online ML Comm Otology Korean J Otorhinolaryngol-Head Neck Surg 13;56:339-45 / pissn 92-5859 / eissn 92-6529 http://dx.doi.org/1.3342/kjorl-hns.13.56.6.339 Hearing Rehabilitation of Single-Sided Deafness: Benefit and Selection Criteria of Bone Anchored Hearing Aid and Contralateral Routing of Signal Hearing Aid Mi Na Park 1,2, Shin Young Yoo 2, Young-Myung Chun 2, In Seok Moon 1 and Sung Huhn Kim 1 1 Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul; and 2 Soree Ear Clinic, Seoul, Korea 일측성전농환자에서의청력재활 : 바하와크로스보청기의이득과선택기준 박미나 1,2 유신영 2 전영명 2 문인석 1 김성헌 1 연세대학교의과대학이비인후과학교실, 1 소리귀클리닉 2 Received March 25, 13 Revised May 16, 13 Accepted May, 13 Address for correspondence Sung Huhn Kim, MD, PhD Department of Otorhinolaryngology, Yonsei University College of Medicine, 5 Yonsei-ro, Seodaemun-gu, Seoul 1-752, Korea Tel +82-2-2228-3622 Fax +82-2-393-58 E-mail FLEDERMAUS@yuhs.ac Background and ObjectivesZZThere are two ways to route sound from a deaf hemifield to a functional ear: the bone anchored hearing aid () and the contralateral routing of signal hearing aid (). uses transcranial bone conduction; on the other hand, CROS HA uses air conduction. The objectives of this study were to evaluate the benefit of these auditory rehabilitation devices objectively and subjectively, and to analyze factors that affect daily using time. Subjects and MethodZZWe retrospectively reviewed the medical records of 19 patients who selected and 9 patients who selected to undergo rehabilitation of unilateral hearing loss. Preoperative pure tone air and bone conduction thresholds, -aided thresholds and -aided thresholds were measured. Hearing in noise test (HINT) was measured with unaided and aided in signal to noise ratio 1 (signal 75 db HL, noise 65 dba). Bern Benefit in Single-Sided Deafness Questionnaire (BBSS) was evaluated for all patients to assess subjective satisfaction and also, daily device using time was investigated. ResultsZZThe aided pure tone audiometry was 44.58 db HL, 42.71 db HL for in and, respectively, whereas the unaided PTA was 111.29, 13.28 db HL for and, respectively. The aided HINT was 63.3 and 64.6%, whereas the unaided HINT was 22.13% and 37.44% for and CROS, respectively. BBSS showed more satisfactory results with and when compared unaided in all items. Daily using time did not correlate with the degree of satisfaction, better ear hearing levels or etiology. ConclusionZZIt was found that not only the preoperative rod test and HA trials but also the customized and detail counseling were needed for single sided deaf patients to use auditory rehabilitation devices frequently. Korean J Otorhinolaryngol-Head Neck Surg 13;56:339-45 Key WordsZZBone anchored hearing aids ㆍ Contralateral routing of signal hearing aid ㆍ Hearing rehabilitation ㆍ Single sided deafness. 