Cochlear re-implant rates in children: 20 years experience in a quaternary paediatric cochlear implant centre

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1 Eur Arch Otorhinolaryngol (2015) 272: DOI /s OTOLOGY Cochlear re-implant rates in children: 20 years experience in a quaternary paediatric cochlear implant centre Marilena Trozzi Harry R. F. Powell Shamim Toma Waseem Ahmed Christopher G. Jephson Kaukab Rajput Lesley A. Cochrane Received: 30 January 2014 / Accepted: 18 July 2014 / Published online: 9 August 2014 Springer-Verlag Berlin Heidelberg 2014 Introduction This study was presented at the 2013 American Academy Otolaryngology Head and Neck Surgery Annual Meeting, October 1st, 2013, Vancouver BC, Canada. M. Trozzi H. R. F. Powell S. Toma W. Ahmed C. G. Jephson L. A. Cochrane Department of Paediatric Otolaryngology, Great Ormond Street Hospital, London, UK M. Trozzi (&) Bambino Gesù Children s Hospital, Rome, Italy marilena.trozzi@opbg.net K. Rajput Department of Paediatric Audiology, Great Ormond Street Hospital, London, UK Cochlear implants are now well established as the gold standard management for children with severe-to-profound hearing loss. Complications following cochlear implantation (CI) and device failure have been comprehensively reported in the literature [1 3]. The operative approach has evolved to encompass improvements in surgical technique and it is now considered a safe and effective procedure [4, 5]. The number of paediatric cochlear implants has increased significantly worldwide and earlier detection of hearing loss through the newborn hearing screening programme has lead to implantation being considered at a younger age [6]. In the UK the implementation of the National Institute of Health and Clinical Excellence (NICE) guidelines recommending that children, meeting the criteria, should be considered for bilateral or sequential implantation has also contributed to this increase [7]. At our institution, a quaternary referral paediatric centre, nearly 800 implanted devices have been inserted in children since Identification of risk factors for failure is important to increase awareness and improve future management of an increasing number of paediatric patients undergoing CI. Guidelines have been developed to report and research this further [8, 9]. To date there have been few studies to

2 2668 Eur Arch Otorhinolaryngol (2015) 272: investigate this. There is evidence to demonstrate that children, who developed meningitis before CI, are at an increased risk of device failure [1]. The aim of this study is to evaluate the incidence and aetiology of CI failure, explantation and cochlear implant re-implantation (CIri) in our population of children compared to those in the published literature. Methods The Great Ormond Street Hospital (GOSH) CI database was used to identify all patients who underwent multichannel cochlear implant surgeries between February 1992 and January 2013, following approval by the Hospital s research ethics board. This study included patients implanted at other institutions (2.2 %) and followed up at our institution for more than 3 years. Patients affected by device failure or requiring CI explantation were determined from this cohort and included in the study. Twenty-seven patients, 5 % of the total CI population had been lost to follow-up. A retrospective case note review was performed to collect demographic data, aetiology of hearing loss, age at implantation, age at explantation, co-morbidities, surgical details, CI manufacturer, and the cause of failure/reason for explantation. The European Consensus Statement on cochlear implant failure and explantation was used to categorise our results [8, 9]. Statistical analysis was performed using the v 2 test to compare the aetiology of hearing loss in our overall population with that in our CIri population. Our practice All children referred to the cochlear implant team follow the GOSH assessment pathway which is carried out by a multi-disciplinary team of experts. This includes genetic testing and aetiological investigations, audiological assessment, radiological investigations of the brain and inner ear, assessment of communication, developmental and non-verbal skill. This culminates in a multi-disciplinary team (MDT) discussion for all patients where suitability for implantation is discussed and management decisions made. All parents are advised that children undergo pneumococcal vaccination pre-operatively. Our surgical approach to cochlear implantation has evolved since An extended endaural incision with fixation of the receiver stimulator component to the skull was utilised until 1999, an extended post-auricular incision until 2003, and over the last decade a c-shaped minimal post-auricular incision with drilling of custom fit seat for the implantation device has been used. Patients receive intra-operative prophylactic intra-venous antibiotics (Co- Amoxiclav). After device insertion, intra-operative neural response telemetry is performed to provide guidance for future programming, and impedance is checked to make sure the electrodes are functioning according to specification. Postoperative plain radiographs (Stenver s views) are obtained to document the electrode array position. When medically fit for discharge the patients are allowed home and complete a 7-day course of broad-spectrum antibiotic prophylaxis (Co-Amoxiclav). Audiological follow-up is arranged 2 weeks post-operatively to allow surgical review and initiate switch-on of the device. Patients are subsequently reviewed on a fortnightly basis by the cochlear implant team until a stable implant map is achieved. The surgical team reviews all patients 3 months post-operatively and thereafter on an annual basis or as required if there are concerns. Follow-up ends conventionally at 18 years of age, except in those with significant co-morbidities requiring continuing care over this age limit. Results A total of 778 cochlear implants were inserted between 1992 and January Three hundred and ninety-seven children received a unilateral CI, 139 bilateral simultaneous CI and 103 contralateral sequential CI. Patients were between 3 months and 16 years of age at the time of implantation, with the median age being 3 years 1 month. In total, 40 CI failures were identified in 38 patients (of which three were implanted at different institutions), equating to an incidence of 5.14 % in our centre. The median age at implantation for those patients with implant failures was 3 years 5 months (range months). Aetiology of hearing loss A variety of causes of deafness in the CIri group were noted (Table 1). This distribution was compared to all children with a documented hearing loss in our CI program database. There was no significant difference between CIri population for: meningitis n = 4(P = 0.317), Connexin 26/genetic cause n = 7 (P = 0.108), syndromic/cochlea malformation n = 10 (P = 0.654), infective n = 1 (P = 0.479) and unknown n = 18 (P = 0.083). Causes for failure Twenty-two (55 %) failures were attributable to device failure and 18 (45 %) were due to medical reasons. Of the device failures, 15 were secondary to hardware failure

3 Eur Arch Otorhinolaryngol (2015) 272: (including six CI512 devices with known manufacturing faults) and 7 were due to performance decrement. Of the 18 medical failures, 8 were due to infection, 4 secondary to acquired cholesteatomas, 4 required CIri due to misplacement, and the remaining 2 patients were explanted due to trauma. Figure 1 summarises these results. Numbers of explantation and re-implantation Cochlear explantation was performed on 36 occasions for 35 patients. The mean time between implantation and explantation was 3 years 10 months (range 3 days 14 years). Four were not explanted; two due to risk of cerebrospinal fluid gusher, one patient had surgery for cholesteatoma and the other was implanted in Egypt with minimal follow-up until arriving in the UK (she had a progressive performance decrement and past history of recurrent otitis media). All have subsequently received a sequential implant. Cochlear re-implantation (same side) was indicated for 30 patients. Twenty-six of which were done at the time of explantation. Four patients had delayed re-implantation (range 3 9 months) after explantation for infective reasons Table 1 Causes of deafness in the CIri group and correlation with the failures: there was no significant difference in the prevalence of the failure between the different aetiology of hearing loss Aetiology of hearing loss Failures (n) Failures GOSH implant population v 2 test (P = 0.05) Meningitis P = Connexin P = /genetic Syndromic/ cochlear malformation P = Infective P = Unknown P = and required time for healing. Four patients that were explanted have subsequently undergone sequential implantation. Two patients have not been re-implanted; one due to poor perceived outcomes 3 years post-implantation and, therefore, family declined further intervention, the remaining bilateral implant patient is currently awaiting reimplantation after explantation for a unilateral package site infection. One patient had a double failure, the first due to package site infection and the second due to a known device defect (CI512). Another patient had a sequential failure (originally implanted in Egypt) due to misplacement of the electrode array. All implants explanted were sent to the manufacturer for further assessment. All the device failures were confirmed, including two damaged due to trauma. Manufacturers and models Historically at Great Ormond Street Hospital only Cochlear TM devices were being implanted until 2007, with subsequent introduction of Advanced Bionics (HiRes 90K) and Med-El devices in Device choice is a joint decision undertaken by patient and parents during the preoperative counseling process. A breakdown of the failures by device manufacturer and model is given in Table 2. Discussion Rate of CIri in our cohort Thirty patients underwent CIri in our series during the past 20 years. Our re-implantation rate is low, 3.8 % (30 out of 778). There were a total of 40 (5.1 %) failed implants in 38 patients. As demonstrated by Fig. 2, the number of patients undergoing implantation has increased dramatically over the last few years, the number of explantations has remained relatively stable (suggestive of a reduced overall Fig. 1 Distribution of failure by cause in our cohort: in blue? red, failure attributable to device malfunction (22) and failures due to medical reasons (18)

