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Bilateral implantation in children with cochleovestibular nerve hypoplasia
International Journal of Pediatric Otorhinolaryngology 73 (2009) 1470–1473
Contents lists available at ScienceDirect
International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Case report
Bilateral implantation in children with cochleovestibular nerve hypoplasia N. Oker a,*, N. Loundon a, S. Marlin b, I. Rouillon a, N. Leboulanger a, E.N. Garabe´dian a a b
ENT Department, Armand Trousseau Children’s Hospital, 75012 Paris, France Genetic Department, Armand Trousseau Children’s Hospital, France
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 March 2009 Received in revised form 20 June 2009 Accepted 25 June 2009 Available online 7 August 2009
To report on the outcomes of sequential bilateral cochlear implantation (CI) in children with inner ear malformation. The study design is a retrospective case study. The setting is a tertiary reference center. Two children presenting a profound bilateral congenital hearing loss with bilateral hypoplasia of the cochleovestibular nerves and hypoplasic external semicircular canal had a cochlear implant at respectively 16 months and 33 months. A second implant was proposed at respectively 17 and 20 months after the first implant. The main outcome measures are audiometry, perceptive results in closed and open set words (CSW and OSW) and oral production at follow-up. The first cochlear implant gave respectively mean thresholds at 60 dB and 70 dB. Bilateral CI showed mean threshold at respectively 40 dB and 55 dB. In case 1, perceptive assessment was 83% and 70% in respectively CSW and OSW with oral production and comprehension of sentences after 1 year follow-up. In case 2, the perceptive assessment showed no perceptive or linguistic evolution at 6 months follow-up. In cochleovestibular nerve hypoplasia, bilateral implantation could be discussed in cases of limited result after unilateral implant. ß 2009 Elsevier Ireland Ltd. All rights reserved.
Keywords: Cochlear implant Children Bilateral Sequential Auditory nerve Inner ear malformation Hypoplasia of cochleovestibular nerve CHARGE syndrome
1. Introduction
2. Cases reports
Since the advent of cochlear implantation, the indications for surgery have been more precisely defined and broadened. The main indicator remains in children with profound deafness showing limited gain with a powerful hearing aid [1–3]. Results of unilateral implants are variable. There are known factors such as the age at implantation, additional disabilities, cochlear malformation and/or ossification, and neuropathies. Absence or limited results can be caused by device failure, tuning defaults, insufficient stimulation or neurological problems [4]. Revision implantation appears to be a safe and effective procedure [5,6]. After the mechanical problems have been eliminated and the tuning checked, other causes for those limited results must be researched [7]. In these cases of limited or absent response of the first implantation, the interest of sequential bilateral implantation should be discussed. We report the case of two children with hypotrophic auditory nerve and inner ear malformation who had poor results with a unilateral implant. In those cases, sequential bilateral implantation was realized and their results are discussed in the following case report.
2.1. Child 1: girl, born November 2005
* Corresponding author. Tel.: +33 668860801. E-mail address: [email protected] (N. Oker). 0165-5876/$ – see front matter ß 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2009.06.017
Profound deafness was confirmed with the auditory brainstem response (ABR) at 12 months of age, the evoked otoacoustic emissions (OAE) were present bilaterally. The mean audiometric thresholds in free field testing were at 70 dB with hearing aids (HA). CT scan revealed normal cochlea and hypoplasic external semicircular canals (SCC) (Fig. 2). The magnetic resonance imaging (MRI) visualized normal cochleovestibular nerves (Fig. 3a–c). Genetic research remained negative (Connexine 26/30, mutation Q829X Otoferline, mitochondrial mutations). Suspicion of Waardenburg type II and minor CHARGE syndrome have been eliminated (respectively PAXS, MITF, SOX10 and CHD7). A right cochlear implantation (CI) was performed at 16 months of age (Nucleus1 24 RECA). There was no response with the preoperative neural response telemetry (NRT). At 6 months post-implant mean hearing responses with CI were at 50 dB. She showed some noise recognition capacities but 0% recognition in closed set words (CSW). There was no response to the neural telemetry (NRT) at this time. At 11 months postimplant, the parents described a drop in the auditory performance. The hearing level with CI was above 70 dB. Re-mapping with wider stimulation was not clinically efficient and did not improve NRT. Integrity test did not show device dysfunction; however;
N. Oker et al. / International Journal of Pediatric Otorhinolaryngology 73 (2009) 1470–1473
Fig. 1. Case 1: Hearing thresholds. FF: free field without HA/CI; CI RE: with cochlear implant right ear; CI LE: with cochlear implant left ear; CI RE + LE: with cochlear implant right + left ears, 12 months after bilateral implantation.