서론 일측성전농환자들은한쪽귀가정상청력임에도의사소통에어려움을겪는다. 이런환자들은농방향에서들어오는소리식별에어려움을겪고, 음원의방향성을식별하는능력 이감소되며, 특히소음상황에서청취에어려움을겪는다. 1,2) 이러한일측성전농환자의불편함을감소시키기위한청력재활수단이개발되었으며, 크게골도보청기와기도보청기로나누어볼수있다. 골도보청기는처음에안경이나헤어밴드형태로개발이되 Copyright 13 Korean Society of Otorhinolaryngology-Head and Neck Surgery 339
Korean J Otorhinolaryngol-Head Neck Surg 13;56:339-45 었으며, 근래에는 bone anchored hearing aid() 가개발되어일측성전농인환자에서유용하게사용되고있다. 기도보청기는과거유선형태로개발되었으며, 현재는무선형태로발전되었다. 단순 CROS 보청기 (contralateral routing of signal hearing aid) 는일측이정상이고반대측이고도난청인경우마이크로폰을나쁜쪽으로장착하고좋은쪽에수화기를위치시켜나쁜귀쪽에서들리는소리를좋은귀쪽에서듣게하는장치이다. 양측 CROS 보청기는양측난청으로나쁜쪽의귀로는보청기로도들을수없고좋은귀의청력도중등도혹은고도난청이있는환자에서, 나쁜쪽에마이크로폰을설치하고좋은쪽에서증폭하여양쪽에서들어오는소리를들을수있게하는장치이다. 3) 현재대부분의병원에서 와 CROS 보청기에대한선택기준이마련되어있지않아, 환자의선호도에따라청력재 활수단을선택하고있다. 따라서본연구에서는첫째, 일측성전농환자에서 와 CROS 보청기의기능적이득 (functional gain) 을객관적, 주관적측면에서평가하였으며, 둘째, 와 CROS 보청기의하루착용시간 (daily using time) 에영향을미치는요소의분석을통해 와 CROS 보청기의선택기준을알아보고자하였다. 대상및방법 대상 9년 1월부터 12 년 12월까지일측성전농환자중 혹은 CROS 보청기를청력재활수단으로선택한 28명을대상으로하였다. 성별은남자 8명, 여자 명이었고, 연령은 26세에서 77세까지평균 53.67세였다. Table 1. Individual patient data Subject Gender Etiology Age (yr) Deaf duration (yr) Device using period (mo) Group* B1 F COM 57 42 B B2 F COM 52 43 B B3 F COM 5 29 B B4 F COM 49 3 12 B B5 F Congenital HL 49 49 19 A B6 F Sudden SNHL 44 4 A B7 F Meniere disease 62 1 21 A B8 F COM 61 13 13 B B9 M Unknown 59 1 12 A B1 F Congenital HL 59 59 12 B B11 F COM 63 15 12 B B12 F Unknown 64 2 12 B B13 F Unknown 62 1 12 B B14 F Unknown 26 1 12 B B15 M COM 49 1 B B16 F COM 53 9 A B17 F COM 53 17 1 B B18 M Congenital HL 41 41 5 A B19 M Sudden SNHL 62 1 3 B C1 F Sudden SNHL 44 1 3 B C2 F COM 47 3 B C3 M Unknown 28 4 3 A C4 F Unknown 77 1 3 B C5 F Unknown 56 1 3 B C6 F COM 71 5 3 B C7 M COM 63 5 3 B C8 M Unknown 42 2 4 A C9 M Unknown 6 2 3 B *all patients divided to group A or group B according to hearing level of better ear (group A is normal hearing in better ear and group B is mild/moderate HL in better ear). : bone anchored hearing aid, COM: chronic otitis media, HL: Hearing loss, SNHL: sensorineural hearing loss, : contralateral routing of signal hearing aid 3
