10.14639/0392-100X-N2096
Objective. To report the authors’ experience in a series of patients treated with cochlear implant (CI) revision surgery due to medical problems. Methods. Revision CI surgeries performed in a tertiary referral centre for medical reasons not related to skin conditions were reviewed; patients were included if device removal was required. Results. 17 cochlear implant patients were reviewed. The main reasons requiring revision surgery with device removal were: retraction pocket/iatrogenic cholesteatoma (6/17), chronic otitis (3/17), extrusion in previous canal wall down procedures (2/17) or in previous subtotal petrosectomy (2/17), misplacement/partial array insertion (2/17) and residual petrous bone cholesteatoma (2/17). In all cases surgery was performed through a subtotal petrosectomy. Cochlear fibrosis/ossification of the basal turn was found in 5 cases and uncovered mastoid portion of the facial nerve in 3 patients. The only complication was an abdominal seroma. A positive difference was observed between the number of active electrodes and comfort levels before and after revision surgery. Conclusions. In CI revision surgeries performed for medical reasons, subtotal petrosectomy offers invaluable advantages and should be considered as first choice during surgical planning.
text/xml
1827-675X
2096
en
Maurizio Falcioni
http://creativecommons.org/licenses/by-nc-nd/4.0
ACTA Otorhinolaryngologica Italica
ear surgery
Revision cochlear implant surgery for clinical reasons
Text.Serial.Journal
https://www.actaitalica.it/
43
Otology
2023-02-27
2022-04-05
2023-02-28
2023-02-28
65-73
1
Maurizio Falcioni
2023/02/27
10.14639/0392-100X-N2096
65
Department of Otorhinolaryngology and Otoneurosurgery, Azienda Ospedaliero-Universitaria di Parma, Parma, Italy
1827-675X
ear surgery
en
73
Revision cochlear implant surgery for clinical reasons
https://www.actaitalica.it/article/download/2096/920
43
ACTA OTORHINOLARYNGOLOGICA ITALICA 2023;43:65-73; doi: 10.14639/0392-100X-N2096




Otology


Revision cochlear implant surgery for clinical reasons
La chirurgia di revisione dell’impianto cocleare eseguita per problemi medici
Federica Canzano1, Filippo Di Lella2, Maurizio Guida2 , Enrico Pasanisi2, Marco Govoni2, Maurizio Falcioni3
1
  Department of Otorhinolaryngology, Azienda Ospedaliera di Pescara, Pescara, Italy; 2 University of Parma, Department of Medicine
and Surgery, Department of Otorhinolaryngology and Otoneurosurgery, Parma, Italy; 3 Department of Otorhinolaryngology and
Otoneurosurgery, Azienda Ospedaliero-Universitaria di Parma, Parma, Italy


SUMMARY
Objective. To report the authors’ experience in a series of patients treated with cochlear
implant (CI) revision surgery due to medical problems.
Methods. Revision CI surgeries performed in a tertiary referral centre for medical reasons not
related to skin conditions were reviewed; patients were included if device removal was required.
Results. 17 cochlear implant patients were reviewed. The main reasons requiring revi-
sion surgery with device removal were: retraction pocket/iatrogenic cholesteatoma (6/17),
chronic otitis (3/17), extrusion in previous canal wall down procedures (2/17) or in previ-
ous subtotal petrosectomy (2/17), misplacement/partial array insertion (2/17) and residual
petrous bone cholesteatoma (2/17). In all cases surgery was performed through a subtotal
petrosectomy. Cochlear fibrosis/ossification of the basal turn was found in 5 cases and un-
covered mastoid portion of the facial nerve in 3 patients. The only complication was an
abdominal seroma. A positive difference was observed between the number of active elec-
trodes and comfort levels before and after revision surgery.
Conclusions. In CI revision surgeries performed for medical reasons, subtotal petrosectomy
offers invaluable advantages and should be considered as first choice during surgical planning.
KEY WORDS: revision surgery, cochlear implant, subtotal petrosectomy, ear surgery

