fourteen-years experience with cochlear implantation in ... for...

J Med Assoc Thai Vol. 93 No. 12 2010 1399

Correspondence to:Kasemsuwan L, Department of Otolaryngology, Faculty ofMedicine, Ramathibodi Hospital, Mahidol University,Rama 6 Rd, Bangkok 10400, Thailand.Phone: 0-2354-7293E-mail: [email protected]

Fourteen-Years Experience with Cochlear Implantationin Ramathibodi Hospital

Lalida Kasemsuwan MD*,Wichit Cheewaruangroj MD*, Jumroon Tungkeeratichai MD*,Thongchai Bhongmakapat MD*, Cheamchit Thawin MA**,

Krisna Lertsukprasert MA**, Rattinan Tiravanitchakul MA**,Rada Dara MA**, Jiraporn Laothamatas MD***

* Department of Otolaryngology, Faculty of Medicine, Ramathibodi Hospital, Bangkok, Thailand** Audiology and Speech Division, Department of Otolaryngology, Faculty of Medicine,

Ramathibodi Hospital, Bangkok, Thailand*** Department of Radiology, Faculty of Medicine, Ramathibodi Hospital, Bangkok, Thailand

Objective: To review the cochlear implant program in Ramathibodi Hospital and share experience of cochlear implantationemphasized on clinical and surgical outcomes.Material and Method: Retrospective review of 143 ears (140 patients) operated with cochlear implant between 1995 and2009. The demographic data including etiology of deafness and findings from temporal bone CT scans were reviewed. Theauthors’ experience with cochlear implant surgery in terms of patient selection, patient advisory clinic, necessary equipment,pre- and postoperative evaluations, surgical techniques and complications were discussed.Results: Most congenital origin was unknown etiology and congenital rubella was the most common known cause. From theCT scans of congenital deafness, vestibular aqueduct dilatation was the most common and found in 29.31% while Mondinimalformation was shown to be 16.37%. The authors’ surgical technique of using the pocket method and designed bony ridgeat cortical mastoid rim had helped stabilizing the implant and electrode fancoil. During the last two years, no complication orrevision surgery was detected.Conclusion: Cochlear implant surgery in both children and adults can result in good surgical outcome and fewer complicationsunder experienced surgeons and a good team.

Keywords: Cochlear implant, CT scans of temporal bone, Cochleostomy, Hearing loss

Cochlear implantation is accepted as aneffective treatment for profound hearing loss anddeafness. It bypasses damaged parts of the inner earcochlea and delivers sound signals directly to stimulatethe auditory nerve and send sound information to thebrain. The young deaf children with cochlear implantshad significantly greater rates of language growththan the non-implanted ones. Actually, these rates oflanguage growth in children with cochlear implantwere similar to those rates expected in normal hearingchildren. Most studies had provided strong evidence

that cochlear implants resulted in an improved spokenlanguage(1,2).

About 500 cases had been operated inThailand by the end of 2009(3). Ramathibodi Hospitalstarted the cochlear implantation program in 1995(4,5).Between December 1995 and December 2009, 143 earswere operated on with three different kinds of devices(Table 1). The first case was done with a Nucleusdevices (Cochlear Corporation, Melbourne, Australia)in 1995, three years later a second case was done. By2002, 11 cases were operated with Nucleus device. In2003, the MED-EL device (MED-EL, Innsbruck,Austria) was used during the operation. In 2006, theHiRes 90K Auria and Harmony devices (AdvancedBionics Corporation, Valencia, CA, USA) wereintroduced. The objective of the presented paper wasto review the fourteen-year experience with cochlear

J Med Assoc Thai 2010; 93 (12): 1399-405Full text. e-Journal: http://www.mat.or.th/journal

1400 J Med Assoc Thai Vol. 93 No. 12 2010

implant in Ramathibodi Hospital, emphasizing on thesurgical outcomes.

Material and MethodClinical and CT scan of temporal bone

findings from cochlear implant patients wereretrospectively reviewed.

Patient selectionPatients who met the general criteria for

cochlear implantation were selected. The candidacy wasdefined as 1) patient with bilateral, severe to profoundhearing loss (pure tone average of > 90 dB in both ears)who received little or no benefit from hearing aids andspeech discrimination scores less than 50% in adultswith post-lingual deafness. The exclusion criteria were1) patient with cochlear aplasia or total calcification,2) patient with neurological deficits or mentalretardation, 3) patient with bilateral eight-nerve aplasiaor tumor, 4) patient with severe medical conditions andwould not be able to tolerate the surgery.

