7.1 Introduction; children should not be treated as young adults
Counselling adults, who according to their audiogram should profit from amplification, is not always successful. Adults might deny their hearing problems or postpone a hearing aid trial. If their attitude is more positive, they might only be interested in hardly visible devices, even if speech recognition with such devices is not optimal.
For children, there is less room to move because the better the hearing the higher the chance that the child will develop normally. According to Northern and Downs (1991; chapter 1), indeed, children need (sub)normal hearing (15 dB HL or less) to ensure normal development of speech and language. Therefore, when counselling the parents of a child with conductive or mixed hearing loss, sufficiently powerful amplification options should be advocated (section 4.3).
The central issue during (any) device fitting is audibility (Amlani et al., 2002). A popular tool to assess audibility of speech is the Speech Intelligibility Index (SII). SII predicts the proportion of normal speech that is audible to a patient with a specific hearing loss. The SII can range from 0 to 100, zero means that normal speech is not audible and 100 means that the patient is able to hear normal speech completely. The SII is based on the idealized spectrum of conversational speech with a +/- 15 dB range, often referred to as the speech banana. The speech banana can be represented in the audiogram, see Figure 7.1. To calculate the SII, for each frequency band (1/3 octave wide), the proportion of speech in that band that is audible is weighted according to the contribution of that band to speech intelligibility (weighting factors indicated by the density of the dots in the figure). In the simplified model presented in the figure, the speech banana stretches from 20 dB HL up to 50 dB HL, over a frequency range of 250 to 6000 Hz (Mueller and Killion, 1990; Killion and Mueller, 2010). The number of dots (max is 100 dots) is the SII; so, one dot counts for 1% of the speech cues. In the figure, post intervention hearing thresholds are presented of two different interventions. Counting the dots shows that the SII is 90 and 22 for intervention 1 and 2, respectively. In their paper, Killion & Mueller (2010) published the relationship between the SII and word recognition scores (their Figure 3). The SII of 90 and 22 equal word recognition scores of 90% and 20%, respectively. Evidently, treatment 1 is much more effective than treatment 2. The figure further suggests that when the maximum 15-dB-hearing-loss criterion of Northern & Downs is fulfilled, SII is 100, thus optimal.
Especially in children, hearing aid fitting should be bilaterally, as bilateral input leads to improved hearing and might enable spatial hearing (Dun et al., 2013). Consequently, speech recognition over-a-distance improves as well as in noisy places (binaural summation; use of head shadow, see chapter 6). Lately, it has been shown that young deaf children with bilateral devices (cochlear implants) compared to those with a unilateral device developed better cognitive skills. Statistics showed that this improvement could fully be ascribed to better perception of soft sounds and better speech perception in noisy places (de Raeve et al., 2015). The factor in between better hearing and better cognitive development is incidental learning. Most things that children learn are acquired in informal everyday situation.
Figure 7.1. Audiogram format with speech area according to Mueller and Killion (gray area). Aided thresholds are shown of two interventions, 1 (red line) and 2 (green line). The SII of the two interventions is determined by counting the dots above the hearing threshold (Source: Mueller and Killion, 1990).
Only approximately 1/3 of their knowledge is acquired in structured, more or less noise-free settings (e.g. in class). The remaining 2/3 during playing, watching TV, talking with parents and other persons, etc. (de Raeve et al., 2015). Especially under these latter conditions, the children profit from bilateral devices.
Probably, the observation that children with unilateral hearing loss (second ear normal) might display delayed educational development, has the same cause (Kuppler et al., 2013). This underlines that hearing with two ears is of utmost importance for the development of speech and language in children.
7.2 Literature review: why some interventions don’t work
Let us use the speech audibility concept to find the best intervention for a child with congenital conductive or mixed hearing loss. A literature search was carried out with as search terms: children, conductive hearing loss, mixed hearing loss, and (Baha or Ponto or Sophono or softband or Vibrant Soundbridge or surgery or conventional bone conduction or Bonebridge). Next, those papers were selected in which 1. two interventions were compared, 2. with n>10, 3. unilaterally fitted and 4. published after 2006. Most of the included studies addressed children with congenital hearing loss.
