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PDF hosted at the Radboud Repository of the Radboud University Nijmegen The following full text is a publisher's version. For additional information about this publication click this link. http://hdl.handle.net/2066/25465 Please be advised that this information was generated on 2017-10-20 and may be subject to change. COCHLEAR IMPLANTATION IN DEAF CHILDREN M o h a m m a d J.A. M akhdoum , m b b s , AFSA; A d F .M . Snik, MSc, PhD; Paul van den Brock, m d . I-Res, Phi) A cochlear implanl (Cl) is a hearing device introduced in the 1980s for profoundly deaf subjects who gained little or no benefit from powerful hearing aids. This device comprises an electrode array inserted in (lie cochlea, connected to an internal receiver, and an externally worn speech processor. The Cl transforms acoustic signals into electrical currents which directly stimulate the auditory nerve. Since the early 1990s, cochlear implantation in children has been developing rapidly. Although it is still difficult to predict how a child will perform with a cochlear implant, the success of cochlear implantation can no longer be denied. In this paper, some recent papers anti reports, and the results of the various Nijmegen cochlear implant studies, are reviewed. Issues about selection, examinations, surgery and the outcome arc discussed. Overall, our results were comparable with those of other authors. It can be concluded that cochlear implantation is an effective treatment for postlingually deaf as well as prelmgually (congenital or acquired) deaf children with profound bilateral sensorineural deafness. Ann Saudi M e d 1997; 17(5):533-539> Cochlear implantation is widely accepted as a routine clinical procedure for selected deaf children. It restores deaf c h ild re n 's perception of sound through the use of a special electronic device. T h e C l system co m p rise s an electrode (single or multi-channel) placed in the cochlea, connected to an im planted receiver, and an e x te r n a lly worn microphone, signal processor and transmitter. T h e speech processor analyzes the sound signal from the m ic ro p h o n e and transmits it Iran scut an eou sly to the internal receiver. T he electrical stimulation by the Cl bypasses the n o n ­ functional parts o f the cochlea and delivers sig n a ls directly to the auditory nerve. Because of the direct stim ulation o f the nerve, most Cl users perceive hearing sen sation s that cannot be obtained with even the m o st powerful conventional bearing aid. Owing to technological evolution, different types of Cl devices have been introduced. T he difference between the v ariou s types is in the electrode designs and/or speech processing strategies. However, they all consist o f similar basic elem ents. In recent years, remarkable progress has been m ade in the application of pediatric cochlear im plantation, from the research stage to regular clinical application. At least 3 40 0 subjects under IK years have received C l w orldw ide. O f them, 400 were under the age of three years when implanted and a further 1250 were between three and six From the Depart men is of Otorhinolaryngology. St. Radboud University Hospital (Drs, Makhdoum, Snik, Van den Brock), Nijmegen, The Netherlands and Alnour Specialist Hospital (Dr. M akhdoum ), Makkah, Saudi Arabia. Address reprint requests and correspondence to Dr. M J .A , Makhdoum: Department of Otorhinolaryngology, St. Radboud University Hospital, P.O. Box 9101, 0500 HB Nijmegen, The Netherlands. Accepted lor publication 10 June 1997. Received 30 February 1997, y e a r s .1 T h e m ain goal of Cl application is to restore h e a r in g in children with profound hearing loss, thus e n h a n c i n g their ability to participate in aural-oral co m m u n icatio n . Studies have revealed that the majority of children using a Cl with a prelingual (before three years of age) or post ling Liai (after three years of age) onset of deafness obtain significant benefit from this prosthesis. However, speech perception abilities vary widely, ranging from the sim ple identification o f sounds to the recognition o f norm al open speech," '’ Most users benefit more from their Cl than from conventional h e a rin g a id s .l,u,K The problem of post-implant, variable speech perception abilities continues to challenge research teams, and efforts are being m ade to find a m eans of predicting the result prior to cochlear implantai ion. So far, no p ré o p é râ tive factor has been found that can predict the outcom e of cochlear im plantation. However, it is known that som e biographical factors, such as age at the onset of deafness and the duration of deafness, play a roie.,‘‘* T o obtain a good result, it is generally reported that careful candidate selection is necessary, and that a rehabilitation program should follow cochlear im plantation. Success in this Held can no longer be denied, in spite of initial skepticism in the scientific world and the d e a f c o m m u n i t y . 