Hearing Rehabilitation of Single-Sided Deafness: and Park MN, et al. 일측성전농의기준은순음청력검사상청력역치가 9 db 이상이고, 어음분별치가 % 미만으로하였다. 일측성전농 환자 28 명중 8 명은반대측좋은귀가정상청력 ( 순음청력검 사상청력역치 25 db 이상, 어음분별치 8% 이상 ) 이었고, 나 머지 명은경도에서중등도의감각신경성난청 ( 순음청력검 사상청력역치 25~5 db, 어음분별치 75~9%) 이었다. 일측 성난청의원인은만성중이염이가장많았고, 원인미상, 돌발성 난청, 선천성난청, 메니에르병의순이었다. 또한좋은귀의청 력이정상인경우를그룹 A, 좋은귀의청력이경도에서중등 도의난청이있는경우를그룹 B 로분류하였다 (Table 1). 본연 구는헬싱키선언을준수하여연구가진행되었다. 청력재활수단 (Cochlear) 는 9 년 1 월부터 12 년 4 월까지시술 되었으며, 모든환자에서 BP1 모델을사용하였다. 는 무선 CROS 보청기가출시되기전일측성전농환자의주된 Signal 75 db HL X* Noise 65 db A Fig. 1. Speaker configurations for HINT. The subject was seated 1 m from the speaker arc. *X means deaf ear. HINT: hearing in noise test. 청력재활수단으로사용되었다. CROS 보청기의경우 Phonak사의 모델중나쁜귀에는 CROS BTE(Stäfa, Switzerland) 를사용하였고, 좋은귀에는 Audéo S SMART III(Stäfa, Switzerland) 를사용하였다. 방법상기대상환자의의무기록을후향적으로검토하였으며순음청력검사및어음청력검사를시행하였다. 객관적평가를위해보청기미착용시 (unaided) 헤드폰을이용하여청력역치및어음명료도치를검사하였으며, 음장 (sound field) 검사로 및 CROS 보청기착용시청력역치및어음명료도치를검사하였다. 또한 hearing in noise test(hint) 를음장검사로시행하였다. HINT는환자로부터 1 m 떨어진두개의스피커를이용하여나쁜귀쪽에 75 db HL의신호를주었고, 좋은귀쪽에서 65 dba의소음을주었다 [signal to noise ratio=1, 1 db(s/n)](fig. 1). HINT 검사시문장은한국표준문장표 (Korean Standard-Sentence List for adults, KS-SL-A) 를사용하였으며, 총 개의목표어절중환자가맞게대답한어절개수를퍼센트로산출하였다. KS-SL-A 는일상생활의문장을사용하여어음인지도를검사하도록 CID 일상생활문장검사 (Central Institute for the Deaf Every day Sentences Test) 의문장선정기준과한국어및청각학적특성을고려하여제작되었으며, 만 13세이상을대상으로사용할수있도록되어있다. 4) 주관적평가를위해서는 Bern Benefit in Single-Sided Deafness Questionnaire(BBSS) 를사용하였다. BBSS는 Kompis 등 5) 에의해일측성전농환자에게 가도움이되는지를알아보기위해개발되었다. 총 1개의항목으로구성되어있으며, 1번항목부터 9번항목까지 9가지상황에서의만족 Table 2. Bern benefit in single-sided deafness questionnaire Please rate your perceived benefit from your aid in the following situations by a vertical line. 1. To hold a conversation with one person in a quiet environment. For me, this is: 2. To understand a TV or a radio speaker. For me, this is: 3. To listen to music. For me, this is: 4. To follow a conversation from some distance (5 m/15 ft or more). For me, this is: 5. To follow a conversation with background noise. For me, this is: 6. To hold a conversation while driving in a car. For me, this is: 7. To understand speech in a reverberant room, such as a large entrance hall or a church. For me, this is: 8. To participate in a group conversation with 3 or more participants. For me, this is: 9. To localize a sound source, such as a honking car. For me, this is: 1. Over all, for me hearing is: Much easier without the aid somewhat easier Similar with and without somewhat easier Much easier with the aid -5-4 -3-2 -1 1 2 3 4 5 www.jkorl.org 341
