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Identification and revision of a displaced cochlear implant electrode in the internal auditory canal

Authors:
Ingo Todt at Klinikum Bielefeld
Ingo Todt
Grit Rademacher
Grit Rademacher
Grit Rademacher
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Arne Ernst
Arne Ernst
Arne Ernst
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Objective: The aim of the report is to underline the importance of a radiological technique which allows three-dimensional (3D) imaging of the cochlear implant electrode position postoperatively in cases of cochlear malformation, and to show a technique to prevent a repeat of cochlear implant electrode insertion in the internal auditory canal (IAC). Clinical presentation: This report describes the management of a case of insertion of a cochlear implant electrode into the IAC in a 1.5-year-old patient with an incomplete partition (IP) III cochlear malformation. Intervention and technique: The commonly used single plain postoperative X-ray is not sufficient to be certain of detecting the incorrect insertion of a cochlear implant electrode in the case of a malformed cochlea. In this case, 3D radiology allowed the incorrect insertion to be detected. The original cochlear implant electrode was temporarily left in place under the assumption that it would block the entrance to the IAC and prevent IAC insertion of the replacement electrode. Conclusion: Postoperative 3D radiological observation after cochlear implant surgery should be done in cases of malformation. Leaving the original electrode in place can help to prevent a repeat electrode malinsertion.
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Case report
Identification and revision of a displaced
cochlear implant electrode in the internal
auditory canal
Ingo Todt, Grit Rademacher, Arne Ernst
Department of Otolaryngology, Head and Neck Surgery and Radiology, Unfallkrankenhaus Berlin, Germany
Objective: The aim of the report is to underline the importance of a radiological technique which allows three-
dimensional (3D) imaging of the cochlear implant electrode position postoperatively in cases of cochlear
malformation, and to show a technique to prevent a repeat of cochlear implant electrode insertion in the
internal auditory canal (IAC).
Clinical presentation: This report describes the management of a case of insertion of a cochlear implant
electrode into the IAC in a 1.5-year-old patient with an incomplete partition (IP) III cochlear malformation.
Intervention and technique: The commonly used single plain postoperative X-ray is not sufficient to be certain
of detecting the incorrect insertion of a cochlear implant electrode in the case of a malformed cochlea. In this
case, 3D radiology allowed the incorrect insertion to be detected. The original cochlear implant electrode was
temporarily left in place under the assumption that it would block the entrance to the IAC and prevent IAC
insertion of the replacement electrode.
Conclusion: Postoperative 3D radiological observation after cochlear implant surgery should be done in cases
of malformation. Leaving the original electrode in place can help to prevent a repeat electrode malinsertion.
Keywords: Cochlear implant, Cochlear malformation, IAC
Introduction
Displacement of an inserted cochlear implant elec-
trode is a rare complication of cochlear implant
surgery. Apart from variations of the intrascalar pos-
ition and folding back of the tip of the array, the
most commonly described sites of incorrect insertion
are the hypotympanum, mistaken for the round
window, and the semicircular canals as the result of
an incorrect insertion angle (Tange et al., 2006;
Ramalingam et al., 2009).
Malformed inner ears increase the risk of cochlear
implant array displacement. The risk of displacement
of an electrode array can be related to the type of mal-
formation: incomplete partition type I (IP I), IP III,
and common cavity malformations bear an increased
risk of electrode insertion into the internal auditory
canal (IAC) (Sennaroglu, 2010). In three different
types of malformation, insertion of the array into the
IAC has been described as follows: common cavities
(McElveen et al., 1997; Bloom et al., 2008), IP III
with an irregular ossification of the floor of the basal
turn (Wooten et al., 2006; Incesulu et al., 2008), and
cochlear hypoplasia (Tucci et al., 1995). So far,
reinsertion techniques have been rarely described
(Bloom et al., 2008; Wooten et al., 2006) since the
surgical technique itself and even the identification
of an incorrect insertion can be challenging.
The aim of the present paper is to present a case of
an IP III malformation with insertion of the electrode
array into the IAC. The radiological and perioperative
findings, the follow-up, and the surgical techniques are
described in detail.
Case report
A 1.5-year-old boy was referred to our clinic because
he did not accept the cochlear implant (CI) after CI
surgery in another center. Audiological fitting of the
speech processor was unsuccessful. The child suffered
from a severe sensorineural hearing loss without
hearing/speech development.
An X-linked association could not be confirmed.
