|Year : 2020 | Volume
| Issue : 2 | Page : 24-29
Cochlear implant surgery: Analysis of changes in surgical strategies for better outcomes
Naresh K Panda, Gyan Ranjan Nayak, Roshan Kumar Verma, Jaimanti Bakshi, Ramandeep Singh Virk
Department of Otolaryngology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
|Date of Submission||19-Jun-2020|
|Date of Acceptance||25-Jan-2021|
|Date of Web Publication||19-Feb-2021|
Dr. Naresh K Panda
Department of Otolaryngology, Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012
Source of Support: None, Conflict of Interest: None
Objectives: Like any surgical procedure, the cochlear implant surgery is constantly in evolution. This paper highlights the various modifications in the surgical strategies that have been incorporated into the surgical procedure with regard to the changes in incision, the route of insertion of electrodes, the depth of electrode insertion, and ultimate outcome in the patients. The modifications in the surgical strategy have been based on scientific evidence. Methods: A retrospective analysis of 220 cochlear implant procedures done with the posterior tympanotomy approach has been performed. The cases performed with the alternate technique, and cochlear anomalies have been excluded. The various surgical strategies which wer evaluated included the incision, the periosteal flap, the drill hole technique, the route and depth of insertion and the surgical outcome. Results: The incorporation of mini incision drastically reduced the incidence of postoperative infection and exposure of implants (P < 0.05). The authors classified the round window membrane at posterior tympanotomy and graded them accordingly. The depth of insertion of electrodes was also evaluated prospectively. The use of modified tie down technique reduced the operative time. The vascularized temporoparietal fascia flap helped in saving 5/9 implants with exposure. Conclusions: The cochlear implant surgery is constantly evolving. This paper highlights the critical appraisal of different steps in surgical strategies that have been incorporated into the surgical procedure. This reflects the surgical audit of our cases. These surgical strategies have resulted in reducing the incidence of complications in our series and improving outcomes.
Keywords: Cochlear implantation, round window insertion, surgical modifications, surgical strategy
|How to cite this article:|
Panda NK, Nayak GR, Verma RK, Bakshi J, Virk RS. Cochlear implant surgery: Analysis of changes in surgical strategies for better outcomes. Ann Indian Acad Otorhinolaryngol Head Neck Surg 2020;4:24-9
|How to cite this URL:|
Panda NK, Nayak GR, Verma RK, Bakshi J, Virk RS. Cochlear implant surgery: Analysis of changes in surgical strategies for better outcomes. Ann Indian Acad Otorhinolaryngol Head Neck Surg [serial online] 2020 [cited 2021 Sep 21];4:24-9. Available from: https://www.aiaohns.in/text.asp?2020/4/2/24/309782
| Introduction|| |
The understanding of the electrophysiology of the auditory system has led to certain changes in surgical technique of cochlear implantation. The surgery for cochlear implantation has therefore become more safe and reliable for the successful placement of the devise.
The cochlear implant surgery comprises many steps commencing from preoperative preparation, incision, raising of periosteal flap, and exposure of the round window area for proper placement of the electrodes. These steps of surgery have been topic of discussion for over two decades. The consensus of various approaches to the cochlea unfortunately has not been reached.
The earliest approach to the scala tympani was through the round window. The round window membrane is placed at around 90° angle to the oval window. It has a bony overhang and is conical in nature with the horizontal posterosuperior part which is closure to the osseous spiral lamina and vertical membranous anteroinferior part along which the electrode array is inserted., The anatomical difficulty of smooth passage of electrodes due to a ridge of bone the crista fenestra was highlighted by Banfai 1978 and Franz et al. 1987., This ridge located anteroinferiorly offered resistance to the insertion of the electrode array. Following this finding, some surgeons started to drill a cochleostomy located anteroinferiorly to the round window niche. The justification was an easy access to the basal turn. The clock completed a full circle when many surgeons started using the round window approach for insertion of electrode array.,,,,
The various factors which result in loss of residual hearing include surgical trauma during the cochleostomy or during the insertion of the electrode. Hence, Lehnhardt in 1993 proposed the soft surgery technique for cochlear implantation in order to reduce the insertion-related trauma.
The receiver stimulator package with its coil microcircuitry also needed to be put beneath the skin on the bone in such a way that there is no pressure on the overlying skin. In addition, the package had to be kept in a well and required fixation to the skin. This was using ties. Some surgeons have advocated the periosteal pocket technique tor safe and secure placement of the receiver stimulator unit.
