Diseases Of The Nose Throat And Ear

CHRONIC SUPPURATIVE OTITIS MEDIA 329

occurs as two histological types, epidermoid cholesteatoma and cholesterol
granuloma.

Epidermoid cholesteatoma consists of a matrix of keratinizing stratified
squamous epithelial cells from which masses of squamous epithelial cells
are cast off to form a smooth glistening cystic swelling initially occupying
the attico-antral region. The contents of the swelling accumulate, and as
cholesteatoma expands osteitis and bone absorption occur. It is unlikely

Fig. 169. Removal of aural polypus with the cold wire snare.

that pressure of cholesteatoma alone is sufficient to cause erosion of bone,
but the exact process is not known. It is, however, a fact that the erosion
exposes other vital structures, infection of which leads to intracranial
complications.

Cholesterol granuloma is identified microscopically by the presence of
cholesterin crystals surrounded by foreign body giant cells in fibrous granu-
lation tissue. Blood pigments may be present and the dark coloured viscid
secretion has been encountered in mastoid air cells, generally in children.
There is often a discoloration of the tympanic membrane referred to as
'blue drum'.

PATHOLOGY, (i) Congenital cholesteatoma may arise from an embryonic
rest in any of the bones of the skull. It may occur in the petrous bone as a
primary epidermoid tumour and by its growth it will eventually break
through to the middle ear cleft from which it becomes infected. It is not
considered that the congenital origin is likely to be more than a very rare
cause of attic cholesteatoma. (ii) Acquired cholesteatoma. A distinction is
made between primary acquired cholesteatoma which arises in the attic or
in the posterosuperior part of the middle ear without previous history of
otitis media, and secondary acquired cholesteatoma occurring in ears which
are or have been the seat of chronic infection of which there is clinical
evidence.

Most otologists believe that ingrowth of epithelium from the external
auditory meatus or the outer surface of the drumhead is the cause of acquired
cholesteatoma. -In the primary type the preliminary stage is characterized by
indrawing or retraction of the membrane flaccida into the attic. The pre-
disposing cause of the retraction is thought to be the negative pressure in
the attic resulting from Eustachian tube dysfunction, non-suppurative otitis