RIASSUNTO
Obiettivo. Scopo dello studio è stato quello di riportare l’esperienza degli Autori su una         Received: March 31, 2022
serie di pazienti sottoposti a chirurgia di revisione dell’impianto cocleare (IC) per problemi     Accepted: September 15, 2022
medici.
Metodi. Valutazione retrospettiva dei pazienti sottoposti a chirurgia di revisione con rimo-       Correspondence
zione dell’IC in un Centro di riferimento.                                                         Federica Canzano
Risultati. Sono stati esaminati 17 pazienti. Le indicazioni all’intervento di espianto e revi-     Department of Otorhinolaryngology, Azienda
sione sono state: tasche di retrazione/colesteatoma iatrogeno (6/17), otite cronica (3/17),        Ospedaliera di Pescara, via Fonte Romana 8, 65010
estrusione del cavo/ricevitore-stimolatore da cavità di mastoidectomia aperta (2/17) o in          Pescara, Italy
petrosectomia subtotale (2/17), malposizionamento/inserzione parziale dell’array (2/17),           Tel. +39 0854252413; +39 0854252682
colesteatoma della rocca residua (2/17). In tutti i casi è stata eseguita una petrosectomia        E-mail: federica.canzano@gmail.com
subtotale. Riscontri intraoperatori addizionali sono stati: fibrosi/ossificazione del giro ba-
sale della coclea in 5 casi e porzione mastoidea del nervo facciale scoperta in 3. È stata           How to cite this article: Canzano F, Di Lella
osservata una differenza positiva tra il numero di elettrodi attivi prima e dopo la revisione.       F, Guida M, et al. Revision cochlear implant
Unica complicanza è stato un sieroma addominale.                                                     surgery for clinical reasons. Acta Otorhi-
                                                                                                     nolaryngol Ital 2023;43:65-73. https://doi.
Conclusioni. Nella chirurgia di revisione dell’impianto cocleare la petrosectomia subtotale          org/10.14639/0392-100X-N2096
rappresenta una tecnica sicura ed efficace, da considerare come prima opzione terapeutica.
PAROLE CHIAVE: chirurgia di revisione, impianto cocleare, petrosectomia subtotale,                 © Società Italiana di Otorinolaringoiatria
                                                                                                   e Chirurgia Cervico-Facciale
otochirurgia
                                                                                                                  OPEN ACCESS

                                                                                                   This is an open access article distributed in accordance with
Introduction                                                                                       the CC-BY-NC-ND (Creative Commons Attribution-Non-
                                                                                                   Commercial-NoDerivatives 4.0 International) license. The
Global failure rate has been used in major cochlear implant (CI) centers as a tool                 article can be used by giving appropriate credit and mentio-
                                                                                                   ning the license, but only for non-commercial purposes and
to ascertain device survival from both primary and revision surgery 1. Medical                     only in the original version. For further information: https://
conditions determining the need for revision CI surgery are mainly related to                      creativecommons.org/licenses/by-nc-nd/4.0/deed.en




                                                                                                                                                             65
F. Canzano et al.




cutaneous problems at the site of the receiver/stimulator and
can often be managed while preserving device integrity 2.
Besides skin conditions, there have been few published
cases of other medical problems requiring revision surgery
with device removal 3,4; surgery in these conditions may
present difficulties and even preclude the possibility of re-
implantation.
The aim of this study was to report the authors’ experience
in a series of patients who needed CI revision surgery with
device removal and a subsequent re-implantation attempt.

