Imaging description

Cholesteatoma is a unique, mass-like, destructive and expansile soft tissue lesion of the middle ear, which is a sequela of the reparative process of a perforated tympanic membrane. The stratified squamous epithelial tissue, while attempting to heal the perforation, leads to a ball of exfoliated keratin material surrounded by granulation tissue with lytic enzymes [1].

Pars flaccida cholesteatoma is considered primary cholesteatoma. It begins in the posterosuperior portion of the tympanic membrane, which is more susceptible to infections, and is situated superior to the lateral process of malleus. Pars flaccida accounts for about 80% of all acquired cholesteatomas. It is usually seen in Prussak’s space, associated with blunting of scutum, and extends medially to the posterior part of epitympanum and mesotympanum (Fig. 65.1).

Pars tensa cholesteatoma accounts for 10–20% of all acquired middle ear cholesteatomas and is considered secondary acquired cholesteatoma. It is generally seen in relation to the lower two-thirds of the tympanic membrane, at the site of perforation or retraction pocket at the pars tensa portion of the tympanic membrane. It is seen as a soft tissue mass in the posterior mesotympanum, situated medial to the ossicles, and may involve the region of sinus tympani, facial nerve recess, and aditus ad antrum (Fig. 65.2). Erosion of auditory ossicles, especially the long process of incus and superstructure of stapes, is common. It is locally aggressive, and erosion of the adjoining bony structures and auditory ossicles is both characteristic and diagnostic [2].