Introduction
Cochlear implantation in patients with a canal wall down mastoid cavity is challenging, especially in patients with persistent or recurrent inflammation due to underlying inflammatory middle-ear disease such as chronic otitis media or cholesteatoma. In such cases, there is an increased risk of labyrinthitis, meningitis and electrode array extrusion into the external auditory canal through the soft tissue cover of the mastoid cavity.Reference Hunter, O'Connell and Wanna1,Reference Issing, Schonermark, Winkelmann, Kempf and Ernst2 A variety of surgical techniques have been described to minimise peri- and post-operative complications, including maintenance of the cavity with soft tissue coverage of the electrode, overclosure of the external auditory meatus with and without mastoid obliteration or Eustachian tube plugging, reconstruction of the posterior external auditory canal wall, as well as middle fossa approaches to the cochlea.Reference Kojima, Sakurai, Rikitake, Tanaka, Kawano and Moriyama3–Reference Colletti, Fiorino, Carner, Sacchetto and Giarbini8
Subtotal petrosectomy with external auditory canal overclosure is considered a safe procedure amongst the various proposed surgical techniques. However, overclosure of the external auditory canal is associated with several complications, such as post-operative infections, meningitis due to masked cavity infection because of residual or recurrent cholesteatoma, as well as fat necrosis, and dehiscence of the meatoplasty.Reference Issing, Schonermark, Winkelmann, Kempf and Ernst2,Reference Casserly, Friedland and Atlas9–Reference Postelmans, Stokroos, Linmans and Kremer12
For this reason, in patients with a stable cavity after a canal wall down mastoidectomy and a large meatoplasty, a multi-layer obliteration of the mastoid cavity with conchal cartilage and temporal fascia plus a two-layer closure technique of the post-auricular incision, when feasible, may be considered a safe and reliable option.
This study evaluated the results obtained with this technique in seven patients where cochlear implantation was performed after a canal wall down mastoidectomy with a large meatoplasty.
Materials and methods
We reviewed a retrospectively acquired database of all surgical procedures for cochlear implantations performed at Son Espases University Hospital between January 2011 and December 2018. A total of 296 surgical procedures were performed, but only those patients who had previously undergone canal wall down mastoidectomy and a large meatoplasty because of cholesteatoma or chronic otitis media were included in the study. In all cases, cochlear implantation was performed at least two years after the canal wall down mastoidectomy. Physical examination and magnetic resonance imaging (MRI) (in the case of cholesteatoma surgery) had been used to rule out cavity disease recurrence in all patients prior to cochlear implantation surgery. The mean follow-up duration was 4.5 years (range, 3–7 years).
We analysed the characteristics of patients, length of hospital stays, and rates of post-operative complications (such as cochlear implant exposure or extrusion) and revision surgery. Our preferred surgical technique is described.
Surgical technique
The surgery is conducted under general anaesthesia and, in all cases, an orotracheal tube and facial nerve monitoring is used. The patient is placed in a supine position with their head turned to the contralateral side. Local infiltration with lidocaine and adrenaline (1:100 000) is used for anaesthesia. A post-auricular incision is made, 1 cm posterior to the retroauricular sulcus. If possible, two flaps are prepared: a superficial flap that includes the skin and subcutaneous tissue, and a deeper fascio-muscular flap to reduce the risk of device extrusion.Reference Carnevale, Tomás-Barberán, Til-Pérez and Sarría-Echegaray13 Haemostasis is achieved with monopolar or bipolar electrocautery. However, once the implant is in the surgical field, bipolar electrocautery is mandatory.
The cartilage palisade used for tympanic membrane reconstruction and mastoid obliteration is removed, and the cavity is explored. If necessary, the posterior border of the round window niche is drilled and the cavity is irrigated with dexamethasone. Then, the bone bed for the cochlear implant is drilled and prepared below the temporal muscle. The array is inserted through the round window membrane, which is always sealed with temporal fascia and fibrin glue. Then, the implant is fixed into the exact position with a suture.
After confirming the correct introduction of the electrode by intra-operative radiography, the conchal cartilage plates are used for partial obliteration of the cavity, for covering of the array and for eardrum reconstruction in an overlapping fashion (Figure 1). The reconstruction is buttressed with two or three thin, overlapping (1.3 mm) blue silicone sheets, before the cavity is packed with gelatine sponges (Gelita Medical, Eberbach, Germany) soaked with ciprofloxacin solution.
