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AJA Review Audiologic Management of Auditory Neuropathy Spectrum Disorder in Children: A Systematic Review of the Literature Patricia Roush,a Tobi Frymark,b Rebecca Venediktov,b and Beverly Wangb Purpose: This review summarizes current evidence related to the audiologic management of children with auditory neuropathy spectrum disorder ( ANSD). Method: A systematic search of the literature was conducted in 25 electronic databases (e.g., PubMed, CINAHL, and ERIC) using key words such as auditory neuropathy, auditory neuropathy spectrum disorder, auditory neuropathy/ dyssynchrony, and hearing loss. Eighteen studies met the inclusion criteria by addressing 1 or more of 8 clinical questions. Studies were evaluated for methodological quality, and data regarding participant, intervention, and outcome variables are reported. Results: Fifteen of the 18 studies addressed the use of cochlear implantation, and 4 addressed conventional acoustic amplification. All participants demonstrated improved auditory performance; however, all 18 studies were considered exploratory, and many had methodological limitations. Conclusion: The clinical evidence related to intervention for ANSD is at a very preliminary stage. Additional research is needed to address the efficacy of acoustic amplification and cochlear implantation in children with ANSD and the impact of this disorder on developmental outcomes. A Although it was recognized that “neuropathy” does not apply in all cases, the term has become widely used in reference to this population. The etiology of ANSD is multifactorial and includes genetic, congenital, and acquired conditions. Both syndromic (e.g., Charcot-Marie-Tooth disease and Friedreich’s ataxia) and nonsyndromic genetic forms of ANSD (DFNB9/OTOF; Varga et al., 2003; Yasunaga et al., 1999) have been reported. Risk factors reported include prematurity, hyperbilirubinemia, ototoxic drug exposure (Madden, Rutter, Hilbert, Greinwald, & Choo, 2002; Rance et al., 1999), and various neurological disorders such as mitochondrial disease (Deltenre, Mansbach, Bozet, Clercx, & Hecox, 1997; Starr et al., 1996). Initially, ANSD in children was thought to be a rare form of sensorineural hearing loss (SNHL). However, a recent systematic review by Vlastarakos, Mikopoulous, Tavoulari, Papacharalmous, and Korres (2008) indicated that ANSD accounts for approximately 8% of the newly diagnosed cases of hearing loss in children each year. Other studies suggest that ANSD occurs in 2.4% to 15% of pediatric cases identified with permanent hearing loss (Rance, 2005; Sininger, 2002; Tang, McPherson, Yuen, Wong, & Lee, 2004). Among the clinical characteristics reported are speech perception difficulties that are often disproportionate to hearing threshold levels (Starr et al., 1996), and difficulty hearing in noise (Kraus et al., 2000; Rance et al., 2007). Furthermore, degree of hearing loss, based on detection levels, ranges from normal to profound and in some cases may be transient or degenerative in nature (Deltenre et al., uditory neuropathy, a condition first described in the mid-1990s by Starr, Picton, Sininger, Hood, and Berlin (1996), is a disorder characterized by absent or severely abnormal auditory brainstem response (ABR) with intact outer hair cell function, as evidenced by the presence of evoked otoacoustic emissions and /or cochlear microphonics. Although current terminology implies dysfunction of the auditory nerve, possible causes include damage to the inner hair cells, to the synapse between the inner hair cell and auditory nerve, or in the auditory nerve itself (Buchman et al., 2006; Rance, Cone-Wesson, Wunderlich, & Dowell, 2002). Recently the term auditory neuropathy was expanded to auditory neuropathy spectrum disorder (ANSD) to acknowledge the heterogeneous and multifaceted nature of this condition (Guidelines Development Conference, 2008). a University of North Carolina, Chapel Hill American Speech-Language-Hearing Association, Rockville, MD Correspondence to Tobi Frymark: [email protected] Editor: Sheila Pratt Associate Editor: Ruth Litovsky Received August 4, 2010 Revision received March 7, 2011 Accepted July 18, 2011 DOI: 10.1044/1059-0889(2011/10-0032) b Key Words: auditory neuropathy, auditory neuropathy spectrum