Korean J Otorhinolaryngol-Head Neck Surg 13;56:339-45 도와 1 번째항목의전반적인만족도로구성되며, 각항목은 -5 점부터 5 점까지시각적아날로그척도 (visual analog scale) 로조사하도록구성되어있다 (Table 2). 모든환자에서 나 CROS 보청기착용전에 BBSS 설문을시행하였으며, 착용 후에 BBSS 설문을다시시행하여착용전, 후의만족도를비 교하였다. 하루에청력재활수단을사용하는시간 (daily device using time) 을조사하고이것에영향을주는요소 (factor) 를알 아보기위해사용시간과만족도, 사용시간과좋은귀의청력 상태, 사용시간과원인질환과의상관관계를분석하였다. 또한 및 CROS 보청기를사용하지않는환자가있었다면, 이들에게사용하지않는이유를조사하였다. 결과변수에따라서 SPSS 12.(SPSS Inc., Chicago, IL, USA) 의대응표본 t 검정 (paired t test of difference), 일표본 t 검정 (one-sample t test), 크루스칼 - 왈리스검정 (Kruskal Wallis test), 상관관계분석 (linear regression) 을사용하였다. 모든결 과는 로표현하였으며, p-value.5 미만인경우 통계적으로의미가있는것으로보았다. 결 과 와 CROS 두그룹에서보청기착용시청력역치가평 균 44.6±12. db HL 과 42.7±14.8 db HL 로미착용군의 Hearing threshold (db HL) A Speech discrimination (db HL) B 1 1 8 6 1 9 8 7 6 5 3 1 * * Unaided Unaided * * Aided Aided Fig. 2. Unaided and aided pure-tone thresholds (in db hearing level, HL) in and (A). Speech discrimination (in percentage) in and (B)( n=19, n=9, Paired t test of difference). : bone anchored hearing aid, : contralateral routing of signal hearing aid. *p<.5. 111.3±11.9 db HL 과 13.3±16. db HL 에비해감소되었고, 어음명료도치 76.2±17.2% 와 78.6±13.9% 로미착용군의.5 ±1.9% 와 15.4±16.7% 에비해높게나왔으며, 통계적으로유 의하였다 (p=.)(fig. 2). HINT 에서도, CROS 보청기그룹모두보청기착용 시 63.±28.3%, 64.1±33.3% 로미착용시의 22.1±25.4%, 37.4 ±26.1% 에비해유의하게높게나타났다 (p<.1, p=.16) (Table 3). BBSS 모든항목에서, CROS 보청기그룹 모두청력재활수단착용후가착용전에비해모든항목에서 만족도가유의하게높은것으로나타났다 (: p<.5, CROS: p<.5)(table 4). 하루에청력재활수단을사용하는시간은만족도와상관 관계가없었으며 (: R 2 =.5, p-value>.5, CROS: R 2 =.32, p-value>.5)(fig. 3), 좋은귀의청력역치와도상 관관계가없었으며 (: R 2 =.2, p-value>.5, CROS: R 2 =-.14, p-value>.5)(fig. 4), 청력소실의원인질환과도 상관관계가없었다 (p=.261)(table 5). 총대상환자 28 명중 환자 5 명이하루중전혀착용 을하지않는다고대답을하였는데, 그이유는청력재활수 단의이득 (benefit) 이없다는것외에사용시불편함 (inconvenience), 피부반응 (recurrent skin reaction), 피드백현상 (feedback) 발생등이었다. 요약해보면첫째, 일측성난청환자에서 나 CROS Table 3. Hearing in noise test ( n=19, n=9, paired t test of difference) Unaided (%) Aided (%) p-value 22.1±25.4 63.±28.3 <.1 37.4±26.1 64.1±33.3.16 : bone anchored hearing aid, : contralateral routing of signal hearing aid, SD: standard deviation Table 4. Bern benefit in single-sided deafness questionnaire (onesample t test) Question p-value p-value 1 2.7±1.6 <.1 2.8±1.4.3 2 2.6±1.8 <.1 2.2±1.1.3 3 2.2±1.6 <.1 2.2±1.1.3 4 1.6±1.6.6 1.4±1..27 5 1.9±1.7.2 1.4±1..13 6 1.7±1.4 <.1 2.8±1.1 <.1 7 1.6±1.7.16 2.8±.8 <.1 8 2.4±1.3 <.1 2.9±.8 <.1 9 1.4±1.3.3 2.4±1.2.3 1 2.5±1.5.3 3.1±1.5.3 Each numerals indicate visual analog scale. : bone anchored hearing aid, : contralateral routing of signal hearing aid, SD: standard deviation 342
