Chapter 14 Canal Wall Reconstruction Tympanomastoidectomy
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The primary goal in the surgical management of chronic otitis media with cholesteatoma is the creation of a dry, safe ear through removal of disease and the alteration of anatomy to prevent recurrence. This goal can be accomplished effectively with preservation (canal wall up) or removal (canal wall down) of the posterior canal wall, both of which are described in other chapters 16 and 17. This chapter describes the technique of canal wall reconstruction tympanomastoidectomy with mastoid obliteration. Canal wall reconstruction tympanomastoidectomy combines elements of the canal wall up and canal wall down procedures to optimize surgical exposure for removal of disease, and creates a blockage of the attic that prevents recurrence of retraction pockets and recurrence of cholesteatoma.
Many authors have described reconstruction of the posterior canal wall and mastoid obliteration using various methods, including composite osteoperiosteal flaps,1 composite cartilage/titanium grafts,2 ceramic alloplasts,3–7 bone pâté,8–10 costal cartilage,11 and bone cements.12–14 Canal wall reconstruction tympanomastoidectomy with mastoid obliteration was originally described by Mercke in 1987.15 Important modifications to the Mercke technique have been have been published by the senior author16 and are described in detail in this chapter.
ADVANTAGES AND DISADVANTAGES OF CANAL WALL UP AND CANAL WALL DOWN TECHNIQUES
Canal wall down tympanomastoidectomy is the gold standard for surgical management of cholesteatoma.17,18 The enhanced exposure to the attic, antrum, and middle ear afforded by removal of the posterior canal wall provides for optimal visualization and removal of disease in cases of extensive cholesteatoma. Removal of the canal wall and lateral attic also prevents retraction and recurrent cholesteatoma formation. In addition, all nitrogen-absorbing mucosa of the mastoid cavity and epitympanum is removed, and ultimately is replaced by stratified squamous epithelium after healing has occurred. When performed properly, the canal wall down procedure can result in a recidivism rate of 2%.17
Preservation of the posterior canal wall in cholesteatoma surgery has many advantages, including the elimination of the need for periodic cleaning and avoiding the need for water restrictions. The recidivism rate has been reported to be 36% in adults and 67% in children,19 however, higher by many reports than the incidence of recurrent disease seen with canal wall down procedures.18,20 The high rate of recidivism seen in canal wall up procedures can be due to numerous factors. First, exposure of the attic, antrum, and facial recess is more limited in canal wall up procedures compared with canal wall down approaches, which may lead to difficulty in complete removal of all involved air cell tracts and elimination of cholesteatoma at the initial procedure. Second, the epitympanum and mastoid cavity are ultimately relined with nitrogen-absorbing cuboidal mucosal epithelium after canal wall up procedures. The presence of this nitrogen-absorbing mucosa is thought to lead to negative middle ear and mastoid pressures, especially when continued inflammation with associated hypervascularity affects the mucosal layer.21 This large surface area of nitrogen-absorbing epithelium along with underlying eustachian tube dysfunction can lead to progressive retraction of the tympanic membrane postoperatively, and ultimately to recurrence of cholesteatoma.16 Eustachian tube dysfunction exacerbates this scenario in children.