Figure 7.2. Mean aided thresholds versus the sensorineural hearing loss component (SNHLc) of several study groups of children fitted with: percutaneous BCDs (red symbols, 5 studies*; summed 86 children), transcutaneous BCDs (yellow symbols; 4 studies*; 130 children) and children with atresia repair (blue symbols, 3 studies*; 109 children). The black dots refer to three studies* in which the VSB was used (without a reference device; 54 children).
* see note at the end of this chapter for references.
Figure 7.2 shows data obtained in children with conductive or mixed hearing loss. Concerning the percutaneous BCD devices, overall a mean aided threshold of 19 dB HL was found. That is close to the value that is mentioned in the ‘Practise Guidelines’ for fitting percutaneous devices (17.5 dB HL; Roman et al., 2011) and the 15 dB HL, which is the upper limit for a handicapping hearing loss for children according to Northern & Downs (1991). Concerning the transcutaneous BCDs, viz. the combined data of conventional BCDs (three studies, 49 children), BCDs on softband (two studies, 23 children) and the Sophono BCD (one study, 15 children) show a mean of 29 dB HL. Such a value is expected, owing to the 10 to 15 dB poorer effectiveness of transcutaneous stimulation compared to percutaneous stimulation (Hakansson et al., 1984). Only one study was identified concerning the Sophono device with a mean aided hearing threshold of 33 dB HL (Denoyelle et al., 2015). That mean aided threshold was close to that reported in the original paper introducing the Sophono device by Siegert & Kanderske (2013; mean of 27 dB HL; 27 children).
With regard to surgical atresia repair, the mean long-term hearing threshold is 41 dB HL (three studies). That value is in good agreement with data from Nadaraja et al. (2013) who performed a systematic review of the literature. In fact, the outcomes of two interventions displayed in Figure 7.1 are Farnoosh et al.’s data (2014), with intervention 1 referring to percutaneous BCD application and 2 to atresia repair. The pre-intervention audiograms of the two groups were similar.
On the left side of the figure, the SII is presented calculated according to Killion and Mueller (2010), assuming a ‘flat SNHLc’ (not unusual for predominantly conductive hearing loss). It is obvious that audibility is the highest when using percutaneous BCDs; the SII ranges from 85 to 100. Results with the transcutaneous BCDs are lower. Spread is larger and audibility ranges from subnormal to insufficient; (SII ranging from 75 to 50). Children with such a low SII might be prone to developmental delays. The SII after reconstructive surgery is low, namely < 50. Indeed, Evans & Kazahaya (2007) reported that 90% of their operated children still needed some form of amplification after atresia repair surgery.
Concerning the use of the VSB with its actuator coupled to one of the cochlear windows, no studies were found that presented results compared to another amplification device. However, three studies on VSB application in children with conductive loss were identified with at least 10 children involved. The mean aided thresholds of these three studies with VSB users are presented in Figure 7.1 as black dots. These data are in the same range as those of the transcutaneous BCDs what is somewhat disappointing and might be described to the experimental character of these studies. More data are needed (see update 2020, new section 7.2.1). So far, the Bonebridge device has hardly been applied in children (Sprinzl & Wolf-Magehe, 2015) and is not further considered here (see update 2020, new section 7.2.1).
Children with acquired conductive or mixed hearing loss because of chronic inflammation will benefit from amplification in the same way as those with congenital conductive hearing loss. Mostly, for this indication, BTEs are contraindicated for medical reasons.
Figure 7.2 presents data that can be used for counselling parents of children with conductive hearing loss. In short:
Reconstructive surgery in case of congenital aural atresia is, on the average, the least effective treatment for children.
For children with predominantly conductive hearing loss, today’s percutaneous BCDs provide more adequate gain than transcutaneous BCDs, what might enable a better spontaneous development. While fitting transcutaneous devices, focus should be on audibility of speech.
