CT is the modality of choice for the diagnostic assessment of cholesteatoma, due to its ability to demonstrate the fine bony anatomy of the temporal bone. Cholesteatomas appear as regions of soft tissue attenuation, exerting mass-effect and resulting in bony erosion. 

Findings depend on the part of the tympanic membrane that the cholesteatoma arises from: 

• pars flaccida (82%) 
  • superior extension: most common, it expands into Prussak's space, eventually eroding the scutum and displacing the ossicles medially
  • inferior extension : less common, but more frequently seen in children
• pars tensa (18%)
  • posterosuperior (78%): extends medial to the incus and displaces the ossicles laterally
  • anterior and inferior (22%)

The following questions should be addressed in a patient with a cholesteatoma ¹:

• what is the relationship of the mass to the ossicles?
• is the tegmen tympani intact?
• is there potential for fistulisation into the membranous labyrinth?
• is the facial nerve canal eroded by the mass?
• is there opacification of the sinus tympani?