Fig. 2. Case 1: CT scanner (axial): bilateral abnormal external semicircular canal.
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Fig. 4. Case 2: Hearing thresholds. FF: free field without HA/CI; CI RE: with cochlear implant right ear; CI LE: with cochlear implant left ear; CI RE + LE: with cochlear implant right + left ears, 6 months after bilateral implantation.
MRI re-lectures suggested hypotrophic auditory nerves on both sides. A second implant was performed at 33 months of age (Nucleus1 24 RECA), no NRT response at surgery. One year after bilateral implantation, the audiogram showed thresholds at 70 dB when switching on the right CI (+30 months post-operative), 60 dB when switching on the left CI (+12 months). With both CI, thresholds were at 40 dB (Fig. 1). She showed 83% in CSW, 70% in OSW, and had acquired oral production (short sentences) and oral comprehension. 2.2. Child 2: boy, born January 2004
reimplantation was programmed (same device). Pre-operative NRT test was negative. Three months after reimplantation, hearing threshold with CI remained at 70 dB, in spite of several tuning adjustments. She showed some noise detection but 0% identification in CSW. Speech production was limited to a few words.
Profound deafness was confirmed at 16 months with the ABR, the OAE were absent. The mean audiometric thresholds with HA were at 70 dB. He had persistent arterial canal, cryptorchidism and syndactyly. The CT scan described bilateral dilation of the vestibule and of the superior SCC, agenesis of the lateral SCC, normal cochlea (Fig. 5). The MRI showed hypotrophic cochleovestibular nerves on
Fig. 3. Case 1: (a) MRI (parasagittal); internal auditory canal; left ear. (b) MRI (parasagittal); internal auditory canal; right ear. (c) MRI axial; inferior vestibular nerve branch only, no cochlear branch visible.
Fig. 5. Case 2: (a) CT scanner (axial) left ear: dilation of the vestibule and of the superior semicircular canal. (b) CT scanner (axial) right ear: dilation of the vestibule and of the superior semicircular canal.
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N. Oker et al. / International Journal of Pediatric Otorhinolaryngology 73 (2009) 1470–1473
both sides (Fig. 6a–d). Minor CHARGE syndrome was confirmed by genetic research. The sequencing of the gene CHD7 found a heterozygote mutation of the splicing site of the intron 33: IVS33 + 1G > A [10,11]. He received a right CI at 33 months of age (Nucleus1 24RECA), no interpretable NRT was obtained. Three months after CI, the thresholds with CI showed 70 dB. The child showed no recognition in CSW. Reimplantation with the same device was proposed (same device) with the same results. Re-mapping with wider stimulation was not efficient clinically and did not change the clinical and the NRT responses. A contra lateral implant was achieved 20 months after the first implant (Nucleus1 24RECA); no NRT pre-operative responses. At 6 months follow-up, the mean thresholds with bilateral CI were at 60 dB in free field (Fig. 4). Perceptive assessment showed 0% recognition in CSW and no linguistic evolution. 3. Discussion Malformations of the inner ear were initially considered to be a contraindication to surgery. Expanding selection criteria and increasing numbers of cochlear implantations have revealed several challenging cases with regard to surgical and medical perspectives. Cochlear implantation of congenitally deaf children with inner ear malformations may involve difficulties in preoperative evaluation, surgical approach and postoperative followup [8,9]. Hypoplastic cochleovestibular nerve remains among the most difficult cases [10]. Our two patients had similar inner ear malformations, associating hypotrophic cochleovestibular nerve with abnormal SCC. In both cases, the first suspected diagnosis was a CHARGE syndrome confirmed in case 2 [11–13]. In children the interpretation of the cerebral magnetic resonance imaging can be challenging. In case 1 the hypoplasia of cochleovestibular nerve was skipped in the first place, probably because of the moderate quality of the images. After the first CI, the clinical evolution led to the reinterpretation of the MRI images. To allow precise analysis of the four nerves, high quality MRI is essential. A classification based on a 1 mm (or less) axial and parasagittal MRT images reconstruction has been proposed [14]. The