Materials and methods
Charts of patients who underwent revision CI surgery be-
tween January 2015 and November 2019 in a tertiary re-
ferral University Hospital Otorhinolaryngology and Oto-
neurosurgery Department, were retrospectively reviewed.
Patients were included if: 1) revision surgery was per-
formed for medical reasons not related to skin conditions
and 2) device removal was required. For each case, reason         Figure 1. Axial high-resolution CT scan, left ear. Patient 14. The cochlear
for removal, time interval between first and revision sur-        implant array/connecting cable can be seen in the lateral portion of the cavity.
gery, previous procedures, operative findings and compli-         A mass of soft tissue density fills the middle ear cavity and ossification of the
cations were analysed. Number of active electrodes and            cochlear lumen is evident.
mean comfort levels (C-levels) measured in current units
before and after revision surgery, were evaluated as well.        (# 12 and 14); in 1 (# 14), the extrusion was the result of an
                                                                  in-office cleaning of the cavity (Fig. 1).
Results                                                           Retroauricular extrusion of the connecting cable/receiver-
                                                                  stimulator occurred in 2 cases previously treated with a SP
Seventeen patients were included, 5 males and 12 females;         (# 6 and 16). In both patients device exposure led to infec-
13 patients were older than 18 years at the time of the study.    tion of the surgical cavity with breakdown of the closure of
Mean age was 45.64 years (range 5-78 years). Some pa-             the external auditory canal (EAC) in one.
tients have been reported in previous publications: patients      Five cases of erosion of the posterior wall of EAC were
1, 2, 4, 6, 7, 8, 9, 10, 11, 14, 15 in a 2020 case series 5 and   included: in 2 patients it resulted in extrusion of connecting
patient 5 in a 2011 case report 6 (Tab. I). All patients under-   cable (# 2 and 8), while in 3 it progressed to an iatrogenic
went temporal bone CT scan before revision surgery.               cholesteatoma (# 1, 9 and 13). An additional cholesteatoma
Different brands of CI were involved: Cochlear (Cochlear          through a marginal perforation occurred in one case (# 4).
Company, Sydney, Australia) in 8 cases, Oticon Medical            Two cases were treated for residual petrous bone cholestea-
(Oticon, Vallauris, France) in 8 cases and MedEl (MedEl,          toma (# 5 and 17). One patient showed a misplaced array into
Innsbruck, Austria) in 1 case.                                    the petrous carotid canal (# 15), while another (# 10) had only
Three cases (17.65%) had received primary surgery at au-          11 functioning electrodes due to intraoperative cerebrospinal
thors’ Institution and 13 elsewhere (82.35%). Four of the adult   fluid (CSF) leak.
patients had already undergone at least 1 revision surgery.       In 3 cases revision surgery was performed for chronic otitis
The mean time interval between previous surgery and revi-         media (# 3, 7 and 11); one of these had already undergone
sion was 94.9 months (ranging from 2 to 264 months).              miringoplasty with a reperforation (# 7).
Revision surgery was always performed through a subto-
tal petrosectomy (SP); 5 patients had already been treated        Preoperative device functionality
through a SP during first surgery.                                In 6 cases the device was not functioning at the time of re-
Table I shows demographics and clinical conditions lead-          vision surgery; 2 had complete extrusion of the array from
ing to revision surgery.                                          the cochlear lumen (# 14 and 16).
There were 2 cases of connecting cable and/or array extru-        Eleven implants were explanted while the CI was still func-
sion in previous canal wall down (CWD) mastoidectomy              tional; some showed reduction of performance and/or incre-



66
                                                                                                   Revision cochlear implant surgery for clinical reasons




                                                                                 Mean follow-up time was 39.82 months (range 16-64
                                                                                 months); 15 patients have been followed using CT, while
                                                                                 in the 2 cases of petrous bone cholesteatoma MRI was per-
                                                                                 formed after magnet removal. At last follow-up, 13 patients
                                                                                 were actively using the implant.