Flat panel-tomographic estimation of the electrode
position showed a curled Nucleus Contour Advance
array in a single plane (Fig. 1). However, three-dimen-
sional (3D) radiological reconstruction of the array in
the temporal bone showed a regular position of the
array on the floor of the basal turn but without the
Correspondence to: Ingo Todt, Department of Otolaryngology,
Unfallkrankenhaus Berlin, Warener Str. 7, D-12683 Berlin, Germany,
Email: todt@gmx.net
©W.S.Maney&SonLtd2013
DOI 10.1179/1754762812Y.0000000015 Cochlear Implants International 2013 VOL. 14 NO. 4236
normal ascent of the array entering the first turn. In
fact, a downward deflection of the array into the
IAC was found (Fig. 2a and b).
Surgery was begun by re-opening of the mastoid
and the posterior tympanotomy. The electrode was
cut off close to the entrance into the cochlea and left
there as a positioner. The initial cochleostomy was
found to be at or close to the round window.
A second cochleostomy was drilled anterior to the
old electrode (Fig. 3). A gusher occurred and within
the cochlea a basilar membrane was visible but no
electrode contacts of the first array could be seen.
The new electrode (Nucleus Advance) was inserted
smoothly using the stylet (Fig. 4). Finally, the old
electrode and stylet were pulled out and the
round window/cochleostomy packed with fascia and
covered with fibrin glue. Intraoperative measurements
showed normal neural response telemetry (NRT)
response levels only at the apical part of the electrode.
Intraoperatively, a single plain X-ray showed normal
curling of the new electrode in the cochlea. Flatpanel
tomography confirmed the position of the array in
Figure 2 (a) Electrode in the basal turn (axial plane).
(b) Passage of the electrode into the IAC (arrow indicates
basal turn, star indicates IAC).
Figure 3 Second cochleostomy placed anterior to the first
electrode (arrow indicates second cochleostomy).
Figure 1 Contour advance electrode apparently curled
within the cochlea (coronal plane).
Figure 4 Both electrodes in place (first arrow indicates first
electrode, second arrow indicates new electrode).
Todt et al. Identification and revision of a displaced cochlear implant electrode
Cochlear Implants International 2013 VO L. 14 NO. 4237
the scala vestibuli (Fig. 5). Radiological 3D recon-
struction showed a correct insertion of the curled
array in the first turn (Fig. 6).
The audiological programming of the speech pro-
cessor (after a healing period of 6 weeks) was success-
ful and the boy fully accepted the CI.
Discussion
Cochlear implantation in a malformed cochlea is
associated with an increased risk of complications, e.g.
facial nerve lesions, liquorrhoea, meningitis, and displa-
cement of electrode arrays. Sennaroglu (2010) described
a classification of cochlear malformations, including
three different types of incomplete partition (IP).
Descriptions of IAC-displaced cochlear implant
arrays are rare, but bear the risk of multiple insertion
attempts (Bloom et al., 2008).
Intraoperative radiological control in malformations
is useful in guiding electrode insertion if an intraopera-
tive 3D reconstruction of the array position can be per-
formed (Bloom et al., 2008). This is currently not the
case in the majority of CI implanting centers. Relying
only on plain postoperative radiography can carry
potential medical and medico-legal risks for the
surgeon. In our case, the combination of intraoperative
findings (NRT, microscopically identified basilar mem-
brane, and 2D X-ray) provided sufficient evidence that
we had achieved a correct intracochlear position of the
electrode array. Incesulu et al., 2008 described pulling
back of an IAC-positioned electrode to reposition the
array in an IP III patient. Wooten et al., 2006 used
the drill-out technique in an IP III patient. The surgical
technique of leaving in place the electrode originally
positioned in the IAC in this case of IP III malfor-
mation should decrease the risk of repeating the false
insertion. Removal of the original wrongly placed
array and insertion of the new array into the previous
cochleostomy could have led to a reinsertion into the
route of the previously misplaced array. The radio-
graphs done preoperatively at our institution showed
the old electrode covering the floor of the basal turn
so that we used it as positioner to guide the new elec-
trode intracochlearly. The old electrode was left in
place while inserting the new one. In this way, the
IAC was covered and we could be confident that we
were not repeating the previous incorrect insertion.
In our case, it was not clear from the radiology if
it was a type I or III IP (Sennaroglu, 2010). In contrast
to IP II, these both types have a defect between IAC
and cochlea. IP I should have no intracochlear
septae. During surgery we were able to identify the
basilar membrane, after opening the scala vestibule,
but were not able to identify any sign of the elec-
trode array or contacts. This confirmed that this was
an IP III case based on the current classification
(Sennaroglu, 2010). Intraoperative NRT measure-
ments with normal NRT levels at the apical contacts
and a normal intraoperative 2D X-ray with a correct
curling angle of the array confirmed a correct position.
