Auditory Training in Children Wearing Hearing Aids and/or Cochlear Implants: A Scoping Review Mapping the Diversity of Intervention Types and Outcome Measures

You have accessThe ASHA LeaderFeature1 Mar 2005Aural Habilitation Update: The Role of Speech Production Skills of Infants and Children With Hearing Loss Sheila R. Pratt Sheila R. Pratt Google Scholar More articles by this author https://doi.org/10.1044/leader.FTR2.10042005.8 SectionsAbout ToolsAdd to favorites ShareFacebookTwitterLinked In It is well known that the development of speech is extremely limited without adequate auditory input and feedback. An obvious example is that hearing loss in infancy and early childhood usually affects all as pects of speech production unless there is early and consistent use of sensory aids as well as substantive sensorimotor and linguistic training. The speech development of infants and children with hearing loss hinges on their abilities to use audition not only to learn the sounds of their language, but also to use their articulators to produce those sounds and make use of auditory feedback to refine their speech over time. As such, the speech of children with prelingual hearing loss is particularly susceptible to delay and disorder, es pecially if the severity of the hearing loss is substantial and intervention is delayed or inadequate. Speech Development During the first six months of life (and possibly in utero) auditory perceptual learning is vital for acquiring oral language and speech, although the maturation timeline for the speech production in normal-hearing children is relatively lengthy. This protracted timeline may account for the long-term training and treatment needs of many children with hearing loss, even those identified and fitted early with sensory aids (Yoshinaga-Itano & Sedey, 2000). Young children with normal hearing typically begin babbling around 5–6 months of age and start verbal expression around 12 months of age. However, their speech production skills continue to be refined through the school-age years and well beyond when their basic phonological inventories have been established. For example, vowel space, voice-onset times, and vocal control adjust throughout early childhood (Assmann & Katz, 2000; Koenig, 2001; Lee, Pontamianos, & Naray anan, 1999). Furthermore, substantial acoustic variability is a hallmark of children’s speech production until late childhood. Although the research is somewhat mixed on the development of coarticulation, children appear to be less able than adults to coarticulate their speech gestures in a consistent manner, and as a consequence, their speech is less intelligible than that of adults (Katz, Kripke, & Tallal, 1991; Nittrouer, 1993). The refinement of auditory processing of speech has a similar developmental timeline. Child ren may apply different rules or weights to speech cues than adults, and these weights change throughout childhood (Nittrouer, 2003; Nit trouer, Crowther, & Miller, 1998). Their auditory processing of speech also appears to be more susceptible to acoustic and linguistic perturbations than is observed with adults. Children are more adversely affected than adults by background noise, reverberation, talker variability, re ductions in signal bandwidth, and the number of signal channels (Eisenberg et al., 2000; Ryalls & Pisoni, 1997; Kortekaas & Stelmachowicz, 2000). The Role of Audition in Speech Development and Production For mature speakers, audition acts as an error detector and a means of monitoring speaking conditions. It is considered to be slower than other forms of sensory information (i.e., proprioception) generated during speech, and therefore is likely limited to a feedback role (Perkell et al., 1997). Speakers use audition to determine if their articulators have produced sounds that are acoustically off-target. Audition also provides information for corrective adjustments, and as a consequence, is a contributor to the maintenance of speech integrity. Studies of frequency and spectrally shifted speech feedback have shown that adults rapidly adjust to minor acoustic perturbations with compensatory and/or matching strategies (Bauer & Larson, 2003; Houde & Jordan, 2002; Jones & Munhall, 2002, 2003). They appear to adjust their articulators so that their speech productions match their internal representations. In addition to acting as an error detector, hearing is used by mature speakers to determine how they should adjust their speech in various acoustic, linguistic, and social environments. For example, adults know when to speak slower, louder, softer, or more precisely in order to accommodate their listener or the environmental conditions (Perkell et al., 1997). In contrast, many young children are unable to adjust the clarity of their speech, even when explicitly directed to do so (Ide-Helvie et al., 2004). Audition also allows the development of articulatory organization by providing information about how to position, move, and coordinate the articulators for speech, movements that can differ from those associated with vegetative functions of the mechanisms (Moore & Ruark, 1996). For ex ample, infants use audition to learn how to shift from a vegetative breathing pattern to a pattern that can support speech. They learn how to position and move their tongues and to judge the acoustic consequences of those gestures. Coord ination of the larynx with the vocal tract and upper airway articulators is refined over years but requires an intact auditory system (Koenig, 2001; Tye-Murray, 1992). The lip and jaw movements associated with speech in infants and young children are highly variable but distinct from sucking, chewing, and smiling (Green et al., 2000; Green, Moore, & Reilly, 2002; Moore & Ruark, 1996). The implication is that although the same peripheral mechanisms are used across oral and respiratory functions, the differing goals require substantially distinct coordination and feedback efforts. The coordination needed to chew and swallow efficiently develops over early childhood but is largely independent of hearing, whereas the coordination required to move between vowel and consonant gestures, particularly in a coordinated and coarticulated manner, is strongly influenced by hearing (Baum & Waldstein, 1991; Guenther, 1995; Tye-Murray, 1992; Waldstein & Baum, 1991). Audition has a primary sensorimotor role in the development of speech, but it also is fundamental to infants and young children learning the sounds of their language. Furthermore, it helps them learn how specific speech