Clinical and Surgical Pitfalls and Tips for Canal WallUp and Canal Wall Down Approaches

It is not the purpose of this essay to go through a step-by-step detailing of the technique of canal wall-up and canal wall-down mastoid surgery. However, based on the author's experience, some very commonly encountered pitfalls are worth considering in both the planning and execution of these techniques.

1. Inadequate surgical objectives: Despite total elimination of cholesteatoma, persistent or recurrent otorrhea may ensue. In cases of chronic active otitis media with cholesteatoma, the principal focus of the operating surgeon may be the cholesteatoma itself. However, it should be recognized that the surrounding reaction, including granulation, suppuration, or sequestration of air cells, in both the mastoid and the middle ear, may result in persistent or recurrent drainage.22 Analysis of failed mastoid tympanoplasty, particularly those without cholesteatoma, provide insight to common locations for residual disease.11'23-25 In my experience, residual suppurative disease occurs commonly in sequestrated tegmental and sinodural cells, mastoid tip, facial recess, and the hypotympanum.23,24

2. Remember the hypotympanum: A common cause for failure of tympanomastoidectomy may be residual disease in the hypotympanum. Despite the name chronic "otitis media," it is commonly assumed that the principal site of persistent otorrhea is infection in the mastoid compartment. Although classic training would suggest that edematous mucosa in the middle ear should be preserved in mastoid surgery and that inflammatory changes will subside during the postoperative period, nevertheless, suppuration in hypotympanic and infralabyrinthine cells may be contributory or, in some cases, is the sole cause of persistent otorrhea, particularly in revision cases.24,26,27

3. Adequate intraoperative exposure is not sufficient, particularly in the canal wall-down technique: Overlooking important ancillary procedures designed primarily for postoperative rather than intraoperative exposure can result in failure. Thus, Sade et al.28 found a direct correlation between persistent postoperative otorrhea and the size of the mastoid cavity, height of the facial ridge, and adequacy of meatoplasty. A high facial ridge may make it impossible to clean the mastoid cavity thoroughly during the postopera-

PREVIOUS CWU

PREVIOUS CWD

Recurrent cholesteatoma with or without otorrhea

CT Scan Revision Tympanomastoidectomy (CWU or CWD)

No cholesteatoma

"Dry" ear

Elective Tympanoplasty (after 6 mos.)

Chronic or recurrent otorrhea

No otorrhea

Recurrent cholesteatoma with or without otorrhea

Revision CWD

with mastoid obliteration

No cholesteatoma (Chronic or recurrent) otorrhea

Bacteriology ^ (including anaerobes)

Bacteriologic Elective Culture Tympanoplasty

Rx with otic topical drops ± oral antibiotic r~

Dry ear

Rx with Topical and oral antibiotics

Persistent or recurrent ^ otorrhea

STSG

Dry ear i

Continued chronic or recurrrent otorrhea

CT Scan

Revision tympano-mastoidectomy CWU or CWD

Persistent or recurrent ^ otorrhea

CT Scan

Revision CWD tympanomastoidectomy with mastoid obliteration

Figure 38-2 Algorithm for management of recurrent chronic otitis media (surgical failure). CWU, canal wall-up; CWD, canal wall-down.

tive period. In chronic otitis media with suppuration, it is probably more important to do a thorough exenteration of residual air cells in the canal wall-down technique than in the canal wall-up approach because the healing phase in the two approaches is fundamentally different. In the canal wall-up technique after complete exenteration of disease, a mucosalized and aerated mastoid air space is the objective. However, in the canal wall-down technique, residual air cells, even if not previously infected, may become subject to suppuration because of surgical sequestration. This is clearly demonstrated in fenestration surgery. In these cases, despite the fact that none had preoperative infection, postoperative residual air cells may become chronically infected due to surgical sequestration of air cells and inability to clean the mastoid cavity because of a high facial ridge or stenotic meatus.