accuracy can be reduced because of the children’s movement if not practised under general anaesthesia, as seen in case 1. The MRI is part of the preoperative assessment of CI and if necessary proposed under general anaesthesia [15,16]. The results of the CI seem to depend on the severity of the nerve’s malformation. In most case of aplasia, poor or limited results have been reported, even though some reported cases of good results after CI in aplasia have been reported [17,18]. In those cases, the perceptive results could be due to auditory fibres contained in the facial nerve [14]. Some auditory experience and/or evidence of electrical auditory brainstem response or response at electrical promontory stimulation are elements that can support the hypothesis of a functioning auditory system [17–19]. In both of our cases, the clinical observation guided the decision of reimplantation but the analysis of the device did not lead to diagnosis of hard failure, and the revision of the cochlear implant was not effective [20–22]. In those two cases, the hypoplasia of the cochleovestibular nerve was the only explanation for the limited results of the unilateral CI. Fig. 6. Case 2: (a) MRI (parasagittal) internal auditory canal, left ear. The facial nerve, the vestibular superior and vestibular inferior branches are visible. (b) MRI (parasagittal) internal auditory canal, right ear. The facial nerve, the vestibular
superior and vestibular inferior branches are visible. (c) MRT (axial): inferior vestibular branch, no cochlear branch visible. (d) MRI (axial): superior vestibular branch and facial nerve.
N. Oker et al. / International Journal of Pediatric Otorhinolaryngology 73 (2009) 1470–1473
The advantage of bilateral CI has been established, in particular in specific indications (Usher Syndrome, Meningitis) [3,23]. Bilateral electrical stimulation provides the foundation for the potential advantages of the head-shadow effect, binaural redundancy and squelch effect, all of which combine, leading to improved speech comprehension and localization ability [24–26]. In cases of cochleovestibular nerve hypoplasia, the observed benefit of bilateral CI could be explained by the summation effect in the central auditory pathways. In the first case, we observed this improvement with both implants switched on. In the second case, we did not observe the same benefit at this time of follow-up. It is uncertain whether we will observe the same kind of improvement: the anatomic situation was poorer, with a very thin nerve. The aetiology and the delay between both implantations could also be responsible for poorer result. Facing the question of a second surgery one must remain cautious regarding the risks and the limits of the second implantation. The complications include pre-operative injury of the facial nerve, post-operative bilateral vestibular dysfunction and increased risks of meningitis [27,28]. In case of cochleo-vestibular malformation, the risks of gusher at cochleostomy, of electrode internal auditory canal migration and of meningitis are increased and should be discussed looking to the possibility of limited results with the second implant [29]. Moreover the absence of auditory nerve at MRI and major inner ear malformation should lead to reconsider the indication of a second surgery. 4. Conclusion In case of cochleovestibular nerve hypoplasia, perceptive results can remain limited with unilateral CI. Our experience shows that bilateral implantation can improve perceptive and linguistic results in some cases. Nevertheless the absence of auditory nerve at MRI and major inner ear malformation should lead to express reservations toward the possibility of enhancing the rehabilitation. References [1] N. Deggouj, M. Gersdorff, P. Garin, S. Castelein, J.M. Gerard, Today’s indications for cochlear implantation, B-Ent 3 (2007) 9–14. [2] NIH consensus conference, Cochlear implants in adults and children, JAMA 274 (1995) 1955–1961. [3] N. Cohen, A. Ramos, al. Ramsden Ret, International consensus on meningitis and cochlear implants, Acta Otolaryngol. 125 (2005) 916–917. [4] M. Cote, P. Ferron, F. Bergeron, R. Bussieres, Cochlear reimplantation: causes of failure, outcomes, and audiologic performance, Laryngoscope 117 (2007) 1225– 1235. [5] European consensus statement on cochlear implant failures and explantations. Otol. Neurotol. 26 (2005) 1097–1099.
