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Abdulmalik A Alkhodair*, Abdulrahman F Aljadoa, Mohammed S Alobayli, Sahar M Bin Dehaish and Fahad N Altamimi
Department of Otolaryngology Head and Neck Surgery, King Saud Medical City, Saudi Arabia
Submission:June 28, 2020; Published:July 14, 2020
*Corresponding author:Abdulmalik A Alkhodair, Department of Otolaryngology Head and Neck Surgery, King Saud Medical City, Riyadh, Saudi
How to cite this article: Abdulmalik A A, Abdulrahman F A, Mohammed S A, Fahad N A, Sahar M Bin Dehaish. Electrode Migration: A Review Article.
Glob J Oto, 2020; 22(5): 556099. DOI: 10.19080/GJO.2020.22.556099
Cochlear implant (CI) is considered as safe, and effective surgical procedure for patients with Sensory Neural Hearing Loss (SNHL). The cochlear implant is an electronic device implanted behind the ear, with electrode arrays which are inserted into the Scala Tympani of the cochlea to stimulate the auditory pathway. The complications rate of cochlear implant surgery is very low, and more common in pediatrics. Furthermore, electrode migration is one of the complications which are defined as gradual slipping out of electrode from cochlea or extrusion from tympanic membrane. Data were being collected through search engines included PUBMED, Google Scholar, and BMJ. The process of sorting out of articles as per inclusion criteria which has an outcome related to electrode migration in post cochlear implant. After removal of duplicate studies, total of 12 articles were found eligible for review analysis. Electrode migration is more common as previously reported, it has shown that fixation techniques should be more reliable to avoid migration of electrode. The purpose of this study is to get a detailed review of electrode migration causes and prevalence in post cochlear implant patients and what factors can lead to migration intraoperative and post-operative cases.
Cochlear implant (CI) is a well-known, safe, and effective surgical procedure for patients with Sensory Neural Hearing Loss (SNHL), which is a type of hearing loss due to either inner ear pathologies, or Vestibulocochlear nerve (VIII) damage . Moreover, it is reported that 20% of patients with congenital SNHL have a concurrent inner ear malformation . Despite of multiple treatment options have been applied; however, cochlear implant (CI) surgery is the mainstay of surgical treatment. In addition, Cochlear implant is an electronic device implanted behind the ear, with electrode arrays which are inserted into the scala tympani of the cochlea to stimulate the auditory pathway [3,4]. Moreover, cochlear implant device has two types of electrodes: Straight lateral wall (LW) electrode arrays, and Perimodiolar electrode arrays .
As any other surgical procedures, the complication rate of cochlear implant surgery is very low, and reported around 3-10% of all CI surgeries, common in pediatric patients . Furthermore, electrode migration or extrusion is an important complication in CI surgery, which affects the hearing level, and induce facial nerve stimulation, that may require a revision. Electrode migration is defined as a complication due to gradually slip out of electrodes
from cochlea or extrusion from the tympanic membrane  due to
raise the level of impedance values in basal side electrodes. As well as, it can be due to cochlear ossification (Figure 1) . Moreover, it has been reported that 1-15% of patients who underwent revision CI surgery have had an electrode migration [9,10]. The purpose of this study is to get a detailed review of electrode migration causes and prevalence in post cochlear implant patients and what factors can lead to migration intraoperative and post-operative cases.
The study design was cross sectional review study. Data were being collected through search engines included PUBMED, Google Scholar, and BMJ. Quality assessment of an article done as per defined criteria. Previously published article searched based on electrode migration post Cochlear implant (CI). An electronic search as per medical subject headings (Mesh) was carried out and by using different search engines like Google scholar, PUB MED, WEBMED to increase sensitivity of electrode migration after CI. A Literature search done and in a systematic way of previously published articles and limited to English language.
Each article was critically analyzed and appraised as per study inclusion criteria and fulfilling the following criteria.
a) Article published between in 2008-2019.
b) Article in which complications of CI are found.
c) Article which emphasize on electrode migration post CI.
d) Article gives prevalence and incidence of complications
in post CI and clearly
e) Found with respect of duration of the implant.
f) Article published in English language.
Articles published during 2008 to 2019 duration were added
as their electrode migration considered as a rare and underrated
complication after CI, therefor better approach and to understand
the possible factors affecting on electrode migration. While
conference papers, articles in abstract form and duplicated were
excluded from the search. The authors extracted data in the form
of sample size, study settings, publication year, study point and
overall theme of article from articles which was included in study.
Authors also confirmed the quality of articles in term of the title
Of the first 98 peer review articles found on electrode
migration in post cochlear implant in which include bone grove
electrode migration and perimodiolar electrode migration were
segregated as per search method in (Figure 2). Furthermore,
Figure 2 summarizes the process of choice of articles as per
inclusion criteria and which has an outcome and comparison
related to electrode migration in post cochlear implant. After
removal of duplicated studies and those studies which are
inappropriate and irrelevant to do with electrode emigration in
post cochlear implant. A total of 12 articles were found eligible for
review analysis. These articles included of 583 total patients. The
patient age range is from 2.5 years to 79 years, with duration of
follow up period in selected studies were 6 months to five years.