Fig. 1. Cochlear implantation and cartilage multi-layered palisade reconstruction in the right ear of patient 4, who had previously undergone canal wall down mastoidectomy.
Finally, the meatoplasty is restored and the incision is closed by suturing the two previously described flaps and applying a pressure dressing to the wound.
Results
Between 2011 and 2019, a total of seven patients who had previously undergone canal wall down mastoidectomy underwent cochlear implantation in our hospital.
Aetiology of hearing loss and characteristics of the patients are described in Table 1. There were two cases of chronic otitis without cholesteatoma and five cases of cholesteatoma.
Table 1. Characteristics of patients
Pt no. = patient number; y = years; F = female; R = right; M = male; COM = chronic otitis media; mo = months; L = left
The cochlear implantation procedures were performed after at least two years of follow up and were uneventful in all cases. There were four males and three females, with a mean age of 46.8 years (range, 28–71 years). There were two left side and six right side ears (one patient needed revision surgery).
In all cases, the array was inserted in the scala tympani of the basal turn of the cochlea, through the round window membrane. Patients were discharged 2 days after surgery, and the cochlear implant was activated after 3 weeks.
No post-auricular abscess or skin infection was observed in this series during a follow up of at least three years (range of three to eight years). No cases of otorrhoea due to superficial inflammation of the mastoid cavity skin cover were observed after implantation. There was no hint of cholesteatoma recurrence, and all patients have been free of symptoms and infection during follow up. Only one patient (patient 5) showed cable extrusion six months after surgery, and implantation of the contralateral ear was needed (Figure 2).
Fig. 2. Cable extrusion following cochlear implantation in the right ear of patient 5, who had previously undergone canal wall down mastoidectomy. Implantation of the contralateral ear was needed.
Discussion
In the context of cochlear implantation, the presence of a canal wall down mastoid cavity represents a challenge for peri- and post-operative management, especially when there is a large meatoplasty. Many surgical techniques and different approaches have been developed to obtain good results with low complication rates, but no technique is currently considered the ‘gold standard’.
Many authors advocate subtotal petrosectomy with overclosure of the external auditory canal, combined with Eustachian tube plugging and fat obliteration, for managing radical cavities prior to cochlear implantation. This technique was introduced in the late 1950s, and Ugo Fisch introduced the term ‘subtotal petrosectomy’ in 1965.Reference Prasad, Roustan, Piras, Caruso, Lauda and Sanna14 In the early years, subtotal petrosectomy was considered hazardous in light of increased incidences of recurrent disease, and there was a general hesitancy amongst surgeons in adopting this procedure. However, over the past couple of decades, there has been a growing interest in subtotal petrosectomy, and the indications for the procedure have also increased. In fact, with the development of MRI and diffusion-weighted MRI in particular, and refinements in the surgical techniques and better microscopes, a significant reduction in residuals and recurrences has been observed.Reference Prasad, Roustan, Piras, Caruso, Lauda and Sanna14 The rationale for using subtotal petrosectomy in these cases is to obtain an isolated cavity with a low risk of infections, and to diminish the risk of extrusions.Reference Free, Falcioni, Di Trapani, Giannuzzi, Russo and Sanna5,Reference Polo, Del Mar Medina, Aristegui, Lassaletta, Gutierrez and Aranguez15,Reference Karatzanis, Chimona, Prokopakis, Kyrmizakis and Velegrakis16
Polo et al.,Reference Polo, Del Mar Medina, Aristegui, Lassaletta, Gutierrez and Aranguez15 in an interesting series with 110 cases, described their vast experience with subtotal petrosectomy. A very low rate of array extrusion (4.55 per cent) is reported, but only 33 patients had previously undergone canal wall down mastoidectomy and the percentage of array extrusion in this subgroup of patients is not specified. Previously, Vincenti et al.Reference Vincenti, Pasanisi, Bacciu, Bacciu and Zini17 reported the long-term results of 12 patients after subtotal petrosectomy and one- or two-stage cochlear implantation after open cavity surgery. They reported one patient with residual cholesteatoma and one with wound breakdown at the external meatus. Good results were also reported by Szymanski et al.;Reference Szymanski, Ataide and Linder18 these authors did not observe any complications in seven patients where a subtotal petrosectomy was performed after previous open cavity surgery. In the largest series of subtotal petrosectomy cases reported in the literature, published in 2017, Prasad et al.Reference Prasad, Roustan, Piras, Caruso, Lauda and Sanna14 analysed the results of 460 patients. In 91 cases, subtotal petrosectomy and cochlear implantation was performed, with a very low rate of electrode extrusion of 1.1 per cent. A previous surgical procedure was the indication for cochlear implantation with subtotal petrosectomy in only 48.3 per cent of cases. The type of surgery performed and the exact number of patients with a previous large meatoplasty is not specified.