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[6] S. Waltzman, J.T. Roland Jr., M. Waltzman, W. Shapiro, A. Lalwani, N. Cohen, Cochlear reimplantation in children: soft signs, symptoms and results, Cochlear Implants Int. 5 (2004) 138–145. [7] C.S. Kim, S.H. Oh, S.O. Chang, H.M. Kim, D.G. Hur, Management of complications in cochlear implantation, Acta Otolaryngol. 128 (2008) 408–414. [8] T.P. Nikolopoulos, K. Kiprouli, Cochlear implant surgery in challenging cases, Cochlear Implants Int. 5 (Suppl. 1) (2004) 56–63. [9] B.C. Papsin, Cochlear implantation in children with anomalous cochleovestibular anatomy, Laryngoscope 115 (2005) 1–26. [10] J. Bradley, T. Beale, J. Graham, M. Bell, Variable long-term outcomes from cochlear implantation in children with hypoplastic auditory nerves, Cochlear Implants Int. 9 (2008) 34–60. [11] K.D. Blake, C. Prasad, CHARGE syndrome, Orphanet. J. Rare Dis. 1 (2006) 34. [12] M.C. Jongmans, R.J. Admiraal, al. van der Donk KPet, CHARGE syndrome: the phenotypic spectrum of mutations in the CHD7 gene, J. Med. Genet. 43 (2006) 306–314. [13] R.J. Admiraal, P.L. Huygen, Vestibular areflexia as a cause of delayed motor skill development in children with the CHARGE association, Int. J. Pediatr. Otorhinolaryngol. 39 (1997) 205–222. [14] J.W. Casselman, F.E. Offeciers, P.J. Govaerts, et al., Aplasia and hypoplasia of the vestibulocochlear nerve: diagnosis with MR imaging, Radiology 202 (1997) 773– 781. [15] O.F. Adunka, V. Jewells, C.A. Buchman, Value of computed tomography in the evaluation of children with cochlear nerve deficiency, Otol. Neurotol. 28 (2007) 597–604. [16] H. Ma, P. Han, al. Liang Bet, Multislice spiral computed tomography imaging in congenital inner ear malformations, J. Comput. Assist. Tomogr. 32 (2008) 146–150. [17] D.E. Bamiou, S. Worth, P. Phelps, T. Sirimanna, K. Rajput, Eighth nerve aplasia and hypoplasia in cochlear implant candidates: the clinical perspective, Otol. Neurotol. 22 (2001) 492–496. [18] D. Zanetti, M. Guida, M.G. Barezzani, et al., Favorable outcome of cochlear implant in VIIIth nerve deficiency, Otol. Neurotol. 27 (2006) 815–823. [19] P.J. Govaerts, J. Casselman, K. Daemers, C. De Beukelaer, M. Yperman, G. De Ceulaer, Cochlear implants in aplasia and hypoplasia of the cochleovestibular nerve, Otol. Neurotol. 24 (2003) 887–891. [20] J.N. Fayad, L.S. Eisenberg, M. Gillinger, M. Winter, A.S. Martinez, W.M. Luxford, Clinical performance of children following revision surgery for a cochlear implant, Otolaryngol. Head Neck Surg. 134 (2006) 379–384. [21] A. Rivas, A.L. Marlowe, J.E. Chinnici, J.K. Niparko, H.W. Francis, Revision cochlear implantation surgery in adults: indications and results, Otol. Neurotol. 29 (2008) 639–648. [22] T.J. Balkany, A.V. Hodges, C.A. Buchman, et al., Cochlear implant soft failures consensus development conference statement, Otol. Neurotol. 26 (2005) 815– 818. [23] E. Offeciers, C. Morera, J. Muller, A. Huarte, J. Shallop, L. Cavalle, International consensus on bilateral cochlear implants and bimodal stimulation, Acta Otolaryngol. 125 (2005) 918–919. [24] B.R. Peters, R. Litovsky, A. Parkinson, J. Lake, Importance of age and postimplantation experience on speech perception measures in children with sequential bilateral cochlear implants, Otol. Neurotol. 28 (2007) 649–657. [25] J. Wolfe, S. Baker, T. Caraway, et al., 1-year postactivation results for sequentially implanted bilateral cochlear implant users, Otol. Neurotol. 28 (2007) 589–596. [26] K.L. Galvin, M. Mok, R.C. Dowell, R.J. Briggs, 12-month post-operative results for older children using sequential bilateral implants, Ear Hear. 28 (2007) 19S–21S. [27] E. Jacot, T. Van Den Abbeele, H.R. Debre, S.R. Wiener-Vacher, Vestibular impairments pre- and post-cochlear implant in children, Int. J. Pediatr. Otorhinolaryngol. 73 (2009) 209–217. [28] F. Venail, M. Sicard, J.P. Piron, et al., Reliability and complications of 500 consecutive cochlear implantations, Arch. Otolaryngol. Head Neck Surg. 134 (2008) 1276–1281. [29] J.H. Ahn, J.W. Chung, K.S. Lee, Complications following cochlear implantation in patients with anomalous inner ears: experiences in Asan Medical Center, Acta Otolaryngol. 128 (2008) 38–42.
