A retraction pocket is to be differentiated from the common and usually benigh simple retracted tympanic membrane, which is often detected in a child with a simple upper respiratory infection.
A retraction pocket is to be differentiated from the common and usually benign simple retracted tympanic membrane (TM), which is often detected in a child with a simple upper respiratory infection. Inflammation from Eustachian tube (ET) dysfunction, chronic otitis media, or both may cause a weakening of the collagen fibers in the lamina propria of the TM.1 This produces a circumscribed round or oval-shaped atrophic area of the TM, the foundation for the development of a progressive retraction pocket.
Tympanic membrane retraction pockets are invaginations of a weakened circumscribed portion of the TM. Most retraction pockets occur in the posterior superior quadrant of the pars tensa, behind the posterior malleolar fold of the pars flaccida. The next most common location is in the pars flaccida itself (Shrapnell's membrane), and a small number are located in the inferior half of the pars tensa.2
Once a retraction pocket develops and persists, there may be a dynamic progression. This can lead to destruction of middle ear ossicles, chronic otitis media, and/or the development of a cholesteatoma.
TYPES AND STAGING
Retraction pockets can be classified according to a modification of the classification of Sade.5 A stage 1 pocket is a mobile retraction pocket located in the posterior superior quadrant of the pars tensa that may, in time, touch the incus. A stage 2 pocket is a pars tensa retraction pocket that is adherent to the incus or a pars flaccida retraction pocket that touches the head and neck of the malleus part of the epitympanic (scutum) osseous border. A stage 3 pocket is a pars tensa deep retraction pocket that is in the inferior half of the TM and touches the promontory of the temporal bone. A stage 4 retraction pocket is located in the posterior superior quadrant of the pars tensa and is firmly adherent to the lenticular process of the incus (incudopexy) or to the incudostapedial joint.