4. Utility of mastoid obliteration: In the canal wall-down technique, obliteration of the mastoid cavity serves several important functions with the objective of achieving a dry ear. Even in the most extensive exenteration, residual air cells that are mucosalized still persist. Although this may not be a problem in the canal wall-up technique, it certainly may become a problem in the canal wall-down technique if these residual air cells become sequestrated and infected. Thus, obliteration prevents surface contamination. Second, a healthy soft tissue layer between bone in the outside world results in a more suitable and stable substrate for skin grafts and healthy skin. Third, hygiene of the mastoid bowl is markedly improved by reducing volume and hidden and troublesome crannies.

5. Remember the limitations imposed by the dysfunctional auditory tube: Most cases with chronic otitis media have abnormal eustachian tube function that will persist after active suppuration has been controlled. As previously stated, an important objective of mastoid surgery is the prevention of recurrent disease, which is best accomplished by altering the anatomy to avoid recurrence of retraction, cholesteatoma, and suppuration. The restoration of normal-appearing anatomy may fall short of achieving this goal. Thus, in limited attic cholesteatoma, in which an anterior atticotomy is all that is necessary to remove the disease, an attempt should be made to prevent re-retraction of the tympanic graft into the attic and aditus, for example, by the use of cartilage grafts.

6. Remember the utility of skin grafting: A mastoid procedure is not fully healed until the canal, tympanic membrane, and bowl, if any, are fully epithelialized with squamous epithelium. It is my practice to use split-thickness skin grafts intraoperatively in almost all cases, in an effort to speed this epithelialization and to lessen the chance of postoperative stenosis and blunting of the anterior angle between the tympanic membrane and the anterior canal wall. In addition, split-thickness skin grafting may be helpful during the postoperative period and, in some cases, may control chronic suppuration in the problematic mastoid bowl. Thus, despite skin grafting used during the course of mastoid surgery, the recipient bed, including exposed bone and an avascular tympanic graft, may not be suitable recipients for a split-thickness skin grafting until a number of weeks postoperatively. In the problematic mastoid bowl, removal of the pyogenic granulation tissue and the application of split-thickness skin grafts, which can easily be done in the office under local anesthesia, may be curative. At the very least, this approach serves to separate those cases in which the infection is superficial from those with sequestrated disease in residual mastoid cells for which revision surgery is indicated.

7. Remember the limitations placed by the histologic changes that occur in the tympanomastoid compartment after longstanding suppuration: Fibrous tissue deposited in the submucosal plane, or "fibrocystic sclerosis," is a consequence of chronic suppuration, and may produce loculation of pneumatized spaces, in both the middle ear and mastoid and limit the reconstructive potential for hearing improvement, especially when this disease occurs in the round window niche.29 Similarly, tympanosclerosis is common in chronic active otitis media. Not only can it produce changes in the tympanic membrane, it may fix one or more of the ossicles.

8. Hearing reconstruction: staged versus unstaged: When the canal wall-up approach is used for chronic otitis media with cholesteatoma, it is the author's practice to perform a second-look procedure approximately 8 to 12 months after the first procedure, as has been advocated by others15'30-32 with the exception of limited middle ear or attic cholesteatoma.33 The added safety of a second-look procedure, however, does not preclude primary reconstruction of the ossicular chain in most cases. Thus, it is unnecessary to commit the patient to months of a large or maximal conductive loss just because a second-look procedure may be indicated at a later time. It is my practice to delay ossicular reconstruction only in certain circumstances, such as cases in which the middle ear mucosa has been replaced by granulomatous disease, in which time is necessary to achieve a mucosalized and aerated middle ear compartment, or in such cases in which the footplate is fixed and stapedectomy will be necessary for hearing reconstruction. When the ossicular chain is incomplete, necessitating an interposition, the author prefers autolo-gous bone grafts, except when the superstructure of the stapes is missing. In such cases, a hydroxyapatite TORP is generally used.

0 0

Post a comment