10,11 T h is paper presents an overview of the current concepts o f c o c h le a r im plantation and reviews the results of Cl studies at the University Hospital Nijmegen. In Nijmegen, the pediatric cochlear implantation p ro g ra m was initiated in 1989 in close cooperation with the Institute for the Deaf in ST. Michielsgeslel. Initially, the one-channel Med, B1 device was used, but later on, the 22-channel Nucleus Anmils o f Suurii Mt'iHi'itii', Vol i l , No S. / W 533 MAKHDOUM h t a i. device was introduced. By th e e n d o f 1996, 4 4 profoundly d e a f children had been im p la n te d (T able 1). Selection C riteria and P reoperative Tests Pf e o p e }cilive A ssesm ien is Pediatric c o c h le a r im p la n ta tio n requires medical, audiological and psychological evaluation. A ro u tine E N T e x a m in a tio n forms the initial p a r t o f the evaluation, Radical m a s to id e c to m y or ty m p an op lasty , w ithout any lo n g -te rm p ro b lem s, are not considered as c o n train d icatio n s. I2,1'\ l n g e n e ra l, preoperative audiological a ss e s sm e n t is considered as the m a jo r factor to d eterm in e the suitability o f a child for c o c h le a r im plantation. T h e audiological test batteries consist o f play au d io m etry or visual rei n foreem ent a u d io m etry , ty m p a n o m e try and speech perception tests. A u d io lo gical assessm en t should confirm profound, bilateral se n so rin e u ral h e a rin g loss, without useful residual hearing. T o d e te r m in e the potential of residual hearing, the use o f pow erful h e a rin g aids with an a p p ro p ria te au d ito ry reh abilitatio n period is essential. G enerally, speech perception tests q u a n tify a c h i l d ’s ability to use h is/h er residual h e a r i n g effectively. Such data obtained preo p erativ ely are also valuable as a reference for c o m p a ris o n with p o s tim p la n t scores. To confirm the results of behavioral h e a r in g tests, .live electrophysiologieal tests, such as au dito ry brain stem resp o nse (ABR) a n d /o r e le e tro co ch leo g rap h y m e a s u re m e n ts , are often u s e d . 11 gic evaluation in c lu d es high-resolulion n c o m p u te d to m o g ra p h y (H R C T ) scanning» which is a p rerequisite to d e te rm in e possible ossification o f the cochlea a n d co n genital a n o m a lie s as well as anatom ical l a n d m a r k s . 1*1"17 G enerally, ossification o f the cochlea is not co n sid ered as a surgical co n tra in d ic atio n for cochlear im p la n ta tio n ,7,13,17,18 However, in such cases full insertion of the electrodes is not alw ays possible and the results o f im p la n tatio n m ig h t be poor. C h ild re n u n d e rg o psychological testing as part o f the preoperalive assessm ent, to rule out a n y severe problems. T h e expectations and m o tiv a tio n of the child and the p aren ts h a v e to be realistic.7,,iJ Evolution o f flic Select ion Criteria Over the years, the selection c rite ria have changed as greater insight has been g a in e d into the effect of several biographical factors u p o n CI p e rfo rm a n c e . V arious studies have revealed that p o stlin g u a lly d e a f adults perform better with their CI than p re lin g u ally d e a f a d u lt s .1 T h e difference in p e rfo rm a n c e between pre- and postlingually d e af children is far less p r o n o u n c e d .2,20 P relin g u ally d e af w h o ■eceived an im p la n t d u r in g childhood achieved a high er level of p e r f o r m a n c e than those w ho 534 Annals o f Saudi Medicine . Voi 17, No 5, 1997 Biographical data on the children (<14 vr.vj who received a cochlear implant in Nijmegen. T abu * I. Prelinguai Postlingual 38 13 25 6 Age at unset of deafness Range, yrs Mean, yrs 0.0 - 2 .9 1.2 3.1-6.9 4.2 Duration of deafness Range, yrs Mean, yrs 1.9-13.4 5.4 1.3-7.9 4.4 Age al cochlear implantation Range, yrs Mean, yrs 2.9-13.4 (1.6 4.3-12.3 Duration oJ'CSI use Range, yrs Mean, yrs 0,5-6.9 2.7 0.6-4.2 3.4 N um ber o f children Male Female 5 1 8.6 received CI d u rin g a d u l t h o o d / 1 Dowell et a l.2 review ed the speech perception results of all the children and adolescents (up to 19 years of age) im p la n te d