Cochlear implant advisory clinicPrior to surgery, all candidates and relatives

who were interested in the cochlear implant program

were invited to attend the cochlear implant advisoryclinic. This 2-hour clinic would explain the generalknowledge about the devices, the eligible candidates,the surgical methods, the risks and complications andfinally the intensive rehabilitation program. They wereallowed to make their own decision in selections ofdevice. The eligible candidates who had decided tohave cochlear implants were further evaluated by anaudiologist, speech pathologist, psychologist andotologist. For those with congenital deafness, geneticanalysis was also consulted.

InvestigationHigh resolution CT scan of the temporal

bone is one of the prime investigations for cochlearimplant eligibility. From this scan, the evaluationreveals mastoid status, middle ear cavity, theossicles, the inner ear abnormality especially thepatency of the cochlear duct, and the internalacoustic canal (IAC). MRI scan is selectivelyindicated only for those who were post meningitiswith possibility of intracochlear obliteration andthose with small IAC suggestive of cochlear nerveabnormality. Other basic preoperative evaluations areapplied.

Year Devices Total

Nucleus MED-EL Advanced bionics

22 channels 24 channels Combi 40+ Pulsar CI 100 Sonata HiRes 90K HiRes 90K Auria Harmony

1995 1 ** 11999 2 * ** 22000 1 * ** 1 ** 22001 1 ** 3 * ** 42002 2 * ** 22003 2 * ** 22004 11 ** 112005 10 **(9) 102006 10 3 132007 4 12 3 8 272008 3 8 11 20 422009 1 10 1 + ***(1) 3 12 27Total 5 6 41 30 1 + ***(1) 20 40 143

* Cases reported in ref. 4** Cases reported in ref. 5*** Case operated in 2004 had revision surgery from Combi 40 to Sonata because of device failure

Table 1. Number of ears operated with different cochlear implant devices


Method of surgeryThe surgery is performed under general

anesthesia. Facial nerve monitoring (NIMS, Metronics,Minneapolis, USA) is generally applied. A postauricularincision and standard transmastoid facial recessapproach is used to approach the middle ear. Allpatients receive intraoperative intravenous antibioticsand continue for at least 24 hour before changing tooral form and discharge. All reviewed data weresummarized in term of frequency and percentage forpresenting demographic characteristics causes ofdeafness CT scan findings and complications.

ResultsDemographic data

During the 14-year study period betweenDecember 1995 and December 2009, 143 ears(140 patients) underwent cochlear implantation inRamathibodi Hospital. One hundred and thirtyseven patients had unilateral implantation whilethree patients had bilateral implantation. As mentionedbefore, the first 11 cases received the nucleus devices,which had 22 channels in five cases and 24 channels insix cases. Three of the 11 cases needed revision surgerydue to incorrect position of cochleostomy and theelectrode arrays were inserted into the hypotympaniccells instead of scala tympani. They finally hadsuccessful revision cochleostomy and electrodeinsertion.

Seventy-two ears (71 patients) receivedMED-EL devices. One patient had bilateral implantation.Four patients needed revision surgery performed onthe opposite side from the inability to find thecochleostomy lumen due to basal turn ossifican inthree patients and dislodging electrode out of thecochlea in one. The device models for 72 ears includedCombi 40+ in 40 ears, Pulsar CI 100 in 30 ears, andSonata in two ears. (One who had dislodged electrodehad changed from Combi 40+ to Sonata).

For the 60 ears receiving Advanced Bionicsdevices, eighteen ears received the HiRes 90K Auriaand 42 ears received the HiRes 90K Harmony systems.Two cases had the second ear implanted with HiRes90K Harmony while the first sides were previouslyimplanted with Combi 40+ of MED-EL devices. Ofthese 60 cases, only one case had revision surgerydue to incorrect position of the electrode.

Among the 140 patients who receivedcochlear implant, there were 82 male and 58 female. Theyoungest candidate was 1.5 years while the oldestwas 68 years old. There were 111 children (age 1-17),

this comprised of 79.28% and adults clarified as aged18 years up comprised of 29 patients (20.71%).

Among the children age group, 31 cases werebetween 1-2 years, 31 cases were between 3-6 years(55.85%) and 49 cases were between 7 -17 years(44.14%).

Children were mostly pre-lingual deaf excepttwo were post-lingual deaf. They were 5 and 17 yearsold, both had suffered from meningitis one yearearlier. Although most adults (68.96%) were post-lingualdeaf, nine of 29 adults (31%) aged between 18 and 46were pre-lingual deaf.

Overall, among 140 patients, 118 patients(84.58%) including 109 children and 9 adults were pre-lingual deaf while 22 patients (15.71%) including 20adults and two children were post-lingual deafness.

