Chapter 16 Mastoidectomy—Intact Canal Wall Procedure
Mastoidectomy can be performed in two ways in cases of cholesteatoma. The canal wall down technique is discussed in Chapter 17. This chapter addresses the canal wall up, or intact canal wall, technique. When the senior author would teach residents and fellows, he would emphasize that the call wall is intact, rather than “up.” The canal wall can be taken down surgically or left intact. The intact canal wall procedure is commonly referred to as canal wall up; however, in this chapter, the nomenclature is intact canal wall. In addition to the technique for intact canal wall, this chapter discusses the evolution of the technique, controversies in regard to intact canal wall versus canal wall down techniques, indications for canal wall down procedures, facial nerve in surgery for chronic ear disease, and management of the labyrinthine fistula.
The common mastoid operations performed for chronic ear infections are defined in this section. Technical surgical variations peculiar to each surgeon do not alter the fundamental classification. The basic classifications have remained unchanged since 1974.1
Radical mastoidectomy is performed to eradicate middle ear and mastoid disease in which the mastoid antrum, tympanum, and external auditory canal are converted into a common cavity exteriorized through the external meatus. This operation involves removal of the tympanic membrane and ossicular remnants, with the exception of the stapes, and does not involve any reconstructive or grafting procedure. Frequently, the surgeon places a plug of soft tissue in the tubotympanum or may lay soft tissue over the middle ear to assist in healing, but this does not alter the name of the procedure. This is an uncommon procedure in the junior authors’ clinical experience.
Modified radical mastoidectomy is performed to eradicate mastoid disease, in which the epitympanum, mastoid antrum, and external auditory canal are converted into a common cavity exteriorized through the external meatus. This technique differs from the radical operation in that the tympanic membrane, or remnants thereof, and ossicular remnants are retained to preserve hearing. (This operation does not involve any reconstructive procedure.) This is an infrequently performed operation in the junior authors’ clinical experience.
Tympanoplasty with mastoidectomy is performed to eradicate disease in the middle ear and mastoid and to reconstruct the hearing mechanism, with or without tympanic membrane grafting. There are three variations of this operation; the classic procedure involves permanent exteriorization of the epitympanum and mastoid, a canal wall down procedure. A different approach is to perform a canal wall down procedure and obliterate the cavity or reconstruct the external auditory canal. The third variation is the intact canal wall procedure, the intact canal wall tympanoplasty with mastoidectomy, which is the subject of this chapter.
Before the mid-1950s, there were two operations for chronic otitis media with cholesteatoma: radical mastoidectomy and modified radical mastoidectomy. These are classic operations that are still indicated, but they are performed infrequently. Their objects are to create a safe ear by exteriorizing the disease and to preserve hearing, if possible.
When tympanoplasty was first introduced by Wullstein2 and Zollner,3 exenteration of the mastoid was the rule. Two problems eventually became apparent. Moisture in the cavity had a deleterious effect on the full-thickness skin used to graft the tympanic membrane, and the narrowed middle ear space created in the classic types III and IV tympanoplasty was prone to collapse, nullifying any hearing improvement (see Chapter 13).
It became apparent that if satisfactory hearing results were to be obtained, some method of avoiding a narrow middle ear space would be necessary. Many investigators thought that the best way of solving this problem was by not creating an exteriorized cavity, but by reconstructing the tympanic membrane in a normal position, and then inserting some type of tissue or prosthetic device to re-establish the sound pressure transfer mechanism (see Chapter 13). Although this concept led to better hearing results, many problems developed over the years, some of which are still seen.
The physicians at the House Ear Clinic began performing intact canal wall tympanoplasty with mastoidectomy in 1958, under the direction of William House.4 By 1961, more than half of all cholesteatoma cases were managed at the House Ear Clinic with an intact canal wall technique. Many revision operations were required for correction of recurrence of cholesteatoma resulting from retraction pockets. As a result, many physicians at the House Ear Clinic reverted to taking the canal wall down and then obliterating the cavity with muscle, based on a procedure suggested by Rambo.5 In 1963, 50% of cholesteatoma cases were managed this way.
By 1964, it was realized that the technique of obliteration did not eliminate the cavity and the problems involved. In addition, the routine use of plastic sheeting through the facial recess in the intact canal wall procedure was reducing the number of cases that had to be revised because of retraction pockets (recurrent cholesteatoma). From that point on, the percentage of cases managed by a canal wall down technique gradually decreased to 10% in 1970. Since then, although there have been fluctuations, on average 15% to 30% of chronic ear surgery is managed by canal wall down procedures.6
The controversy over intact canal wall versus canal wall down centers mostly on safety—safety of the operative procedure and safety over the ensuing years.7 The technical ability of the surgeon also should be taken into consideration. In the surgery of aural cholesteatoma, be it intact canal wall or canal wall down, judgment and technical ability are major factors in the outcome.8 Let us assume that the technical ability and judgment are superior in the two groups. Why is there a difference in opinion as to what is best for the patient?
Are hearing results a factor? Experienced otologic surgeons do not find much difference in hearing results. Surgeons are very careful not to narrow the middle ear space (see Chapter 13) and stage the operation almost as frequently as in an intact canal wall operation (see Chapter 18).
Is there a difference in the healing? Intact canal wall procedures, with lateral surface grafting (see Chapter 9), may take 6 to 8 weeks to heal. Open cavities frequently require 3 to 4 months and occasionally 6 to 8 months, and there is a small percentage that are never free of minor moisture problems.
What about residual and recurrent disease? Some surgeons would argue that a primary canal wall down approach results in one operation, not two. Most experienced surgeons who use intact canal wall and canal wall down procedures find little difference in the incidence of middle ear residual disease, or disease left behind. They also find little difference in the incidence of staging the operation (see Chapter 18).