in M e lb o u r n e and Sydney. In agreem ent with o th e r authors, they observed that the range o f speech p erceptio n p e rfo rm a n c e was wide. T heir results indicate that the age at onset o f h e a rin g loss and the age at the time o f co chlear im p la n ta tio n d o not have any significant effect on speech perception. However, the duration of deafness a n d the duration o f i m p l a n t use h ad a significant effect. In the recent literature, the youngest children im p la n te d were u n d e r tw o years. Implantation at such a young age is only feasible if profound bilateral sensorineural h e a r in g loss can be diagnosed with complete certainty, and if the child has not benefited from co n v en tio nal h e a rin g aids. C o chlear implantation at a y o u n g age m ay m i n i m i z e the negative effect of auditory deprivation a n d in the c a s e of meningitis, it m ight help to prevent labyrinthitis ossification which would impede later im plan tatio n . C o h en a n d W a lt/.m a n 10 reported that eight ch ildren u n d e r two years received CI at their institute and showed significant benefit. T h e Hannover group has a ls o im p la n ted such young children, with encouraging results (personal c o m m u n ic a tio n ) . Nevertheless, more data are required to sh o w the benefits of early implantation and t0 £ U1(^C ^utuïü policy. Surgery Surgical Technique C i surgery can be perform ed successfully in children, in spite of som e difficulties, particularly with an ossified c o c h l e a . 1* Access to the cochlea is obtained by a mastoid a n d facial recess approach, as is used in surgery SPECIAL COMMUNICATION: COCHLEAR IMPLANTATION /V y \ i 1' ' if 1 ~* * * f . ,• . . *. / A FIGURE I A. Diagram of an endaural incision. IB, A retro-auricular incision employed for cochlear implantation. Condensed dots indicate the site of placement of the receiver. for chronic otitis media. T he receiver-stim ulator is positioned just above and behind the p in n a (Figures 1A and IB). T h e incision should be made at least 1 cm away from the p lanned site for the internal receiver. Several types o f skin flap design have been advocated, a n d the basis for the designs is to maintain a good v ascu lar supply to the flap. In Nijmegen, two types of incision are used: an endaural incision (Figure I A) or a retro-auricular incision (Figure IB). Both curve upwards and backwards, high over the parietal region. Due to the dimension of a c h i l d 's skull, the thinness o f the skin and the later grow th o f the skull, the incision is made right down to the bone, T he temporal muscle is lifted from the parietal portion of the temporal bone, with the subcutaneous tissue a n d skin as a single layer flap. This surgical modification m in im iz e s problems with w ound healing and possible electrode extrusion. After elevation of the skin flap, the d u ra m ater is sometimes exposed when drilling the well for p la c in g the receiver-stimulator. It is usually necessary to gently push the dura m ater down with a thin piece o f bone to accom m odate the receiver coil, Following m astoidectom y, a facial recess approach is used to gain access to the ^I m iddle ear and round w indow niche." T h e facial recess is opened, the facial nerve is skeletonized, a v o id in g ex p o su re o f the nerve sheath. Cochleostomy can be p erfo rm e d in two ways: through the prom ontory anterior to the round w indow m em brane, or through the ro u n d w in d o w m em b ran e itself.11,21 T h e electrode array s h o u ld be inserted gently to p reven t d a m a g e to the delicate cochlear structures as m u c h as possible. Ossification of the cochlea, as is often found in postm en in g itis cases, needs drilling to open the seala tympani for insertion o f the electrode array. In som e cases with severe ossification, extensive drilling o f 6 to K m m is necessary. If no fluid-filled lumen is found, this may result in partial in s e r tio n .15 H a r tr a m p f et a I.lH reported that in cases with cochlear ossification, at least seven electrodes of the N ucleus 22-channel system can be inserted. After insertion, the cochleostomy is sealed with bone dust or soft tissue a n d glue. In general, the electrode lead is placed in a groove created in the superior part of the mastoidectomy fossa and fixed in the fossa incudis. T his is because the distance from there to the round w indow does not change after birth. T h e receiver-stimulator should be tied down securely. Complications T h e surgical complication rate of the implant procedure is low in children. Largely, the com plications