events relate to their phonology, so that with development, young children become more able to use their hearing to inform them about the sequencing of speech gestures and the correctness of subsequent productions. Over time children learn to use audition to monitor ongoing speech, detect errors, and make corrective adjustments. Hearing Loss and Speech Production Hearing loss is common in the general population but its effects on speech production are most pronounced with individuals whose hearing loss is congenital or acquired in early childhood. Most adults who acquire their hearing losses later in life suffer little or no deterioration in intelligibility, likely because their residual hearing provides sufficient feedback since their mature speech production systems rely more on orosensory than auditory information to maintain proper control (Guenther, 1995; Goehl & Kaufman, 1984; Perkell et al., 1997). The speech differences that they do exhibit are subtle and usually imperceptible, even in cases of complete or nearly complete adventitious hearing loss. Nonetheless, some adventitiously deafened adults exhibit reduced speaking rate, and compromised articulatory and phonatory precision (Kishon-Rabin et al., 1999; Lane & Webster, 1991; Lane et al., 1995; Leder et al., 1987; Waldstein, 1990; Perkell et al., 1992). These speech differences are similar in nature, but not in severity, to those observed with prelingually deafened speakers. Most infants and young children with hearing loss demonstrate disordered phonation and articulation, as well as delays in the acquisition of sound categories. The entire speech production system can be affected, from respiratory support to the coarticulation of ongoing speech (Pratt & Tye-Murray, 1997). This is especially true if the hearing loss is identified late or after a period of protracted hearing loss. Furthermore, the overlap and interaction of disordered sound production and linguistic delay contribute to poor speech integrity and restricted speech development. Babbling generally does not appear before 12 months of age (Oller & Eilers, 1988; Oller et al., 1985) and canonical babbling has been observed as late as 31 months in this population (Lynch, Oller, & Steffens, 1989). Infants also produce fewer instances of canonical babble and include a more limited range of consonants in their babble (Stoel-Gammon, 1988; Stoel-Gammon & Otomo, 1986; Wallace, Menn, & Yoshinaga-Itano, 2000). However, later speech intelligibility is better predicted by the consonant inventory used in emerging spoken language during the second year of life than during babble (Obenchain, Menn, & Yoshinaga-Itano, 2000). The phonetic repertoires of infants with severe-to-profound hearing loss often are restricted when compared to their normal-hearing peers, although there is abundant individual variability (Lach, Ling, Ling & Ship, 1970; Stoel-Gammon & Otomo, 1986; Wallace et al., 2000; Yoshinaga-Itano & Sedey, 2000). The early speech inventories of infants with severe-to-profound hearing loss predominately consist of motorically easy sounds such as vowels and bilabial consonants. The sounds of their inventories also contain more low frequency information, which is more audible. For example, the babbling of infants with hearing loss often has a high concentration of nasals and glides, which include low-frequency continuant cues (Stoel-Gammon & Otomo, 1986). Without early intervention and appropriate fitting of sensory aids the speech-sound inventories of many children with hearing loss usually do not attain full maturity. Yoshinaga-Itano and Sedey (2000) found that children with moderate-to-severe hearing losses did not reach an age-appropriate complement of vowel and consonant sounds until about 4 and 5 years respectively, and many children with profound hearing loss had restricted inventories even at 5 years of age. Children with profound hearing loss often reach an early plateau in their speech skill development. For instance, the speech characteristics of many children with severe-to-profound hearing loss demonstrate little improvement in sound inventory and intelligibility after 8 years of age, even with the initiation of extensive training (Hudgins & Number, 1942, McGarr, 1987; Smith, 1975). Such results imply that, like auditory and language interventions, speech production therapy should be an important component of early intervention, and that the common practice of delaying speech training in children with hearing loss until they have functional language is developmentally untenable if the goal is for them to be oral communicators. In addition to the relationship between age-of-onset and speech impairment severity, there also is a moderately positive relationship between the severity of hearing loss and the extent of the associated speech difficulties (Boothroyd, 1969; Levitt, 1987; Smith, 1975). For example, children with mild-to-moderate hearing loss, particularly if well aided, tend to exhibit speech differences that are mild (Elfenbein, Hardin-Jones, & Davis, 1994; Oller & Kelly, 1974; West & Weber, 1973). Elfenbein and colleagues found that children with mild-to-moderate hearing loss exhibit good intelligibility but had higher than normal rates of affricate and fricative substitutions. Mild hoarseness and resonance problems also are present in 20% to 30% of this group of children. Moreover, they tend to have increased rates of voicing irregularities, difficulties with /r/ production, and omissions of back and word-final consonants. Early studies of children with profound prelingual hearing loss showed that most rarely acquired speech skills sufficient to interact easily using spoken language. On average, less than 20% of their words were intelligible to listeners who were not familiar with their speech (Hidgins & Numbers 1942; Markides, 1970; Smith, 1975). Smith (1975) evaluated 40 children with varying levels of hearing loss and, on average, only 18.7% (0% to 76%) of their words could be identified by inexperienced listeners. As expected, overall intelligibility was inversely related to the frequency of segmental and suprasegmental errors. However, with early identification of hearing loss and early intervention (i.e., fitting of sensory devices, behavioral training, and parent counseling), the numbers of children with severe-to-profound hearing loss and intelligible speech has increased (Uchanski & Geers, 2003). Many more children are developing sufficient speech perception to support development of speech production and oral language, but