Chapter 9 The goal of modern otologic surgery is to maintain or restore normal anatomy. This maxim, however, sometimes persuades surgeons performing tympanomastoid surgery to do anything to leave the canal wall intact, despite the fact that there are clear intraoperative reasons for removing it. First and foremost, in most patients having chronic otitis media with cholesteatoma, the mastoid cell system is usually significantly sclerotic, and therefore a properly done canal-wall-down (CWD) procedure results in a small, manageable mastoid bowl to maintain. Second, middle ear grafting is more than possible with a CWD procedure together with reconstruction of the middle ear and transformer mechanism when indicated and when feasible. Third, in ears with extensive cholesteatoma where disease itself and anatomic constraints indicate the need for a CWD procedure, residual disease usually results when the surgeon persists in attempting to remove disease with the wall intact. Additionally, in certain situations (for instance, low-hanging middle fossa tegmen), complications such as injury to the tegmen and dura and/or sigmoid sinus can occur when attempts are made to remove disease without removing the canal wall. The controversy continues and was discussed in two landmark papers by Sade1 in 1987 and Paparella et al2 in 1989. Three distinct periods in the evolution of mastoidectomy are outlined. In the 1950s, surgery for cholesteatoma usually resulted in radical mastoidectomies. In the 1970s, canal-wall-up operations became very “fashionable,” and otologic surgeons are now performing more CWD operations. Another controversy continues regarding the management of cholesteatoma in the pediatric age group, and the options have been well debated in the literature.3–9 The consensus, with which I agree, is to perform canal-wall-up operations in most children. The following are indications to remove the wall to accomplish a modified radical mastoidectomy. This option is defined as exteriorizing the ear canal with the mastoid while maintaining or grafting the middle ear space. 1. Large, bony defect. A large, bony attic defect or a posterior superior bony defect is almost always caused by cholesteatoma. In removing disease from such a defect, additional bone is usually curetted from its margin, thus further enlarging the defect. If a decision is then made to leave the wall intact (and in view of the fact that continued eustachian tube dysfunction is a given), then attic retraction, despite measures such as bone or cartilage graft placement, will usually occur. Therefore, in these situations the wall should be removed. 2. Extensi v e disease. This is another important reason for removing the canal wall. In a sclerotic mastoid, the middle fossa tegmen is always low and the surgeon’s ability to remove cholesteatoma from any part of the epitympanum (particularly anteriorly in the sinodural angle) will result in two common problems: injury to the tegmen and/or dura with cerebrospinal fluid (CSF) leak and bleeding, or thinning and eventual penetration of the superior part of the bony canal wall. A second site where disease is difficult or impossible to remove is in the facial recess. Even with removal of the incus and enlarging the facial recess, disease can be trapped on both sides of the superior part of the recess with resulting difficulty in total removal. Doing extensive facial recess enlargement can result also in a retraction pocket. 3. Recurrent disease. A new attic retraction pocket with disease following a previously performed canal-wall-up procedure should have a CWD operation. 4. Lateral semicircular canal fistula in the only hearing ear. This is an absolute indication for removing the canal wall in surgery for chronic otitis media. It is often, but not exclusively, a situation in an older patient who has no hearing in the opposite ear due to an earlier childhood event affecting that ear. These patients present with dizziness, positive fistula testing, large cholesteatomas, and strong evidence clinically and radiographically of a lateral semicircular canal fistula. There is often no measurable hearing in the other ear, and the hearing in the available ear often has compromised sensorineural components due to the fistula and because of the age of the patient. The best surgical strategy in these patients is to clean the middle ear in the usual manner and then graft it, and then upon exploring the mastoid, remove the canal wall and leave the squamous epithelium or matrix over the lateral canal fistula. In patients with good to normal hearing in the opposite ear, different strategies can be pursued, including lifting up the matrix and repairing the canal directly and then lining the area with fascia and then leaving the canal wall up. In instances where there is no hearing in the opposite ear, it is absolutely mandatory to avoid exposing the fistula and instead leave it covered with the matrix.
CANAL-WALL-DOWN MASTOIDECTOMY
INDICATIONS FOR CANAL-WALL-DOWN MASTOIDECTOMY
PROCEDURE
PREOPERATIVE EVALUATION
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