are c o m p a ra b le with those o f m iddle ear surgery. In addition to surgical com plications, device migration or failure may occur. N o m ajor com plications occurred in any of the 44 children w ho received a Cl in Nijmegen. However, postoperative com plications were found. A m inor wound infection occurred in one child, while another child had a surgical h e m a to m a . In live children, only partial insertion o f the electrode eiectroae arrav array was possible due to severe ossification o f the cochlea. Annals o f Saudi Medicine, Vol 17. No 5, ï W 535 MAKI IDO UM Kl ,\i Revision surgery can be perform ed either to upgrade the Cl system or to replace a tailin g device. It is possible to explant and re im p Ian I w ith ou t d a m a g e to the cochlea or the auditory nerve.21 Preoperative Imaging and Surgical Results H R C T s c a n n in g has proven to be a valuable tool for the preoperative assessm ent of cochlear patency. However, minor or m a jo r cochlear ossification encountered d u rin g surgery is not always visible on preim plant radiological studies.13,17,22 i f the H R C T scan seems to be normal in children with a history of meningitis, the surgeon should suspect obliteration of the ro u n d w indow and part of the basilar turn. A Dutch study on the predictive value of H R C T scanning carried out in 88 subjects (children and adults) with a C l show ed a relatively large n u m b e r o f falsenegatives, m a in ly in children, when com pared to the intraoperative findings. T h e data are presented in Table 2. This m eans that in spite o f its value, the accuracy of preoperative H R C T scanning is not optimal. Elecu vphysi olog icaI Me asuren xeiiIs To achieve the best results with a Cl, it is im portant to adjust the processor output to the u se r’s dynam ic range. 1 “3 This may be a problem in young c h i l d r e n / ' To tackle this problem, several investigators performed m easurem ents to assess threshold and com fortable levels directly after placement o f the Cl, while the child was still under general anesthesia. For this purpose, electrically evoked ABR measurements (E A B R ) and /or electrically evoked stapedius muscle reflex (ESR) m e asu rem en ts were perform ed.2"1'"’1 A technical restriction o f the E A B R m easurem ent is that it is m ore susceptible to noise and electrical artifacts than the E S R m easurem ent. A specific problem with intraoperative ESR m e asu rem en t is that anesthetic agents influence the o u tc o m e .'2A'2* T o illustrate this, Figure 2 shows an ex am p le of E S R thresholds recorded imraoperatively. D uring the measurement, the concentration o f an anesthetic agent (Halothane) was increased and later readjusted to the original level. A significant effect of the H alothane concentration was seen. Figure 2 also show s the postoperative value obtained six months after device filling. In general, postoperative ESR were lower than those m easured d u rin g surgery.2“' O w in g to the technical restrictions and the poor relationship with the behavioral results, intraoperativc EA B R and E S R data should be used with caution for p ro g ra m m in g . Kill i Rehabilitation The aim o f the rehabilitation program is to achieve 536 Aniuitx a f Saudi Medicine, Vnl 17, No 5, l (W Electrode: 220 -»-5 ^w2 0 0 * 15 CD g 180 £ 160 CO w -i 4o 120 'X 1 i\o\ P o\o\ I o\o\ V & O .0 Measurement (% Halothane) FIGURE 2. A typical example of electrical-evoked stapedius reflex thresholds (0SRT) recorded imraoperatively from electrodes 3 and 20, while the concentration o f the anesthetic agent (Halothane) was varied from 0.6% ( I d ) to 2.0% (102) and back again to 0.6% (103). Postoperative results obtained six months after device fiiiiim are also indicated. optimal use o f a Cl. New auditory abilities should be utilized to develop new auditory and com m un ication skills. Generally, speech perception skills improve after cochlear im plantation. After the initial rehabilitation period, normal learn in g in daily life contributes to the optimal use of a CL1" Collaboration of the Cl team with tutors in a setting for the d e a f is essential, especially for children. If a child does not receive rehabilitation and encouragem ent for spoken language, the outcome of cochlear implantation is likely to be disappointing. In cooperation with the Institute for the D ea f in St. Michielsgestel, the initial rehabilitation period in Nijm egen takes two weeks. After this period, implanted children return once every month for tutoring for at least one year. After rehabilitation, they should be able to con tinu e learning