Modified radical mastoidectomy: Techniques to prevent failure
Becvarovski, Zoran
The aims of surgical treatment for cholesteatoma include complete removal of disease, the formation of a dry, self-cleaning ear, and hearing reconstruction. This presentation concentrates on the techniques of open mastoid surgery or Modified Radical Mastoidectomy (MRM) required to achieve a successful cavity. This study analyses both primary and revision mastoid surgery referred to the senior author over a short period allowing for adequate follow up. Thirty nine patients were included in the series comprising 21 primary and 18 revision cases. All patients presented with otorrhoea. Two patients presented with facial paralysis, one with labyrinthine fistula, and one with oval window fistula.
The group of patients underwent modified radical mastoidectomy because of the presence of a sclerotic mastoid with extensive cholesteatoma. The main method of hearing reconstruction in an open cavity with a mobile stapes was Type III tympanoplasty, leading to an improvement in the average air bone gap following surgery in both the primary and revision groups. The major causes of discharging ears that were found when revising mastoid cavities included incomplete removal of air cell tracts and inadequate mastoid cavity formation without a sufficient meatoplasty. Techniques of open mastoid or modified radical mastoidectomy that are required to avoid failure are discussed and illustrated.
Introduction The major aim of cholesteatoma surgery is to achieve a dry, safe, self cleaning ear. A review of the literature shows fluctuating trends in the numerous techniques that have been developed and used by otologists throughout the years of mastoid surgery (Sheehy 1988, Smyth 1987, Sade 1987, Toner 1990). Early otologists believed that formation of radical mastoid cavities was the treatment of choice. Intact canal wall techniques were first popularised by Jansen (Jansen 1985), but much controversy continues in establishing the optimal technique for managing cholesteatoma.
The philosophy of the senior author tends towards the creation of an open cavity, in most cases, rather than intact canal wall surgery to reduce the risk of recurrent and residual disease. The techniques of Modified Radical Mastoidectomy that are described in this paper have led to eradication of disease, with the opportunity to restore ossicular chain continuity.
The objectives of this study were to assess the Modified Radical Mastoidectomy technique in eradicating disease, achieving a dry self cleaning ear with satisfactory hearing, and prevention of recurrent disease.
There has been a longstanding problem with terminology but the authors have defined MRM as an operative technique that includes extensive removal of tympano-mastoid air cell tracts, and exteriorisation of air cells to create an open cavity. The middle ear and drum are then reconstructed.
Methods The medical notes of 39 consecutive patients who underwent primary or revision Modified Radical Mastoidectomy for cholesteatoma were retrospectively reviewed which allowed for an adequate follow up period. The hospital records and correspondence with clinicians were used for follow-up.
The following information was obtained: age and sex of patients, symptoms on admission and post-operatively, the duration of follow-up, and the post-operative cavity status. Intra-operative findings with particular attention to the stapes-superstructure and the footplate status were recorded. For the revision cases, the time from the original surgery was noted, along with the specific sites and cause of failure.
All patients underwent surgery by the senior author. The referral sources were otolaryngologists and general practitioners. The average post operative air bone gap at 0.5, 1, 2, and 4 kHz (i.e. difference between the average bone conduction and the average air conduction) was used as an indicator of objective functional hearing.
Modified Radical Mastoidectomy was utilised in all patients when cholesteatoma was extensive. Extensive pneumatisation of the temporal bone was the only indication for intact canal wall mastoidectomy. The remainder underwent Modified Radical Mastoidectomy.
Surgical Technique The important surgical concepts involved in open modified radical mastoidectomy are related to extensive and complete removal of air cell tracts, and the creation of a well constructed cavity (Fisch and May 1994). The skin incision must provide access to the mastoid tip, sinodural angle, and must provide sufficient anterior exposure to allow access to the anterior epitymanum and canal wall.
The mastoidectomy involves wide removal of bone from the middle fossa dura, sinodural angle, sigmoid sinus, and digastic ridge (Figure I).
The facial nerve is identified in the mastoid or vertical portion in the region of the stylomastoid periostium. The digastric muscle is clearly exposed and the stylomastoid periostium provides an important landmark for the vertical facial nerve and allows removal of the mastoid tip at a later stage. The facial “ridge” is then lowered to the level of the facial nerve as far as the second gems (Figure 2).
