APPROACHES TO CHOLESTEATOMA WITH AN INTACT OSSICULAR CHAIN: COMBINED USE OF MICROSCOPE, ENDOSCOPE AND LASER

Adrian L. James

Department of Otolaryngology – Head and Neck Surgery, University of Toronto, Hospital for Sick Children, Toronto, Canada

Introduction

Cholesteatoma surgery focuses on complete removal of the disease in order to obtain a safe, dry ear. Because surgical access to cholesteatoma can be obstructed by the ossicles, traditional approaches remove the incus and head of malleus in order to complete extirpation of the disease. Using an exclusively endoscopic permeatal approach to cholesteatoma, preservation of an intact ossicular chain has been reported in 57% of cases.1 A combined permeatal and transmastoid canal-wall-up approach with KTP laser but without endoscopy allowed preservation of the intact ossicular chain in 71% of cases.2

This report proposes that the combined use of the endoscope and operating microscope though the ear canal and also trans-mastoid when necessary, in conjunction with a fibre-guided laser such as KTP, has the potential to maximize the likelihood of preserving an intact ossicular chain when clearing cholesteatoma, and so improve hearing outcomes. The selection of instruments and approach would be governed by location of the cholesteatoma in relation to the morphology of the ear canal and mastoid, in addition to the preference of the surgeon.

Surgical technique

When considering ossicular preservation, the most challenging location for removal of cholesteatoma is the medial epitympanum.1 The surgical approaches can be considered in the quadrants demonstrated in Figure 1, divided approximately by the coronal plane of the incudo-malleolar joint and the axial plane under the head of malleus to body of incus.

a.Postero-inferior epitympanum (tympanic isthmus)

An approach through the ear canal (permeatal, end-aural or post-aural) is clearly optimal for the tympanic isthmus (Fig. 1, quadrant a). Either microscope or endoscope can be utilized to visualize and remove choles-teatoma from the stapes superstructure and from under the long process of incus. Curettage of the posterior scutum is likely to be necessary. Selection of microscope or endoscope may depend upon whether the surgeon feels a two-handed approach is necessary. Caution with positioning of the tip of the endoscope is paramount when operating close to the stapes.

b.Posterior epitympanum (medial to body of incus)

The space under the body of the incus is difficult to access through the meatus if the stapes and long process of incus are intact. A trans-mastoid approach is therefore needed if the ossicular chain is to be preserved.

image

Fig. 1. CT scan of the left ear (Parasagittal plane from multi-planar reconstruction with 3-D rendering). The black cross lies along the axis of the incudo-malleolar joint and along the base of the malleus head and incus body. This divides the medial epitympanum into four quadrants for planning surgical access to cholesteatoma: a. tympanic isthmus via ear canal; b. posterior epitympanum via mastoid; c. anterior epitympanum via ear canal or mastoid; d. supra-tubal recess via ear canal.

Rotation of the patient’s head away from the surgeon after drilling of the mastoid back to the sino-dural angle can often provide a clear view of the medial epitympanum with the operating microscope.3 However, the anteriorly placed sigmoid of a poorly pneumatized mastoid, or medialized oscciular heads can limit microscope access. Selection of an endoscope or microscope for trans-mastoid access to quadrant b (Fig. 1) will depend on the morphology of the individual temporal bone as well as the surgeon’s preference.

c. Anterior epitympanum

1) Surgical access to the anterior limit of the medial epitympanum, i.e., the space under the head of the malleus, is typically clearer with angled endoscopes than with a microscope. Placement of the endoscope through the ear canal or under the ossicular chain trans-mastoid can be more or less helpful according to tortuosity of the ear canal and medialization of the ossicular heads respectively. In some cases, a combined approach using one route for the endoscope and the other for instrumentation can be effective.

2) The most challenging location for cholesteatoma with an intact ossicular chain is on the antero-medial surface of the malleus head. Combination of all currently available techniques can prove inadequate for a convincing clearance of matrix from this location. A conventional permeatal atticotomy with curette plus or minus drill can provide quite good access. A microscope may or may not be used to open up the approach, but an endoscope is likely to provide optimum visualization for cholesteatoma removal. If the tegmen tympani/ floor of the middle fossa is sufficiently high, drilling of the mastoid can be continued toward the root of the zygoma, the cog drilled away and access achieved using a microscope through the mastoid. Placement of a mirror trans-mastoid or canal may improve the permeatal microscope view. The mirror can also be used to reflect the KTP laser beam on the anterior surface of the malleus head with the aim of reducing the likelihood of residual cholesteatoma in this hidden recess.

d) Supra-tubal recess and medial to malleus head

This area (Fig. 1, d) is best approached through the ear canal. Clear visualization is not possible with the microscope as a direct view is obstructed by the malleus handle. Angled endoscopes are ideally suited to removal of cholesteatoma from the supra-tubal recess and even the antero-medial epitympanum. Optimal access is provided by elevating the tympanic membrane from off the malleus handle.

