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 cavity has been produced by a cholesteatoma. The cholesteatoma had eroded a considerable amount of the scutum before "burning itself out".