7.2.1 Update of Figure 7.2 using data published between 2016 and 2020
Update of the data presented in figure 7.2 is based on an additional search of the literature; search period: 2016 (end previous search period) until early 2020. For details of the selection process, see note at the end of this chapter. Seven additional studies were identified, describing 11 groups of subjects with different treatments. Data of the latest evaluation moment were used. The table below presents all the data averaged (viz. the mean post-intervention thresholds and the mean bone-conduction thresholds) per type of treatment, including the data of the previous search (taken from Figure 7.2). The table shows that the mean bone-conduction threshold per type of treatment was rather comparable. Furthermore, the mean post-intervention thresholds varied between 20 dB HL and 41 dB HL.
Using all the studies (from the previous and new literature search) that presented frequency-specific post-intervention thresholds, the mean post-intervention threshold was calculated per frequency and per intervention. Next, the count-the-dots procedure was used to determine the SII and the associated word recognition score. The last column of the table presents these word scores and suggests once more that these treatments are not equivalents. As concluded before, especially the outcomes of atresia repair are disappointing.
The data in the table should be considered with some caution: regarding the Sophono device and the VSB, 2 and 4 studies, respectively, were identified, all published before medio 2016.
|Mean post intervention threshold with (range)||Estimated WRS; % correct|
|Atresia repair||5||199||11 dBHL||41 (33-47) dBHL||25%|
|Percut. BCD||6||135||11||20 (15-22)||95|
|Conv. BCD||8||126||11||33 (27-45)||70|
Percut. stands for percutaneous; conv. for conventional BCD, including BCD on softband; bc for bone conduction; WRS for word recognition score
7.3 Age at intervention and stability
After neonatal hearing screening and a diagnosed bilateral conductive hearing loss few amplification options are available. When the tympanic membrane is visible, BTEs might be used. A transcutaneous BCD with headband or softband can be used in all the other cases. In neonates, mostly a conventional BCD with softband is chosen. It is easier to use and thus better accepted than a steel headband (Hol et al., 2005). The position of stimulating bone-vibrator over the skull can be changed. Aided sound field thresholds with such devices typically lay between 25 dB HL and 30 dB HL (Verhagen et al., 2008; Denoyelle et al., 2015), which seems to be acceptable but only for basal language learning (Northern & Downs, 1991; Verhagen et al., 2008). Therefore, replacement of a BCD on head/softband by a percutaneous BCD or other powerful solutions should remain on the agenda and, meanwhile, speech and language development should be monitored.
The use of percutaneous BCDs involves implantation of a skin penetrating titanium coupling. Concerning the youngest age at which such implantation is feasible, thickness of the skull plays an important role: 3 mm or more is preferred (Snik et al., 2005). This implies that the child must be approximately 4 years old. Nevertheless, the loss of implants in children, in relation to follow-up, is 3 times higher than in adults (e.g. Dun et al., 2010). Children as young as 2 years have been implanted with varying rates of success. McDermott et al. (2009) reported that implant loss was high amongst the under fives (40% of the implanted children lost an implant) and much less in older children. For children over 10 years implant loss was approx. 1%. Other studies didn’t find such a distinct dependence of implant loss on age at implantation (de Wolf et al., 2008). Recently, improved titanium implants have been brought to the market with, in adults, a significantly better stability, see paragraph 5.1.2. However, application of one of these rather new implants in children was not successful (BI300; Den Besten et al., 2015).
The magnet for coupling a Sophono and Baha Attract device can be implanted from age 5 onwards, according to the companies. Reviewing the literature, Bezdjian et al. reported 3 serious adverse reaction in 99 patients using the Sophono device, mainly children (Bezdjian et al., 2017). Dimitriadis et al. (2016;2017) reported as well that complication rate with the Baha Attract was low, when compared to the percutaneous BCD.
