Relevant issues in revision canal-wall-down mastoidectomy

Abstract

The role of canal-wall-down (CWD) versus intactcanal-wall (ICW) mastoidectomy in the treatment of chronic otitis media with or without cholesteatoma remains a debated issue. Although past conventional wisdom has held that CWD mastoid surgery leads to a “safe” ear and is technically less demanding than the more controversial ICW mastoidectomy, this is often not the case. Although our preference is an ICW technique when possible, 47 of 109 (43%) mastoid procedures for chronic otitis media performed between January 1993 and June 1996 involved a CWD mastoid cavity. More than two thirds of these procedures (32 of 47) represented revision surgery, the most common indication being a poorly contoured, preexisting CWD mastoidectomy with persistent otorrhea. A dry, well-epithelialized ear was obtained in 90% of cases. Our preferred method of ossicular reconstruction (double cartilage block ossiculoplasty) is detailed, and hearing results according to American Academy of Otolaryngology-Head and Neck Surgery guidelines are reported. (Otolaryngol Head Neck Surg 1999;121:18-22.)

The goal of surgery for chronic otitis media (COM) with or without cholesteatoma is eradication of disease and achievement of a healed, noninfected ear. Despite the controversy over intact-canal-wall (ICW) versus canal-wall-down (CWD) mastoidectomy as a means to this end, either management approach is capable of realizing this goal. A long-held, but poorly documented, misconception exists that ICW mastoid surgery is technically more demanding than CWD. Also, the belief that removal of the posterior canal wall automatically translates into a “safe” ear has been ingrained in the minds of many surgeons. Glasscock 1 has pointed out the fallacy of this belief in the literature.

Although the goal of this article is not to address the ICW versus CWD issue, the management philosophy of the senior author (S.A.H.) is use of an ICW tympanomastoidectomy with facial recess approach whenever possible. A planned second-stage ossicular reconstruction is performed 6 to 18 months later, depending on the age of the patient. However, a CWD technique is decided on either before or during surgery, as the individual case demands. Indications for selection of a CWD procedure include unresectable disease, suspicion or certainty of poor or inadequate patient follow-up, significant posterior canal wall erosion, disease in an only hearing or significantly better hearing ear, significant recurrent or residual cholesteatoma at a planned second-stage procedure, and treatment of the medically infirm. Many of these indications have previously been discussed in the context of CWD mastoidectomy. 2

In our experience a CWD approach is required in the most severely diseased ears, where an ICW mastoidectomy (even with opening the facial recess) would result in significant retained cholesteatoma or granulation tissue. Because of the severity of disease addressed by CWD surgery, the execution of the technique should not be undertaken in a cavalier or indifferent manner. The technical aspects of this approach can be just as demanding as with ICW mastoidectomy. Lack of attention to detail often leads to a postoperative management problem with the following characteristics 3 : (1) small meatus allowing inadequate visualization of the entire cavity; (2) high facial ridge with incomplete posterior canal wall removal; (3) overhanging lateral epitympanic wall; (4) retained mastoid tip that harbors debris and trapped moisture; and (5) persistent or recurrent mucopurulent drainage with areas of mucosalization or granulation tissue in the mastoid or middle ear.

CWD mastoidectomy for the treatment of COM was used long before ICW procedures became accepted, and the surgical steps necessary to create a relatively trouble-free cavity have been addressed in the literature. 4 However, this study was prompted by the perception that a significant number of the CWD mastoidectomies being performed were revision procedures, especially of prior CWD operations. The purposes of this retrospective review are to (1) determine whether prior mastoidectomy is common in patients undergoing CWD surgery; (2) review associated factors leading to the need for a CWD approach; (3) determine the extent to which a dry, well-healed ear was obtained in this patient population; and (4) analyze hearing results in accordance with guidelines proposed for reporting conductive hearing loss by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery. 5

METHODS AND MATERIAL

A retrospective chart review of all mastoidectomy procedures for COM with or without cholesteatoma between January 1993 and June 1996 revealed 109 cases performed by the senior author. Of these, 47 (43%) were CWD operations and comprised the subject material for this article. Patient age ranged from 5 to 84 years (mean 39.5 years) with 26 male and 21 female patients. No cases were bilateral. A procedure was classified as revision surgery if a prior mastoidectomy (either ICW or CWD) had been performed. Surgery on an ear that had undergone previous tympanoplasty, ossiculoplasty, atticotomy, or a similar procedure without mastoidectomy was not classified as a revision.

