Cholesteatoma vs granulation tissue: a differential diagnosis by DWI-MRI apparent diffusion coefficient

To diagnose cholesteatoma when it is not visible through tympanic perforation, imaging techniques are necessary. Recently, the combination of computed tomography and magnetic resonance imaging has proven effective to diagnose middle ear cholesteatoma. In particular, diffusion weighted images have integrated the conventional imaging for the qualitative assessment of cholesteatoma. Accordingly, the aim of this study was to obtain a quantitative analysis of cholesteatoma calculating the apparent diffusion coefficient value. So, we investigated whether it could differentiate cholesteatoma from other inflammatory tissues both in a preoperative and in a postoperative study.

This study included 109 patients with clinical suspicion of primary or residual/recurrent cholesteatoma. All patients underwent preoperative computed tomography and magnetic resonance imaging with diffusion sequences before primary or second-look surgery to calculate the apparent diffusion coefficient value.

We found that the apparent diffusion coefficient values of cholesteatoma were significantly lower than those of non cholesteatoma. In particular, the apparent diffusion coefficient median value of the cholesteatoma group (0.84 × 10^- 3 mm²/s) differed from the inflammatory granulation tissue (2.21 × 10^- 3 mm²/s) group (p < 2.2 × 10^- 16). Furthermore, we modeled the probability of cholesteatoma by means of a logistic regression and we determined an optimal cut-off probability value of ~ 0.86 (specificity = 1.0, sensitivity = 0.97), corresponding to an apparent diffusion coefficient cut-off value of 1.37 × 10^- 3 mm²/s.

Our study has demonstrated that apparent diffusion coefficient values constitute a valuable quantitative parameter for preoperative differentiation of cholesteatomas from other middle ear inflammatory diseases and for postoperative diagnosis of recurrent/residual cholesteatomas.