                                                                                 Discussion
                                                                                 Many causes for CI revision surgery are reported in the lit-
                                                                                 erature and most studies involve patients operated and fol-
                                                                                 lowed in a single Institution and deal with soft/hard device
                                                                                 failure and overall implant survival time 7-9.
                                                                                 Revision surgery for clinical reason may represent a challenge
                                                                                 even for the most experienced surgeons 4-10. Identification of
                                                                                 causative factors is of paramount importance; in the present
Figure 2. Intraoperative picture, left ear, surgical position. Patient 13. The   series most medical complications requiring revision can be
cochlear implant array has been sectioned near the round window. Fibrosis
and ossification can be seen surrounding the array; multiple manoeuvers were     considered secondary to preventable faults occurred during
performed with fraying of the array to achieve removal.                          the primary surgery or to inaccurate selection of the approach.
                                                                                 Some surgical steps should be kept in mind when perform-
                                                                                 ing a revision CI surgery. While revision procedures for hard
ment of stimulation levels at the last controls before revision.
                                                                                 and soft CI failure is usually performed through the standard
Due to the clinical problems, only 3 patients were daily im-
                                                                                 transmastoid approach, revision surgery for medical compli-
plant users before final revision surgery (# 1, 2 and 8).
                                                                                 cations may be far more complex and often require a SP. Ad-
                                                                                 vantages of the latter technique include unimpeded access to
Intraoperative findings
                                                                                 the promontory, better identification of anatomical landmarks
Cochlear fibrosis/ossification requiring additional drilling of
                                                                                 such as carotid canal, jugular bulb and facial nerve, and com-
the basal turn was found in 5 cases (29.4%) (Fig. 2), while
                                                                                 fortable access to the round window. In adjunct, isolation of
the mastoid portion of the facial nerve was uncovered in 3                       the surgical cavity from the external environment allows easy
(17.6%).                                                                         handling of CSF leak when required, as in patient 10 in this
Re-implantation was not possible due to extended cochlear                        series 5,11. When performing a cochlear implantation in the
ossification in 1 case (# 16) and to subtotal cochlear drilling                  context of a SP, the receiver-stimulator should be positioned
to achieve total removal of residual petrous bone cholestea-                     in a more posterior and superior position. The lack of the
toma in another (# 17).                                                          bony support of the EAC inevitably leads to a retroauricular
                                                                                 retraction 5 with a higher risk of extrusion of the connecting
Postoperative device functionality                                               cable/receiver-stimulator in this area.
A new device was inserted in 15 patients. During first fit-                      Selection and management of the array may be a critical
ting all the electrodes were active, except for 2 cases (# 9                     point in revision surgeries. The previous array is kept in
and 11). One patient, despite full re-insertion, did not show                    place until the last steps of the procedure and should be re-
any hearing sensation (# 7).                                                     moved just after positioning of the new receiver-stimulator.
In 9 cases, it was possible to insert more active electrodes                     The old connecting cable is usually cut as soon as possible
into the cochlear lumen than in the preoperative setting.                        at the level of the posterior tympanotomy in order to avoid
In 4 patients, the number of electrodes remained the same                        unintentional early array extraction from the cochlear lu-
while in one decreased.                                                          men. This reduces the risk of contamination of the inner ear
Evaluation of C-levels was performed in 13 patients for                          (especially in presence of active infection) and prevents the
which data were available both before and after revision                         entrance of blood and/or bone dust. At the same time, the
surgery; mean C-levels were reduced in 10 cases.                                 presence of the array avoids collapse of the fibrotic reactive
                                                                                 tissue that grows around the array itself. In case of difficult
Complications and follow-up                                                      array removal, this manoeuver should be completed be-
No major complications were reported; a subcutaneous ab-                         fore opening the new device. Whenever the surgeon is not
dominal seroma was drained in the office before activation                       sure of the patency of the cochlear lumen, the preliminary
in one case (# 8).                                                               use of a dummy electrode is advisable. The new array size



                                                                                                                                                     67
F. Canzano et al.                                                                                                                                                                                                                                                                Revision cochlear implant surgery for clinical reasons