these advances may have added to the overall heterogeneity of the population (Higgins et al., 2003). Other factors contribute to the diversity of speech production skills observed with these children. For instance, cognitive skill (particularly nonverbal intelligence) has been found to be an important predictor of functional speech and oral language in children with hearing loss (Geers et al., 2002; Tobey et al., 2003). Auditory experience in infancy and early childhood, even of limited duration, positively influences the speech production skills of children who have severe-to-profound hearing loss (Geers, 2004). The use of sensory aids has a substantial impact on speech outcomes, but somewhat surprisingly, the age at which infants and young children are fitted with cochlear implants has not surfaced in studies of speech production as a significant predictor of later speech intelligibility (Geers et al., 2002; Tobey et al., 2003). Early implantation (less than 2 years) is, however, related to more normal oral communication development as a whole (both speech and oral language) (Geers, 2004). It may be that the age of implantation is not easily separated from other influences of intervention, like the orientation of the habilitation program and parent involvement, which relate strongly to children being auditory perceptual learners and users of auditory feedback. Another consideration is that many early-implanted children may be implanted too late to observe a clear impact on speech production. The critical ages at which hearing aids should be fitted has not been investigated, but like cochlear implants, it is assumed that earlier is better. The oromotor integrity and language skills are additional factors that often are neglected in studies of speech development in children with hearing loss. A substantial number of infants and children with hearing loss present with secondary handicapping conditions, such as neurological disorders. When these neurological disorders include the speech mechanism, the development of functional speech is difficult even if audition is optimized. As such, is it not unusual for a child with hearing loss to have a coexisting dysarthria along with the speech impairment secondary to the hearing loss. A subset of children with hearing loss also may have an apraxia of speech, but separating the impact of hearing loss from an apraxia of speech is difficult because the associated speech characteristics overlap (McNeil, Robin & Schmidt, 1997). Language disorders also are commonly observed in children with hearing loss, and are frequently evidenced in phonological disorder and lexical delay. As a result, extricating the sensorimotor impact of hearing loss on speech production from the influences of language disorder in individual children is not always straightforward (Peng et al., 2004). Habilitation: Sensory Aids and Treatment Most speech training approaches are dependent on optimizing the use of residual hearing although some approaches use other modalities (Pratt, Heintzelman, & Deming, 1993; Pratt & Tye-Murray, 1997). Correspondingly, it is generally believed that speech is learned most easily if infants and children learn and monitor their speech through their auditory systems. Therefore, the proper and early fitting, and consistent use of sensory aids, along with auditory and language training are important components of speech production training. In support of this auditory-based approach is the relationship between the severity of prelingual hearing loss and the extent of speech delay/disorder found in children (Boothroyd, 1969; Levitt, 1987; Smith, 1975), as well as any history of previous hearing (Geers, 2004). The relationship between audiometric configuration and speech intelligibility also argues for the importance of audition if the goal for a child is oral communication (Levitt, 1987; Osberger, Maso, & Sam, 1993). There is a growing literature supporting the positive impact of cochlear implants on speech development, as well as the role that auditory-oral-based training programs play in communication outcomes of children fitted with cochlear implants (Geers et al., 2002; Tobey et al., 2003). There is, however, limited efficacy data for children with less severe hearing loss who are typically fitted with hearing aids. The lack of research in this area is glaring because wearable electroacoustic hearing aids have been available for more than 50 years (Lybarger, 1988) and are a fundamental component of treatment approaches for most children with hearing loss. Furthermore, more infants and children are fitted with hearing aids than cochlear implants. Preliminary data reported by Stemachowicz and her colleagues (2004) on three infants fitted early with hearing aids suggested delays in sound category acquisition consistent with patterns previously reported in the literature. Sound inventories were impoverished, consonants were more affected than vowels, and sound containing high-frequency cues were particularly limited. Additional data by Pittman and colleagues (2003) observed that the amplitude of high-frequency speech cues directed to and produced by children wearing hearing aids may not be sufficient, although they did not connect their results directly to speech production outcomes. Pratt, Grayhack, Palmer, and Sabo (2003) found that differences in hearing aid configuration could alter vowel spacing of children even though the children in their study had intelligible speech, and the speech tokens measured were limited to acceptable productions. Their data indicated that hearing aids could alter the speech of children, but provided little information about the impact that hearing aids may have on speech development. Given the paucity of data-as well as the expansion of universal infant hearing screening programs-it is critical that more research be done in this area. Increasing numbers of infants with hearing loss will be identified shortly after birth and, if we are to effectively treat them, more should be known about the impact that hearing aids and other sensory aids have on speech and auditory system development. Aural Habilitation References Assmann P. F., & Katz W. F. (2000). Time-varying spectral change in the vowels of children and adults.Journal of the Acoustic Society of America, 108, 1856–1866. CrossrefGoogle Scholar Baum S., & Waldstein R. (1991). Perseveratory coarticulation in the speech of profoundly hearing-impaired and normally hearing children.Journal of Speech and Hearing Research, 34, 1286–1292. LinkGoogle Scholar