4 2670 Eur Arch Otorhinolaryngol (2015) 272: Table 2 Failure s rate by device manufacturer and model Device CI22M CI20?2 CI24M CI24R CI24RE CI512 Advanced Bionics HiRes90K Failures n Medical failure (n) Device failure (n) 6 (15 %) (2.5 %) (12.5 %) (20 %) (27.5 %) 7 (17.5 %) (5 %) Total Implanted since (year) with 13/58 of the original surgeries carried out in other institutions. Buchman et al. [16] had a 13 % revision rate in their series of 224 adult CI surgeries, similar to the Baltimore group s figure of 13 % from 482 paediatric cochlear implantations [2]. Table 3 shows the rates, causes of failure, and the timing of failure in our series compared with other large series in the available literature. There appears to be considerable variation when defining trauma, medical failure and device failure within previously published series, resulting in possible differences when classifying and reporting CI failure. This makes meaningful comparison within the literature difficult. Eskander et al. for example, reported a low failure rate of 2.9 %, but their institution only implanted the CI512 over a 15-month period; 32 CI performed and no failures reported for this model compared with six CI512 device failures in our series. They excluded patients who underwent implantation at other centres, a total of seven in their series. They base their experience on only one manufacturer [1], whereas our series includes those patients implanted elsewhere and devices produced by all three major manufacturers, which may account for our slightly higher reimplantation rate. The average time between initial implantation and explantation was 50 months. This differed depending on the aetiology: medical failures had a mean time interval of 36 months whilst explantation for device failure (hard and soft) was on average 62 months after initial surgery. Our interval of 50 months is in the middle of the pack when compared with other series with a range from 18 to 91 months from other institutions (Table 3). Aetiology of deafness and CIri Fig. 2 Rate failure/implantation by years: the number of patients undergoing implantation has increased dramatically over the last few years, whilst the number of explantations has remained relatively stable suggesting a reduced overall explantation rate explantation rate), whilst the proportion of medical and device failures has not significantly changed. Possible reasons for this may be an improvement in surgical learning curves for CI and advances in device durability. Our rate is at the lower end of the literature reported paediatric re-implantation rate range of % [1 3, 5, 10 14]. The Toulouse group had a 4.5 % re-implantation rate in children [17], Lassig et al. [13] report an overall revision/re-implantation rate of 5.1 % (adults and children) In our series, the aetiology of hearing loss in the explantation/ CIri cohort is similar to that of all implanted children. Recently published evidence has suggested a possible association of explantation risk and meningitis [1]. Having examined the underlying cause for hearing loss in our explantation patients, no one cause appears to increase the risk of either medical or device failure. At our institution, meningitis as an aetiological factor for deafness accounts for 15 % of all patients receiving CI, higher than that reported by Eskander et al. They also state that children developing meningitis prior to CI are at higher risk of subsequent failure [1]. Our series revealed only 10 % of the CI failures were deaf as a result of meningitis, compared to higher variable rates stated within the literature (18 52 %) [1, 12, 13, 15]. Rates of CIri in relation to device The literature suggests that the rates of re-implantation may be device-dependent. Buchman et al. [16] reported

5 Eur Arch Otorhinolaryngol (2015) 272: Table 3 Rates, causes of failure, and the timing of failure in our series compared with other large series in the literature Values are for paediatric series unless otherwise stated, adult values are italicised GOSH Great Ormond Street Hospital, A? P adult and paediatric, NAS non-auditory stimulation GOSH Marlowe et al. [2] Eskander et al. [1] Lassig et al. [13] Sorrentino et al. [17] Buchman et al. [16] Number (pts) surgeries (A? P) 487 (A? P) 224 (A) Failures 5.1 % 12.9 % 3.6 % 5.1 % (all) 4.2 % P 3.8 % A 13 % 4.5 % P Mean time to failure (months) A 47 P 18 A 91 P Hard Soft Infection/scalp flap Electrode position Cholesteatoma 10 3 Trauma 5 Technology upgrade Unknown 3 (NAS) (medical) 6 (NAS) 41 significantly fewer explantations for MED-EL CI compared to Cochlear TM and Advanced Bionics devices. Other series have looked at survival of devices. Evolution in the manufacturing of devices and the limited follow-up reported has made it difficult to determine factors that may influence re-implantation. Reviewing our device failure cases, we examined the possible relationship between device manufacturer/model type and the time to failure. Due to the small numbers of respective devices/models, variation in