Table I. Patient demographics, clinical data and electrophysiological values.
 Patient n. Gender       Age at          Time                                                         Causes for CI revision surgery                                                        First surgery     Active     Previous        CI        Follow-up    N. of active      N. of active         Mean comfort Mean comfort
                        revision       interval                                                                                                                                               in Parma      infections   revision      brand       (months)     electrodes      electrodes after           level         level
                         (years)      between                                                                                                                                                                                                                      before           revision            pre-revision post-revision
                                      first and                                                                                                                                                                                                                  revision
                                       revision
                                       surgery
                                      (months)
                                                               Extrusion in           Extrusion in        Misplacement/            Chronic           Retraction            Residual
                                                              previous CWD            previous SP         partial insertion         otitis        pocket/Iatrogenic          PBC
                                                                                                                                                   cholesteatoma
 1^                  F           78             48                                                                                                        x                                                     x          No         Cochlear        53           21/22             22/22*               144.5           124.75°
                                                                                                                                                                                                                                                                      U                 U
 2^                  F            8             84                                                                                                          x                                     x             x          No         Cochlear        39           22/22             22/22                187.25         143.75°
                                                                                                                                                                                                                                                                      U                 U
 3                   F           16             156                                                                                     x                                                                                  No         Cochlear        16              0              22/22*                130            150.75
                                                                                                                                                                                                                                                                     NU                 U
 4^                  F           63             157                                                                                                         x                                                              No          Oticon         62           20/20             20/20                  44            23.25°
                                                                                                                                                                                                                                                                     NU                 U
 5§                 M            71             96                                                                                                                              x                                          No          Oticon         51           20/20             20/20                  37             26.5°
                                                                                                                                                                                                                                                                     NU                 U
 6^                  F           48             122                                          x                                                                                                    x             x          Yes        Cochlear        55           20/22             22/22*               200.5           147.5°
                                                                                                                                                                                                                                                                     NU                 U
 7^                 M            17             204                                                                                     x                                                                       x          No         Cochlear        26            0/22       0/22 (full insertion)        -                -
                                                                                                                                                                                                                                                                     NU                NU
 8^                  F           31             264                                                                                                         x                                                              No         Cochlear        30           10/22             22/22*                184            116.25°
                                                                                                                                                                                                                                                                      U                 U
 9^                 M            73             84                                                                                                          x                                                   x          No          Oticon         60           18/20             15/20                 92.5            45.3°
                                                                                                                                                                                                                                                                     NU                NU
 10^                 F            5             48                                                                 x                                                                              x                        No         Cochlear        25           11/22             22/22*               204.25          172.5°
                                                                                                                                                                                                                                                                     NU                 U
 11^                 F           66             20                                                                                      x                                                                                  Yes         Oticon         32           10/15             16/20*                32.5            53.5
                                                                                                                                                                                                                                                                     NU                 U
 12                  F           51             60                    x                                                                                                                                         x          No          Medel          21           12/12             12/12                 28.5           20.45°
                                                                                                                                                                                                                                                                     NU                 U
 13                  F           14             84                                                                                                          x                                                   x          No          Oticon         16           17/20             20/20*               36.75            29.5°
                                                                                                                                                                                                                                                                     NU                 U
 14^                M            57             85                    x                                                                                                                                         x          No          Oticon         64              0              20/20*
                                                                                                                                                                                                                                                                     NU                 U
 15^                 F           71              2                                                                 x                                                                                                       No          Oticon         55            0/20             20/20*
                                                                                                                                                                                                                                                                     NU                 U
 16                  F           64             84                                           x                                                                                                                  x          Yes         Oticon         40           0/20                NR
                                                                                                                                                                                                                                                                     NU
 17                 M            43             16                                                                                                                              x                               x          Yes        Cochlear        32            0/22               NR
                                                                                                                                                                                                                                                                     NU
 Mean             45.64         94.94                              39.82
 (min-max)        (5-78)       (2-264)                            (16-64)
^
 : patients already published (reference 5); § patient already published (reference 6) *: patients in which more active electrodes were inserted during revision surgery; °: patients in
which C-levels were reduced after revision surgery. U/NU (user/non user). CI: cochlear implant; CWD: canal wall down; SP: subtotal petrosectomy; PBC: petrous bone cholesteatoma