disorder, cochlear implantation, acoustic amplification, hearing loss American Journal of Audiology • Vol. 20 • 159–170 • December 2011 • A American Speech-Language-Hearing Association 159 1999; Franck, Rainey, Montoya, & Gerdes, 2002; Kraus et al., 2000; Madden et al., 2002; Starr et al., 1998). As universal newborn hearing screening has expanded and as audiologists have become more familiar with the disorder and its diagnosis, additional information has emerged regarding treatment for children with ANSD. Still, the heterogeneous nature of the disorder, compounded by the broad range of auditory abilities, makes the audiologic management for these children challenging and at times uncertain. Currently, two technologies—acoustic amplification and cochlear implantation—are recommended for children with ANSD. Not surprisingly, there has been considerable debate among clinicians and investigators regarding the choice of and expected benefit from these technologies. Those opposed to conventional amplification emphasize the presumed limited benefits of hearing aid (HA) use for individuals with normal outer hair cell functioning, arguing that acoustic amplification offers only louder, more distorted signals (Berlin, 1999). Others have expressed concern regarding the potential consequence of acoustic trauma to existing outer hair cells (Doyle, Sininger, & Starr, 1998). Concern has also been raised regarding cochlear implant (CI) candidacy for children with ANSD based on the reported involvement of the auditory nerve (Miyamoto, Kirk, Renshaw, & Hussain, 1999). Others have expressed concern regarding cochlear implantation because of spontaneous improvement in hearing thresholds reported in a subset of children, especially those with hyperbilirubinemia (Madden et al., 2002). Although much has been learned about ANSD since its original description by Starr and colleagues (1996), many gaps remain in our knowledge of the clinical presentation and audiologic management of the disorder in children. In its most recent position statement, the Joint Committee on Infant Hearing (JCIH, 2007) recommended that children with auditory neuropathy-type hearing loss undergo a trial with amplification and that decisions regarding continued HA use be guided by the benefits derived from amplification. In an effort to provide further guidance to clinicians working with this population, consensus guidelines were recently developed by an expert panel at an international conference (Guidelines Development Conference, 2008). Although the guidelines generated by the panel were not based on a systematic review of the evidence, panel members examined the literature in their areas of expertise and prepared summary statements as a resource for clinicians involved with the identification and management of infants presenting with ANSD. The panel noted that many of the recommendations made for assessment and management of ANSD were consistent with those recommended by the JCIH (2007); however, additional considerations for acoustic amplification, cochlear implantation, and habilitation were outlined. The panel also emphasized the need for further research on all aspects of the disorder, including a more in-depth examination of the scientific literature. In light of the diverse nature of ANSD, the unresolved controversies surrounding intervention recommendations, and the high degree of interest among audiologists (American SpeechLanguage-Hearing Association [ASHA], 2008), a systematic review was undertaken to examine the current state of the evidence. This report documents the findings of an evidence-based systematic review (EBSR) conducted by ASHA’s National Center for Evidence-Based Practice in Communication Disorders. The primary aim of this review was to synthesize and analyze existing evidence pertaining to audiologic treatment of children, birth to 18 years of age, diagnosed with ANSD. The EBSR highlights the current state of evidence for children diagnosed with ANSD and characterizes findings by severity and type of intervention. The report is intended to serve as a resource to clinicians as they weigh options for and against various treatment approaches for children with ANSD. The findings reported here, along with other crucial factors such as social/emotional development, speech-language skills, and