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Received: November 18^th 2014

Accepted: April 28^th 2015

 

Postoperative complications of cochlear implant: eight years of experience

 

Daniela Yépez-Pabón,^a Marco Guevara-Sánchez^b

 

^aColegio de Postgrados en Medicina, Escuela de Medicina, Universidad San Francisco, Quito, Ecuador

^a,bServicio de Otorrinolaringología, Hospital Carlos Andrade Marín, Instituto Ecuatoriano de Seguridad Social, Quito, Ecuador

Communication with: Daniela Yépez-Pabón

Telephone: 593 2 3319861

Email: dyp_doc@hotmail.com

Background: Cochlear implant surgery has a low morbidity and mortality. Postoperative complications can be minor and major. Minor complications require conservative management; major complications require reoperation or implant removal. The aim is to determine our complications and compare them with international and Latin American series.

Methods: 275 operated cases were retrospectively analyzed from December 2005 to December 2013. Children and adults between 11 months to 82 years old are included. Demographic data, unilateral or bilateral placement, type of surgery and postoperative complications were evaluated. The follow-up was made for 20 months.

Results: The 57.46 % are children and adolescents, youth and adults are 33.81 %; and 8.73 % are seniors. The complication rate is 12 % (n = 33), 6.91 % for women and 5.09 % for men. There are more complications among 19 to 60 years old. Minor complications account for 7.6 %: local infection (n = 9), delayed transient facial palsy (n = 7), vertigo (n  = 3) and tinnitus (n = 2). These are prevalent in children and adults. Major complications are 4.36 %: postoperative hematoma (n = 8), extrusions (n  = 2) and inadequate electrode placement (n = 2). These predominate in adults among 19 to 60 years. No deaths or cases of meningitis occurred.

Conclusions: Cochlear implantation has a low incidence of complications. Our results, the only reported at the national level, are comparable with those mentioned in literature.

Keywords: Cochlear implants, Infection, Replantation

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The cochlear implant is an implantable active medical device, high-tech and high-precision, designed to transmit acoustic information via the central auditory pathway through direct electrical stimulation of the auditory nerve fibers to restore hearing in patients with severe or extreme deafness.¹

The cochlear implant surgery, like any surgical procedure, is not without risk, but relatively is not prone to complications.² Previous international studies have shown a low rate of postoperative complications of cochlear implant therefore it is considered to be a relatively safe procedure.^3-5

The overall complication rate has been reported between 5 and 13%, depending on the study.^2,6 Cohen, in 1995, divided the postoperative complications of this surgery in two categories: minor and major complications.^6-8

Minor complications are those that may or may not produce a decrease in the function of the implant, but resolve spontaneously or with conservative treatment, without need for further surgery. These include: local infection of the surgical wound, tinnitus, dizziness, altered taste and transient late facial paralysis. The literature cites an incidence between 7 and 37%.^2,8,9

Major complications are those requiring reoperation. These include flap complications leading to extrusion of the device and requiring reoperation, formation of cerebrospinal fluid leaks, meningitis, and failure (technical or medical) of the implanted device, requiring it to be explanted and / or reimplanted.^9-11 The incidence of major complications in the literature is reported between 2.5 and 15%.^2,5,8-10

The Servicio de Otorrinolaringología of the Hospital Carlos Andrade Marín of the Instituto Ecuatoriano de Seguridad Social (IESS) implemented the Cochlear Implant Program in December 2005. By December 2013 275 implants were placed. Our series is the only reported nationwide.

This study aims to revise the caseload of these surgeries in the Servicio de Otorrinolaringología, Hospital Carlos Andrade Marín and compare our results with international and Latin American studies.

Methods

Design: A descriptive and retrospective study.

Sample: information was obtained from the medical records of 275 patients who underwent cochlear implant placement in the Servicio de Otorrinolaringología, Hospital Carlos Andrade Marín, Instituto Ecuatoriano de Seguridad Social of Quito, in the period December 2005 to December 2013. They included pediatric and adult patients. All patiensts were followed up for 20 months.

Analysis: descriptive statistics were used to analyze quantitative variables of patients, with the intention to find out its demographic distribution and characteristics in terms of unilateral or bilateral implant placement, the type of surgery performed (primary or sequential) and rates of postoperative complications (minor or major) that were presented. All data were tabulated with the statistical program Microsoft Excel.

Results

The study included children and adults from 11 months to 82 years old.

There was an equal distribution between genders (50.54% of men versus 49.46% women). The average age in the group of children under 3 years was 1.9 years; in young adults, 29 years old, and in the group of adults, 51 years old.

The 57.46% of the surgeries were performed in pediatric and adolescent patients. Children under 3 years represented the group with the highest number of interventions (100/275), equivalent to 36.37% of the total. The group of young people and adults up to 60 years of age accounted for collectively the second largest group for the surgery (33.81%). In our causal investigation, the group of seniors accounted for only 8.73%. These results are summarized in Table I.