Contents lists available at ScienceDirect
International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Case report
Bilateral implantation in children with cochleovestibular nerve hypoplasia N. Oker a,*, N. Loundon a, S. Marlin b, I. Rouillon a, N. Leboulanger a, E.N. Garabe´dian a a b
ENT Department, Armand Trousseau Children’s Hospital, 75012 Paris, France Genetic Department, Armand Trousseau Children’s Hospital, France
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 March 2009 Received in revised form 20 June 2009 Accepted 25 June 2009 Available online 7 August 2009
To report on the outcomes of sequential bilateral cochlear implantation (CI) in children with inner ear malformation. The study design is a retrospective case study. The setting is a tertiary reference center. Two children presenting a profound bilateral congenital hearing loss with bilateral hypoplasia of the cochleovestibular nerves and hypoplasic external semicircular canal had a cochlear implant at respectively 16 months and 33 months. A second implant was proposed at respectively 17 and 20 months after the first implant. The main outcome measures are audiometry, perceptive results in closed and open set words (CSW and OSW) and oral production at follow-up. The first cochlear implant gave respectively mean thresholds at 60 dB and 70 dB. Bilateral CI showed mean threshold at respectively 40 dB and 55 dB. In case 1, perceptive assessment was 83% and 70% in respectively CSW and OSW with oral production and comprehension of sentences after 1 year follow-up. In case 2, the perceptive assessment showed no perceptive or linguistic evolution at 6 months follow-up. In cochleovestibular nerve hypoplasia, bilateral implantation could be discussed in cases of limited result after unilateral implant. ß 2009 Elsevier Ireland Ltd. All rights reserved.
Keywords: Cochlear implant Children Bilateral Sequential Auditory nerve Inner ear malformation Hypoplasia of cochleovestibular nerve CHARGE syndrome
1. Introduction
2. Cases reports
Since the advent of cochlear implantation, the indications for surgery have been more precisely defined and broadened. The main indicator remains in children with profound deafness showing limited gain with a powerful hearing aid [1–3]. Results of unilateral implants are variable. There are known factors such as the age at implantation, additional disabilities, cochlear malformation and/or ossification, and neuropathies. Absence or limited results can be caused by device failure, tuning defaults, insufficient stimulation or neurological problems [4]. Revision implantation appears to be a safe and effective procedure [5,6]. After the mechanical problems have been eliminated and the tuning checked, other causes for those limited results must be researched [7]. In these cases of limited or absent response of the first implantation, the interest of sequential bilateral implantation should be discussed. We report the case of two children with hypotrophic auditory nerve and inner ear malformation who had poor results with a unilateral implant. In those cases, sequential bilateral implantation was realized and their results are discussed in the following case report.
2.1. Child 1: girl, born November 2005
* Corresponding author. Tel.: +33 668860801. E-mail address: [email protected] (N. Oker). 0165-5876/$ – see front matter ß 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2009.06.017
Profound deafness was confirmed with the auditory brainstem response (ABR) at 12 months of age, the evoked otoacoustic emissions (OAE) were present bilaterally. The mean audiometric thresholds in free field testing were at 70 dB with hearing aids (HA). CT scan revealed normal cochlea and hypoplasic external semicircular canals (SCC) (Fig. 2). The magnetic resonance imaging (MRI) visualized normal cochleovestibular nerves (Fig. 3a–c). Genetic research remained negative (Connexine 26/30, mutation Q829X Otoferline, mitochondrial mutations). Suspicion of Waardenburg type II and minor CHARGE syndrome have been eliminated (respectively PAXS, MITF, SOX10 and CHD7). A right cochlear implantation (CI) was performed at 16 months of age (Nucleus1 24 RECA). There was no response with the preoperative neural response telemetry (NRT). At 6 months post-implant mean hearing responses with CI were at 50 dB. She showed some noise recognition capacities but 0% recognition in closed set words (CSW). There was no response to the neural telemetry (NRT) at this time. At 11 months postimplant, the parents described a drop in the auditory performance. The hearing level with CI was above 70 dB. Re-mapping with wider stimulation was not clinically efficient and did not improve NRT. Integrity test did not show device dysfunction; however;
N. Oker et al. / International Journal of Pediatric Otorhinolaryngology 73 (2009) 1470–1473
Fig. 1. Case 1: Hearing thresholds. FF: free field without HA/CI; CI RE: with cochlear implant right ear; CI LE: with cochlear implant left ear; CI RE + LE: with cochlear implant right + left ears, 12 months after bilateral implantation.