parent preference, will assist clinicians in determining what type of intervention approach best meets the needs of children with ANSD. The findings also elucidate the quality and level of existing evidence in order to highlight areas where further study is needed. Eight clinical questions were established, a priori, to address the specific population, interventions, and outcomes of interest (see Table 1). The population reviewed included children diagnosed with ANSD from birth to 18 years of age. The targeted interventions were (a) conventional acoustic amplification including HAs or frequency modulated (FM) systems and (b) cochlear implantation. Several outcomes were considered, including the impact of HAs and CIs on a child’s functional hearing and communication skills, speech and language skills, academic performance, and social skills. Auditory outcomes included, but were not limited to, Table 1. Clinical questions included in the evidence-based systematic review. Question number 1 2 3 4 5 6 7 8 160 American Journal of Audiology • Vol. 20 • 159–170 • December 2011 Clinical question Amplification For children with the diagnosis of auditory neuropathy, what is the effect of acoustic amplification on auditory outcomes? For children with the diagnosis of auditory neuropathy, what is the effect of acoustic amplification on speech and language outcomes? For children with the diagnosis of an auditory neuropathy, what is the effect of acoustic amplification on academic outcomes? For children with the diagnosis of an auditory neuropathy, what is the effect of acoustic amplification on social emotional/parent outcomes? Cochlear implantation For children with the diagnosis of an auditory neuropathy, what is the effect of cochlear implantation on auditory outcomes? For children with the diagnosis of auditory neuropathy, what is the effect of cochlear implantation on speech and language outcomes? For children with the diagnosis of an auditory neuropathy, what is the effect of cochlear implantation on academic outcomes? For children with the diagnosis of an auditory neuropathy, what is the effect of cochlear implantation on social emotional/parent outcomes? unaided and aided pure-tone and speech detection thresholds, unaided and aided speech perception measures, hearing in noise, dichotic listening, and temporal processing (e.g., gap detection). Examples of speech and language outcomes included receptive and expressive language abilities and speech intelligibility. With increased access to speech, language, and other environmental sounds and signals, it was considered important to examine the impact of these interventions on academic performance. Academic outcomes included, but were not limited to, reading, written language, spelling, and educational achievement. Finally, as with any intervention, it was considered important to examine the effects of conventional acoustic amplification or cochlear implantation on social and emotional well-being. Social / emotional outcomes targeted measures of the child’s communication attitude or behavior (e.g., communication attitude test, severity rating scales, self-report rating, quality of life indicators, and social and communication measures). Parent outcomes focused on any measure of parent attitude on communication (e.g., parent rating scales and parent surveys) or a change in parental communication (e.g., pre/post parent communication patterns). Method A review of the literature was conducted from October 2009 to July 2010 using search parameters and inclusion/ exclusion criteria set a priori. Approximately 25 databases were searched (e.g., CINAHL [Cumulative Index to Nursing and Allied Health Literature], ERIC [Education Resources Information Center], and PubMed) using key words pertaining to auditory neuropathy, ANSD, auditory dyssynchrony, and hearing loss. A full list of databases and key words is provided in the supplementary material (Appendix A) affiliated with this article. Eligibility criteria for inclusion of studies were as follows: treatment studies published in peerreviewed journals from 1990 to July 2010; publications in English; and studies including children ages ≤18 years diagnosed with ANSD receiving acoustic amplification (HA or FM system) or cochlear implantation as a primary audiologic intervention. Exclusionary