Many incisions and designs for the periosteal flap for cochlear implantation have been described., The standard postauricular incision called the Lazy s incision described by Gibson et al. too has undergone some changes. Chronic suppurative otitis media is not a contraindication for cochlear implantation. Many authors have described approaches for dealing with such patients. The issue of mastoid cavity and cochlear implant also needs to addressed. The authors experience with single-staged cochlear implantation has also been highlighted; during this period, the cochlear Implant surgeons have incorporated numerous changes and modifications into the surgical procedure. The endeavor is to make the surgery safe, less cumbersome, minimize complications, and improve surgical outcomes. This paper aims to highlight the changes in surgical strategies and protocols in cochlear implant surgery at our center.
| Methods|| |
A retrospective analysis of 313 cases of cochlear implantation in the department of Otolaryngology between 2005 and 2018 was carried out. Out of these, 83 cases were done with the alternate Veria technique and excluded from the analysis. Ten cases with various anomalies were also excluded. The data of 220 cases were performed with the conventional posterior tympanotomy approach were included for analysis. This included 199 children and 21 adults. An informed consent was obtained from all the parents or the patients. The Institute Ethics Committee approval was also obtained. Five out of 21 adults were with long-standing mastoid cavities. They were implanted with a single-stage technique using a blind sac closure of the external auditory canal complete removal of epithelium from the middle ear and mastoid, obliteration of the cavity with temporoparietal fascia flap, and electrode insertion. The standard preoperative protocol consisted to sterile hair washing, hair clipping, and prophylactic antibiotic administration of injection amoxycillin and clavulanic acid half an hour before the incision.
For the sake of analysis of various surgical strategies, the following parameters were evaluated. Age of implantation, incision used, the periosteal flap design, drilling a well (bone recess) for the receiver stimulator unit, and tie down-hole technique for securing the implant, insertion route (conventional vs. round window insertion), depth of insertion issues and final outcome in relation to adverse outcomes. Statistical analysis using the SPSS (Statistical package for social sciences-IBM SPSS) for ANOVA and Chi-square tests was employed.
| Results|| |
One hundred and thirty one patients were <5 years. Forty six patients were in the age group of 5–10 years and 22 patients were in the age group of 10–13 years (older prelinguals).
The lazy S incision was used initially in 39 patients. Rest of the 181 patients were performed with the mini incision. The mini incision did not extend beyond the hair line. The patients with the mini incision had significantly less infection and exposure (P < 0.05). Compared to the lazy S incision [Figure 1].
The anterior-based large Palva flap was used in all the cases. There was no difficulty for exposure and final coverage of the periosteal flap.
The bone recess
A well or bone recess was created in all the cases.
Tie down-holes T
The tie down-hole technique was modified in the year 2012. After 41 cases up to 2011, we started making only two holes on each side of the bone recess [Figure 2]. The conventional technique is to make four holes each side for the securing the implant.
Up to July 2011, a conventional cochleostomy (anteroinferior to the round window niche) was done in 35 cases. A round window membrane insertion technique has been performed in 164 patients since 2012. Eight of 164 patients could not be inserted through the round window membrane and required conventional technique. We have used the classification from our center to grade the round window membrane in these 164 patients. Our grading system has subsequently been validated.
The round window membrane visibility was graded in 164 patients. The grading was from Grade I to Grade IV. The Type III round window membrane was found to be the 126, most common, i.e., 62/164 (37.80%) [Figure 3].
**The Grade I was when >50% of the round window membrane was visible through the posterior tympanotomy [Figure 4].
- • Grade II was when <50% of round window membrane was visible [Figure 5]
- • Grade III when only a glimpse of round window membrane was visible [Figure 6]
- • Grade IV when round window membrane was not visible.
Depth of insertion and out come
Thirty children in the age group of 2–12 years undergoing cochlear implantation were prospectively analyzed between 2012 and 2014. Subsequently, the study was extended in further 48 patients. The depth and length of electrode insertion were calculated in the postoperative Stenver's view radiograph according to Marsh et al. [Figure 7]. As seen in the picture, the electrode array occupies four quadrants, i.e., 360° insertion. [Table 1] shows the categorization of depth of insertion. The children were followed up to 1 year and were subjected to various outcome measures such as MAIS, ITMAIS, CAP scores, and SIR scores. Statistical analysis was done with Mann–Whitney test for analysis between the groups. The spearman correlation coefficient was calculated to see correlation between different variables and insertion depth. The findings were almost the same with the insertion of 270°–360° having the best outcomes. The study revealed that insertion from 270° to 360° gave optimum hearing benefits compared to insertion beyond 360°.
|Figure 7: The Stenver's view radiograph used for the calculation of angle of insertion|
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The challenging issues having increased potential for complications are depicted in [Table 2].
The complications in the series were 10% of the total. They were major 10/220 (4.5%) and minor in 12/220 (5.45%). The details of the various complications and their management are given in [Table 3]. Out of nine patients with skin necrosis and exposure of the implant, four patients underwent explantation. Five patients underwent re-exploration with temporoparietal fascia flap coverage of the implant [Figure 8]a and [Figure 8]b.
|Figure 8: (a) The temporoparietal fascia flap. (b) the temporopariteal fascia flap covering the receiver stimulator unit|
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|Table 3: Complications and their management in 220 cases (excludes anomalies)|
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| Discussion|| |
The cochlear implantation procedure is constantly evolving over the years. The endeavor of the surgical team is to constantly audit the surgical strategies for better outcomes. We too have tried to look into the various surgical steps so as to modify them for making the surgery of cochlear implantation safe for the patient. It is important for the surgical team to strictly follow the surgical principles and protocols for trouble free surgery.
