Is an isthmus block a prerequisite for the development of an attic retraction cholesteatoma?

Computed tomography (CT) was used to investigate whether an isthmus block was present in 57 cases with attic retraction cholesteatomas. A ventilation route between the mesotympanum and attic was considered to exist in 30% of the cases and occurred predominantly in those ears with a cholesteatoma that did not extend into the antrum. Four cases were also found to have this ventilation route in CT scans taken before and after the development of cholesteatoma. These findings suggest that an isthmus block is not a prerequisite for the development of an attic retraction cholesteatoma.