Of the 275 surgeries performed, 97% were unilateral implant placement and the remaining 3% were bilateral implants. Depending on the type of surgery performed, 96.7% were primary surgeries, 8 cases (2.9%) were sequential surgeries; and 1 case (0.4%) was the first simultaneous placement of cochlear implants in our service.

Of all surgeries performed, 33 patients (12%) had some type of postoperative complication. Minor complications accounted for 7.64% of the total (n = 21), and major complications, 4.36% (n = 12). In the female group the more complications (6.91%) than the male group (5.09%). Table II shows the results.

By correlating results by gender and age, among females, the group aged between 41-60 years presented the most complications (2.18%), followed by the group between 19-40 years (1.82%) and finally, by the group between 3-18 years of age, who presented 1.1% of complications. Adjacent age groups had the lowest complication rates, with 1.1% in ≤ 3 years and 0.36% for over 61 years. In male patients, again the age groups between 41-60 years (1.82%) and 19 to 40 years (1.45%) had the highest average number of complications. Unlike the female group, children ≤ 3 years of age accounted for the group with the third highest incidence of complications (1.1%). Patients between the ages of 3-18 years and over 61 years had a low incidence of complications (0.36% each).

As for the type of complications by gender and age, among women aged 19 to 40 years, and 41 to 60, the highest percentage corresponded to minor complications (1.1% and 1.82%, respectively). However, the third group by prevalence of complications, of patients between 3-18 years, had a higher rate of major complications (1.09%).

The male group presented a larger number of minor complications in each group, representing 0.73% in patients ≤ 3 years old; 1.1% in the group 19 to 40 years and 1.45% in patients between 41-60 years of age. Tables III and IV correlate this data.

The minor postsurgical complications found included: 9 cases of local wound infection (3.27%), 7 cases of late transient facial paralysis (2.55%), 3 cases of postoperative vertigo (1.09%) and 2 cases of tinnitus (0.73%).

Local wound infection was more common in children and adolescents aged ≤ 3 to 18 years who together accounted for 1.81%. All cases of late transient facial paralysis occurred in adult patients ranging from 19 to 60 years. Postoperative vertigo appeared only in the older population between 41-82 years of age. Tinnitus was presented in the groups of young adults 19 to 40 years old and older adults between 41-60 years of age. 

Major postoperative complications were: formation of postoperative hematomas in 8 patients (2.90%), improper placement of electrodes in 2 patients (0.73%), and device extrusion in 2 patients (0.73%). The last 4 cases required reimplantation.

Of postsurgical hematomas, 4 cases occurred in the pediatric population aged ≤ 3-18 years, representing 1.45% of complications, 3 cases (1.09%) in young adults ages 19 to 40, and 1 case (0.36%) in older adults.

The two cases (0.73%) of improper placement of electrodes were both in the population between ≤ 3 to 18 years.

The device extrusion cases were caused by injury to the skin of the surgical area from decubitus (1 case), and infection of the recipient site (1 case), and presented exclusively in the adult population over 40 years of age, together representing 0.73% of complications. Table V summarizes the types of complications by gender and age. No cases of meningitis or deaths occurred.

Making a comparison with the reference to international and Latin American causation studies, we noticed that our percentage of postoperative complications is similar. Table VI compares the results of our experience with the literature review.

Discussion

The analysis of the results of cochlear implant surgery carries some important considerations to be taken into account. It is not the same to implant a child born deaf before 3 years of age, who has been diagnosed promptly and had headphones placed before a year with speech therapy and all recommended care; with a child older than 3 years without previous auditory stimulation or language therapy, expectations are definitely different. It will even be different in the case of a child under 3 years without the recommended prior stimulation. It is considered that the critical age for the greatest auditory neuronal plasticity is within the first 3 years of life, after which it decreases and results in language development will not be the same.^3,4 From this age, critical in children, each case must be analyzed very carefully to decide whether or not to implant, considering the age of diagnosis, time of deprivation and prior auditory stimulation, language development, the degree of parental involvement, etc.; with these elements one can determine expectations.

For adolescents the situation is complicated because self-esteem issues are added because of their disability, discrimination by society and those around them, issues of exclusion, etc. that make patients accept or not accept the intervention, or use the language processor or not.⁵

In post-lingual adults the result is more predictable,^6,12 in general they are highly motivated patients and their adaptation to the device is very good. In young adults up to age 40 and older adults up to age 65, surgery to promote their rehabilitation and reintegration into society is fully justified, since they are economically productive age, otherwise they would become a burden on society. In the older adult group, sometimes the debate is the issue of resources, but we believe that they have full rights. Our institution, the Instituto Ecuatoriano de Seguridad Social (IESS), is determined by law to cover this surgery in this population. 

These are the considerations to analyze our results in these 5 age groups and the complications that arise in each.

Reports of cochlear implant surgical complications are classified as major and minor with the purpose of unifying criteria and establishing valid comparisons.^2,4 There are numerous reviews that refer to the total percentage of such complications, placing it between 5 to 13%,^2,6

In our study we found an overall complication rate of 12%, concurring within the references described.