Bauer J. J., & Larson C. R. (2003). Audio-vocal responses to repetitive pitch-shift stimulation during a sustained vocalization: Improvements in methodology for the pitch-shifting technique.Journal of the Acoustical Society of America, 114, 1048–1054. CrossrefGoogle Scholar Boothroyd A. (1969). Distribution of hearing levels in the student population of the Clarke School for the Deaf. Northampton, MA: Clarke School for the Deaf. Google Scholar Elfenbein J., Hardin-Jones M., & Davis J. (1994). Oral communication skills of children who are hard of hearing.Journal of Speech and Hearing Research, 37, 216–226. LinkGoogle Scholar Eisenberg L., Shannon R., Martinez A. S., & Wygonski J. (2000). Speech recognition with reduced spectral cues as a function of age.Journal of the Acoustical Society of America, 107, 2704–2710. CrossrefGoogle Scholar Geers A., Brenner C., Nicholas J., Uchanski R., Tye-Murray N., & Tobey E. (2002). Rehabilitation factors contributing to implant benefit in children.Annals of Otology, Rhinology, and Laryngology—Supplement, 189, 127–130. CrossrefGoogle Scholar Goehl H., & Kaufman D. (1984). the effects of adventitious include disordered of Speech and Hearing LinkGoogle Scholar J. R., Moore C. A., M., & R. W. (2000). The development of speech and jaw of & Hearing Research, LinkGoogle Scholar J. R., Moore C. A., & J. (2002). The development of jaw and lip control for of and Hearing Research, LinkGoogle Scholar F. Speech sound coarticulation, and effects in a of speech CrossrefGoogle Scholar E. A., A. & (2003). in children’s speech and after cochlear and CrossrefGoogle Scholar Houde J. F., & of speech and of and Hearing Research, LinkGoogle Scholar C., & Numbers F. An of the intelligibility of speech of the Google Scholar D. L., W. A., C., A. J., & used to speech clarity by normal-hearing children.Journal of the Acoustical Society of America, CrossrefGoogle Scholar Jones J. A., & (2002). The role of auditory feedback during Studies of of CrossrefGoogle Scholar Jones J. A., & (2003). to produce speech with an vocal The role of auditory of the Acoustical Society of America, CrossrefGoogle Scholar Katz W. F., C., & P. (1991). coarticulation in the speech of adults and young perceptual and of Speech and Hearing Research, 34, LinkGoogle Scholar L., R., & The of hearing on speech production of deafened adults with cochlear of the Acoustical Society of America, CrossrefGoogle Scholar characteristics of in children’s and of developmental of Speech and Hearing Research, LinkGoogle Scholar Kortekaas R., & P. (2000). effects on children’s perception of the Acoustical auditory and clarity of and Hearing Research, LinkGoogle Scholar R., Ling Ling L., & Early speech development in of the Google Scholar Lane H., & J. W. (1991). Speech deterioration in deafened adults.Journal of the Acoustical Society of America, CrossrefGoogle Scholar Lane H., J., M., M., & Perkell J. in the speech of cochlear implant An of of the Acoustical Society of America, CrossrefGoogle Scholar Leder S., J., J. C., C., & F. of adventitiously cochlear implant of the Acoustical Society of CrossrefGoogle Scholar S., A., & Acoustic of children’s of and spectral of the Acoustical Society of America, CrossrefGoogle Scholar the speech and language H., N., & D. Development of language and communication skills of hearing-impaired children. ASHA Google Scholar A R. of hearing aid MA: Google Scholar M., Oller & Development of in a child with congenital of The of CrossrefGoogle Scholar skills of hearing-impaired children in for the H., N., & D. Development of language & communication in hearing children. ASHA Google Scholar R., Robin D. A., & R. A. of and of sensorimotor speech disorders Google Scholar A. The speech of and hearing children with to factors of of CrossrefGoogle Scholar Moore C. A., & J. speech from earlier oral of Speech and Hearing Research, LinkGoogle Scholar (2002). to fricative perception and how it the of the Acoustical Society of America, CrossrefGoogle Scholar S., C. S., & E. The of acoustic in the perception of by children and & CrossrefGoogle Scholar L., & Yoshinaga-Itano C. (2000). speech development at months in children with hearing loss be predicted from information available in the second year of Google Scholar Oller R., & A. of a A with normal of Speech and Hearing Research, LinkGoogle Scholar Oller & C. of a of Speech and Hearing LinkGoogle Scholar J., M., & Speech intelligibility of children with cochlear implants, aids, or hearing of Speech and Hearing Research, LinkGoogle Scholar S., A. L., H., & production and language skills in children with cochlear of and CrossrefGoogle Scholar Perkell J., Lane H., M., & J. Speech of cochlear implant A study of vowel of the Acoustical Society of America, CrossrefGoogle Scholar Perkell J. S., L., Lane H., F. H., R., J., & P. Speech Acoustic auditory feedback and internal CrossrefGoogle Scholar Pittman A. L., Stemachowicz P. D. & (2003). characteristics of speech at the for in children.Journal of and Hearing Research, LinkGoogle Scholar Pratt R., A. & E. The efficacy of using the to treat young children with hearing of Speech and Hearing Research, LinkGoogle Scholar Pratt R., & Tye-Murray A. Speech impairment secondary to hearing of sensorimotor speech disorders Google Scholar Smith C. hearing and speech production in the of Speech and Hearing Research, LinkGoogle Scholar P. Pittman A. L., M., D. & P. The importance of high-frequency in the speech and language development of children with hearing of and CrossrefGoogle Scholar Stoel-Gammon C. of hearing-impaired & normally hearing A of of Speech and Hearing LinkGoogle Scholar Stoel-Gammon C., & Babbling development of hearing-impaired and normally hearing of Speech and Hearing LinkGoogle Scholar Tobey E. A., Geers A. Brenner C., & (2003). associated with development of speech production skills in children implanted by age and CrossrefGoogle Scholar Uchanski R. M., & Geers A. E. (2003). Acoustic characteristics of the speech of young cochlear implant A with normal-hearing and CrossrefGoogle Scholar Waldstein R. of on speech for the role of auditory of the Acoustical Society of America, CrossrefGoogle Scholar Waldstein R., & Baum (1991). coarticulation in the speech of profoundly hearing-impaired and normally hearing children.Journal of Speech and Hearing Research, 34, LinkGoogle Scholar Wallace L., & Yoshinaga-Itano C. (2000). babble the to speech for all A study of children who are or hard of Google Scholar Sheila R. Pratt, is in the of & at the of her at With With Additional to in Mar &