Approaches to cholesteatoma with an intact ossicular chain

Findings

Ethical approval was obtained to search a prospective consecutive database of 256 cases of paediatric choles-teatoma operated on by a single surgeon between 2005 and 2012. Forty-nine ears (19%) were noted to have an intact ossicular chain at the time of surgery. Most cases (94%) with intact ossicles were small cholesteatomas occupying one or two sub-sites within the tympanomastoid system. Cholesteatoma was confined to the mesotympanum alone (including the hypotympanum and retrotympanum) in 33 cases (66%). Cholesteatoma was found in the epitympanum in 16 cases (32%). Extension into the mastoid antrum was only present in three cases (two via the aditus and one via the facial recess).

It was possible to preserve the intact ossicular chain in 47 (96%) of cases. In two cases, the head of the malleus was removed to facilitate removal of cholesteatoma from the anterior epitympanum, leaving the incus in situ. A combined approach tympanomastoidectomy was used in one of these cases and atticotomy with cartilage scutumplasty in the other. Both were completed before the introduction of endoscopic dissection or endoscopic laser to the series.

Hearing threshold

Pre- and post-operative audiometry was available for 45 of the cases with intact ossicular chains (inadequate follow up for post-op test in three; soundfield test only available in one young child). Average hearing levels in cases with preserved ossicular chain were unchanged after surgery with median pre- and post-operative air conduction thresholds of 19 dB HL. Thirty-six ears had normal pre-operative hearing levels (i.e., air conduction threshold < 30 dB HL) and 37 had normal post-operative hearing. Hearing deteriorated from normal to abnormal in only two cases (4%) after ossicular preservation surgery (mean 25 dB HL to 35 dB HL air conduction; mean change in bone conduction 9 dB HL). Mean air conduction hearing thresholds in the two cases in which the malleus head was removed deteriorated from 25dB HL to 53dB HL (mean post-op bone conduction 7dB HL).

As shown in Figure 2, the proportion of children with normal hearing was significantly greater in those with intact ossicles, than in those with incomplete ossicular chains.

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Fig. 2. Hearing thresholds before and after surgery for cholesteatoma. Mean four tone average air conduction thresholds before surgery are plotted against post-operative thresholds. Cases to the left of the vertical line had normal hearing before surgery and cases below the horizontal line have normal hearing after surgery. Hearing improved with surgery in those below the diagonal line and deteriorated with surgery in those above the diagonal line. Ossicular preservation was associated with a greater chance of normal hearing (p < 0.001 Chi-square test).

Conclusion

The combination of permeatal and trans-mastoid approaches, and utilization of the operating microscope and endoscopes, facilitate preservation of an intact ossicular chain when removing cholesteatoma. Ossicular preservation can be worthwhile even if the head of the malleus and body of the incus are significantly eroded. Care has to be taken to avoid the sensorineural hearing loss from cochlear trauma that could result from excessive manipulation of the ossicular chain, but this complication was not found in this series or others.1,2,4 The KTP laser facilitates removal of matrix from the ossicles without mechanical trauma.2,5 Preservation of the ossicular chain maintains normal hearing thresholds in the vast majority of children with cholesteatoma.

References

1.Marchioni D, Alicandri-Ciufelli M, Molteni G, Villari D, Monzani D, Presutti L. Ossicular chain preservation after exclusive endoscopic transcanal tympanoplasty: preliminary experience. Otol Neurotol 32:626–631, 2011

2.Hamilton JW. Systematic preservation of the ossicular chain in cholesteatoma surgery using a fiber-guided laser. Otol Neurotol 31:1104–1108, 2010

3.Hamilton JW. Functional Orthogonal Cholesteatoma Surgery http://www.jhamilton-ear.com/functional-orthogonal-cholesteatoma-surgery.asp, 2011

4.Sanna M, Facharzt AA, Russo A, Lauda L, Pasanisi E, Bacciu A. Modified Bondy’s technique: refinements of the surgical technique and long-term results. Otol Neurotol 30:64–69, 2009

5.Nishizaki K, Yuen K, Ogawa T, Nomiya S, Okano M, Fukushima K. Laser-assisted tympanoplasty for preservation of the ossicular chain in cholesteatoma. Am J Otolaryngol 22:424–427, 2001

Address for correspondence: Adrian James DM, FRCS(ORL-HNS). adr.james@utoronto.ca

Cholesteatoma and Ear Surgery – An Update, pp. 333–336

Edited by Haruo Takahashi

2013 © Kugler Publications, Amsterdam, The Netherlands