The retrolabyrinthine, retrofacial, and epitympanic air cells are completely removed. The wide removal of the epitympanic air cells provides exposure to the supralabyrinthine and supratubal air cell tracts. The removal of supratubal and supralabyrinthine air cell tracts requires careful dissection in the region of the tympanic and labyrinthine portions of the facial nerve.
The anterior epitympanum dissection extends as far as the root of the zygoma and is made continuous with a wide anterior canal wall enlargement. The tympanic annulus must be completely visible. The wide canalplasty is then extended inferiorly as far as the digastric ridge to create a circular cavity (Figure 3).
The mastoid tip is then removed after complete mobilisation along the digastric ridge lateral to the stylomastoid periostium and anterior to the facial nerve. The tip is dissected from the underlying digastric muscle with care to avoid the stylomastoid foramen and facial nerve (Figure 4).
The tympanoplasty does not involve the use of prosthetic material. A type III tympanoplasty is usually carried out in the presence of an intact and mobile stapes. Temporalis fascia is placed under the anterior tympanic membrane and over the enlarged, inferior canal wall. The graft is either placed directly over the stapes head or a small piece of cartilage is placed in between. The tensor tympani tendon is carefully preserved, if possible, to provide important structural support to the handle of the malleus and drum.
Results Thirty nine patients who underwent MRM for cholesteatoma were evaluated including 21 men and 18 women with a mean age of 49.5 years (range, 18 to 78 years). Of these, 18 cases were referred to the senior author after undergoing mastoid surgery at other centres. The clinical presentation of the two groups varied.
Primary Modified Radical Mastoidectomy All patients in the primary MRM surgical group had not previously undergone mastoid surgery. These patients presented with persistent otorrhea and hearing loss of either a conductive or mixed nature. Cholesteatoma was found in all patients. Vertigo was present in 19% of patients (Table 1).
The stapes superstructure was present and intact in all patients. A Type III tympanoplasty using a cartilage graft placed onto the stapes suprastructure was performed in 17 (80%) patients. The remainder underwent Type III tympanoplasty with the tympanic membrane placed directly over the stapes suprastructure.
Following surgery, a dry ear was achieved in all patients. The vertigo in the four patients was cured but no labyrinthine fistula was found at surgery. Subjective hearing improved in 15 (71%) patients, remained the same in 6 (29%), and no patient reported further hearing loss. An average Air Bone Gap (ABG) of less than 10dB was found in 18% of patients, and an ABG of less than 20dB was found in 47% of patients (Table 2).
Revision Modified Radical Mastoidectomy Eighteen patients underwent revision MRM. The initial surgery was performed by other Otolaryngologists in 17, and in one case, by the author. The mean time from the original surgery was 7.9 years (range 4 days to 45 years). Recurrent persistent discharge and deafness was the main complaint in this group. Vertigo was present in 22%, and facial paralysis in 11% of patients (Table 1).
Following surgery, a dry ear was achieved in all patients. The vertigo was cured in all patients of which one was found to have a labyrinthine fistula and one an oval window fistula. Subjective hearing improved in 14 patients (77%), remained the same in 4, and no patient reported further hearing loss. Facial paralysis in the two patients improved.
Cholesteatoma was found at operation in all patients. The stapes superstructure was present and intact in 11 (61%) patients. In the remaining 7 patients, 6 had only a footplate (of these, one had a labyrinthine fistula), and one patient had no footplate (consequently an oval window fistula).
A Type III tympanoplasty using a cartilage graft placed onto the stapes suprastructure was performed in 11 (61 %) patients.
Following surgery, an average ABG of less than 10dB was found in 7% of patients, and an ABG of less than 20dB was found in 39% of patients (Table 2). Further, among patients in which the stapes superstructure was present, 16% had an ABG of less than 10 dB, and 44% had an ABG of less than 20 dB. When the stapes suprastructure was absent, only 16% had an ABG of less than 20 dB (Table 3).
The mean follow-up period for the primary cases was 21.4 months (range 5 to 43) and for the revision cases was 10.2 months (range 5 to 27 months).
