media and impaired mastoid pneumatization. In this stage of *pre-epider-
mosis* the retracted membrane forms a pouch or sac which becomes filled
with desquamated epithelial cells. As the sac enlarges it becomes further
invaginated into the attic to occupy the spaces of the tympanic cavity in
which secondary infection leads to the stage of manifest disease.
Others are of the opinion that the cholesteatoma is produced by a meta-
plasia of the epithelium of the middle ear cleft as a result of chronic sup-
puration. The theory of metaplasia is more acceptable in cases of prolonged
irritation, i.e. in cases of the secondary acquired type. Acute necrotizing
otitis media may be accompanied by severe loss of tissue of the drumhead.
Healing may occur with migration of squamous epithelium into the middle
ear from the external meatus, particularly when the perforation is marginal,
or the flattened epithelium of the attico-antral area may undergo a meta-
plasia to squamous epithelium as a result of the infection.
Whereas primary acquired cholesteatoma may remain latent for a period
of years, secondary acquired cholesteatoma is easily recognized by its charac-
teristic foul-smelling discharge and the presence of white epithelial debris.
Cholesteatoma is treated by mastoid surgery, as this is the only means
of eradicating the spread of the condition.