should be similar to the previous one, as adoption of longer                                     arrays, with Oticon ZTI and Cochlear 512 and 612 the most                                 Causes for revision surgery                                         when planning primary surgery 12. Recurrence of the
or larger arrays could impede complete insertion due to the                                      frequently adopted. Use of the same CI brand is also ad-                                  Based on this series, six main causes for revision surgery          chronic otitis exposes the patient to infective risk and de-
presence of the peri-electrode fibrous capsule. Thin atrau-                                      vised, if not in presence of selective implant problems and/                              were identified:                                                    vice malfunction that can lead to revision procedures 4.
matic arrays are not the first option in most of the revi-                                       or specific wishes of the patient, in order to maintain the                               1. Chronic Otitis. Cochlear implants candidates with a              SP is suggested by the Authors in presence of a tympanic
sion surgery. Whenever possible the authors prefer stiffer                                       same stimulation modality.                                                                   history of chronic otitis media require special attention        perforation accompanied by device malfunctioning, as in



68                                                                                                                                                                                                                                                                                                                                  69
F. Canzano et al.




Figure 3. Preoperative picture, right ear, surgical position. Patient 16. Re-
traction with extrusion of the connecting cable in the retroauricular region after
                                                                                     Figure 4. Intraoperative picture, left ear, surgical position. Patient 13. Erosion
subtotal petrosectomy.
                                                                                     of the posterior external auditory canal wall can be appreciated with skin de-
                                                                                     bris and cholesteatoma filling the previously performed mastoidectomy cavity.

   all 3 cases of the series. Two had a history of otorrhoea
   since before the first CI (one had already undergone a                               necting-cable and may pull the array out of the cochlear
   tympanoplasty), while in another a myringoplasty after                               lumen, as in patient n. 8. Three additional patients (not
   CI resulted in a reperforation.                                                      included in the study) with the connecting cable visible
2. Connecting cable extrusion in previous CWD. Position-                                behind the EAC skin are presently conservatively man-
   ing of a CI in a canal wall down mastoidectomy should                                aged at authors’ Institution.
   be avoided for the high risk of cable extrusion (patient                          5. Residual cholesteatoma. Residual skin debris in an inac-
   12 and 14), as in the 2 cases in the series. SP is strongly                          cessible cavity represents the main drawback of SP 16. In
   recommended during the primary surgery.                                              presence of a CI, residual cholesteatoma is difficult to be
3. Retroauricular extrusion in SP. A higher and more pos-                               detected, due to the large artifact observed in the diffu-
   terior positioning of the receiver-stimulator in SP is of                            sion weighted imaging (DWI) sequences of MRI. The 2
   utmost importance in order to avoid retroauricular extru-                            cases included in the series were both originally affected
   sion of the connecting cable/receiver-stimulator in the                              by petrous bone cholesteatomas. While in the first case
   “danger zone” represented by the unavoidable post-sur-                               it was possible to re-implant a new device, in the second
   gical retraction area. In 2 of 3 SP patients, this was con-                          case complete cholesteatoma removal required subtotal
   sidered as the causative problem for the revision (Fig. 3).                          cochlear drilling. When positioning a CI in a cholestea-
   One of the authors (MF) experienced an additional case                               toma patient the risk of a residual lesion should always
   at the beginning of his experience (unpublished data).                               be considered, and prolonged follow-up is mandatory. In
4. Retraction/cholesteatoma. Iatrogenic cholesteatoma has                               doubtful cases, a staged strategy may be kept in consid-
   been reported as a rare complication after cochlear im-                              eration and must be balanced with the delay in hearing
   plantation 2,15. This condition is probably induced by a                             rehabilitation 17.
   combination of over-drilling of the medial portion of the                         6. Array misplacement/partial insertion. Extracochlear ar-
   posterior wall of the EAC during primary surgery and                                 ray positioning have been reported with the hypotym-
   of subsequent pressure exerted by the connecting cable.                              panic air cells and the semicircular canals as the most
   Development of a retraction pocket which, in turn, may                               frequent locations 18. Violation of the cochlear lumen
   lead to cable extrusion and/or cholesteatoma formation,                              require immediate surgical revision as intracochlear in-
   may require years; the 6 cases in this series (2 retrac-                             flammatory reaction may lead to fibrosis and ossifica-
   tion pockets with connecting cable extrusion and 4 cho-                              tion. This occurred in 1 otosclerosis case (patient n. 15),
   lesteatomas) were revisioned after 4 to 27 years (Fig. 4).                           in which the array, after entering the cochlear lumen,
   Simple retraction without extrusion does not represent                               followed a false route entering the carotid canal. The pa-
   an indication for immediate revision, but frequent oto-                              tient was sent for consultation after 2 months and basal
   scopic and electrophysiologic follow-ups are required                                turn drill-out was required due to a severe cochlear ossi-
   as the skin of the EAC progressively envelops the con-                               fication. Violation of the carotid canal may be managed



