Learning Objectives: - Know the value of CT (CBCT) and non-EPI DWI in the diagnosis of cholesteatoma - Be familiar with the cholesteatoma mimickers and know how to avoid false positive and negative results - Be aware of the strenght of MR in the post-operative follow-up.
For many years CT was the only available technique. Its accuracy was however low as it failed to visualise new and residual lesions in partially or completely non-aerated middle ears and post-operative cavities.
Characterization of lesions in the middle ear with MR became possible in well-, partially- and non-aerated middle ears. Cholesteatomas do not enhance, scar tissue and/or granulation tissue in postoperative cavities sometimes enhances only after 30 to 40 minutes. Therefore scar tissue can only be distinguished on contrast-enhanced T1W images made 45 minutes after contrast injection. However this technique is time consuming and requires gadolinium injection and false positive and negative results were reported.
Cholesteatomas have a very characteristic high signal intensity on non-EPI DWI images. High resolution non-EPI DWI is able to detect lesions down to 2 mm. False negatives are rare and are due to movement or metal artefacts, auto-evacuation etc.
Studies showed that non-EPI DWI is the only sequence needed, making cholesteatoma screening very short (< 8 min.) and obviating the need for contrast materials.
After CWU surgery, the bony walls of the EAC are still intact and therefore post-operative clinical inspection is limited. Hence the need for imaging to detect residual cholesteatoma.
The value of this technique is even more crucial in patients who were treated with a “bone obliteration technique” or “mastoid/middle ear/external auditory canal exclusion technique”. Post-operative inspection or second look surgery is not a real option in these patients. The accuracy of pre- and post-op non-EPI DWI is high is therefore replacing CT and second look surgery throughout the world. Finally today excellent software is available which allows matching of non-EPI DWI and Cone Beam CT images. These images provide the surgeon with all necessary information in one 3D image series. All the above will be discussed and illustrated during this presentation.
