chronic suppurative otitis media

CHOLESTEATOMA
T.H.J.Lesser
A cholesteatoma is a three-dimensional epidermal structure exhibiting independent growth, replacing
middle-ear mucosa, resorbing underlying bone and tending to recur after removal. Put more simply, it is
‘bad skin in the middle-ear cleft’. The incidence is approximately 10 cases per 100 000 per annum.
Classification
Cholesteatoma can be classified into congenital and acquired types. These are distinct pathological entities.
1. Congenital cholesteatoma. Congenital cholesteatoma has been shown by Michaels to be the result of
the persistence of a small nidus of epidermoid ectoderm that occurs in the first trimester in the normal fetus
and is normally resorbed. It usually manifests itself as an anterior attic pearl behind an intact drum in the
first year or so of life. It may present later in childhood with extensive disease in an often cellular mastoid.
2. Acquired cholesteatoma. There is no definitive classification of acquired cholesteatoma, but it can be
divided into three groups with reference to the tympanic membrane.
(a) Primary acquired cholesteatoma associated with a defect in the pars flaccida.
(b) Secondary acquired cholesteatoma associated with a defect in the pars tensa.
(c) Tertiary acquired cholesteatoma exists behind an apparently normal eardrum as a result of implantation
or previous middle-ear infection.
Aetiology
There are a number of well-established, but unproven, theories regarding the aetiology of cholesteatoma.
1. Primary acquired cholesteatoma. This is the most common.
(a) The single most important fact about the skin of the eardrum is that in health it migrates from the centre
of the drum outwards along the external ear canal, carrying keratin and wax debris with it. Therefore
this skin is self-cleaning. Negative middle-ear pressure tends to pull the pars flaccida into the attic and
may form a retraction pocket. Although initially self-cleaning, the epithelium eventually loses its
capacity to migrate out of the pocket and is trapped. The pocket fills with epithelial debris, which in
turn becomes infected and further expands under tension. As it expands the isthmus tends to narrow,
compounding the problem and continuing the cycle.