70
                                                                                     Revision cochlear implant surgery for clinical reasons




   with or without removal of the malpositioned array 19-21.       cochlea. Circular drilling around the previous array was
   In patient 15, the tip of the array was cut and left in place   necessary in 2 patients; in this situation SP allows a com-
   in order to reduce the risk of a vascular complication 21.      plete control of the promontory if compared to a standard
   Possible array misplacement strongly support the neces-         approach. Facial nerve dehiscence at the level of the mas-
   sity of a postoperative radiological control, at least in the   toid portion is relatively common (17.6% in the present
   unusual CI cases 22.                                            series), but usually does not represent a problem if facial
Additional considerations can be discussed when planning           stimulation does not occur. In one case the contact between
surgery in particular situations.                                  the connecting cable and the completely uncovered mas-
                                                                   toid portion of the nerve had produced a temporary facial
Active infection                                                   nerve palsy (recovered after corticosteroid therapy before
Ten patients showed active infection at the moment of revi-        re-implantation).
sion surgery, and in 2 cases had been active for more than 2
years. Bacterial infection in the context of a CI is particu-      Electrophysiological results
larly dangerous for the risk of meningitis or intracranical        Revision surgery does not guarantee anatomical or func-
abscess 23. In this series, additional consequences of active      tional success. Positioning of a new array may be impos-
infection were also identified: 2 cases of focal ossification at   sible or not advisable (# 16 and 17 in this series). Even
the level of the cochleostomy required circumferential drill-      complete re-insertion may result in absence of auditory
ing around the old array to allow removal; 1 ossification of       sensation (# 7).
the basal turn requiring a promontorial drill-out; 1 complete      In the literature, the number of active electrodes after re-
extrusion of the array from the cochlea with a massive os-         implantations is usually higher, but the data mainly refer
sification that precluded re-implantation, 1 complete erosion      to revision for technical failure 10. In the authors’ series,
of the modiolus (in spite of a successful reinsertion of the ar-   it was possible to observe more active electrodes than in
ray the patient did not experience any auditory sensation) 24.     the preoperative setting in 9 cases, while the same number
These data support the concept that middle ear infection           was maintained in 4 patients; only 1 patient had a fewer
in presence of a CI must be treated as an emergency; even          numbers of functioning electrodes after revision (# 9).
without intracranial complications, consequences of infec-         The mean value of C-level decreased postoperatively in
tion may preclude re-implantation in the same ear (2 cases) 4.     10 over 13 patients. This was probably justified by the im-
The option of staged surgery may also be considered 25.            provements in performances of the new electrodes and to
                                                                   the better distribution of electrical stimuli in cases with
Surgical revision of subtotal petrosectomy                         larger number of post-revision active electrodes. Position-
Five patients required a revision of the pre-existent SP. The      ing of arrays in pristine cochlear areas may also contribute
failure of the first surgery was due to incomplete disease         to lower C-level values in cases where the basal turn was
removal in 2 cases (residual petrous bone cholesteatomas)          drilled.
and inaccurate execution of the primary surgery in the oth-
ers. Incomplete exenteration of mastoid air cells, infection       Complications and follow-up
of the mastoid cavity and anterior positioning of the device       One subcutaneous seroma in the site of abdominal fat
were identified as the major causes of failure.                    harvesting was recorded in the series. The short mean
Even if in the authors’ opinion the SP may offer a mul-            follow-up time of 39.82 months (range 16-64 months)
tiplicity of advantages in non-standard cases of cochlear          does not allow to exclude problems in the future, such
implantation, the surgical technique should be perfectly           as development of entrapment cholesteatoma. In CI pa-
mastered to avoid failures.                                        tients, diffusion weighted MRI sequences are disturbed
                                                                   by the artifact and distortion produced by the implant
Unpredicted intraoperative findings                                even after magnet removal. Two different follow-up strat-
In the present series 5 cases of cochlear ossification and 3       egies may be adopted: 1) serial CT scan, comparing di-
facial nerve dehiscences were encountered. Prolonged mid-          rect and indirect signs such as progressive enlargement
dle ear infection may represent a factor in developing of a        of hypodense round masses in the context of fat filled
severe ossification that can also preclude re-implantation.        cavity or appearance of new bony erosions (this allowed
Cochlear ossification may also be related to infection, sur-       detection of lesion in 1 of reported patient) (Figs. 5A, B)
gical trauma, or foreign body reaction 2. When facing this         and 2) using standard T1 and T2 MRI sequences that pro-
situation, delicate traction should be applied to the old ar-      duce a smaller artifact. MRI preceded by removal of the
ray, in order to avoid breaking part of the latter into the        magnet under local anesthesia is usually reserved to adult