Hearing Rehabilitation of Single-Sided Deafness: and Park MN, et al. 8 5 Satisfaction (VAS score) 6 4 2 R 2 =.5 p>.5 Hearing threshold (db HL) 3 1 R 2 =.2 p>.5 A 1 2 3 4 5 A 2 4 6 8 5 5 Satisfaction (VAS score) 4 3 2 1 R 2 =.32 p>.5 Hearing threshold (db HL) 3 1 R 2 =-.14 p>.5 B 2 4 6 8 1 12 14 B 2 4 6 8 1 12 14 Fig. 3. Correlation between satisfaction and daily using time in (A), in (B)[linear regression, (A): R 2 =.5, p-value >.5, (B): R 2 =.32, p-value>.5]. : bone anchored hearing aid, : contralateral routing of signal hearing aid, VAS: visual analog scale. Fig. 4. Correlation between hearing level in better ear and daily use time in (A), in (B)[linear regression, (A): R 2 =.2, p-value>.5, (B): R 2 =-.14, p-value>.5]. : bone anchored hearing aid, : contralateral routing of signal hearing aid. 보청기와같은청력재활수단은청각학적인면에서기능적이득이있다. 하지만, 기능적이득이있다고모든환자가해당청력재활수단을잘사용하는것은아니었으며, 또한하루기기착용시간은만족도, 좋은귀의청력상태, 청력소실의원인과도특이상관관계가없었다. Table 5. Correlation of etiology and daily use time (Kruskal Wallis test) Chi-square 5.266 Degree of freedom 4. p-value.261 고찰 나쁜귀쪽에서좋은귀로소리를전달시켜주는것은일측성전농환자에서유용한청력재활방법이며, 대표적인것이 와 CROS 보청기다. 본연구설계의특이한점은다음과같다. 의이득을평가하고자했던타논문들은 환자의 HINT 검사시어음분별력이 5% 가되는 signal to noise ratio(snr) 을측정하고 SNR 값이낮을수록어음분별력이높은것으로연구설계를하였다. 6-8) 하지만본연구에서는이와다르게 SNR 값을 1으로고정하고이때어음분별력의퍼센트를구하였다. 이 것은환자들이청력재활수단착용후소음환경하에서향상된어음분별력을쉽게이해하도록하기위한환자중심의설계 (setting) 이다. 또한나쁜귀에소음 (noise) 을주는것은당연히나쁜귀에소리신호 (signal) 를주는것보다어음분별력이낮게나올것이므로본연구에서는이과정을생략하였다. 주관적평가를위해사용된 BBSS는 Kompis 등 5) 이일측성난청환자에서 를선택할지거부할지의사결정을예측할수있는설문으로의미가있다고보고하였고, 현재일측성난청환자에서 사용후주관적만족도를확인하는방법으로널리사용되고있다. 이식의가장흔한적응증은만성이과질환과선천 www.jkorl.org 343
Korean J Otorhinolaryngol-Head Neck Surg 13;56:339-45 성외이도폐쇄증과같은전도성난청이었으나, 2년일측성난청환자에대해서도 Food and Drug Administration 승인이되면서일측성전농환자에서그적용이확대되고있다. 는난청이있는귀쪽에서소리를받아두개골을통한골전도를통해청각기능이온전한반대측귀로전달해주는역할을하게되며기본적으로머리가림효과를최소화해준다. 9) 무선 CROS 보청기는기도전도 (air conduction) 를통해전농방향에서들어오는소리를마이크가잡아서좋은귀의원격계측기수화기 (telemetric receiver) 쪽으로소리를전달해준다. 과거일반적 CROS 보청기는미용적인문제로인한사회적낙인, 좋은귀의폐쇄효과 (occlusion effect) 로인한환자불편감, 전반적인불완전한청력향상등의문제점등이있었다. 1) 하지만최근포낙 (Phonak, Stäfa, Switzerland) 에서무선미니오픈형 [wireless mini receiver in the canal(ric)] 형태가우리나라에들어오면서수술을하지않지않아도된다는점, 비용이 에비해저렴하다는점, 스파이스칩 (spice chip) 의개발로무선으로도양귀의시간차이 (time difference) 를 6 마이크로초로줄여방향성구분이유리한점, BiCROS 기능이있어좋은귀에경도에서중등도의난청이있는경우도움을받을수있다는장점이있다. 