at home and at school, at their own speed and in their own manner. Outcome of Cochlear Implantation Several studies have focused on speech perception skills in children with a CI. Gantz ct al.2i) studied the benefit o f the Nucleus multichannel Cl in 54 children. perception skills of T h e y found that the posUingually d e a f children improved significantly during the first year after implantation. T h e prelingually deaf children progressed at a slower rate than their postlingual counterparts. However, some of the prelingually deaf children attained comparable, and in some instances better, SPFCIA1, COMMUNICATION: C O C H U iA R IMPLANTATION Tahi.i- 2. Preoperative high-resoludon cam pu ted tomography findings in 3 year 60 o CD 8 40 v O n v . 20 0 0 0,5 1.0 1.5 2.0 2.5 3.0 Follow-up (years) FIGURE 3. The mean score on the picture-word identification test as a function of follow-up of the three groups o f children with full electrode insertion subdivided according to their age at the time o f onset o f deafness. The white bars indicate the mean scores o f the children with acquired deafness between 0.3 and 2 years o f age (n=5). The gray bars indicate the mean scores o f the children with acquired deafness between 2.1 and 3 years of age (iv=6 ) and the black bars indicate the mean scores o f the children whose age at the onset of deafness was above 3 years (n=5). The values at a follow-up o f 0 are the mean scores obtained before surgery with the children's own previous conventional hearing aids. T h erefo re, results of a m ore basal speech perception test will be presented. The test used was a su pra-segm ental test in w h ic h the children only had to identify th e n u m b e r of syllables per word. Figure 5 shows the ran g e (vertical lines) and the mean scores of the partial insertion group (w hite bars) and the average of the other three groups (g ra y bars). T h e values at the beginning of the follow-up are the m e a n scores obtained before surgery fro m the c h ild re n w ith their own previous conventional h e a rin g aids. T h is figure illustrates that the children with partial in sertio n are relatively poor performers, even after a threeyear period o f daily use. Therefore, to achieve the best result, th e electrode array should be inserted into the coch lea over its full length. However, this cannot always be ach iev ed in the case o f severe ossification o f the cochlea. N ev erth eless, K em ink et al.28 reported that the p e r fo rm a n c e of children with partial insertion was c o m p a ra b le to that o f children with illII insertion. O ur fin d in g s a n d those of other g ro u p s11,29 showed that partial insertion leads to inferior long-term results. In s u m m a ry , our results a n d those o f other studies " ’ ’ show ed th at significant (but variable) cochlear im p la n ta tio n outcomes can be achieved in children. T h e age at the onset of deafness and the m ethod of insertion of the e lectro d e array, either fully or partially inserted, play a role. 1 / Conclusion 80 □ 0.3-2 year 2.1-3 year co 60 > 3 year Û) o o CO O 40 0) o o x O A S 20 0 0 0.5 1.0 1.5 2.0 2.5 3.0 Follow-up (years) FIGURE 4. The mean score o f the open-set speech perception test as a function o f follow-up o f the three groups o f children with full electrode insertion subdivided according to their age at the time o f deafness. The while bars indicate the mean scores o f the children with acquired deafness between 0.3 and 2 years of age (n=5). The gray bars indicate the mean scores o f the children with acquired deafness between 2 . 1 and 3 years o f age (n = 6 ) and the black bars indicate the mean scores o f the children whose age at the onset o f deafness was above 3 years (n=5). The values at a follow-up o f 0 are the mean scores obtained before surgery with the children’s own previous conventional hearing aids. 538 Annuls o f Scuuli Medicine* Vo! 17, No 5, 1997 N o w a d a y s, cochlear im plantation is generally fconsidered to be o f significant value for pre- and p o s tlin g u a lly profoundly d eaf children. A d eq u ate re h a b ilita tio n is most crucial for the children to m a x im iz e the benefits of cochlear im plantation. M an y studies reported that auditory perfo rm an ce with a C l varies am o n g ch ild re n . Until now, there has been no com pletely satisfactory explanation for this observation. However, p e r f o r m a n c e seems to be best in children with a short d u ra tio n o f deafness, w ho acquired speech and lan g u ag e before th e ir deafness occurred. Present results suggest that such c h ild re n m ay acquire