The antibiotic prophylaxis employed at various centers has also changed with little differences between centers to center. Our antibiotic prophylaxis has changed from giving intravenous antibiotics for 7 days to a period of 72 h, since the year 2013. The patients are discharged after a two night stay in the hospital. Thus, early discharge of the patient has become the norm at most centers including ours. The incision employed in cochlear implantation has been constantly being modified. After using the Lazy S incision for couple of years, we too have changed over to the mini incision. The mini incision has the distinct advantage of avoiding the hair line of the scalp. This avoids the hair follicles which could be harboring the normal bacterial commensals. These organisms have the potential of becoming pathogenic. O'Donoghue et al. too have reported the use of the mini incision. They observed that there was less risk of flap complications. They found that minimal access approach for pediatric cochlear implantation was very well accepted. We have used this in all the children with the exception of very young children < 2 years and our observation has been the same. The periosteum and the skin flap have the probability of being very thin in very young children and require added attention and may be risky for using mini incision in them. We have been using the large anteriorly based Palva for all of our patients. It has the advantage of offering good coverage of the receiver stimulator unit, and there is no resultant tension in the flap while suturing. One more distinct advantage of the flap is that the closure line of the flap and the skin sutures lie at a distance and hence safe for the patient according to surgical principles.
The modified technique of making only two tie down holes instead of four on each side of the bone recess shortened the operative time and had no adverse outcomes. We had no case of slippage of the implant from the bone recess. The preservation of residual hearing has emerged as an area of concern in cochlear implantation. Residual hearing preservation maximizes the chances of better hearing outcomes. The soft surgery technique is in vogue among the surgeons.
Hence, majority of surgeons are using the round window approach for electrode insertion. Moreover, the round window insertion is gaining acceptability due to less drilling, less perilymph loss, and less bone dust. The round window was described by Gabriel Fallopius in the 16th century. Antonio Scarpa described it as secondary tympanic membrane. Its shape can best be described as hyperbolic and parabolic. It has a dimension of 2 mm × 2 mm. It has two segments: the posterosuperior which is horizontal and anteroinferior which is vertical in its orientation. The vertical segment becomes the portal of entry to the scala tympani. While approaching the round window intentioned cases, the round window membrane is obscured by the niche. Roland et al. stated that the visibility of round window membrane increases by three folds after drilling of the niche. The visibility of the round window membrane after an adequate posterior tympanotomy determines the amount of drilling required for access of the round window membrane. The classification system proposed by us was later validated in 195 patients at two centers. The Grade III type of round window membrane has been found to be the most common in the subcontinent. Our standalone classification preempts the surgeon about the amount of drilling required for a smooth round window insertion. Grade I to III would suggest an easy membranous insertion, whereas the presence of Grade IV round window membrane cautions the surgeon for a possible conventional cochleostomy. Our classification is different to that of Leong et al., in which the round window overhang was first removed and then classified. The visibility of round window membrane through the posterior tympanotomy ensures less drilling less vascular injury and has more probability of hearing preservation.
There is a mixed opinion regarding the relationship between insertion depth and performance. A greater correlation has been observed by many authors between deep insertion and better hearing outcomes. Gstoettner et al. reported that as the cochlear canal cross sectional area diminishes near the apex, deeper insertions may cause mechanical trauma. And have no advantage in hearing outcomes.
Our prospective study conducted during 2012–2014 was first of its kind and focused on depth of insertion and hearing outcomes of children. The cohort has further been extended 48 patients. The results obtained in these 48 patients have validated the findings of our previous study. The Surgical team should ensure an insertion from 270° to 360° to get good results.
Our rate of complications and adverse events is comparable to the latest reports of complications by Halawani et al. (7%), and Raghunandhan et al. 10%. The acceptable incidence of complications in our series can be attributed to many factors. They are primarily the use of mini incision, use of large anterior based periosteal flap, creating a large posterior tympanotomy, and the round window insertion technique used in majority of our cases. We were fortunate not to have any case of postoperative hematoma in our series. This was due to the protocol of putting a pressure dressing with elastic bandage (Crepe bandage) for 24 h. The mastoid dressing is kept for another 24 h and subsequently the child is discharged.
Exploration of the wound in children with skin necrosis and implant exposure requires extra attention. On the part of the surgical team, removal of granulations and all the devitalized skin is the key. It is advisable to lift the receiver stimulator unit off the bone recess and clear the granulations, the implant may need to be secured to a new bone recess. In addition, the coverage with well-vascularized temporoparietal fascia flap has made a huge difference for favorable outcome. A good blood supply from the anterior branch of superficial temporal artery gives this flap superiority compared to a nonvascularised flap.
To conclude, it is important for the cochlear implant surgeon to constantly innovate so as to provide the best care to the patients undergoing cochlear implantation. Our paper emphasizes the importance of constantly modifying the surgical strategies based on evidence for better outcomes as has been done in our tertiary referral center.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2], [Table 3]