Following surgery, a dry ear was achieved in all patients without serious complications (meningitis, CSF leak, facial paralysis) and only one of patients required subsequent surgery (Table 4). It is important to note that these hearing results are achieved without a second stage ossicular chain reconstruction.
Discussion Cholesteatoma is a histologically benign disease. However, the natural behaviour may be characterised by locally aggressive and invasive properties associated with significant morbidity and occasional mortality. Interleuken-1 alpha, a cytokine found in cholesteatomatous keratinocytes has been shown to activate neutrophils and lymphocytes during the inflammatory processes, stimulate osteoclasts, and to release collagenase and prostaglandin E-2 from fibroblasts. Granulation tissue associated with cholesteatoma has been shown to contain a parathyroid– hormone-related protein. These features may all lead to consequent bony destruction and complications of cholesteatoma (Atlas and Paramaesvaran 1996).
The major aims of cholesteatoma surgery are removal of the disease and the creation of a dry, safe ear. The technique must prevent recurrent or residual cholesteatoma and reconstruct the ossicular chain mechanism. The procedure of intact canal wall mastoidectomy and tympanoplasty is designed to accomplish these aims without removing the external auditory canal. The limitations of this approach are reflected by an unacceptably high rate of recurrent and residual cholesteatoma.
An understanding of recurrent and residual cholesteatoma following mastoid surgery is important. Residual cholesteatoma refers to keratinising epithelium that remains after a surgical procedure. Recurrent cholesteatoma is defined as the presence of a secondary acquired cholesteatoma that appears following the complete removal of previous cholesteatoma. The rate of residual cholesteatoma varies greatly but has been reported in up to 57% of cases following intact canal wall surgery (Sheehy et al 1977, Sheehy and Patterson 1967, Schuring et al 1990, Gristwood and Venables 1990, Rosenfeld et al 1992). The intact canal wall technique is characterised by limited access to the sinus tympani and anterior epitympanum in a poorly pneumatised temporal bone. This may lead to inadequate removal of cholesteatoma with residual disease or inadequate ventilation of the epitympanum leading to recurrent cholesteatoma. The major sites of residual cholesteatoma following intact canal wall surgery are in the region of the attic, stapes and sinus tympani (Gyo et al 1996). Further surgery involving a “second look” procedure is mandatory following closed cavity surgery.
Modified radical mastoidectomy, when performed as described, is associated with a low rate of recurrent, and residual disease (Fisch and May 1994). A frequently described disadvantage of modified radical mastoidectomy with tympanoplasty is the production of a wet, discharging cavity. The results of this series show that a discharging cavity can be avoided in nearly all cases with meticulous surgical technique and is caused by inadequate bone removal.
The principle of creating a dry and self-cleaning mastoid cavity involves extensive surgery. The major sites of residual air cell tracts that were found to be contributing to discharging cavities at the time of revision mastoid surgery were the retrolabyrinthine and supralabyrinthine areas. The surgical technique must remove these air cell tracts when significantly involved with disease. The wide access approach provides panoramic exposure of the epitympanic, retrolabyrinthine, and supralabyrinthine regions which are exteriorised with the remainder of the open cavity.
The long term hearing results obtained following intact wall surgery are not significantly better than open cavity hearing levels despite the preservation of a more anatomically normal middle ear (Toner and Smyth 1990). The authors recommend that the decision with regard to the technique of mastoid cholesteatoma surgery be based upon the patient’s needs and the experience of the surgeon. In general, the judgement between open and closed surgery is based upon the degree of pneumatisation of the temporal bone and the extent of the cholesteatoma. Therefore, the major indication for intact canal wall surgery is extensive pneumatisation but with localised cholesteatoma. The remainder are dealt with using the described open technique.
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Zoran Becvarosvki F.R.A.C.S. Marcus D. Atlas F.R.A.C.S. Department of Otolaryngology St Vincent’s Hospital, Sydney, Australia
Correspondence: Prof. M.D. Atlas Department of Otolaryngology Sir Charles Gairdner Hospital Perth, Western Australia 6009 Telephone: (08) 9346 3633 Fax: (08) 9346 3637
Copyright Australian Society of Otolaryngology Head & Neck Surgery Ltd. Jan 2001
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