Introduction
When attending meetings on the topic of cochlear implantation or discussing outcomes with colleagues, one is often left with the impression that this procedure is almost without complications. Several years ago, much attention was directed towards patients developing meningitis following cochlear implantation.Reference Bluestone1–Reference Reefhuis, Honein, Whitney, Chamany, Mann, Biernath, Broder, Manning, Avashia, Victor, Costa, Devine, Graham and Boyle5 However, with the development of a modified implant (by Advanced Bionics, Valencia, California, USA) and the initiation of pneumococcal vaccination, the incidence of meningitis as a complication of cochlear implantation seemed to decrease. Nevertheless, a detailed search of the literature yielded reports of both minor and major complications associated with cochlear implantation.Reference Cunningham, Slattery and Luxford3, Reference Arnoldner, Baumgartner, Gstoettner and Hamzavi6–Reference Proops, Stoddart and Donaldson19 Such complications are a concern to patients and their families, and to the healthcare staff involved in their care, and awareness of such complications is thus essential. Furthermore, the resulting additional in-patient workload, as well as the burden to the health economy, are also relevant. Assessment of cochlear implant complications should take into account the drastic increase in the number of procedures performed at our department since 1998 (Figure 1).
Fig. 1 Number of cochlear implantations per year.
In our institution, patients undergo initial ambulatory investigation and diagnosis within the audiology department. The expected clinical course for admitted patients is: operation on day one, discharge on day two and removal of surgical strips on day seven. The audiology department begins auditory stimulation after four weeks. Thereafter, hearing and communication skills should develop in accordance with the patient's age and previous hearing experience.
Our clinical hypothesis is that all patients will follow the expected course. However, as we (and others, as mentioned above) have observed, for a few patients this is not the case. Thus, the aim of this study was to identify the range of post-operative problems and complications associated with cochlear implantation.
Materials and methods
Over a nine-year period from January 1998 to March 2007, a total of 313 implantations were performed in 300 patients by three surgeons at the cochlear implantation centre in West Denmark (Figure 1). Eleven patients underwent bilateral cochlear implantation. Two patients required re-operation on the same side. In nine patients, a previously implanted, single channel electrode was removed and a multi-channel device inserted. In 294 patients, various generations of the Nucleus® multi-channel device (Cochlear, Sydney, Australia) were used. In the remainder of the patients, an Advanced Bionics (Valencia, California, USA) device was implanted.
One hundred and eighty (60 per cent) patients were children (ages zero to 17 years included). Their median age at the time of operation was 2.8 years (range six months to 17 years). Fifty-three per cent were girls and 47 per cent were boys. The median follow-up time after surgery was 44 months (range five to 115 months).
One hundred and twenty adult patients (40 per cent) were included, with a median age of 50 years (range 18 to 79 years). Of these patients, 50 per cent were female and 50 per cent male, and the median follow-up time was 32 months (range five to 114 months).
Antibiotics were administered only peri-operatively, except in cases of inner-ear malformations or previous meningitis or skull base fracture. In such cases, patients were treated for 24 hours post-operatively with intravenous antibiotics, followed by oral antibiotics for a week.
Problems and complications were considered in terms of: longer length of hospital stay, additional out-patient visits, readmissions, and further treatment with antibiotics and/or surgical intervention. The abnormal clinical courses were categorised by time of onset of complications (i.e. early, intermediate or late) and complication severity (minor or major). They were also categorised by the presence or absence of: anterior swelling (in the temporal region and/or periorbitally, leading to longer hospital stay or extra out-patient visits); wound problems; skin problems; ear or central nervous system infections; or device-related problems.
Patients with complaints related to the external part of the device, to vertigo or to taste disturbance were excluded. (At the time of writing, a separate, prospective study regarding vertigo and taste disturbances following cochlear implantation was being conducted at our department, and data will be presented elsewhere. However, the total incidence of these complaints was approximately 5 per cent).
Finally, the treatment modality used to manage the complication was recorded.
Results
A total of 49 abnormal clinical courses were identified involving 45 patients, corresponding to 16 per cent of the entire patient population. Twenty-eight of these aberrant courses (28/45; approximately 62 per cent) occurred in children. These children had a median age of three-and-a-half years (range one to 14 years). The male to female ratio was 1:1.6. The remaining 17 aberrant courses occurred in adults (17/45; approximately 38 per cent), with a median age of 53 years (range 25 to 78 years). In adults, the male to female ratio was 1:2.4.
The complications and their severity are listed in Table I.
Table I Complications of cochlear implantation
* For 313 operations over the study period. †Requiring surgery. MRSA = methicillin-resistant Staphylococcus aureus
The most frequent complication was difficulty in wound healing (e.g. swelling, discoloration, defects, exposure of sutures, haematoma and abscess); this was seen in almost half of the aberrant courses. Included in this category were five children (aged one-and-a-half to three-and-a-half years) who injured themselves on the operated side of the head. Three of these patients developed haematomas or abscesses in the area of the surgical wound, and two developed necrotic skin over the implant.