All but two pre-lingual deaf patients werecongenital in origin, two children had acquired deafnessfrom ototoxic drugs, one at the age of two years oldsuffered from chemotherapy and the other at the age ofthree years from treatment of infection at 3-months old.Therefore, deafness from congenital origin was foundin 116 cases (82.86%) and acquired in 24 cases (17.14%).The etiology of deafness both congenital and acquiredis shown in Table 2. Most congenital origin wasunknown etiology in which genetic evaluation had beenunder carrying out and the report would be publishedlater. Of all the known congenital origin, congenitalrubella was the most common cause. From CT scan ofcongenital origin, Mondini malformation (incompleteturn of cochlea) was found in 19 of 116 patients(16.37%). Vestibular aqueduct dilatation either unilateralor bilateral was more common and found in 34 patients

Cause Number %

Congenital rubella 10 7.14CHARGE syndrome 1 0.71Usher’s syndrome 2 1.42Waardenburg syndrome 2 1.42Noonan syndrome 1 0.71Congenital meningocele 1 0.71Ototoxic hearing loss 2 1.42Chronic otitis media 1 0.71Bacterial meningitis 5 3.57Progressive hearing loss 11 7.86Traumatic hearing loss 3 2.14Unknown 101 72.14Total 140 100

Table 2. Causes of deafness


(29.31%). Mondini malformation was not found to beassociated with any other congenital origin except twocases were congenital rubella. Abnormal vestibularapparatus, mostly dilated, was less common, andfound in 15 patients (12.93%). Thirteen cases (11.20%)had coincidence of both cochlear and vestibularabnormalities (Table 3).

Among three cases with bilateral implantation,they had sequential implantations. The first case wasperformed at 17 and 19 years, the second case at 2 and7 years. Both had different systematic devices on eachside by using Combi 40+ (MED-EL) on the first sidesand later had Hires 90K Harmony (Advanced Bionics)on the other sides. For the third case, she had an intervalof a year between both sides with Combi 40+ andPulsar CI 100, which were from the same systematicdevices (MED-EL) but different models.

Review the surgical technique and outcomeThe surgical techniqueBoth extended and minimally extended

postauricular incisions were performed with stepincision at periosteum. A standard transmastoid facialrecess approach is used to approach the middle ear.Cochleostomy was performed through the promontoryat the antero-inferior to round window membrane.

Creation of a bone bed for the implant, thelateral skull was drilled at supero-posterior to themastoid cavity and approximately 3.5 cm from theposterior part of external auditory canal. This willallow the magnet to be in a proper distance from theear-anchored processor in order to avoid the unwantedinteractions from the magnet to the processor. An

extended bony recessed channel was created forplacing the electric fancoil from the implant case to thecortical mastoid (Fig. 1). The authors designed a bonyridge created at the mastoid rim to help prevent thefancoil dislodging (Fig. 2). Previously using tie-downsuture holes at the tegmen mastoideum or later usingthe pocket method without suture fixation wereperformed to stabilize the implant. The landmark forcochleostomy into the scala tympani was just anteriorand slightly inferior to the round window, this wasperformed by using a 1 mm burr (Skeeter, Metronics,Minneapolis, USA) (Fig. 3). The cochlear implantprocedure is completed by positioning the internaldevice at the bone bed and intimate insertion of theelectrode arrays into the cochleostomy lumen manuallyor by using the insertion tool stylet depended on themodel device (Fig. 4). Finally packing the cochleostomyand posterior tympanostomy with tissue muscle graftwill prevent the leakage of perilymph and help toprevent the dislodging of the electrode arrays. Tightsuture especially the periosteum was performed forstabilizing the implant in the pocket under the periosteallayer. Intraoperative telemetry of electrode impedanceand nerve response (NRI) were routinely measured butthis procedure was not performed in the earlier casesdue to recent development of the program.

The surgical complication outcomesRevision surgery was totally carried out in

eight pediatric patients (5.71%). Three cases were due

CT temporal bone findings Numberof ears

Cochlear abnormality (Mondini malformation) 19Vestibular aqueduct syndrome 34Vestibular abnormality 15Cochlear and vestibular abnormalities 13Cochlear abnormality and 3 vestibular aqueduct syndromeVestibular abnormality and 9 vestibular aqueduct syndromeCochlear and vestibular abnormalities 7 and vestibular aqueduct syndromeNormal inner ear 48

Table 3. Findings from CT scan of temporal bone in116 cases with congenital deafness

Fig. 1 Bone bed for the implant case was drilled at lateralskull, supero-posterior to mastoid cavity. Extendedbony recessed channel was created for placing theelectric fancoil connecting the implant to the corticalmastoid


to inability to find the cochleostomy lumen, anotherthree cases were due to wrong position of the electrodeinto the hypotympanic cells, one case had misplacedelectrode into the superior semicircular canal, and thelast case had dislodging of electrode arrays from thecochleostomy lumen of unknown reason. Five caseshad successful revisions on the same ears and threecases had to change to the other ears due to obliterationof the cochlear duct.