A cochlear implant (CI) 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 the cochlea, connected to an internal receiver, and an externally worn speech processor. The CI 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 and reports, and the results of the various Nijmegen cochlear implant studies, are reviewed. Issues about selection, examinations, surgery and the outcome are 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 prelingually (congenital or acquired) deaf children with profound bilateral sensorineural deafness.

THE ARGUMENT FOR FITTING BIMODALLY If you see a child tomorrow with a hearing loss in both ears, will you recommend one hearing aid or two? The obvious answer is two. You would have a hard time finding a dispensing professional today who does not agree that the benefits of bilateral hearing aid fitting make it the standard of care for those with binaural hearing loss. While the benefits of binaural hearing and the advantage of bilateral fitting are beyond the scope of this article (e.g., see Litovsky et al.,1 Kochkin2), these facts are undisputed in hearing healthcare circles. The industry's confidence in bilateral hearing aids is supported by current trends in fitting. In 1980 only 27% of hearing aid fittings were bilateral.3 Today, it is an amazing 86% for those with binaural hearing loss.4 So, what is bimodal fitting and why should dispensing professionals care? Bimodal fitting means different stimuli are presented to each ear. For the purposes of this paper, it means a cochlear implant in one ear and a hearing aid in the other. But, you may ask, don't cochlear implant audiologists take care of that? The answer is no, at least not usually. Personal experience (first author), communication with cochlear implant audiologists, and the literature5 suggest that most hearing aids in bimodal devices are fitted outside the cochlear implant center. Thus, if you have a patient who receives a cochlear implant in one ear, you will most likely be the one responsible for the continuing care of the hearing aid in the contralateral ear. It is in the best interests of both your patient and you to know how to optimize the hearing aid fitting for the best bimodal performance. If you fit hearing aids on children, the question is not if you will be responsible for managing a child with bimodal devices, but rather when. The number of unilateral cochlear implant recipients who continue to use contralateral hearing aids is clearly increasing (Figure 1). The conventional wisdom that cochlear implants and hearing aids should not be used simultaneously is archaic,6,7as we will show in this paper.Figure 1: Percentage of unilateral cochlear implant users choosing to wear a hearing aid in the contralateral ear. Sources: Tyler et al.,8 Cowan and Chin-Lenn9.BIMODAL DEVICE USE IN CI WEARERS Significant advances over the years in cochlear implant technology, speech-coding strategies, and surgical techniques have resulted in substantial improvements in the auditory-only speech-understanding abilities of cochlear implant recipients.10 As a result, the candidacy criteria approved for cochlear implantation in the United States has progressively expanded. When Cochlear Corporation, Ltd., introduced the original Nucleus® cochlear implant in 1985, the only candidates approved by the Food and Drug Administration were adults with profound bilateral sensorineural hearing loss of post-linguistic origin who had 0% open-set speech recognition using hearing aids. Now, under the FDA criteria approved in 2005, candidates can be adults or children aged 12 months and older, and can have either pre- or post-lingual onset of hearing loss. Although mid- and high-frequency hearing must still be profound (hearing thresholds >90 dB HL), low-frequency hearing loss can be moderate for adults (hearing thresholds >40 dB HL) and severe for children over age 2 (hearing thresholds >70 dB HL). Further, best-aided pre-operative speech-recognition criteria have been raised from 0% to <60%. Figure 2 shows the current criteria for each age group.Figure 2: Current FDA-approved audiometric and speech-recognition criteria for cochlear implantation with the Nucleus device, by age group. (For children, the open-set word-recognition test recommended is the Lexical Neighborhood Test [LNT] or Multisyllabic Lexical Neighborhood Test [MLNT], which are available from www.auditec.com.)For persons with bilaterally profound sensorineural deafness (the purple-shaded area in Figure 2), cochlear implants are clearly the intervention of choice because many obtain little or no benefit from hearing aids. However, for children aged 2 years and up and for adults, there is a range of low-frequency thresholds (the green and yellow areas, respectively) that fall within the approved audiometric range for cochlear implants. Hearing aids often fail to provide adequate performance for these patients,11but a unilateral cochlear implant alone does not provide all the known benefits that arise from listening with two ears rather than one. Binaural benefits from perception of interaural differences in time and intensity are well known to improve speech-recognition performance, particularly in background noise, due to a combination of head shadow, binaural redundancy, and binaural squelch effects (e.g., see Byrne, 198112 for a review). Further, bilateral inputs provide the potential for good localization ability. Finally, a strong argument can be made for bilateral stimulation, especially in children, in light of the impact of auditory deprivation on perception. When a hearing-impaired ear remains unaided, speech-recognition ability in that ear significantly deteriorates over time,13,14 and there appears to be a limited window of opportunity for auditory system stimulation if the patient is to achieve maximal binaural functioning.15 Bilateral implantation is not for everyone. For example, there might be significant usable hearing in one ear. There may be insurance reimbursement or financial barriers. Parents may worry about surgery or preserving one ear for possible future technology or treatments. These concerns may or may not be well-founded. Insurance reimbursement is not the obstacle it once was. Cochlear brand implants are designed to be “backward compatible” so future advances can be applied to implants done today. Cotanche reported that treatment, e.g., hair cell regeneration, may be 20 years or more away.16 However, unilateral versus bilateral implantation in children is ultimately the parents' choice and their wishes must be respected. The less expensive, non-invasive fitting of a hearing aid on the ear contralateral to a cochlear implant allows preservation of hearing in that ear and may provide the benefits of binaural stimulation. SUMMARY OF THE LITERATURE The bimodal fitting approach was first reported in the literature in the early 1990s (e.g., Shallop et al., 199217). Concerns were initially expressed that patients might be unable