Most minor postsurgical complications occur immediately after surgery, but tend to resolve over time. Among these, the failure of scarring associated with surgical wound infection is the most common problem. The overall rate of infections reported in the literature varies from 1.7 to 16.6%.^10,11,14,16 In our study, 7.64% of postsurgical complications observed were minor, and of these, the wound infection was the main surgical complication, accounting for 3.27%.

Local wound infection was more common in the pediatric population aged ≤ 3-18 years, probably because of failure in the postoperative recommendations and the child’s manipulation of the wound.

Another possible minor complication very commonly reported is late transient facial paralysis, whose incidence varies from 0.31 to 14%.¹¹ Our findings found an occurrence of this complication in 2.55% of cases. All of these cases appeared in adult patients ranging from 19 to 60 years, with complete and satisfactory recovery without sequelae.

An incidence of postoperative vertigo between 8 to 39% has been reported in the literature, while tinnitus is seen in about 1% of cases.^2,10 In our study, these two types of minor complications occurred in very low percentages, representing 1.09% and 0.73%, respectively. Postoperative vertigo appeared only in the older population between 41-82 years of age, while tinnitus was presented in groups of young adults 19 to 40 years old and older adults between 41-60 years old. Patients with vertigo had gradual and complete clinical improvement. The patient group 41-60 years who presented tinnitus symptoms persisted and required recalibration of the external component of the cochlear implant to mitigate noise, controlling the problem. In the second case of tinnitus, it let up spontaneously at 3 months.

Major complications, meanwhile, have been reported in the range between 2.5 and 15%.^9,13,15 In our study, these accounted for 4.36%, an acceptable range and comparable with the international literature.

Among the possible major complications, those relating to the injury of the flap are reported at a frequency of 0-5%.^15,17 These complications can occur as hematomas, ulcerations and / or necrosis of the skin incision, dehiscence, infection of receptor site, etc. As a consequence, they cause partial or complete extrusion of the internal cochlear implant component.^2,11

In our study we found that the formation of postoperative hematomas was the most frequent adverse outcome, representing 2.91% of all major complications. This result was presented mainly in the pediatric population and young adults. We believe that predisposing factors could be failed hemostasis powered by likely bad postoperative management, especially in infants, whose parents reported handling and contusions on the site of the surgical incision. 

Moreover, only 1.45% of all cochlear implants that were placed in our study required reimplantation, the main causes being improper placement of electrodes and extrusion by skin lesion at the surgical site because of decubitus and infection of the receptive area.

We had two cases in the pediatric population of improper placement of electrodes. This complication was suspected by the lack of response of the electrode chain in the telemetry during surgery and confirmed after performing a skull radiograph. After the relocation of the implant in the same surgery, telemetry responses were positive for the entire chain of electrodes, in both cases.

A patient in the over 40 age group presented skin lesion in the surgical area because of decubitus, secondary to his failure to adhere to established  and explicit recommendations. He used reading glasses immediately post-surgery, injuring the area of ​​the incision, which was then compounded by prolonged rest in the lateral position on the operated side. It was explanted and a new device was repositioned after eight months in the contralateral ear, without complications.

The patient with infection of the recipient site was the only case in our series so far, and we do not know why. In our surgical protocol we use Clarithromycin solution both on the surgical site and on the implantable device prior to its introduction so that it can counteract the formation of biofilms. We proceeded to explant and a new one was relocated in a second surgery, without further complications.

Other major postoperative complications reported frequently in the literature are of perilymph fistulas and neurological infections.^10,11 However, in our study we did not have these outcomes. Likewise, no death was presented because of surgery or post-surgical complications.

The analysis and comparison of our study with large-scale patient causal investigations allow us to establish that our results are within the expectations for this type of procedure.^18-25

Among the current studies reported, the Spanish multicenter study of Manrique and collaborators of the year 2006,²¹ is the most important by the number of cases reported. This is set at 10.48% the total postoperative complications, with minor at 7.06% and major at 3.42%.

Our Latin American references are the studies of Zernotti and collaborators in 2012 (Argentina) and Velandia y Rivas et al in 2011 (Colombia). Zernotti²³ includes a caseload of 208 patients and reports an overall complication rate of 10.5%, with major at 2.88% and minor at 7.69%. The Velandia y Rivas²⁵ study in Colombia and covers a greater caseload (598 cases), and its results are comparable to those reported in other studies, reporting a 8.2% total rate of complications, presenting minor complications at a higher rate (5.7%) versus major (2.5%).

Conclusions

From the results of our study we can draw the following conclusions:

 

• The cochlear implant surgery has a low rate of postoperative complications.
• Our results are comparable with those reported in international and Latin American studies.
• Our statistics are the only reported at the national level and therefore more important.
• Most of the outcomes of this surgery are fortunately minor complications that require only watchful waiting, monitoring and / or outpatient clinical treatment.
• In our study, the pediatric population and young adults had the highest number of minor complications, with local wound infection the leading cause. These findings highlight the importance of making postoperative recommendations care very clear to patients and families.
• The main major complication encountered was the formation of postoperative hematomas in both pediatric and adult population, which raises the need for meticulous intraoperative hemostasis review and appropriate outpatient management.

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