VSB with the transducer placed in the round window niche has been applied in children as young as 2 months (Mandala et al., 2011). Since then, little has been published. Only one paper was found (with n>5); Leinung et al. (2017) presented results obtained in 13 young children with aural atresia. Age at implantation varied from 1.3 to 4.2 years with an average of 2.5 years. While the mean bone-conduction threshold (at 0.5, 1, 2, 4 kHz) of the whole group was 8 dB HL, the mean aided threshold was 40 dB HL, which is poor compared to the data presented in Table 7.1. In order to advocate VSB implantation in toddlers and young children, more evidence is needed.
The preferred age at intervention for reconstructive surgery (atresia repair) is 5-6 years and only relatively mild cases should be considered (e.g. Declau et al., 1999). Concerning stability, revision surgery might be necessary in up to one-third of the cases as reported by Farnoosh et al. (2014). These authors compared atresia repair with percutaneous BCD application, amongst other, with respect to medical complications. Percentage of revision surgery after atresia repair was almost 3 times higher than that after BCD implantation. Therefore, it was suggested that, also in terms of medical aftercare, percutaneous BCDs might be a better choice than atresia repair.
7.4 Percutaneous or transcutaneous BCDs in children, counselling issues
Parents might choose for transcutaneous BCD instead of percutaneous BCD, because of stability issues, daily care of the skin around the penetrating implant and/or emotional problems to accept titanium implants sticking out, through the skin. Then the amplification options are to use either the Sophono device (Alpha 2 MPO) or the Baha Attract, applicable from age 4 or 5 years. First data showed that, as expected, the Baha Attract is as effective as Baha on a Softband (Kurz et al., 2014). Nowadays, as sound processor, the Baha 5 power is advocated, which is more powerful than the standard Baha. The use of the Baha power will improve the MPO by several dBs. When bilateral transcutaneous devices are used, in predominant conductive hearing loss, aided thresholds are expected between 20 dB HL and 25 dB HL, with corresponding SII values between 100 and 80. This seems safe but suggests that these children should be followed-up more closely than percutaneous BCD users concerning their speech and language development. It remains of importance to keep a change to a percutaneous BCD on the agenda.
Another suggestion that has been put forward for children with transcutaneous BCDs is the provision of an additional personal FM system. Those systems, coupled to the child’s BCD might enable better speech recognition, however, mainly in structured situations like classrooms. The benefit of personal FM systems is in debate with respect to incidental learning. In other words, it seems to be better to choose the powerful percutaneous amplification options; the gain and MPO might improve by 10 to 15 dB, compared to transcutaneous BCDs.
Using the data presented by Sylvester et al. (2013) it is evident that if the hearing loss is of the mixed type, even when the sensorineural hearing loss component is just 25 dB HL, the Sophono transcutaneous BCD is not effective. Studies using the Baha Attract in such cases are still missing. In mixed cases it is always better to choose for percutaneous BCDs, and if the sensorineural hearing loss component is advanced, an additionally applied personal FM systems might be helpful.
*Note. References belonging to the studies summarized in Figure 7.2: Claros & Pujol, 2013; Frenzel et al., 2015; Verhagen et al., 2008; Farnoosh et al., 2014; Ricci et al., 2011; Denoyelle et al., 2015; Bouhabel et al., 2012; Evans & Kazahaya, 2007; Christensen et al., 2010; Mandala et al., 2011. The update of figure 7.2 (early 2020) was based on an additional literature search using Pubmed. The search string comprised the words: children, hearing, thresholds, and either a device name (Baha, Ponto, Bonebridge, Sophono, Vibrant Soundbridge) or atresia, surgery. Studies were excluded if aiming at subjects with just unilateral hearing loss, single-sided deafness or sensorineural hearing loss. The inclusion criteria used were: 1. either the aided PTA4 or the aided thresholds at 0.5, 1, 2, 4 kHz should have been reported, as well as bone-conduction thresholds and 2. group size should > 9. The identified studies comprised: Zhao et al., 2016; Fan et al., 2019, Bravo-Torres et al., 2018, Kulasegarah et al., 2018, Ren et al., 2019, Ahn et al., 2018, Zernotti et al., 2019, Ratuszniak et al., 2019.
|Ahn J, Ryu G, Kang M, Cho YS. Long-term Hearing Outcome of Canaloplasty With Partial Ossicular Replacement in Congenital Aural Atresia. Otol Neurotol. 2018 Jun;39(5):602-608.
