During the surgical excision of cholesteatoma, it is sometimes necessary to produce a mastoid cavity to excise all of the cholesteatoma extending into the mastoid bone. A mastoid cavity is found posteriorly in the ear canal and resembles a widening of the posterosuperior part of the canal. The cavity may become filled with wax or become infected.
This mastoid cavity is self-cleaning. The lateral semicircular canal can be seen clearly in the centre of the image. The residual tympanic membrane is significantly retracted and the head of the stapes can be seen.