A total of 10 peer reviewed publication reported on electrode
migration in post cochlear implant was found from the database.
All these articles applied to electrode migration either it is bone
grooving or perimodiolar electrode migration. Characteristics
of each study given in Table 1 which summarizes the electrode
migration with different and advance strategy for cochlear
implant. Studies by J holder et al. and sunde et al.  in which
262 patients were observed after implantation, out of which 9
(25.7%) patients had incomplete insertion of electrodes, and in
2 (6.0%) patients reported with electrode migration which was
observed through CT scan and 0.9% device failure due to electrode
migration respectively [11,12].
Additionally, Kevin D Brown et al has followed up 806 patients
with cochlear implant and it has been found that most common
reason for reimplantation is device failure which is 78% out of
which 55% is hard failure and 23% soft failure which is further
followed by electrode migration that is reported around 9% .
In another study published by Van der et al.  it was analyzed
that electrode positioning evaluated in 35 patients with cochlear
implant out of which 16 patients were with non-positioner
C11 Hi Focus 1 and 19 were with HiRes 90K using multiplanar
reconstruction . This study was a retrospective study and
out of 35 patients, 5 patients were evaluated with complaints
like vertigo, tinnitus and headache and electrode migration
may correlate with implant type, insertion depth or presence
of complaints. It is found that Migrations were detected in 10
There was a significant effect of the implant type in favor of the
HiFocus1, but there is no relation to the original insertion depth of
the device. Out of 35 there are 5 patients scanned because of signs
and symptoms of tinnitus and vertigo, 2 patients with migrations
were detected. Comparison of different electrode types with
clinical symptoms or without complaints is shown in (Figure 3).
The issues of electrode migration of post CI are associated with
lateral wall electrodes by Dietz et al.  and Vaid et al. 
described the factors which are involved in electrode extrusion or
migration, which are classified on the basis of intracochlear which
pushes the electrode, like cochlear ossification [15,16].
Furthermore, extracochlear causes like wire coiling, mastoid
adhesion, electrode type, and electrode depth of insertion. To
elaborate it, electrode with deeper insertion has least chances
of migration after implant while partially inserted electrodes are more prone to migrate. Frequency of electrode migration, and
causative factors after cochlear implant are shown in (Figure 4).
In addition, case report by J Otol et al. 2019 discussed about the
cholesteatoma effect on electrode migration if there are any signs,
symptoms related to it or before going to cochlear implant, must
consider it as it later on causes device failure due to electrode
Electrode migration is an underrated complication of post
cochlear implant; therefore, it is the least discussed topic remained
in research. A review study by Green et al described that 6.25%
complications reported in post cochlear implant out of which
1.25% were of electrode migration in first 6 months of duration
. A study conducted by Ronald et al showed that in 5 years
of duration patients follow up post cochlear implant and there is
no electrode migration reported as in cochlear implant they have
used titman clip and split bridge and it is known for stable fixation
in cochlear implant . In current review it has been cleared that
electrode migration is cause of device failure although use stable
fixation because it is least effective in fully ossified cochlea .
As electrode related device failure like migration,
misplacement and excursion is not a well-known complication,
because sound awareness must detect electrode migration in
post CI patients. A First study by Waltzman et al.  that proved
electrode migration without pain and symptoms can be occurred
. There are advance bionics computerized tomography (CT
scan) considered as important in the measurement of electrode
migration. In this study it has been observed that migration is
irrelevant to insertion depth, and it is shown that only two patients
developed a drop in speech perception to those patients who had
electrode migration more than >1mm [8,18] and Fixation clip
techniques can minimize electrode migration issue.
In a study conducted by Mittman et al has described those
fixation techniques like fixation clips can be thought to minimize
the risk of electrode migration or misplacement . In one study
by Kubo et al described that electrode extrusion is although rare
complication but it can lead to re implantation surgery and it may
occur after a few years from surgery but fixation of the electrode into split made in the buttress part may prevent electrode
migration . If external bony canal has become thinner
during facial recess approach it would be repaired with bone
or cartilage plate [11,12]. Current study gives detailed review
about importance of electrode migration as this is a neglected
complication in post cochlear implant patients. Advance research
design and more precise scientific study is needed to know more
details about possible causative factors for electrode migration.
Electrode migration is not well defined in the literature.
Moreover, different fixation techniques are more reliable to avoid
migration and extrusion of electrode which could cause device
failure. However, there is a need for special attention, particularly
on the fixation of straight electrode arrays. Reducing the force of
migration in the form of advance fixation technique can reduce
the incidence of electrode migration.