Minimum length of follow-up needed to determine whether healing had occurred was defined as 3 months. A healed ear was defined as a completely epithelialized cavity with no intermittent or recurrent drainage, without need for ototopical therapy and no sign of granulation or cholesteatoma.

In accordance with Academy guidelines 5 the range, mean, and SD for the postoperative air-bone gap (ABG), along with the decibel closure of the gap after surgery, are reported. Thresholds at 500, 1000, 2000, and 3000 Hz were used for calculation. The change in high-frequency bone-conduction levels (determined at 4000 Hz) was considered significant if it was 15 dB or more.

SURGICAL TECHNIQUE

Only pertinent highlights are reviewed. In the presence of a posterior canal wall, standard transcanal incisions are made, and the vascular strip skin is elevated. 6 In a prior CWD mastoidectomy, no cavity incisions are created, but the dissection is commenced from the postauricular incision. Epithelium is completely elevated out of the cavity, and the middle ear is exposed. Neo-osteogenesis or overhanging bony ledges are taken down, and the cavity is completely saucerized. Care is taken to skeletonize the tegmen, sinodural angle, and sigmoid sinus. The facial ridge is taken down with sacrifice of the chorda tympani nerve, and the facial nerve always identified in the entire mastoid segment. The digastric ridge is skeletonized, and the entire mastoid tip is amputated at this level unless it contains absolutely no air cells or disease. The inferior canal wall is taken down to expose the hypotympanum and allow this area to smoothly blend into the mastoid cavity. The malleus and incus are routinely removed, and the lateral epitympanic wall is removed to allow the tegmen tympani to smoothly blend into the anterior canal wall. Care is taken to ensure that all diseased mastoid air cells are removed. These steps have been well described in the literature. 1

Fig 1

A-D, Steps in creating the DCB.

In the presence of an intact stapes superstructure, a double cartilage block (DCB) ossiculoplasty, as described by Luetje and Denninghoff, 7 is used. A rectangular block of conchal or tragal cartilage is stripped of perichondrium on one surface (Fig 1). The cartilage is cut in half, and care is taken not to violate perichondrium on the opposite side, which serves as a hinge. The cartilage is folded over, and an acetabulum is created in one leaf to accept the capitulum of the stapes (Fig 2). The DCB serves to augment the effective height of the stapes above the level of the fallopian canal and increase the potential volume for an air-containing middle ear space. Tympanoplasty is performed in the standard fashion (underlay technique), an adequate meatoplasty is created, and a Palva musculoperiosteal flap 8 is used for partial cavity obliteration.

RESULTS

Of the 47 procedures, 25 (53%) were for cholesteatoma, and 22 (47%) were for COM without cholesteatoma. Active drainage, not controlled with oral and/or ototopical antibiotics, was present in 35 cases (75%) before surgery. Surgery involved the only hearing ear in 5 cases (11%), whereas a semicircular canal fistula was present in 7 (15%). The fistula involved the horizontal canal in 5, with 1 each in the superior and posterior canals. No cochlear fistulas were present in this series. Significant facial nerve dehiscence from disease (described as exposure of the entire tympanic or mastoid segment of the nerve) was present in 3 cases (6%). Lesser degrees of nerve dehiscence can be expected and are not included in this number. Significant tegmen erosion with dural attenuation from disease (with risk of subsequent encephalocele formation) was present in 4 cases (8.5%), which required repair. This included 1 overt encephalocele. Small areas of dural exposure were not considered significant and are not included.

Fig 2

Cross-sectional view of DCB in place on the stapes capitulum with tympanic membrane graft in position.

A tympanomastoidectomy was performed in 40 cases (85%); DCB ossiculoplasty was used in 19 of these cases. A Bondy modified radical mastoidectomy was performed in 3 (6.4%) and a classic radical mastoidectomy in 4 cases (8.6%).

Follow-up of at least 3 months was available in 42 cases (range 3 to 52 months, mean 22.1 months). Of these 42 cases, a dry, well-epithelialized ear without intercurrent drainage or residual or recurrent cholesteatoma was obtained in 38 cases (90%) during the follow-up period. Of the 4 failures, 3 went on to further surgery and 2 healed uneventfully, for total control of disease in 40 of 42 cases (95%).