Fig. 2. Case 1: CT scanner (axial): bilateral abnormal external semicircular canal.
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Fig. 4. Case 2: Hearing thresholds. FF: free field without HA/CI; CI RE: with cochlear implant right ear; CI LE: with cochlear implant left ear; CI RE + LE: with cochlear implant right + left ears, 6 months after bilateral implantation.
MRI re-lectures suggested hypotrophic auditory nerves on both sides. A second implant was performed at 33 months of age (Nucleus1 24 RECA), no NRT response at surgery. One year after bilateral implantation, the audiogram showed thresholds at 70 dB when switching on the right CI (+30 months post-operative), 60 dB when switching on the left CI (+12 months). With both CI, thresholds were at 40 dB (Fig. 1). She showed 83% in CSW, 70% in OSW, and had acquired oral production (short sentences) and oral comprehension. 2.2. Child 2: boy, born January 2004
reimplantation was programmed (same device). Pre-operative NRT test was negative. Three months after reimplantation, hearing threshold with CI remained at 70 dB, in spite of several tuning adjustments. She showed some noise detection but 0% identification in CSW. Speech production was limited to a few words.
Profound deafness was confirmed at 16 months with the ABR, the OAE were absent. The mean audiometric thresholds with HA were at 70 dB. He had persistent arterial canal, cryptorchidism and syndactyly. The CT scan described bilateral dilation of the vestibule and of the superior SCC, agenesis of the lateral SCC, normal cochlea (Fig. 5). The MRI showed hypotrophic cochleovestibular nerves on
Fig. 3. Case 1: (a) MRI (parasagittal); internal auditory canal; left ear. (b) MRI (parasagittal); internal auditory canal; right ear. (c) MRI axial; inferior vestibular nerve branch only, no cochlear branch visible.
Fig. 5. Case 2: (a) CT scanner (axial) left ear: dilation of the vestibule and of the superior semicircular canal. (b) CT scanner (axial) right ear: dilation of the vestibule and of the superior semicircular canal.
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both sides (Fig. 6a–d). Minor CHARGE syndrome was confirmed by genetic research. The sequencing of the gene CHD7 found a heterozygote mutation of the splicing site of the intron 33: IVS33 + 1G > A [10,11]. He received a right CI at 33 months of age (Nucleus1 24RECA), no interpretable NRT was obtained. Three months after CI, the thresholds with CI showed 70 dB. The child showed no recognition in CSW. Reimplantation with the same device was proposed (same device) with the same results. Re-mapping with wider stimulation was not efficient clinically and did not change the clinical and the NRT responses. A contra lateral implant was achieved 20 months after the first implant (Nucleus1 24RECA); no NRT pre-operative responses. At 6 months follow-up, the mean thresholds with bilateral CI were at 60 dB in free field (Fig. 4). Perceptive assessment showed 0% recognition in CSW and no linguistic evolution. 3. Discussion Malformations of the inner ear were initially considered to be a contraindication to surgery. Expanding selection criteria and increasing numbers of cochlear implantations have revealed several challenging cases with regard to surgical and medical perspectives. Cochlear implantation of congenitally deaf children with inner ear malformations may involve difficulties in preoperative evaluation, surgical approach and postoperative followup [8,9]. Hypoplastic cochleovestibular nerve remains among the most difficult cases [10]. Our two patients had similar inner ear malformations, associating hypotrophic cochleovestibular nerve with abnormal SCC. In both cases, the first suspected diagnosis was a CHARGE syndrome confirmed in case 2 [11–13]. In children the interpretation of the cerebral magnetic resonance imaging can be challenging. In case 1 the hypoplasia of cochleovestibular nerve was skipped in the first place, probably because of the moderate quality of the images. After the first CI, the clinical evolution led to the reinterpretation of the MRI images. To allow precise analysis of the four nerves, high quality MRI is essential. A classification based on a 1 mm (or less) axial and parasagittal MRT images reconstruction has been proposed [14]. The accuracy can be reduced because of the children’s movement if not practised