Where do cholesteatomas typically arise
A cholesteatoma is squamous epithelium that is trapped in the skull base, often creating expansion and erosion of adjacent bony structures. They frequently occur in the middle ear, in the mesotympanum or epitympanum. Cholesteatomas may be congenital, in which case they are well defined and rounded and typically occur near the level of the tympanic membrane (the anterior mesotympanum). Cholesteatomas may also be acquired as a result of tympanic membrane perforation, in which case they typically occur above the tympanic membrane (the epitympanum), adjacent to the scutum and involve Prussak’s space. CT is often helpful in defining whether there are effects on adjacent bony structures. Radiologists should comment on the integrity of the ossicles, erosion of the scutum, the presence or absence of labyrinthine fistulas, or defects in the roof of the middle ear (tegmen tympani). MRI is not as helpful for evaluating bony structures, but it may be an important problem-solving tool if there are questions concerning intracranial extension and may demonstrate restricted diffusion, helping to differentiate it from simple fluid/effusion.