Canal Wall Reconstruction Tympanomastoidectomy

Advantages And Disadvantages Of Cwu And Cwd Techniques

CWD tympanomastoidectomy is the gold standard for the surgical management of cholesteatoma. ^, The enhanced exposure to the attic, antrum, and middle ear afforded by removal of the PCW provides for optimal visualization and removal of disease in cases of extensive cholesteatomas. 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 are removed and will ultimately be replaced by keratinizing stratified squamous epithelium after healing has occurred. When performed properly, the CWD procedure can result in a recurrence rate as low as 2%.

The disadvantages of the CWD technique include the accumulation of debris in the mastoid cavity, necessitating periodic debridement and, potentially, the need for ongoing water restrictions to help avoid bowl infections. Furthermore, the middle ear space that results after CWD is narrower than that after CWU, which can make ossicular reconstruction more difficult. However, if the eustachian tube fails to function, the hearing results are similar with CWD and CWU. The wide meatoplasty that is a critical component in the CWD technique can present difficulties in the placement of a hearing aid and may have an unacceptable aesthetic appearance to some patients.

Preservation of the PCW in cholesteatoma surgery has a number of advantages, including the elimination of the need for periodic cleaning and avoiding the need for water restrictions. However, the recurrence rate has been reported to be as high as 36% in adults and 67% in children, higher by many reports than the incidence of recurrent disease seen with CWD procedures. ^, The high rate of relapse seen in CWU procedures is due to a number of factors. First, the exposure of the attic, antrum, and facial recess is more limited in CWU procedures than it is with CWD approaches, which may lead to difficulty in complete removal of all the involved air cell tracts and elimination of cholesteatomas at the initial procedure. Second, the epitympanum and mastoid cavity are ultimately relined with nitrogen-absorbing cuboidal mucosal epithelium after CWU 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. This large surface area of nitrogen-absorbing epithelium, along with underlying eustachian tube dysfunction, can lead to progressive retraction of the tympanic membrane (TM) postoperatively, and, ultimately, to the recurrence of cholesteatoma. Eustachian tube dysfunction exacerbates this scenario in children.

Rationale For The Cwr Approach

CWR tympanomastoidectomy with mastoid obliteration is a technique where the PCW is removed en bloc, using a microsagittal saw to provide CWD-like exposure and ensure optimal visualization, aiding complete elimination of disease. The canal wall is replaced after the disease has been removed. The attic and mastoid cavity are then isolated from the middle ear using pieces of cortical bone and obliterated using bone pâté. Replacement of the PCW allows for the preservation of near-normal middle ear anatomy, which can aid with ossicular reconstruction and avoid the need for routine cavity cleanings. Furthermore, physically blocking the attic and mastoid cavities prevents reretraction of the TM by eliminating the negative pressure associated with a nitrogen-absorbing mucosa lining the cavity, as well as limiting TM retraction into the middle ear only.

The CWR approach seeks to achieve the low recurrence rates of the CWD approach gained by improved operative exposure, while maintaining the benefits of an intact canal. Our results suggest that this is achievable. Reports of the rate of recurrent cholesteatomas after intact canal procedures vary (16% to 61%); however, they are accepted as being higher than CWD procedures (7% to 19%), which vary based on the age of the patient and length of follow-up. In a publication of the senior author’s experience with CWR, 253 ears underwent surgery and returned for a “second-look” operation. Of these, recurrence of cholesteatoma was noted in 13% of ears (limited to the middle ear) and all ears went on to have ossicular chain reconstruction. Between 1997 and 2011, 272 ears were followed after CWR; of these, retraction was found in 14%. Originally, Mercke described placing small bone chips to block the attic. The reretraction rate improved when the surgical technique was altered by replacing the small chips with a large cortical bone block from the mastoid tip, used to obliterate the epitympanum (from 14% to 7.1%). The majority of these retractions were self-cleaning; however, 2% required atticotomy and another 2% required conversion to an open-cavity CWD or subtotal petrosectomy to eradicate a recurrent cholesteatoma. As such, recurrence rates for the CWR approach with epitympanic obliteration are equivalent to those of the CWD operation, and only a few secondary operations for recurrence or retractions were required.

These low recurrence rates also occur in pediatric patients. It is often the case that children with cholesteatoma are treated with CWU procedures in the hopes of maintaining a self-cleaning ear; however, recurrent cholesteatomas are more frequent in this population. As such, children are excellent candidates for a CWR procedure. In our cohort, there was a 2.9% failure rate in children.

Patient Selection

The indications for CWR include patients of all ages with congenital or acquired cholesteatomas of the middle ear with extension to the attic, antrum, or mastoid not amenable to simple tympanoplasty or atticotomy. CWR can be performed in patients who have had prior mastoid surgery unless the PCW has been removed or the lateral portion of the PCW has been drilled away in a prior CWU procedure. CWR is not contraindicated in patients with facial paralysis, labyrinthine fistula, or an encephalocele. CWR can be performed in patients with extensive scutum erosion or destruction of the medial aspect of the PCW from cholesteatoma or prior surgery, although there are additional reconstructive considerations in these circumstances. CWR is contraindicated in patients with severe mastoid cholesteatosis that cannot be cleared from all mastoid air cell tracts, as sometimes occurs in young children. Care should be taken in the use of the CWR technique in patients with an extensive infectious component of their disease, although infection in general is not a contraindication to the procedure. In these cases, it is suggested that the patient be treated with saltwater irrigation and antibiotic topical drops for a period of 4 to 6 weeks before the procedure if there are no contraindications to delay.