본연구결과에따르면, 일측성난청환자에서청력재활수단으로 와 CROS 보청기모두청력재활수단을사용하지않았을때에비해청력역치와어음분별치가향상되었다. 또한소음환경에서도 와 CROS 보청기사용했을때가사용하지않았을때에비해 HINT 결과값이상승하였으며주관적인만족도조사에서도두그룹모두만족도가장치를사용하지않았을때에비해서높았다. 따라서일측성전농환자에서청력재활수단으로서 와 CROS 보청기모두객관적, 주관적측면에서효과가있는것을알수있다. 과거연구들을살펴보면청력재활수단에대한만족도가높을수록, Lin 등 6) 은좋은귀에경도혹은중등도의난청이있을수록, Snik 등 11) 은돌발성난청과같이전농기간 (deaf duration) 이짧을수록청력재활수단을사용하는시간이길다고주장하였다. 하지만, 본연구결과에서하루에기기를착용하는시간은만족도, 좋은귀의청력및난청의원인과특이상관관계가없는것으로나타났다. 특히좋은귀의청력정도와기기착용시간간에특이상관관계가없다고나타난것은좋은귀에경도혹은중등도난청이있는경우청력재활수단사용시환자의만족도가더높다는 Lin 등 6) 의연구결과와는상반되는것으로이것은추후더많은환자군에서의추가연구가필요할것으로사료된다. 이와같이 와 CROS 보청기를사용하는것이객관적, 주관적이득이있음에도불구하고실제로청력재활수단을사용하지않는경우가있어환자들이매일청력재활수단을사용하는시간을조사하였다. 조사결과 를선택한 19 명중 5명 (B4, B9, B17, B18, B19) 이 를매일규칙적으로사용하지않았다. 그이유로는불편함 (B4, B17), 반복적인염증 (B9), 피드백현상발생 (B18, B19) 등이었다. B17 환자는직업상두건을매일착용해야하는데두건의아래면이 와겹쳐불편하여사용하지않고있었고, B9 환자는반복적인염증으로 2번재수술을시행받았다. 이러한예들은청력재활수단을사용하여이득이있어도기기사용이불편하거나염증이생기거나피드백이발생하면청력재활수단을사용하지않는다는것을보여준다. 본연구에서 이식환자 19명중 2명 (B9, B19) 은지속적으로접합부 (abutment) 위로피부가과성장 (soft tissue overgrowth) 해서긴접합부로교체하였고이후불편함이해소되었다. 이전연구에서 Pelosi 와 Chandrasekhar 12,13) 도비후성흉터 (hypertrophic scarring) 가쉽게생기는피부를가진사람, 두꺼운두피를가진비만한남자환자에서는 8.5 mm 접합부를사용할것을권고한바있다. 따라서 이식이결정된이후에도환자의여러가지상태에대한세심한배려가필요하다. B7, B19 환자는 HINT(SNR 1) 에서 착용시와미착용시의차가각각 25.5%, 22.5% 로평균값.9% 에비해낮고, 전반적인만족도 (BBSS 1번항목 ) 도낮았다. 이것은두환자가고주파수난청 (high tone loss) 으로저주파수신호 (low tone signal) 는고주파수소리에비해머리가림효과의영향을덜받아비교적반대측으로잘넘어가기때문에좋은귀로전달된저음역신호와열세귀측에서증폭된저주파수신호가혼합되어소음하어음분별력이저하되어나타난결과로생각된다. 이전의 Pfiffner 등 14) 은일측성난청환자에서저주파수신호를감쇠시킴으로써 를통해나타나는소리의왜곡이감소될수있다고보고한바있다. 이는 를맞춤시일반적인기도보청기맞춤과는다른전략및청각사의숙련도가요구됨을보여준다. 본연구대상의 71% 가좋은귀에경도의난청을가지고있었기때문에좋은귀의청력상태에따라연구대상을그룹 A 와그룹 B로나누어서두군의만족도를비교해보았다. 본연구의한계점은 군은 9년부터모여진것에비해, 무선 군은 12년 4월국내에서판매가시작되어 CROS 보청기환자수가적다는것이다. 따라서크로스보청기환자수가더모이면두기기에대한이득비교및선택기준 (selection criteria) 에대한결과가나올수있으리라기대한다. 방향성 (sound localization) 인식과관련하여이전 344
Hearing Rehabilitation of Single-Sided Deafness: and Park MN, et al. 의연구들은 는방향성을향상시키지는못한다고보 고하였다. 8,15,16) 포낙은이번에출시된 CROS 보청기는양귀 간의시간차를 6 마이크로초로줄여방향성을향상시킨다고 주장하고있으나이에대한타당성역시 CROS 보청기환자수 가늘어난이후연구가이루어져야겠다. 본연구이전에본원에서는일측성난청환자에게청력재활 수단을정할때술전 로드테스트 ( rod test) 나 보청기구매전시험착용으로이득 (functional gain) 을확인 하고청력재활수단을권하였다. 하지만본연구결과에따르 면, 청각학적이득이있다고모든환자가청력재활수단을잘 사용하는것은아니며, 청력재활수단사용시간은만족도, 좋 은귀의청력정도, 난청의원인과도특이상관관계가없을가 능성이있다는것을염두에두어야할것으로사료된다. 따라서재활수단결정전에기능적이득만따질것이아니 라, 개인의직업, 피부성상등개인에맞춰진상담 (customized counseling) 및자세한사전상담이필요하겠다. REFERENCES 1) Douglas SA, Yeung P, Daudia A, Gatehouse S, O Donoghue GM. Spatial hearing disability after acoustic neuroma removal. Laryngoscope 7;117(9):1648-51. 