to combine the two very different sound sources for central processing. Fortunately, this has not proven to be the case. In fact, some researchers have argued that bimodal stimulation may provide “complementary” cues for processing of signals that may be advantageous to speech perception.18 Specifically, the lower frequencies provided by the hearing aid can provide information about the fundamental frequencies of a talker's voice and vowel information, while the mid- and high-frequency information from the cochlear implant can provide information needed on manner and place of articulation of consonants. It has also been suggested that localization ability, sound quality, and music perception may be enhanced by bimodal devices compared with bilateral cochlear implants.19,20 Studies have reported significant speech-recognition improvements for bimodal listening compared to either the patients' pre-operative bilateral hearing aid use or their post-operative use of the hearing aid or cochlear implant alone. This has been shown in adults17,21–23 and in children.24–26 For example, in a study by Luntz et al.,26 12 subjects (3 post-lingually impaired adults and 9 pre-lingually impaired adults and children aged 7 and older) were tested on sentences in noise after 7 to 12 months of using bimodal devices. Both speech (at 55 dB HL) and noise (at 45 dB HL) were presented from a frontal loudspeaker. Average speech-recognition scores were only 12.9% for the hearing aid alone and 60.7% for the cochlear implant alone, but bimodal listening produced an average score of 75.6% correct. Localization abilities have been shown to improve with bimodal devices relative to use of either device alone for some, although not all, adult2728 and pediatric1,24 patients. Many users of bimodal devices have also reported higher levels of satisfaction and perceived benefit than with hearing aids worn pre-implantation, although cosmetic and handling concerns of using the two devices have sometimes been expressed,29 emphasizing the need for sufficient counseling and training. It is also important to consider that children may need more time to learn to use bimodal cues.25 There is debate over the relative effectiveness of bilateral cochlear implants versus bimodal devices. Overall, however, the published literature on bimodal devices has been quite positive (e.g. see Ching et al. for a review18). A judicious approach would be to fit a hearing aid contralaterally to the implant on patients who show sufficient benefit from the hearing aid and are able to use the binaural cues provided. FACTORS IN FITTING THE HEARING AID Certain aspects of the fitting need to be considered and possibly modified for optimal use of bimodal devices. Dispensing professionals who follow proven, evidence-based protocols for hearing aid fitting, however, will require minimal adaptation of their normal procedure. The American Academy of Audiology has published a Pediatric Amplification Protocol and all professionals dispensing hearing aids to children should be familiar with it.30 Optimization of the hearing aid in bimodal fittings essentially requires three steps. First, the cochlear implant map must be stable. You will need to communicate with the cochlear implant audiologist to know when this has been accomplished. Second, a frequency response should be selected for the hearing aid that will provide the best speech intelligibility. This is established by starting with a hearing aid that has been fitted and verified using a prescriptive formula. While the first author has had success using NAL-NL1,31 and Ching recommended it as an optimal starting point,32 those who are proficient with DSL[i/o]33 or another validated prescriptive approach should not be discouraged from using it as the starting point. From the initial prescription, two alternate frequency responses should be programmed into the hearing aid and adjusted for equal loudness. This is easy in multiple-memory digital hearing aids. As the limits of the hearing aid permit, program one should be the selected prescriptive formula frequency response. Program two should have 6-dB per octave less amplification in the low frequencies (-6 dB at 1000 Hz, -12 dB at 500 Hz, and -18 dB at 250 Hz). Program three should have 6-dB per octave more amplification in the low frequencies (+6 dB at 1000 Hz, +12 dB at 500 Hz, and +18 dB at 250 Hz). Once the programs are established, the child should listen to connected discourse while the audiologist switches between programs to determine which one provides the clearest speech. This can be done by playing a recorded story or watching a child-friendly video. The cochlear implant should be turned off during this frequency response selection process. Ching reported that this procedure is appropriate for children as young as 6 years.32 For younger children, the professional may choose to default to the prescriptive response. Finally, the third step in the fitting protocol is to match overall loudness between the hearing aid and cochlear implant. Both the implant and the aid are turned on and the child is asked to report if the hearing aid is louder or softer than the cochlear implant. The aid is then adjusted accordingly. This can also be done while the child listens to a recorded story or watches a video. A chart like that in Figure 3 can be helpful for this task. Some children might experience loudness discomfort from amplification. If so, Ullauri et al. suggest starting with a lower volume setting on the hearing aid and raising it over time as acclimatization occurs until the level of balanced loudness is achieved.34Figure 3: Loudness balancing scale. Source: Cochlear in-house material.A flow chart for fitting the hearing aid in bimodal devices is shown in Figure 4. This recommended protocol has been validated in children and found to provide good binaural benefits.24 For the reader wishing more in-depth training, a tutorial is available at www.cochlearcollege.com. Ching et al. have also published excellent articles on fitting and adjusting the hearing aid for children wearing bimodal devices.2,35Figure 4: Optimizing the hearing aid in bimodal fitting. Source: Cochlear in-house material.CONCLUSIONS The use of bimodal devices is the recommended treatment option for children who meet cochlear implant candidacy but who either have some usable hearing in one ear or for other reasons get only one implant. Bimodal devices can be a successful alternative to bilateral hearing aids or to one cochlear implant alone. It is important to remember these three vital rules: (1) Work with the implant center to make sure the implant map is stable. (2) Fit the hearing aid frequency response for maximal speech intelligibility. (3) Balance the loudness with the cochlear implant and hearing aid. Bimodal fitting can provide optimal use of the different, but potentially complementary, bilateral cues provided by the acoustic amplifier and the electric stimulation from the implant.