Ear infections were the second most frequent complication, dominated by one or more episodes of otitis media. In a single case, multiple antibiotic resistant Staphylococcus aureus was isolated from a radical cavity (attributable to nosocomial infection acquired in the intensive care unit after cochlear implantation surgery). The infection was eradicated with the implant in place. Only one case of meningitis was identified, in a four-year-old boy with Klippel–Feil syndrome and a Mondini defect, with presence of a CSF gusher at surgery. Noncapsular Haemophilus influenzae was cultivated from the cerebrospinal fluid. The patient recovered completely with the implant in place. Problems related to the internal part of the device accounted for 16 per cent of cases of complications; these included misplaced, displaced or exposed electrodes. None of the implanted electrodes were dysfunctional.
Almost 75 per cent of the aberrant clinical courses involved complications of minor severity (Table I). The major complications included a case of meningitis, an infection of a radical cavity with multiple antibiotic resistant S aureus, and a diabetic patient with recurrent severe skin infections and complete exposure of the implant for several weeks before readmission. Also included in the group of patients suffering major complications were those who required some form of revision surgery.
The time from surgery to development of complications is shown in Table II. The majority of complications occurred soon after surgery; these comprised primarily anterior swelling and wound problems. The late complications were mainly due to skin problems (five of six patients; two with necrosis over the edge of the implant, one with complete exposure of the electrode, and one each with abscess and haematoma (these two were due to secondary trauma)).
Table II Onset of cochlear implantation complications
* For 313 operations over the study period. Mth = months
Twenty per cent of patients suffering complications required only observation, without antibiotic or surgical intervention (Table III). The majority of patients (71 per cent) were treated with antibiotics alone or combined with minor wound surgery or skin flap reconstruction. The diabetic patient with complete exposure of the electrode and skin defect was ex-planted. In two cases in which the electrode was introduced into the vestibule at surgery, the patients were reimplanted with a new electrode. In the single case in which a well functioning electrode was partly extruded from the cochleostomy, the same electrode was easily reintroduced.
Table III Treatment modalities* used for cochlear implantation
* Several modalities were used in some of the 49 patients resulting in a total of 58 treatments. †Puncture or incision.
Discussion
This retrospective review of 313 consecutive cochlear implantations in 300 patients found that a total of 16 per cent of cases followed an unexpected clinical course, dominated by early problems with wound healing. No fatal outcomes were observed, but major complications occurred in 4.5 per cent of patients. Most problems (e.g. misplaced electrodes and skin flap problems) were corrected with only a small additional risk to the patient. The incidence of major complications in our study is comparable with that of other studies, and was at the lower end of the range, as seen in Table IV. We believe that the centralisation of cochlear implantation, resulting in a large number of procedures being performed by a small number of units and surgeons, is the basis of our low complication rate. Antibiotics were the most common intervention, while surgery played a minor role.
Table IV Cochlear implantation complications: other authors' findings*
* Only studies assessing a minimum of 100 surgical procedures were included. C = children; A = adults; CI = cochlear implantation
• This study assessed post-operative complications associated with 313 cochlear implant operations performed at a teaching hospital
• In the studied setting, cochlear implantation was a safe procedure for correction of bilateral deafness; however, post-operative complications occurred in some patients
• Major complications occurred in 4.5 per cent of patients, requiring either intensive antibiotic treatment and/or re-operation
• It is important that healthcare and teaching staff be aware of the possible problems and complications of cochlear implantation, both early and late onset, so these can be promptly addressed
After audiological fitting of their implant, cochlear implantation patients are mainly in contact with their general practitioner, local hospitals and teaching staff. Therefore, it is of the utmost importance that these professionals are familiar with the possible complications of cochlear implantation, including those that can develop in the long term. Furthermore, with regards to cost-effectiveness, it is important to estimate the additional load on cochlear implantation centres caused by post-operative problems. Most aberrant courses were identified either because the patient presented with a complaint or a planned control at the audiological department. The ensuing consultation at the ENT department of the cochlear implantation centre resulted in medical and/or surgical intervention in eight out of 10 cases. There were only a few cases in which an ENT department consultation seemed unnecessarily delayed. Since complications may occur at any time after implantation, it is difficult to recommend a fixed follow-up regimen. However, due to the risk of silent otitis media, retraction pockets and cholesteatoma (none of which were encountered in our patient population), patients ought to be seen regularly by an ENT specialist. In all cases of suspected post-implantation complications, we recommend that patients should be offered a re-examination at the cochlear implantation centre within a few days.
In comparison with other studies (Table IV), our results are striking in several respects. Our rate of major complications was at the lower end of the range.Reference Cunningham, Slattery and Luxford3, Reference Arnoldner, Baumgartner, Gstoettner and Hamzavi6–Reference Proops, Stoddart and Donaldson19 It should be noted that we did not experience any problems related to the facial nerve, nor (as already mentioned) did we have any cholesteatomas or fatal outcomes. However, it is important to note that the other studies cited may not be comparable regarding study population, surgical methods and implant devices used, follow-up regimen, criteria for inclusion of complications, and treatment of complications, and also regarding other factors such as variations in funding for different departments.
Conclusion
Based on the current study, it can be concluded that cochlear implantation is a safe procedure within the studied setting. However, it is essential that careful attention be paid to surgical planning and technique, and it is important for healthcare staff and patients to be aware of the possible problems and complications.