The preoperative 2D Stenvers view showed a curled
Nucleus advance array, which was initially interpreted
as a normal curling. Only on reviewing the film was an
unusual high curling angle identified. The axial view
finally identified the IAC position of the electrode.
Review of the radiology shows that a radiological pro-
cedure which allows 3D imaging by reconstruction
(flat panel tomography, digital volume tomography
(DVT), multi slice computer tomography (MSCT)) is
strongly recommended postoperatively in this kind of
malformation to identify a displaced electrode.
We usually perform a postoperative flat panel tom-
ography for all CI patients at our center and do it for
all CI patients admitted to our center for special cases.
Conclusion
This case describes the technique of leaving the elec-
trode incorrectly inserted into the IAC in place. This
was helpful during the revision procedure, in order
to prevent reinsertion of the new electrode into the
IAC. Postinsertional radiological axial and coronal
Figure 6 Ascending of the electrode (axial plane).
Figure 5 Curled Contour advance electrode after the
revision.
Todt et al. Identification and revision of a displaced cochlear implant electrode
Cochlear Implants International 2013 VOL. 14 NO. 4238
views are strongly recommended for cases of cochlear
malformation with the risk of an IAC displacement.
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... Misplacement may also be identified intraoperatively in some cases using intraoperative plain films (10). Revision surgery for misplaced electrode arrays typically requires improving exposure to accurately identify key anatomic landmarks for successful placement of the electrode array, which results in auditory perception and potentially improved speech recognition (2,8,(11)(12)(13). ...
... While seven electrodes were placed in the internal carotid canal, no patient experienced significant vascular injury (3,4,9,11,16,17). Misplacement in the internal auditory canal was rare, and typically occurred through the modiolus via either a congenital or acquired defect, as two of the four cases were noted to have incomplete partition (3,8,11,12). ...
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... We found one electrode in the lateral semicircular canal (0.3%) and the other electrode in the middle ear (0.3%). We found that the incidence of the common site in the recent literature greatly varies as follows: superior semicircular canal is the common in the study of Ramalingam,Sorrentino,and Cosetti [10,15,16]; the vestibule [17]; the lateral semicircular canal [18]; may be hypotympanic air cells [19]; and may also found the electrode in the Eustachian tube, internal auditory meatus, and internal carotid artery, according to the recent literature studies by Ying,Todt,and Nevoux,respectively [5,20,21]. The site of extracochlear electrode does not change the decision of revision surgery for two causes: the first to avoid damage to any neurovascular structure, and the second cause to gain benefit from the implant. ...
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... Malposition in the internal auditory canal (Fig. 32) The electrode array enters into the internal auditory canal or may form a more basal slope within the internal auditory canal. The condition of an incomplete partition type III is a risk factor, since there is no bony separation between cochlea and internal auditory canal [69,70]. ...
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... In IAC insertion cases, the electrode can direct to their previous incorrect position during re-implantation, and Todt et al. [10] reported that this can be avoided by leaving the first electrode in its inaccurate place and inserting a second electrode during revision surgery. In our case, we opened a second cochleostomy to enable accurate insertion. ...
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Cochlear implantation in cases with incomplete partition type III (X-linked anomaly)
Article
  • Mar 2008
Incomplete partition-type III anomaly (X-linked deformity) is no common finding in a prospective candidate for cochlear implantation. In this paper, the problems about the cochlear implantation in cases with incomplete partition-type III anomaly (X-linked deformity) and profound sensorineural hearing loss is discussed. High-resolution multidedector computed tomography (MDCT) and magnetic resonance imaging were performed preoperatively in all patients. MDCT revealed that there was bulbous dilatation at the lateral ends of internal auditory canals (IAC) in all patients. There were also enlargements of labyrinthine segments of facial and superior vestibular nerve canals. Patients with the basal turns of cochlea incompletely separated from IAC were also presented. Patients with IP-type III (X-linked deformity) and profound SNHL were implanted. Standard transmastoid-facial recess approach was used and cerebrospinal gusher was encountered after the cochleostomy in all cases. Postoperative performance was very good in all patients. Two patients had complications, which are facial nerve stimulation and device failure. Both patients were reimplanted. Cochlear implantation is a good choice in the patients with IP-type III. However, this anomaly may have special potential risk than the other inner ear abnormalities. Therefore, the surgeon should be aware of them and must be ready to inform the patient and parents.
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