criteria were studies based on animal models, pharmacological models, or studies with mixed ages, mixed populations, or mixed treatments (e.g., combined HA and CI) unless data allowed for separate analyses. Studies in which pretreatment and posttreatment measures or raw data were not reported were also excluded.1 It is important to note that studies were not excluded based on study design. Although limiting studies to group designs or randomized clinical trials would reduce the potential for bias, the inclusion of all studies provides a more comprehensive look at the current body of evidence. Based on the aforementioned criteria, the second and third authors independently reviewed all citations for relevance and completed a hand search of all references. The first author reviewed the full bibliography of studies for 1 When applicable, correspondence with primary author was attempted to obtain missing data. completeness prior to final inclusion/exclusion. Any disagreement among authors regarding study eligibility was resolved by consensus and documented as such. Additionally, the second and third authors, blinded to each other’s results, evaluated studies for methodological rigor based on ASHA’s levels of evidence scheme (Frymark et al., 2009; Mullen, 2007). Studies were evaluated for methodological quality based on the following indicators: (a) adequate description of protocol for sufficient study replication, (b) blinding of assessors, (c) random sampling/allocation procedures, (d) evidence of treatment fidelity, (e) reporting significance ( p values) of findings or providing adequate data to allow for statistical calculations, (f ) reporting of effect size and confidence intervals or providing sufficient data to calculate precision of treatment effects, and (g) use of intention-totreat analyses. In addition to evaluating methodological quality, pertinent demographic, intervention, and outcomes data were extracted from each study. Results Figure 1 outlines the systematic findings of the literature search, which yielded a total of 202 citations, of which 37 were preliminarily accepted. Half of these studies (51%, 19/37) were further excluded upon review of the full text. In total, 184 studies were eliminated from the review for the following reasons: (a) did not examine a target intervention (40%, 73/184); (b) was not the population or age under review (22%, 40/184); (c) was not a study or systematic review of the literature (12%, 22/184); (d) did not provide original data or adequate data for analyses (12%, 22/184); (e) was not a peer-reviewed study (9%, 17/184); or (f ) did not directly address a clinical question (5%, 10/184). Eighteen studies were included in the final analysis (see Appendix B in the supplementary material for a full list of excluded studies and reasons for exclusion). Interrater reliability of study eligibility agreement between coders was good, K = .787 (Cohen, 1960; Landis & Koch, 1977). Participant Characteristics Table 2 details the 115 participants across 18 studies; 60 were male, 39 were female, and gender was not reported for 16. The total number of participants accounts for overlapping subjects reported in two Shallop studies (Shallop, 2002; Shallop, Peterson, Facer, Fabry, & Driscoll, 2001) and two of three cohorts reported in the Teagle et al. (2010) study. Age of ANSD diagnosis was early (≤4 years) for 66 participants. One study (Santarelli, Scimemi, Dal Monte, Genovese, & Arslan, 2006) presented a single case report of a female diagnosed with ANSD at age 14. For the remaining 48 participants, age at diagnosis was not reported. A number of studies (n = 14) provided medical comorbidities or risk factors associated with the disorder (e.g., hyperbilirubinemia, Friedreich’s ataxia, or antibiotic treatments). The majority of the participants (75%, 86/115) exhibited hearing loss ranging from severe to profound, while 18% (21/115) exhibited moderate to severe or moderate hearing loss. Four participants (3%) exhibited mild hearing loss. Hearing severity was Roush et al.: ANSD Systematic Review 161 Figure 1. Literature search selection and identification process for inclusion in the evidencebased systematic review (EBSR). not reported for four participants. Severity of hearing loss was primarily based on author report. Acoustic