Of the patients with cholesteatoma, 20 of 22 (91%) healed, and in the COM without cholesteatoma group, 17 of 19 (89%) had a dry, well-healed cavity. There were no cases of postoperative facial paresis or paralysis.

Table 1

Hearing results: Entire series

	Postoperative ABG (N = 37)	Preoperative to postoperative ABG change (N = 38) ∗
Range (dB)	6.3 to 43.8	-21.3 to 31.3
Mean (dB)	25.2	3.7
SD (dB)	11.1	12.7

N, Number of patients with adequate audiograms available for comparison.

Negative numbers = worsening of ABG.

^∗Dead ear before and after surgery counted as no change.

Of the 47 cases, 32 (68%) represented revision procedures. Nine were previous ICW mastoidectomies, and 23 were CWD mastoidectomies. Thus, of the entire series, 49% of cases were revisions of previously performed CWD mastoidectomies. Of our own revisions, 6 cases were converted to CWD because of significant recurrent or residual cholesteatoma at a planned second stage of a previous ICW operation. Three of our own CWD procedures required further surgery.

Hearing results for the entire group are shown in Table 1. Because of either lack of a postoperative audio-gram or incomplete air and bone thresholds at the necessary frequencies, the sample size is less than 47. The mean postoperative ABG was 25 dB. Negative values represent worsening of the ABG after surgery. An improvement in the ABG by 15 dB or greater was attained in 7 patients, whereas 2 had worsening of 15 dB or more.

High-frequency (4000 Hz) bone threshold changes were examined. Improvement by 15 dB or more was seen in 4 patients, as was worsening by 15 dB or more. A change of less than 15 dB was observed in 29, and no information was available in 10.

Anacusis was present in one ear before surgery, and an additional one developed after surgery. This additional patient had a significant mixed loss before surgery with air thresholds greater than 90 dB and a masking dilemma for bone conduction. After surgery there was no response to air conduction.

Table 2 compares the postoperative ABG for the cholesteatoma group and COM without cholesteatoma. No statistically significant difference (unpaired Student t test at P < 0.05) was present.

Table 3 compares the preoperative and postoperative ABG changes for cholesteatoma versus COM. The mean change in ABG after surgery in the cholesteatoma group was essentially 0 dB, whereas for COM without cholesteatoma, there was improvement by almost 9 dB. This difference was statistically significant (unpaired Student's t test, P = 0.019).

DISCUSSION

The major objective in surgery for COM with or without cholesteatoma remains eradication of disease and creation of a dry, well-healed ear. Depending on the particular clinical situation, this may be achieved with an ICW or a CWD procedure. However, our philosophy is to reserve a CWD format for the most severely diseased ears or those that have a significant preexisting canal wall defect (from either disease or prior surgery). The group of patients requiring an open-cavity technique for control of disease has been labeled the “difficult chronic ear” by Jackson et al. 3 The concept that merely creating an open cavity without proper attention to the contour of the cavity will lead to surgical success is a prescription for failure. This is illustrated in our series, which demonstrates that almost half (49%) of the CWD mastoidectomies performed were revisions of previous open-cavity operations. This figure is even higher in other reported series—56 of 66 revision CWD mastoidectomies (85%) reviewed by Nadol. 9

Table 2

Postoperative ABG: Cholesteatoma versus COM

	Cholesteatoma (N = 19)	COM (N = 18)
Range (dB)	6.3 to 42.5	7.5 to 43.8
Mean (dB)	26.9	23.4
SD (dB)	11.0	11.2

N, Number of patients with adequate audiograms available for comparison.

Proper execution of a CWD mastoidectomy requires removal of all diseased air cells, lowering the facial ridge to (with absolute identification of) the mastoid segment of the facial nerve, complete removal of the lateral epitympanic wall, and mastoid tip amputation. In addition, the inferior canal wall should be lowered to adequately expose the hypotympanum, which allows a smooth transition into the mastoid cavity. The importance of the hypotympanum as a source of disease has been previously stressed. 10 An adequate meatoplasty is also crucial. CWD surgery done correctly is not easier than the ICW approach. Sheehy 4 states that it may be more difficult to perform.

The complex nature of this patient population is further illustrated by active otorrhea in 75% at the time of surgery, an only hearing ear in 11%, and a semicircular canal fistula in 15%.

