Conclusions: Acquired middle ear disease, including cholesteatoma, can follow surgical removal of CC, and long term follow up of all patients is required. Factors at initial evaluation indicative of risk of AC include a significant air-bone gap, otitis media with effusion in the contralateral ear and a smaller mastoid cavity ratio. The use of composite grafts at the time of CC surgery should be considered. Additionally, our findings suggest that the mastoid volume plays a causative role in the development of AC. (C) 2010 Elsevier Ireland Ltd. All rights reserved.