8.5\ Atresiaplasty

8.5.1\ Discussion

Atresiaplasty consists of creating an external auditory canal and tympanic membrane in order to restore hearing in selected patients with congenital external aural atresia. An opening is drilled through the atresia plate, a new tympanic membrane is usually created using temporalis

Fig. 8.6  Atresiaplasty. Preoperative axial (a) and coronal (b) CT images show bony atresia of the left external auditory canal with intact ossicles. Postoperative axial (c) and coronal (d) CT images show interval resection of the atretic plate and partial mastoidectomy, resulting in a passage that communicates with the exterior and neotympanic membrane

fascia, and the external auditory canal is often lined with split-thickness skin grafts (Fig. 8.6). Complications of the procedure include external auditory canal restenosis, lateralization and perforation of the tympanic membrane, ossicular chain refixation, sensorineural hearing loss, facial nerve injury, and cholesteatoma, usually in the created external auditory canal, which appears as globular soft tissue on CT, sometimes with associated bone erosions (Fig. 8.7).

a

b

c

d

Fig. 8.6  (continued)

Fig. 8.7  Cholesteatoma after atresiaplasty. Coronal CT image shows soft tissue material (arrow) within the surgically created external auditory canal, which proved to be a cholesteatoma. There is also scar tissue that tethers the ossicular prosthesis in an abnormal position

8.6\ Myringotomy

and Tympanostomy Tubes

8.6.1\ Discussion

Tympanostomy tubes (pressure equalization tubes) are commonly used to treat the manifestations of Eustachian tube dysfunction including recurrent acute otitis media or chronic otitis media with effusion by providing an alternative outlet for middle drainage and intratympanic pressure equalization via the external auditory canal. Tube placement follows myringotomy, in which an opening is made in the tympanic membrane. Tympanostomy tubes are available in a variety of shapes, sizes, and materials, including plastics and metals, which are readily apparent on CT (Figs. 8.8, 8.9, and 8.10). However, the presence of fluid or malpositioning may make identification of these tubes difficult. The tubes may be found incidentally on CT. Thus, recognizing tympanostomy tubes on imaging is important­ as to

not confuse these with unintended foreign bodies or ossicular dislocation. CT may also be performed to confirm the presence of tympanostomy tubes that are not readily visible on physical exam and to evaluate for suspected complications, such as persistent effusions within the middle ear or mastoid, cholesteatoma, or diffuse tympanosclerosis (Fig. 8.11). Occasionally a tube may be detected in the middle ear space due to a rare incidence of medial migration, but more often a result of accidental loss of a tube within the middle ear during placement. Tympanostomy tubes are normally expelled spontaneously from the tympanic membrane after 3–24 months (Fig. 8.12) depending on the design and shape of the particular tube utilized. The main complications of tympanostomy tubes include formation of a foreign body granuloma on the tympanic membrane immediately adjacent to the tube or chronic otorrhea due to unresolved underlying chronic otitis media or mastoiditis.

Fig. 8.8  Plastic grommet. Axial CT image shows a Teflon grommet appropriately situated across the tympanic membrane

Fig. 8.9  Metal grommet. Axial CT image shows a metal grommet in the tympanic membrane

Fig. 8.10  Plastic shaft tympanostomy tube. Coronal CT image shows a long shaft Teflon tube (arrow)

Fig. 8.11  Medial dislocation of tympanostomy tube. Axial CT image shows a tympanostomy tube in the hypotympanum (arrow). Note the myringotomy, which appears as a gap in the tympanic membrane

Fig. 8.12  Extrusion of tympanostomy tube. Axial CT image shows a tympanostomy tube in the external auditory canal (arrow)