good speech perception a n d as a result, m a y develop n o rm a l aural-oral com m unication. T h e outcom e of partial insertion of m ultichannel e lectro d e arrays is generally poorer than that o f full in se rtio n . T h i s will depend on the position and n u m b er of active electrodes. It is highly questionable w hether c o c h le a r im plantation in a severely obliterated cochlea is w o rth w h ile . O v e r th e years, inclusion and exclusion criteria have g r a d u a lly c h a n g e d with growing knowledge. Generally, etiology a n d age at im plantation do not seem to affect the p o s t-im p la n ta tio n auditory performance. However, the e a rlie r the im plantation, the better the result, especially in p re lin g u a lly d e a f individuals. Nowadays, most C l teams SPECIAL COM M UNICATION: COCHLBAR IMPLANTATION 100 9. if P p tei!'K ïé? f e j h ^ ;; 80 L ^ ÿ îji . c/> < D u~ w «svi !« • I fc "• ^ -• » mmm O O 60 C/3 t/j » 9 9 » • «. : n « . *r ' I } I • I • \ ïîï ; ; 4 ' j •h^' ’ ; " . •;. ; I s :• 12. ••. i':'- 13. ■ 4 I n h f » I « 1 I I I te g j . ; , ■>'?•••'■' r J Ü II. >'5.;' I ;I-sI A' « ï O 0) o 40 10. ■/•.• Wffl o 20 I • 4 y I K S iS fesrlfâ fili hmw 4mm I M-xti 14. 15. mimtet 0 o 0.5 1.0 1.5 2.0 2.5 3.0 Follow-up (years) FIGURE 5. The mean score on the supra-segmental speech identification lesi and its range for the children with partial electrode insertion (white bar) and the averaged mean scores o f the three groups of children with full insertion (gray bar) during a three-year follow-up period after cochlear implantation. The vertical lines indicate (he range in the obtained .scores. The values al follow-up of 0 are the mean scores obtained before surgery with the children’s own conventional hearing aids. 16. 17. 18. 19. 20. only use a limited number of exclusion criteria. The most important exclusion criterion is the ability to utilize any residua] hearing with well-fitted conventional hearing aids. Owing to technological evolution and an increase in experience, the era of cochlear implantation is advancing rapidly. New techniques may enable wider groups of preand postlingually hearing-impaired children to benefit from cochlear implantation. References 1. 2. 3. 4. 5. 6. 7. 8. Summerfield AQ, Marshall DHL Cochlear implantation in the UK 1990-1994. London: HMSO, 1995. Dowell RC. Blarney P.I, Clark GM, Potential and limitations o f cochlear implants in children. Ann Otol Rhinol Laryngol 1995; 104 Suppl 166:324-7. Miyamoto RT, Kirk Kl, Todd vSL, Robbins AM, Osberger MJ. Speech perception skills o f children with multichannel cochlear implants or hearing aids. Ann Otol Rhinol Laryngol 1995; 104 Suppl 166:334-7. National Institutes o f Health Consensus Statement. Cochlear implants in adults and children. 1995; 1 3 :1-30. Tyler RS. Cochlear implants and the deaf culture. A m J Audio! 1993;2:26-32. Walt/man SB, Cohen NL, Gomolin RH, Shapiro W H , Ozdamar SR, Hoffman RA. Long-term results o f early cochlear implantation in congenitally and prelingually deafened children. A m J Otol 19 9 4 ; 15 Suppl 2:9-13. House WF, Berliner KI, Luxforcl WM. Cochlear implants in deal' children. Curr Prob Pediatr 1987;17:345-88. Snik AFM, Vermeulen AM, Geelen CPL, Brokx JPL, Van den Brock P. Speech perception performance of children with a cochlear implant compared to that o f children with conventional hearing aids. Part 2: results o f prelingually deaf children. Acta Otolaryngol (Slockh), in press 1997. 21. «Ur *« " # 24. 25. 26. 27. 28. 29. W alt/m an SB, Fisher SG, Niparko .IK, Cohen NL. Predictors of postoperative performance with cochlear implants. Ann Otol Rhinol Laryngol 1995; 10 4 Suppl 165:15-8, Cohen NL, Waltzman SB. Cochlear implants in infants and young children. Seminars in Hearing 1 9 9 6 ;17 : 2 15-21. Van den Broek P, Cohen N, O'Donoghue G, Fraysse B, Laszig R, Offeciens E. Cochlear implantation in children. J Pediatr Otorhinolaryngol 1995;32 (Suppl):217S-23S. Gantz B JT . Issues o f candidate selection for a cochlear implant. Otolaryngol Clin North Am 1989;22:239-47. Schwartzman JA. Avoidance o f complications with cochlear implants. Ann Otol Rhinol Laryngol 1995; 104 Suppl 166:431-2. Duhm MC, Dietrich B, Reich A, Lenar/. T. The accuracy of preopcrativc higli-resolulion computed tomography in predicting cochlear pathology. Adv Otorhinolaryngol 1995;50:25-30. Gray RF, Evans RA, Freer CEL, Szutowic/, HE, Maskell GF. Radiology for cochlear implants. J Laryngol Otol 1991; 105:85-8. Phelps PD. Cochlear implants for congenital deformities. J Laryngol Otol 1992;106:967-70. 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