Second-look, or “staged,” surgery is a common procedure performed after surgical treatment of middle ear cholesteatoma. It aims at restoring the columellar effect of the ossicular chain and searching for residual lesions of cholesteatoma. In cases of no residual cholesteatoma and fair postoperative auditory function (around 30% of cases), this second-look surgery is useless but remains necessary due to the lack of any tool sensitive enough to detect such lesions.

The development of diffusion-weighted MR imaging provided promising tools to detect residual cholesteatoma pearls. Initially, echo-planar imaging sequences were used, and showed a variable sensitivity for cholesteatoma detection.

In our work, we tried to determine what could be the reasons for such variability. Thanks to the collaboration between our ENT and neuroradiology departments, we evaluated patients before systematic second-look surgery and compared the surgical and radiologic findings, to evaluate EPI sequences against usual sequences and late postenhancement T1 sequences. It appeared that the size of the lesion was the most relevant factor influencing the detection with MRI.

This work raised 2 questions: How could we improve the detection with imaging, and when should we stop the follow-up? Non-EPI sequences appear to have a higher detection rate, detecting lesions with a size as low as 3 mm. However this progress has to be balanced by the fact that the growth rate of residual cholesteatoma is often 1mm/yr, and it may take years for a residual cholesteatoma to reach a significant size.

In our practice, no more second-look surgery is systematically performed if removal of the genuine cholesteatoma was considered complete and if the patient has fair auditory results. We follow patients with T2 and non-EPI DWI every 2 years after surgery, and we consider, based on our experience, that a minimum follow-up of 7 to 8 years is required to rule out the presence of a residual cholesteatoma, especially the invasive forms that can be missed easily on MRI studies.

Our research focuses now on long-term follow-up with non-EPI DWI, to address the question of when the imaging follow-up can be stopped safely; in other words, we are trying to determine when the MRI is sensitive enough to detect residual cholesteatomas, whatever their speed of growth.

 

Read this article at AJNR.org . . .