Other intra-operative complications includedtwo cases who suffered from facial nerve paralysisand included one with transient mild weakness andthe other had total paralysis with partial recovery after2 years. These complications occurred before usingthe facial nerve monitoring (NIMS) as the standardequipment to every case, thereafter no such complicationhappened. Mild perilymph gusher was detected insix cases whereas no subsequent complication suchas infection was detected. Transient immediate post-operative dizziness or vertigo was detected in mostlyadult and elderly pediatric age groups. There was noimmediate wound infection or massive bleedinghowever one patient had late postoperative woundinfection and recovered after incision and drainage.Table 4 shows the complications according to years ofsurgery. Most patients generally had good post-operative recovery and were discharged two daysafter the operation.

DiscussionThe candidates for cochlear implantation

include all patients who have profound sensorineuralhearing loss of more than 90 decibels. It is importantto confirm the hearing loss in the younger pediatricgroup by selectively using OAE, ASSR and ABR(6).

In the earlier cases with extended post-auricular incision, method of implant fixation wasusing the tie-down suture. However, after changing tominimal extended incision, no fixation was done butusing the pocket technique to stabilize the implant inthe bone bed of temporal bone.

Care is seriously taken not to injure the facialnerve. The fully equipped facial nerve monitoring isnecessary since it helps preventing this unwantedserious complication of nerve injury. To provide moreaccuracy of nerve monitoring, the effect of musclerelaxant, if used during intubation, should have beenfully declined. The maximal approach of posteriortympanotomy could be applied at the inferior aspect ofthe facial recess for allowing the better identification ofthe round window and the basal turn of the cochlea atFig. 4 Electrode was fully inserted into the cochleostomy

Fig. 3 Cochleostomy into the scala tympani was performedjust anterior and slightly inferior to the round windowmembrane

Fig. 2 Bony ridge created at the cortical mastoid at the endof bony recessed channel help prevent the implantfancoil dislodging


the promontory. All the landmark structures in themastoid and middle ear, which included short processof incus, incudo-stapedial (IS) joints, stapes, stapediustendon, and round window should be clearly identified.To locate accurately the cochleostomy lumen andensure of the scala tympani approach is critical in somecases. Several anatomic studies have shown thatopening adjacent to the antero-inferior of the roundwindow membrane is the most favorable site for scalatympani cochleostomy. Insertions more superior oranterior to the round window are more likely to enterinto the scala vestibule(7). Fig. 5 shows the alternateway to locate the area for cochleostomy. This isperformed by measuring the width of the incudo-stapedial joint as A then measure the same length as Band as C subsequently in the inferiorly direction. Atthis third part (C), by estimation will roughly be atthe anterior to the round window niche. By usingboth methods to locate the area for cochleostomy,the authors felt more confident in performing theprecise cochleostomy. To insert the electrode arraysis sometimes difficult, the authors found that thisprocedure is more convenient when using theinsertion tool stylet.

The perioperative and 24-hour postoperativeintravenous antibiotics was helpful in preventingbacterial infection in which no serious complicationsuch as meningitis or immediate wound infectionoccurred. One case was found to have late woundinfection with cellulitis. It recovered after incision anddrainage. Another one case suffered from urinarytract infection in which intraoperative catheterizationcould be the cause.

Experience plays a siginificant role in thesuccess of the operation. Although 7.69% of the earsoperated had complications, including 5.59% thatneeded revision surgery from misposition of electrodeand unability to find cochleostomy and 1.39% that hadfacial weakness, the occurrence mostly happened in

the earlier cases. There was no complication detectedin the last two years in which 48.5% of ears wereoperated (Table 4). With careful preoperative evaluationof the images and intraoperative telemetry had helpedlessen the improper position of the electrode andensuring the surgical outcome. Most surgical time innormal cases is generally two to three hours, whichwas lessened markedly from the earlier cases. Thisshould result from gaining more experience inintraoperative care and surgical procedure.

ConclusionThe authors found that cochlear implant

surgery is safe under an experienced surgeon. Thesurgery would be smooth and with fewer complicationsunder well prepared preoperative evaluation, intra-operative antibiotics, intraoperative facial nervemonitoring, and a good team and instruments.