Recurrent cholesteatoma is a different matter. Recurrent cholesteatoma characteristically results from a posterosuperior retraction pocket,9,10 which occurs only in intact canal wall procedures. Surgeons who have reported a 20% to 40% incidence of recurrent cholesteatoma have failed, with rare exceptions, to stage the operation when indicated (75% of the time), and have failed to use plastic sheeting through the facial recess, even when the operation was being performed in one stage. Advocates of the intact canal wall procedure (surgeons who have had extensive experience) have less than a 5% incidence of recurrent cholesteatoma.
When a cavity is created, it is usually necessary to clean (remove dead skin) every 6 to 12 months for the rest of the patient’s life. Patients who have undergone the intact canal wall procedure need to be seen by the physician only once every year. Precautions relative to not getting water in the ear are necessary 50% or more of the time in canal wall down cases, depending on whether the cavity is healed, how large it is, whether an adequately sized meatus was created, and whether the cavity is round instead of bean-shaped. Finally, an adequate-sized meatus is relevant. If one creates a meatus large enough to have a trouble-free ear and allow water in the ear, the size can pose a problem with fitting a hearing aid, if and when there is a need for the aid in the future. The problem consists of getting a secure fit and preventing feedback. The behind-the-ear aid usually solves this problem and is the best aid for use in an ear that may have some drainage from a cavity.
Mastoidectomy may be indicated in tympanoplasty surgery to eliminate disease, to explore the mastoid to ensure that there is no disease, to enlarge the air-containing middle ear–antral space, or occasionally to create temporary postauricular drainage (with a catheter) in patients with compromised eustachian tube problems or uncontrolled mucosal infection.11 The most common indication is the treatment of cholesteatoma and the associated infection.
What about physicians who recommend at least a cortical (“simple”) mastoidectomy in all tympanoplasties? The rationale seems to be that it is “good practice,” and that “it’s better to be safe than sorry.” There are also arguments, mentioned earlier, that this practice can increase the middle ear cleft space, and that this is a good idea if there is compromised eustachian tube function. The indication for mastoidectomy is based on the clinical history and the appearance of the ear in the physician’s office. The final decision is made during surgery. Radiographs and imaging studies play little part in making the diagnosis or the decision to perform the surgery.
The House Ear Clinic physicians prefer not to create a cavity, but they may do so sometimes. That decision may be made preoperatively, but more often than not, the operation is begun as an intact canal wall procedure, and the decision to exteriorize the mastoid is made intraoperatively.12
The decision to perform a canal wall down procedure is made preoperatively in some cases. This decision is based on the consideration of the hearing in the involved ear, the status of the opposite ear, the preoperative complications, the degree of posterior canal wall destruction by disease, and the age and health of the patient.
With rare exceptions, a cholesteatoma requiring mastoid surgery in an only hearing ear is managed with a canal wall down technique. Usually, the procedure is a classic modified radical mastoidectomy, leaving the middle ear and hearing the way they are. A classic modified radical mastoidectomy may be used in cases in which the affected ear has serviceable hearing, and the opposite ear has a severe uncorrectable impairment. One does not wish to jeopardize the only serviceable ear.
In labyrinthine fistula cases, one may decide before the operation to use a canal wall down operation if the mastoid is small, or if the opposite ear has a cholesteatoma that would require surgery. If the hearing is serviceable, one would probably perform a classic modified radical procedure, particularly in patients in poor health or in elderly patients.12–14
A canal wall down operation may be decided on preoperatively if it can be seen that the cholesteatoma has destroyed a significant portion of the posterior canal wall. If the opposite ear already has a cavity, one may elect to create a cavity in the other ear at the time or surgery. In elderly patients or patients in poor health, we are more likely to use a classic modified radical mastoidectomy—the less done, the better.
Advocates of the intact canal wall procedure generally start the operation in this manner unless the decision has been made preoperatively. If one encounters a very contracted mastoid, particularly with an ear canal slanting up and forward, or if one encounters an unsuspected canal wall destruction, one would not hesitate to take the canal wall. Intraoperative decisions normally (at House Ear Clinic) account for two thirds of the decisions for canal wall down procedures.
The diagnosis of cholesteatoma is based on a well-taken history by the physician and a careful examination of the ear under an operating microscope to confirm ingrowth of skin into the middle ear, the epitympanum, or both. The only routine testing is the hearing test. This test is not related to making the diagnosis, but is done to allow proper counseling. Occasionally, the hearing test results in a change of approach to the surgery, as noted in the preceding section. Radiographs and imaging studies play little part in making the diagnosis or directing the surgical approach. These tests are usually obtained if there is a complication, or if one is considered likely (e.g., semicircular canal fistula, facial paralysis, meningitis, or other intracranial complications).14 Under these circumstances, imaging studies rarely make a difference in the overall surgical approach, but should allow the surgeon to predict any complications or sequelae. The patient and family can be counseled properly and forewarned of problems.
How much, if any, treatment of the draining ear is indicated before surgery? Must the ear be dry before the surgery? If so, for how long? How vigorous should treatment be? Are cultures of the drainage indicated?
In an ear without cholesteatoma (the benign central perforation), local treatment is indicated to obtain a dry ear before surgery (see Chapter 8). It is preferable to have the ear dry for 3 or 4 weeks before tympanic membrane grafting. If the ear is draining at the time of surgery, it is probably best to perform at least an antrostomy through the mastoid cortex to ensure drainage while the tympanic membrane graft is healing.11 It is more likely that a mucosal problem could dictate staging the operation if the ear is still draining at the time of surgery (see Chapter 18).