THE VALUE OF MRI DIFFUSION WEIGHTED IMAGES IN PREOPERATIVE AND POSTOPERATIVE ASSESSMENT OF CHOLESTEATOMA

Abstract

Cholesteatoma is a common middle ear pathology that can be congenital or acquired. It may cause serious complication such as hearing loss, facial nerve paralysis or intra-cranial complications in advanced cases. It is mainly diagnosed by otologic examination yet CT examination is essential to confirm the diagnosis in some cases as well as assess its extensions for proper surgical excision. However, CT is poor in differentiation of cholesteatoma from other middle ear pathologies e.g. cholesterol granuloma or granulation tissue in post-operative setting. MRI examination was advocated to confirm the diagnosis of cholesteatoma and differentiate it from post-operative granulation tissue. Delayed post contrast T1 images were used but showed low sensitivity for smaller lesions as well as patient inconvenience due to delayed imaging after 30-45 minutes. In recent years, diffusion weighted sequences have been used in diagnosis of cholesteatoma due to its bright signal on DWIs. Investigators have used a wide range of techniques from traditional spin-echo EPI-based to TSE-based techniques such as HASTE and BLADE. In our study we used thin cut multi-shot EPI diffusion weighted images in the assessment of cholesteatoma suspected clinically or by CT examination or known patients with cholesteatoma with suspected post-operative recurrence. It showed good sensitivity and excellent specificity in detection of cholesteatoma when compared to intra-operative and/or follow up findings yet it could not detect lesions smaller than 4 mm. The use of multi-shot techniques improved its sensitivity compared to single shot images yet it is still relatively less than non-EPI techniques.