In this first section of a two-part article we offer an overview of research on listeners' abilities to learn to hear the spectral-temporal details of simple and complex sounds, both speech and non-speech. In the second article, to appear in the October issue of The Hearing Journal, we will describe a new training system based on that science that has recently completed clinical validation trials with users of hearing aids and of cochlear implants.1,2

Assessing Listening Skills in Children with Cochlear Implants: Guidance for Speech-Language Pathologists

Hearing Preservation in Patients With a Cochlear Implant

Intervention for a Child with Auditory Neuropathy/Dys-synchrony

Improvements in digital amplification, cochlear implants, and other innovations have extended the potential for improving hearing function; yet, there remains a need for further hearing improvement in challenging listening situations, such as when trying to understand speech in noise or when listening to music. Here, we review evidence from animal and human models of plasticity in the brain's ability to process speech and other meaningful stimuli. We considered studies targeting populations of younger through older adults, emphasizing studies that have employed randomized controlled designs and have made connections between neural and behavioral changes. Overall results indicate that the brain remains malleable through older adulthood, provided that treatment algorithms have been modified to allow for changes in learning with age. Improvements in speech-in-noise perception and cognition function accompany neural changes in auditory processing. The training-related improvements noted across studies support the need to consider auditory training strategies in the management of individuals who express concerns about hearing in difficult listening situations. Given evidence from studies engaging the brain's reward centers, future research should consider how these centers can be naturally activated during training.

Clinical practice regarding children's candidature for cochlear implantation varies internationally, albeit with a recent global trend toward implanting children with more residual hearing than in the past. The provision of either hearing aids or cochlear implants can influence a wide range of children's outcomes. However, guidance on eligibility and suitability for implantation is often based on a small number of studies and a limited range of speech perception measures. No recent reviews have catalogued what is known about comparative outcomes for children with severe hearing-loss using hearing aids to children using cochlear implants. This article describes the findings of a scoping review that addressed the question "What research has been conducted comparing cochlear implant outcomes to outcomes in children using hearing aids with severe hearing-loss in the better-hearing ear?" The first objective was to catalogue the characteristics of studies pertinent to these children's candidature for cochlear implantation, to inform families, clinicians, researchers, and policy-makers. The second objective was to identify gaps in the evidence base, to inform future research projects and identify opportunities for evidence synthesis. We included studies comparing separate groups of children using hearing aids to those using cochlear implants and also repeated measures studies comparing outcomes of children with severe hearing loss before and after cochlear implantation. We included any outcomes that might feasibly be influenced by the provision of hearing aids or cochlear implants. We searched the electronic databases Medline, PubMed, and CINAHL, for peer-reviewed journal articles with full-texts written in English, published from July 2007 to October 2019. The scoping methodology followed the approach recommended by the Joanna Briggs Institute regarding study selection, data extraction, and data presentation. Twenty-one eligible studies were identified, conducted across 11 countries. The majority of children studied had either congenital or prelingual hearing loss, with typical cognitive function, experience of spoken language, and most implanted children used one implant. Speech and language development and speech perception were the most frequently assessed outcomes. However, some aspects of these outcomes were sparsely represented including voice, communication and pragmatic skills, and speech perception in complex background noise. Two studies compared literacy, two sound localization, one quality of life, and one psychosocial outcomes. None compared educational attainment, listening fatigue, balance, tinnitus, or music perception. This scoping review provides a summary of the literature regarding comparative outcomes of children with severe hearing-loss using acoustic hearing aids and children using cochlear implants. Notable gaps in knowledge that could be addressed in future research includes children's quality of life, educational attainment, and complex listening and language outcomes, such as word and sentence understanding in background noise, spatial listening, communication and pragmatic skills. Clinician awareness of this sparse evidence base is important when making management decisions for children with more residual hearing than traditional implant candidates. This review also provides direction for researchers wishing to strengthen the evidence base upon which clinical decisions can be made.

