle and inner ear and has a high rate of recurrence. Cholesteatoma is commonly diagnosed clinically and managed surgically, but radiology can help define the disease extent and plan for surgery.
While HRCT is beneficial in defining bony anatomy, it has restrictions in distinguishing cholesteatoma from granulation tissue. This is the reason that otologists search for different modalities for better assessment of the different kinds of pathological lesions that can be present in the ear.
The use of diffusion weighted magnetic resonance imaging (DW MRI) has became increasingly been used in clinical practice for diagnosis of primary and recurrent cholesteatoma, in particular, Two DWI techniques for detecting cholesteatoma have been used; (EPI DWI) and (Non-EPI DWI).
This work aimed to predict middle ear cleft cholesteatoma preoperatively by using DW-MRI and HRCT Scans in a random population and compare it with the intraoperative findings
The cholesteatoma is eradicated from the temporal bone by surgical resection by either radical or modified radical mastoidectomy.
A major disadvantage is the narrow surgical field, a feature that is associated with a high rate of residual and recurrent cholesteatomas.
Diagnosis of recurrent cholesteatoma in an operated middle ear cavity may be difficult.
DWI techniques allow highly specific diagnosis of cholesteatoma, an which may be not possible with CT or conventional MR imaging techniques.
Non-EPI DWI combines the high specificity of DWI for keratin-containing lesions with a high sensitivity for detection of small lesions.
Forty patients were included in this study (28 female and 12 male), of them, 26 cases with de novo disease and 14 cases with recurrent disease.
All patients in this study were subjected to history taking, physical examination, audiological and radiological assessment (HRCT and DW MRI)
These patients were clinically suspected to have primary or recurrent cholesteatoma and EPI diffusion weighted MR imaging sequence was applied to all patients and then compared with the operative results.
The validity of diffusion in prediction of cholesteatoma, with accuracy (81%, 78.5%), sensitivity (83%, 80%), specificity (75%, 75%), PPV (88%, 89%), NPV (67%, 66%) for de novo and recurrent cases respectively. The advances in MRI techniques are currently changing the preoperative evaluation and the postoperative follow-up protocols for cholesteatoma. DW MRI appears to be an accurate method, as opposed to a standard second-look operation, for the follow-up of patients who have undergone a tympanomastoidectomy for treatment of cholesteatoma.
Conclusion
It is important to realize that both EPI and non-EPI based diffusion-weighted sequences may fail to detect cholesteatoma matrix in a retraction pocket in the absence of keratin, as it is the keratin which gives rise to hyperintense signal seen in diffusion-weighted MR scans Diffusion-weighted MR sequences are very sensitive to motion, such as head movement, small molecular motion and micro-movement of the brain tissue due to blood pulsations, these can give rise to phase errors, ghosting and motion artefacts. However, some of these errors can be minimized with reducing scan times and patient preparation with good immobilization, Images in the coronal planes are superior as they display fewer air–bone artefacts at the skull base. It is clear that DW EPI has a role in the visualization of the usually quite large recurrent or relapsing cholesteatoma. Its value in the evaluation of residual cholesteatoma in pre-second-look ears, however, is limited due to the often very small size of these residual cholesteatoma pearls. On the base of our results, we conclude that DWI has an important role in the evaluation of primary acquired middle ear cholesteatoma.
Non-echoplanar DW-MRI provides a much higher-quality image of the petrous bone than echo planar imaging but is not free of artifacts, Image distortions mainly occur in phase encoding direction and may even influence the appearance of a large cholesteatoma. In a small number of patients, over- as well as under estimations of the size have been reported.
Additional improvement of anatomical correlation can be achieved by digital fusion of MR and CT images Non-EPI DWI MRI has been proposed for the reliable detection of smaller cholesteatoma. Non-EPI DWI can detect residual and/or recurrent cholesteatomas with a size limit as small as 2 mm, even if surrounded by inflammation. Mural cholesteatoma are a frequent cause of false negative results, Cholesteatoma may lose their keratin contents because of auto-mastoidectomy or evacuation at the physician’s office, leaving an empty retraction pocket. However the remaining epithelium covering the cavity retains its aggressive potential, In these cases, DW images may be falsely negative since no keratin content persists. Also a possible explanation for FN or FP results on MRI may be inflammation and autoevacuation. Inflammation may destroy squamous cells and alter the DW image, Autoevacuation is a process described in the literature in which debris at least temporarily may drain through the outer ear canal Whether MRI should be performed in a second-look situation depends on the clinical evaluation and the expected size of a possibly hidden residual cholesteatoma. In accordance with the literature, a cholesteatoma less than 2 to 5 mm cannot be detected reliably by MRI, Therefore, MRI may not be sensitive enough to replace second-look surgery too soon after the primary surgery. At last, there were some limitations to our study:
1- First, we are reporting our initial experience in the role of the diffusion in diagnosis of cholesteatoma. 2- Second, the relatively shortage of resources and cost of DW-MRI that was available for collection of patients who fulfill inclusion criteria. This needs further study with a larger number of patients.
3- Third, DWI in the head and neck was still limited by technical problems with regard to susceptibility artifacts and low spatial resolution. Technical developments of DWI sequences with advanced coils in the field of >_3T MRI could overcome these
disadvantages.
4- Increase b value (b= 0 and 1000) which may affect measured ADC.
5- Artifact from air in the head may cause difficult to measures ADC in small lesion.
6- Poor anatomical delineation of ADC map.
7- Qualitative method depend on experience and efficiency of the radiologist.