follow-up period with more established models such as CI22M (first implanted in 1992) compared to more recent arrivals such as CI24RE Nucleus Freedom (as can be seen in Table 2), it is difficult to draw any definitive conclusions. Surgical findings in CIri In all four patients with failure due to cholesteatoma, there were difficulties with either access for the posterior tympanotomy leading to inadvertent damage to the posterior canal wall (2 cases) or damage to the tympanic anulus whilst drilling the PT (2 cases). Therefore, we wish to stress the importance of recognising these complications at the time of surgery and implementing the appropriate repair to minimise the probability of an acquired cholesteatoma. Of the four misplacements, there was bending of the electrode tip in the basal turn of the cochlea on two occasions, and the other two cases had unusual cochlear/middle ear anatomy resulting in misplacement. Types of CI failures Device failure occurs when the device characteristics fall outside the manufacturer s specification and/or result in a loss of clinical benefit [8, 9]. Failure of a CI may also be due to medical reasons such as infection. Guidance from the 2005 Cochlear Implant Soft Failures Consensus Development further divided failures into soft or hard failures. A hard failure refers to measurable hardware abnormalities and soft failures to declining performance, undesirable auditory and non-auditory symptoms, or intermittent function with no loss of communication between internal and external components [8, 9]. We feel that although this classification is useful, as clinicians it is important to further differentiate medical failure and identify the underlying cause in such cases. This will provide important clinical information to aid improved surgical techniques, patient selection and parental counseling for both initial implantation and subsequent reimplantation. Conclusions The rate of CI failure in the paediatric population at our institution is low and comparable with that of other large series. We have not identified any aetiological factors that increase the risk of CI re-implantation. Cochlear implantation in children is increasing. Minimising surgical complications at the time of implantation and maximising

6 2672 Eur Arch Otorhinolaryngol (2015) 272: access to hearing have been well investigated. Further work to determine factors that affect failure is becoming increasingly important in particular to compare the rate of failure with the age of implantation and subsequent factors that may increase risk of medical failure. Cochlear implantation, however, remains a safe and reliable procedure with low rates of device failure. Conflict of interest References None declared for all authors. 1. Eskander A, Gordon KA, Kandhim L et al (2011) Low pediatric cochlear implant failure rate. Arch Otolaryngol Head Neck Surg 137(12): Marlowe AL, Chinnici JE, Rivas A et al (2010) Revision cochlear implant surgery in children: the John Hopkins experience. Otol Neurotol 31(1): Alexiades G, Roland JR Jr, Fishman AJ et al (2001) Cochlear reimplantation: surgical techniques and functional results. Laryngoscope 111(9): Bhatia K, Gibbin KP, Nikolopoulos TP et al (2004) Surgical complications and their management in a series of 300 consecutive pediatric cochlear implantations. Otol Neurotol 25(5): Brito R, Monteiro TA, Leal AF et al (2012) Surgical complications in 550 consecutive cochlear implantation. Braz J Otorhinolaryngol 78(3): Raine C (2013) Cochlear implants in the United Kingdom: awareness and utilization. Cochlear Implant Int 14(Suppl 1):S32 S37 7. Strøm-Roum H, Laurent C, Wie OB (2012) Comparison of bilateral and unilateral cochlear implants in children with sequential surgery. Int J Pediatr Otorhinolaryngol 76(1):95 99 (Epub 2011 Nov 8) 8. Balkany T, Hodges AV, Buchman CA et al (2005) Cochlear implant soft failures. Consensus development conference statement. Cochlear Implant Int 6(3): (2005) European consensus statement on cochlear implant failures and explantations. Otol Neurotol 26(6): Cullen RD, Fayad JN, Luxford WM et al (2008) Revision cochlear implant surgery in children. Otol Neurotol 29(2): Gosepath J, Lippert K, Keilmann A et al (2009) Analysis of fiftysix cochlear implant device failures. ORL J Otorhinolaryngol Relat Spec 71(3): Fayad JN, Eisenberg LS, Gillinger M et al (2006) Clinical performance of children following revision surgery for a cochlear implant. Otolaryngol Head Neck Surg 134(3): Lassig AA, Zwolan TA, Telian SA (2005) Cochlear implant failures and revision. Otol Neurotol 26(4): Tarkan Ö, Tuncer Ü,Özdemir S et al (2013) Surgical and medical management for complications in 475 consecutive pediatric cochlear implantations. Int J Pediatr Otorhinolaryngol 77(4): Parisier SC, Chute PM, Popp AL et al (2001) Outcome analysis of cochlear implant reimplantation in children. Laryngoscope 111(1): Buchman CA, Higgins CA, Cullen et al (2004) Revision cochlear implant surgery in adult patients with suspected device malfunction. Otol Neurotol 25(4): (discussion 510) 17. Sorrentino T, Coté M, Eter E et al (2009) Cochlear reimplantations: technical and surgical failures. Acta Otolaryngol 129(4):