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F. Canzano et al.




                                                                                 B

Figure 5. Axial high resolution CT scan, right ear. Patient 5. (A) postoperative scan few months after primary surgery; (B) four years later a round mass with new
bone erosion (asterisk) is evident in the same section. Revision surgery confirmed residual cholesteatoma.


patients with high-risk of residual disease and was adopted                          ing agencies in the public, commercial, or not-for-profit
in the 2 patients with petrous bone cholesteatoma.                                   sectors.

Conclusions                                                                          Author contributions
                                                                                     MF: concept; MF, FDL: design; MF: supervision; FC, MF,
Revision CI surgery may offer the patient a good chance to                           FDL: resource; MF, FDL, MG, EP: materials; FC, FDL,
achieve performances similar or even better than the pre-op-
                                                                                     MF: analysis and/or interpretation; FC, MG: literature
erative one. The risk/benefit ratio should always be carefully
                                                                                     search; FDL, FC, MF: writing; MF, FDL: critical reviews.
considered as revisions may hide adjunctive difficulties that
can preclude re-implantation. Middle ear infection should
                                                                                     Ethical consideration
be considered as an emergency; in addition to the risk of
                                                                                     This study was approved by the Institutional Ethics Com-
intracranial contamination, prolonged infection can stimu-
                                                                                     mittee (University Hospital of Parma) (Approval number
late an inflammatory reaction in the inner ear. Cochlear lu-
                                                                                     12015). The research was conducted ethically, with all
men violation without array placement during first surgery
should also be considered a rapidly evolving situation with                          study procedures being performed in accordance with the
the risk of severe ossification. In the majority of complex                          requirements of the World Medical Association’s Decla-
revision cases, SP offers invaluable advantages and should                           ration of Helsinki. No animals were involved. Written in-
be considered as first choice during surgical planning.                              formed consent was obtained from each patient for study
                                                                                     participation and data publication.
Conflict of interest statement
The authors declare no conflict of interest.                                         References
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72
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