2) Welsh LW, Welsh JJ, Rosen LF, Dragonette JE. Functional impairments due to unilateral deafness. Ann Otol Rhinol Laryngol 4;113(12): 987-93. 3) Kang SH, Goh EK, Koo JW, Kwon KH, Kwon SH, Kim KR, et al. Otorhinolaryngology Head and Neck Surgery. 2nd ed. Seoul, Korea: Iljogak;9. p.821-2. 4) Lee JH, Cho SJ, Kim JS, Chang HS, IM DH, Lee KW, et al. Korean Speech Audiometry. 1st ed. Seoul, Korea: Hakjisa;1. p.2. 5) Kompis M, Pfiffner F, Krebs M, Caversaccio MD. Factors influencing the decision for Baha in unilateral deafness: the Bern benefit in single-sided deafness questionnaire. Adv Otorhinolaryngol 11;71: 13-11. 6) Lin LM, Bowditch S, Anderson MJ, May B, Cox KM, Niparko JK. Amplification in the rehabilitation of unilateral deafness: speech in noise and directional hearing effects with bone-anchored hearing and contralateral routing of signal amplification. Otol Neurotol 6; 27(2):172-82. 7) Bronkhorst AW, Plomp R. Binaural speech intelligibility in noise for hearing-impaired listeners. J Acoust Soc Am 1989;86(4):1374-83. 8) Hol MK, Bosman AJ, Snik AF, Mylanus EA, Cremers CW. Boneanchored hearing aids in unilateral inner ear deafness: an evaluation of audiometric and patient outcome measurements. Otol Neurotol 5;26(5):999-16. 9) Han KH, Kim H, Jang JH, Yoo JC, Kim YH, Lee JH, et al. Hearing rehabilitation with bone anchored hearing aid: experience in 14 patients. Korean J Otorhinolaryngol-Head Neck Surg 1;53(12): 755-6. 1) Gelfand SA. Usage of CROS hearing aids by unilaterally deaf patients. Arch Otolaryngol 1979;15(6):328-32. 11) Snik AF, Mylanus EA, Cremers CW. The bone-anchored hearing aid in patients with a unilateral air-bone gap. Otol Neurotol 2; 23(1):61-6. 12) Pelosi S, Chandrasekhar SS. Soft tissue overgrowth in bone-anchored hearing aid patients: use of 8.5 mm abutment. J Laryngol Otol 11; 125(6):576-9. 13) Monksfield P, Ho EC, Reid A, Proops D. Experience with the longer (8.5 mm) abutment for Bone-Anchored Hearing Aid. Otol Neurotol 9;3(3):274-6. 14) Pfiffner F, Kompis M, Flynn M, Asnes K, Arnold A, Stieger C. Benefits of low-frequency attenuation of baha in single-sided sensorineural deafness. Ear Hear 11;32(1):-5. 15) Snik AF, Mylanus EA, Proops DW, Wolfaardt JF, Hodgetts WE, Somers T, et al. Consensus statements on the system: where do we stand at present? Ann Otol Rhinol Laryngol Suppl 5;195: 2-12. 16) Wazen JJ, Ghossaini SN, Spitzer JB, Kuller M. Localization by unilateral users. Otolaryngol Head Neck Surg 5;132(6): 928-32. www.jkorl.org 345