Number of ears operated according to years Revision surgery Facial weakness Late wound infection Total

1995-1998 1 0 0 0 01999-2001 8 2 1 0 32002-2004 15 3 1 1 52005-2007 50 3 0 0 32008-2009 69 0 0 0 0Total 143 8 2 1 11

Table 4. Number of complications categorized into period of years and total number of ears operated during each period

Fig. 5 The alternate way to locate for cochleostomy. Itcan be located at C on the promontory by measuringthe width of the incudo-stapedial joint as A, thenmeasure the same length as B and C in the inferiordirection. At C will roughly be just anterior to theround window niche


AcknowledgementsThe authors wish to thank and honor

Assoc. Prof. Chanida Kanchanalarp for her being thepioneer in cochlear implant surgery in RamathibodiHospital.

References1. Eisenberg LS, Johnson KC, Martinez AS, Cokely

CG, Tobey EA, Quittner AL, et al. Speechrecognition at 1-year follow-up in the childhooddevelopment after cochlear implantation study:methods and preliminary findings. AudiolNeurootol 2006; 11: 259-68.

2. Connor CM, Hieber S, Arts HA, Zwolan TA.Speech, vocabulary, and the education ofchildren using cochlear implants: oral or totalcommunication? J Speech Lang Hear Res 2000; 43:1185-204.

3. Chongvisal S, Prakairingthong S, Limviriyakul S.Cochlear implantation: Siriraj experiences. SirirajMed J 2009; 61: 283-6.

4. Kanchanalarp C, Cheewaruangroj W, KasemsuwanL, Thawin C, Sriwanyong S. Pediatric cochlearimplantation: experience in Thai patients. J MedAssoc Thai 2005; 88: 484-91.

5. Kanchanalarp C, Cheewaruangroj W, Thawin C,Lertsukprasert K. Indication and surgicalconsideration of cochlear implantation atRamathibodi Hospital. J Med Assoc Thai 2006;89: 1171-7.

6. American Speech-Language Hearing Association.Technical report: cochlear implants. ASHS 2004;Suppl 24: 1-35.

7. Meshik X, Holden TA, Chole RA, Hullar TE.Optimal cochlear implant insertion vectors. OtolNeurotol 2010; 31: 58-63.

ประสบการณ 14 ปในการผาตด ใสอปกรณรบเสยงฝงหชนใน (cochlear implant) ในโรงพยาบาล

รามาธบด

ลลดา เกษมสวรรณ, วชต ชวเรองโรจน, จำรญ ตงกรตชย, ธงชย พงศมฆพฒน, เจยมจต ถวล,

กฤษณา เลศสขประเสรฐ, รตตนนท ฏระวนชยกล, รดา ดารา, จรพร เหลาธรรมทศน

วตถประสงค: เพอศกษาผลการผาตดผปวยในโครงการผาตดใสอปกรณรบเสยงฝงหชนใน (cochlear implant) ใน

โรงพยาบาลรามาธบด

วสดและวธการ: เปนการศกษายอนหลงในผปวย 143 ห (140 ราย) ทไดรบการผาตดตงแต เดอน ธนวาคม พ.ศ. 2538

ถงเดอน ธนวาคม พ.ศ. 2552 ศกษาผปวยในดานคลนก ถงสาเหตการสญเสยการไดยน และผลการดำเนนงานของ

โครงการนซงประกอบดวย การเลอกผปวย การใหความรผปวย การดแลทงกอนและหลงการผาตด และทายสด

วธการผาตดและปญหาแทรกซอน

ผลการศกษา: การสญเสยการไดยนแตกำเนดสวนใหญไมทราบสาเหต ในกลมททราบสาเหตพบวา มารดาตดเชอ

หดเยอรมนเปนสาเหตทพบมากทสด สำหรบความผดปกตจากภาพถายทางรงสเอกซเรยคอมพวเตอร พบความผดปกต

ของ Vestibular aqueduct dilatation มากทสด (รอยละ 29.31) รองลงมาเปน Mondini malformation (รอยละ

16.37) วธการผาตดดวยการเซาะเยอ periosteum ใหเปนชองกระเปา และออกแบบ การกรอกระดกใหเปนแงงบรเวณ

สวนทตดโพรงกระดกมาสตอยดชวยทำใหอปกรณยดอยกบท

สรป: การผาตดใสอปกรณรบเสยงฝงหชนในสามารถทำผาตดไดผลดทงในเดก และผใหญ พบปญหาแทรกซอนนอย

ในทมงานทมความชำนาญ

fourteen-years experience with cochlear implantation in ... for...

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