Those who advocate maintaining a canal wall down mastoid cavity following cochlear implantation refer to the simplicity of the procedure, the improved post-operative visualisation and the ability to clean the cavity. Furthermore, maintaining the canal wall down cavity decreases the risks related to external auditory meatus overclosure, such as post-operative infections, dehiscence of large pre-operative meatoplasties, development of residual cholesteatomas, fat necrosis, mucoceles, cavity infections, meningitis and complications related to the fat donor site.Reference Free, Falcioni, Di Trapani, Giannuzzi, Russo and Sanna5,Reference Casserly, Friedland and Atlas9,Reference Postelmans, Stokroos, Linmans and Kremer12,Reference Lyutenski, Schwab, Lenarz, Salcher and Majdani19 In particular, the development of residual or recurrent cholesteatomas causing a masked cavity infection with meningitis is a dreaded complication. Thus, early detection of a residual or recurrent cholesteatoma can be considered a priority. For this, maintaining the otoscopic view into the external auditory canal after pseudo mastoid obliteration may be beneficial during the required long-term follow up of patients with cholesteatoma. It is especially important in patients with a cochlear implant, where MRI follow up is limited.
However, maintaining an open cavity is not without risk, and both electrode exposure and extrusion have been reported, including electrode extraction with mastoid cavity cleaning, which is needed in these patients once or twice a year.Reference Issing, Schonermark, Winkelmann, Kempf and Ernst2 In order to reduce the risk of extrusion, many surgical techniques emphasise the meticulous elevation of the cavity's fibroepithelial lining, minimising the risk of leaving residual squamous tissue, while providing adequate soft tissue coverage of the electrode. Several different techniques have been described for electrode coverage, using combinations of bone pâté, fibrin glue, bone cement, perichondrium, bone matrix, cartilage, abdominal fat and local musculoperiosteal flaps.Reference Himi, Harabuchi, Shintani, Yamaguchi, Yoshioka and Kataura20–Reference Craig and Lavy22 The principal limitation is that most published data relative to these techniques are based on small case series, and thus a definitive conclusion about outcomes cannot be obtained.
This retrospective study shows that partial mastoid obliteration with the cartilage palisade technique may be a safe option for cochlear implantation when a large meatoplasty exists and closure of the external auditory meatus is not easy to perform. The decreased blood supply surrounding the open cavity, and the tension placed on the double layer closure of a large meatoplasty, increase the risk of complications related to external auditory canal blind sac closure.
This study's findings are in line with reports on cochlear implantation regarding subsequent and simultaneous reconstruction of the posterior bony canal wall and obliteration of the mastoid cavity.Reference Tamura, Shinkawa, Ishida and Sakai23,Reference Balk, Schwarz, Wolber, Anagiotos and Gostian24
• Cochlear implantation is challenging in canal wall down mastoidectomy cases
• Several techniques have been described to reduce the risk of post-operative complications
• Subtotal petrosectomy, with external auditory canal overclosure and Eustachian tube plugging, is considered safe but not without risk
• In large meatoplasty cases, blind sac closure of the external canal may be difficult and the risk of dehiscence is higher
• This paper describes partial obliteration of the mastoid cavity with cartilage multi-layered palisade reconstruction covering the electrode
• This technique is a feasible alternative in selected patients with a large meatoplasty and stable mastoid cavity
We recognise that there are several limitations to our study. In a similar way to all retrospective reviews, ours is limited by the availability and accuracy of medical records, and we recognise that we are reporting on a small cohort of patients. Despite this, we consider that pseudo-obliteration of the canal wall down mastoid cavity with a cartilage multi-layered palisade reconstruction covering the electrode can be advocated as a feasible alternative technique in selected patients who present with a large meatoplasty and a stable mastoid cavity.
Competing interests
None declared