A Look at AR in the Last Decade

Emotional prosody is known to play an important role in social communication. Research has shown that children with cochlear implants (CCIs) may face challenges in their ability to express prosody, as their expressions may have less distinct acoustic contrasts and therefore may be judged less accurately. The prosody of children with milder degrees of hearing loss, wearing hearing aids, has sparsely been investigated. More understanding of the prosodic expression by children with hearing loss, hearing aid users in particular, could create more awareness among healthcare professionals and parents on limitations in social communication, which awareness may lead to more targeted rehabilitation. This study aimed to compare the prosodic expression potential of children wearing hearing aids (CHA) with that of CCIs and children with normal hearing (CNH). In this prospective experimental study, utterances of pediatric hearing aid users, cochlear implant users, and CNH containing emotional expressions (happy, sad, and angry) were recorded during a reading task. Of the utterances, three acoustic properties were calculated: fundamental frequency (F0), variance in fundamental frequency (SD of F0), and intensity. Acoustic properties of the utterances were compared within subjects and between groups. A total of 75 children were included (CHA: 26, CCI: 23, and CNH: 26). Participants were between 7 and 13 years of age. The 15 CCI with congenital hearing loss had received the cochlear implant at median age of 8 months. The acoustic patterns of emotions uttered by CHA were similar to those of CCI and CNH. Only in CCI, we found no difference in F0 variation between happiness and anger, although an intensity difference was present. In addition, CCI and CHA produced poorer happy-sad contrasts than did CNH. The findings of this study suggest that on a fundamental, acoustic level, both CHA and CCI have a prosodic expression potential that is almost on par with normal hearing peers. However, there were some minor limitations observed in the prosodic expression of these children, it is important to determine whether these differences are perceptible to listeners and could affect social communication. This study sets the groundwork for more research that will help us fully understand the implications of these findings and how they may affect the communication abilities of these children. With a clearer understanding of these factors, we can develop effective ways to help improve their communication skills.

Lessons from LOCHI.

We aimed to determine whether children with severe hearing loss (HL) who use hearing aids (HAs) may experience added value in the perception of speech, language development, and executive function (EF) compared to children who are hard of hearing (HH) or children who are deaf and who use cochlear implants (CIs) and would benefit from CIs over HAs. The results contribute to the ongoing debate concerning CI criteria. We addressed the following research question to achieve this aim: Do children who are HH or deaf with CIs perform better than children with severe HL with HAs with respect to auditory speech perception, and receptive vocabulary and/or EF? We compared two groups of children with severe HL, profound HL or deafness, with CIs or HAs, matched for gender, test age (range, 8 to 15 years), socioeconomic status, and nonverbal intelligence quotient. Forty-three children had CIs (pure-tone average at 2000 and 4000 Hz >85 dB HL), and 27 children had HAs (mean pure-tone average: 69 dB HL). We measured speech perception at the conversational level (65 dB SPL) and the soft speech perception level (45 dB SPL). We established receptive vocabulary using the Peabody Picture Vocabulary Test-III-NL. We tested EF using the Delis Kaplan Executive Function System battery and the Dutch Rey Auditory Verbal Learning Test. We employed the Mann-Whitney U test to compare data between the CI and HA groups. We used Chi-square goodness of fit tests to contrast the CI and HA group distributions with the norm data of children who are typically developing (TD). We harnessed Kendall's Tau-b to investigate relationships between the study variables. Both groups of children, with CIs and Has, obtained ceiling scores for perception of speech on a conversational level. However, the HA group exhibited significantly lower perception on a soft speech level scores (68 %) than the CI group (87%). No difference was present between the receptive vocabulary distributions of the CI and HA groups. The median receptive vocabulary standard scores for both groups were well within the normal range (CI group: 93; HA group: 96). In addition, we did not find any difference in EF between the CI and HA groups. For planning and verbal memory, the distributions of observed scores for children with CIs were different from the expected distributions of children who are TD. In both groups, a large proportion of children obtained below-average scores for planning (CI: 44%; HA: 33%) and for long-term verbal memory (CI: 44%; HA: 35%). In the HA group, perception at a soft speech level was associated with receptive vocabulary and planning. In the CI group, we did not find any associations. Both groups of children with severe and profound HL with HAs exhibit less favorable auditory perception on the soft speech level, but not at a conversational level, compared to children who are HH or deaf with CIs. Both groups, children with CIs and HAs, only exhibit more problems in planning and verbal memory than the norm groups of children who are TD. The results indicate that to obtain age-appropriate levels of receptive vocabulary and EF, the perception at the soft speech level is a necessary but not sufficient prerequisite.

Pediatric Cochlear Implantation: Who is a Candidate in 2020?

Sheila is quietly listening to her audiologist discuss the next steps in the process of getting her first set of hearing aids. They have decided on the style and color of the devices and the audiol...