Amplification Table 3 outlines the intervention characteristics and major findings of the 28 participants contributing data to Clinical Question 1 (see Table 1); the majority of these (n = 26) were in two case series reports (Rance et al., 1999, 2002). Severity of hearing impairments ranged from mild to profound (mild = 14%, moderate = 29%, moderate to severe = 14%, severe = 7%, and profound = 36%), and age of ANSD diagnosis ranged from 2 to 36 months. The authors from three studies (Deltenre et al., 1999; Lin, Chen, & Wu, 2005; Rance et al., 1999) reported that participants were fitted with binaural amplification. Participants from the two Rance et al. studies (1999, 2002) were fitted using the National Acoustics Laboratory prescriptions for gain, frequency response, and output limiting levels for HA fitting (Byrne & Dillon, 1986). The authors also reported that verification of HA settings was completed. Limited information was provided regarding prescriptive fitting method or verification strategy for the Deltenre et al. (1999) and Lin et al. (2005) studies. Of the four included studies, three (Deltenre et al., 1999; Lin et al., 2005; Rance et al., 2002) provided pre- and posttreatment data to investigate the effects of acoustic amplification on pure-tone thresholds. All four studies examined the effects of amplification on speech perception. No studies addressed speech, language, or academic outcomes (Clinical Questions 2, 3, and 4; see Table 1). Unaided and aided pure-tone thresholds were provided for 20 participants with ANSD: 18 from the Rance et al. (2002) case series study and two from the Deltenre et al. (1999) and Lin et al. (2005) case study reports. Children from Rance et al. (2002) were identified with ANSD at a mean age of 6 months, with pure-tone thresholds ranging from mild to profound. Mean pure-tone average (PTA) was 70 dB HL at 0.5, 1, and 2 kHz prior to amplification. HAs were fitted at a mean age of 8 months, with audiologic follow up ≥12 months postintervention. Although aided PTA thresholds were not reported at posttesting, the authors noted improved aided detection thresholds of approximately 30 dB for individual frequencies (see Table 3). The two additional case studies (Deltenre et al., 1999; Lin et al., 2005) revealed similar findings. Deltenre et al. (1999) investigated the unaided and aided performance of a female with auditory neuropathy-type hearing loss with pure-tone thresholds in the moderate range diagnosed at 2 months of age, while Lin and colleagues (2005) examined a male diagnosed with auditory neuropathy-type hearing loss with pure-tone thresholds in the profound range at age 3. Both authors reported improvement in aided PTAs of approximately 20 dB and 60 dB, respectively. The four included studies (Deltenre et al., 1999; Lin et al., 2005; Rance et al., 1999, 2002) also assessed aided speech perception outcomes of participants with ANSD. Of the 24 of 28 participants with probability data reported, half (50%, 12/24) demonstrated no significant difference in aided speech perception abilities. The single case report by Lin et al. (2005) reported no significant difference ( p > .01) on the Mandarin Auditory Perception Test Battery (Wu & Yang, 2003) during a 2-year treatment period; however, it should be noted that the participant in this study had unaided pure-tone thresholds of 111 dB HL and >112 dB HL (fourfrequency PTA). Rance and colleagues (2002) reported mixed speech perception scores for children with ANSD who used amplification for a minimum of 12 months prior to participating in the study. Seven of 15 participants tested exhibited no significant difference in Phonetically Balanced Kindergarten test (PBK; Haskins, 1949) phoneme scores in the aided condition. The remaining eight showed a mean difference in aided versus unaided PBK phonemes of 57% with a mean aided PBK phoneme score of 67%. Interestingly, cortical evoked event-related potentials were present 162 American Journal of Audiology • Vol. 20 • 159–170 • December 2011 Table 2. Subject variables—all included studies. Audiologic findings N Gender (M / F ) Age at diagnosis Buss et al. (2002) 4 NR Birth Deltenre et al. (1999) 1 0/1 2 months Jeong et al. (2007) 9 5/4 M = 20 months Lin et al. (2005) Madden et al. (2002) 1 2 1/0 1/1 Mason et al. (2003) Miyamoto et al. (1999) 