Amlani AM, Punch JL, Ching TY. Methods and applications of the audibility index in hearing aid selection and fitting. Trends Amplif. 2002;6(3):81-129.
Bouhabel S, Arcand P, Saliba I. Congenital aural atresia: bone-anchored hearing aid vs. external auditory canal reconstruction. Int J Pediatr Otorhinolaryngol. 2012;76(2):272-7.
Bravo-Torres S, Der-Mussa C, Fuentes-López E. Active transcutaneous bone conduction implant: audiological results in paediatric patients with bilateral microtia associated with external auditory canal atresia. Int J Audiol. 2018 Jan;57(1):53-60.
Christensen L, Smith-Olinde L, Kimberlain J, Richter GT, Dornhoffer JL. Comparison of traditional bon e-conduction hearing AIDS with the Baha system. J Am Acad Audiol. 2010;21(4):267-73.
Colletti L, Mandala M, Colletti V. Long-term outcome of round window Vibrant Soundbridge implantation in extensive ossicular chain defects. Otolaryngol Head Neck Surg. 2015; 149:134-141
Dun CA, Agterberg MJ, Cremers CW, Hol MK, Snik AF. Bilateral bone conduction devices: improved hearing ability in children with bilateral conductive hearing loss. Ear Hear. 2013;34(6):806-8.
Fan X, Yang T, Niu X, Wang Y, Fan Y, Chen X. Long-term Outcomes of Bone Conduction Hearing Implants in Patients with Bilateral Microtia-atresia. Otol Neurotol. 2019 Sep;40(8):998-1005.
McDermott AL, Williams J, Kuo M, Reid A, Proops D. The Birmingham pediatric bone-anchored hearing aid program: a 15-year experience. Otol Neurotol. 2009;30(2):178-83.
Kulasegarah J, Burgess H, Neeff M, Brown CRS. Comparing audiological outcomes between the Bonebridge and bone conduction hearing aid on a hard test band: Our experience in children with atresia and microtia. Int J Pediatr Otorhinolaryngol. 2018 Apr;107:176-182.
Kurz A, Flynn M, Caversaccio M, Kompis M. Speech understanding with a new implant technology: a comparative study with a new non-skin penetrating Baha system. Biomed Res Int. 2014;2014:416205.
Ratuszniak A, Skarzynski PH, Gos E, Skarzynski H. The Bonebridge implant in older children and adolescents. Int J Pediatr Otorhinolaryngol. 2019 Mar;118:97-102.
Ren R, Zhao S, Wang D, Li Y, Ma X, Li Y, Fu X, Chen P, Dou J. Audiological effectiveness of Bonebridge implantation for bilateral congenital malformation of the external and middle ear. Eur Arch Otorhinolaryngol. 2019 Oct;276(10):2755-2762
Verhagen CV, Hol MK, Coppens-Schellekens W, Snik AF, Cremers CW. The Baha Softband. A new treatment for young children with bilateral congenital aural atresia. Int J Pediatr Otorhinolaryngol. 2008;72(10):1455-9.
de Wolf MJ, Hol MK, Huygen PL, Mylanus EA, Cremers CW. Nijmegen results with application of a bone-anchored hearing aid in children: simplified surgical technique. Ann Otol Rhinol Laryngol. 2008;117(11):805-14.
Zhao S, Gong S, Han D, Zhang H, Ma X, Li Y, Chen X, Ren R, Li Y. Round window application of an active middle ear implant (AMEI) system in congenital oval window atresia. Acta Otolaryngol. 2016;136(1):23-33.
Zernotti ME, Chiaraviglio MM, Mauricio SB, Tabernero PA, Zernotti M, Di Gregorio MF. Audiological outcomes in patients with congenital aural atresia implanted with transcutaneous active bone conduction hearing implant. Int J Pediatr Otorhinolaryngol. 2019 Apr;119:54-58.