Table 3

Change in ABG: Cholesteatoma versus COM

	Cholesteatoma (N = 20)	COM (N = 18)
Range (dB)	-21.3 to 21.3	-16.9 to 31.3
Mean (dB)	-0.1^∗	8.7^∗
SD (dB)	10.5	13.4

N, Number of patients with adequate audiograms available for comparison.

Negative numbers = worsening of ABG.

^∗ P < 0.05.

Tegmen defects, with loss of dural integrity caused by the disease process, were sufficient to require reconstruction (usually cartilage and fascia) in 8.5%. In the series of Jackson et al, 3 the incidence of active drainage at the time of surgery was 59.1%, and an only hearing ear was encountered in 2.8% of patients. In the study by Sheehy 4 on 103 CWD procedures from 1974 to 1981, the incidence of an only hearing ear was 18% (19 of 103). The incidence of labyrinthine fistulas in COM has been extensively addressed in the literature and generally ranges from 5% to 15%. 11 – 14 In Sheehy's 4 series of CWD procedures, labyrinthine fistula was encountered in 18%. However, if considered in the context of all procedures for COM during the same time span, the incidence of this complication dropped to 4%. This reflects the fact that most fistulas were managed with a CWD technique. Our data support a similar philosophy. In our CWD patients, the incidence of fistula is 15% but drops to 6.4% if all mastoid procedures (ICW and CWD) performed during the same time period are considered. We routinely use a CWD procedure for fistulas.

Success measured in terms of a dry, healed ear without evidence of further disease was obtained in 90% of our cases. This is comparable with results in other reported series. Nadol, 9 with at least 1 year of follow-up in 48 patients who underwent CWD mastoidectomies, obtained a completely healed ear in 85% of cases. Jackson et al 3 obtained a dry, safe ear in 89.3% of 541 CWD procedures performed during a 24-year period. Sheehy 4 realized a healed ear in 94%. Thus it appears that the major goal of surgery for COM, namely a relatively trouble-free, dry cavity can be obtained in approximately 90% of our most difficult chronic ears with strict adherence to proper surgical technique.

The issue of hearing results requires consideration of many factors including level of preoperative thresholds, extent of disease and associated infection/inflammation, and status of the ossicular chain (specifically the stapes superstructure). Hearing rehabilitation must be kept in proper perspective in this group of patients and is a secondary goal. Our results suggest that the change in the mean ABG from before to after surgery is small (3.7 dB). We did find a statistically significant improvement in the mean ABG for COM without cholesteatoma compared with that found in the cholesteatoma group. The reason for this is unclear and cannot be explained on the basis of the presence or absence of the stapes superstructure, as this finding was comparable in the 2 groups.

Our mean postoperative ABG was 25 dB. In the series of Jackson et al 3 the postoperative difference in mean air and bone conduction from 500 to 4000 Hz ranged from 10 to 60 dB (progressively smaller gap in the higher frequencies). They concluded that “although operative hearing rehabilitation is not a reasonable expectation in these complicated cases, audiology is rarely worsened in the pursuit of infection control.” 3 Our data would support this statement.

We believe that middle ear prosthetics or biocompatibles have minimal or no role in this population of diseased ears. In an attempt to increase the volume of the middle ear space and obtain a reasonable sound-conducting mechanism, we universally use the DCB when the stapes superstructure is present. Sheehy 4 emphasized the point of increasing the middle ear space and rarely placed the fascia graft directly on the capitulum. In the absence of a superstructure, we tend to use a cartilage strut, although 3 total ossicular replacement pros-theses were used early in this series.

CWD mastoidectomy, although not our initial procedure of choice, maintains a significant role in our management of COM with or without cholesteatoma. We use this technique in more recalcitrant cases, as evidenced by the fact that two thirds of the cases in this series represented revision surgeries. Proper execution, however, should not be considered easier or technically less demanding than ICW operations. This is evidenced by the fact that half of our CWD procedures represented revision of previous open-cavity mastoidectomies. Obtaining a dry, well-healed ear is an achievable goal in most of these badly diseased ears. Improvement in hearing thresholds, although desirable, is of secondary concern, but stabilization is certainly possible.

CONCLUSIONS

The primary goal of a dry, well-healed ear that is of minimal inconvenience to the patient is obtainable in approximately 90% of cases.

Hearing improvement, although a secondary goal, is possible in this patient population, but preservation is more realistic.

CWD mastoidectomy is often used in the context of revision surgery.

Attention to detail is necessary to create a trouble-free cavity that is less likely to require further surgery.

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