under general anaesthesia, as seen in case 1. The MRI is part of the preoperative assessment of CI and if necessary proposed under general anaesthesia [15,16]. The results of the CI seem to depend on the severity of the nerve’s malformation. In most case of aplasia, poor or limited results have been reported, even though some reported cases of good results after CI in aplasia have been reported [17,18]. In those cases, the perceptive results could be due to auditory fibres contained in the facial nerve [14]. Some auditory experience and/or evidence of electrical auditory brainstem response or response at electrical promontory stimulation are elements that can support the hypothesis of a functioning auditory system [17–19]. In both of our cases, the clinical observation guided the decision of reimplantation but the analysis of the device did not lead to diagnosis of hard failure, and the revision of the cochlear implant was not effective [20–22]. In those two cases, the hypoplasia of the cochleovestibular nerve was the only explanation for the limited results of the unilateral CI. Fig. 6. Case 2: (a) MRI (parasagittal) internal auditory canal, left ear. The facial nerve, the vestibular superior and vestibular inferior branches are visible. (b) MRI (parasagittal) internal auditory canal, right ear. The facial nerve, the vestibular
superior and vestibular inferior branches are visible. (c) MRT (axial): inferior vestibular branch, no cochlear branch visible. (d) MRI (axial): superior vestibular branch and facial nerve.
N. Oker et al. / International Journal of Pediatric Otorhinolaryngology 73 (2009) 1470–1473
The advantage of bilateral CI has been established, in particular in specific indications (Usher Syndrome, Meningitis) [3,23]. Bilateral electrical stimulation provides the foundation for the potential advantages of the head-shadow effect, binaural redundancy and squelch effect, all of which combine, leading to improved speech comprehension and localization ability [24–26]. In cases of cochleovestibular nerve hypoplasia, the observed benefit of bilateral CI could be explained by the summation effect in the central auditory pathways. In the first case, we observed this improvement with both implants switched on. In the second case, we did not observe the same benefit at this time of follow-up. It is uncertain whether we will observe the same kind of improvement: the anatomic situation was poorer, with a very thin nerve. The aetiology and the delay between both implantations could also be responsible for poorer result. Facing the question of a second surgery one must remain cautious regarding the risks and the limits of the second implantation. The complications include pre-operative injury of the facial nerve, post-operative bilateral vestibular dysfunction and increased risks of meningitis [27,28]. In case of cochleo-vestibular malformation, the risks of gusher at cochleostomy, of electrode internal auditory canal migration and of meningitis are increased and should be discussed looking to the possibility of limited results with the second implant [29]. Moreover the absence of auditory nerve at MRI and major inner ear malformation should lead to reconsider the indication of a second surgery. 4. Conclusion In case of cochleovestibular nerve hypoplasia, perceptive results can remain limited with unilateral CI. Our experience shows that bilateral implantation can improve perceptive and linguistic results in some cases. Nevertheless the absence of auditory nerve at MRI and major inner ear malformation should lead to express reservations toward the possibility of enhancing the rehabilitation. References [1] N. Deggouj, M. Gersdorff, P. Garin, S. Castelein, J.M. Gerard, Today’s indications for cochlear implantation, B-Ent 3 (2007) 9–14. [2] NIH consensus conference, Cochlear implants in adults and children, JAMA 274 (1995) 1955–1961. [3] N. Cohen, A. Ramos, al. Ramsden Ret, International consensus on meningitis and cochlear implants, Acta Otolaryngol. 125 (2005) 916–917. [4] M. Cote, P. Ferron, F. Bergeron, R. Bussieres, Cochlear reimplantation: causes of failure, outcomes, and audiologic performance, Laryngoscope 117 (2007) 1225– 1235. [5] European consensus statement on cochlear implant failures and explantations. Otol. Neurotol. 26 (2005) 1097–1099.
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