1 1 Rance & Barker (2008) Rance et al. (1999) Rance et al. (2002) Citation Risk factors/ medical comorbidities ABR OAE CM HL severity Previous intervention Roush et al.: ANSD Systematic Review P3 = Mondini’s malformation P1, P2, P4 = NR Hyperbilirubinemia, respiratory distress 2 hyperbilirubinemia – – + Severe-profound HA – – + Moderate NR – + NR None – – NR NR 6 severe-profound, 3 CNT Profound Profound HA 36 months NR 3– 6+ + + 0/1 1/0 NR 48 months None Friedreich’s ataxia – – + + + NR Moderate Profound 10 8 7/3 NR ≤3 months ≤9 months – – + NR + + 18 14/4 M = 6 months – 7– 11+ + Raveh et al. (2007) Rouillon et al. (2006) 4 2 NR 0/2 – NR + NR + NR Santarelli et al. (2006) Shallop (2002)a Shallop et al. (2001)a Teagle et al. (2010) 1 10 5 Group B = 15 0/1 6/4 3/2 9/6 NR P1 = 22 months P2 = 10 months 14 years M = 14 months 38 months NR 6 jaundice, 4 hypoxia 4 jaundice, 3 hypoxia, 1 low birth weight, 1 none 7 jaundice, 6 hypoxia, 1 hydrocephalus, 1 meningitis, 2 none NR Genetic Systemic sclerosis Congenital deafness NR 9 prematurity, 7 bronchopulmonary dysplasia, 3 hyperbilirubinemia, 4 retinopathy – – – – + + + NR + + + + Group C = 26 15/11 NR – NR + 1 1 1/0 0/1 35 months Birth 10 prematurity, 2 bronchopulmonary dysplasia, 1 hyperbilirubinemia, 1 Turner’s syndrome, 1 sensorimotor neuropathy, 11 none NR Hyperbilirubinemia – NR – NR + NR Trautwein et al. (2000) Vermeire et al. (2003) Severe-profound 2 mild, 2 moderate, 4 profound 2 mild, 5 moderate, 4 moderate-severe, 2 severe, 5 profound Severe-profound Profound Severe Severe-profound Severe-profound 2 moderate, 1 moderate-severe, 3 severe, 2 severe-profound, 6 profound, 1 CNT 5 moderate, 5 severe, 16 profound Severe-profound Profound HA HA FM NR HA FM HA None NR HA HA None NR HA HA HA HA HA Note. ABR = auditory brainstem response; OAE = otoacoustic emissions; CM = cochlear microphonics; HL = hearing level; NR = not reported; P = participant; + = present; – = absent; HA = hearing aid; CNT = could not test; FM = frequency modulated system. a Shallop (2002) and Shallop et al. (2001) had overlapping participants. 163 Table 3. Studies examining acoustic amplification. Citation Deltenre et al. (1999) N 1 Age at intervention 48 months Fitting method/model NR/binaural Duration/ compliance 1 NR NR/binaural 30 months Rance et al. (1999) 8 NR BTE/binaural ≤12 months 18 8 months BTE/ NR a Unaided 50 dB PTA Speech identification at 55 dB Phonemes 0% Words 0% a 111 dB/>112 dB PTA (R/L) MAPTB 46% PBK words P13 8% P16 32% Picture Vocabulary Test b P8 3/12 P10 1/12 P12 2/12 P14 2/24 P15 1/12 P17 3/12 c 70 dB PTA 5 kHz NR 1 kHz NR 2 kHz NR 4 kHz NR PBK phonemes (n = 15) 8% 36 months Lin et al. (2005) Rance et al. (2002) Outcomes measured ≤12 months Aided 29 dB 96% 80% 50 dB/51 dB 51% 43% 88% 3/12 1/12 8/12 4/24 8/12 2/12 NR 42 dB 42 dB 44 dB 44 dB 32% Note. PTA = pure-tone average; MAPTB = Mandarin Auditory Perception Test Battery (Wu & Yang, 2003); BTE = behind the ear; PBK = Phonetically Balanced Kindergarten test (Haskins, 1949). a PTA threshold at 0.5, 1, 2, and 4 kHz. Subtest of the PLOTT Test (Plant & Westcott, 1983). c PTA threshold at 0.5, 1, and 2 kHz. b in the group of children with significant open-set speech abilities but were absent in those who had no open-set abilities. In comparison, a matched control group of children with non-auditory neuropathy SNHL from the same study showed a mean difference score of 49%, with a mean aided PBK phoneme score of 66%. Similar findings were reported by Rance et al. (1999), with significant differences found between unaided and aided speech recognition ( p < .01) in four of the eight participants tested. Although probability data were not reported by Deltenre et al. (1999), the authors also reported gains of ≥80% in aided speech recognition for speech presented at 55 dB HL. While outcome data showing the effects of acoustic amplification for children with ANSD are limited, the results of this review suggest that some children with ANSD benefit from improved aided detection levels with use of HAs. There appears to be a subset of children who experience benefits in aided speech perception abilities in addition to improved pure-tone detection thresholds. Cochlear Implantation Fifteen studies (see Table 4) examined the effects of CI interventions for 88 children who had been diagnosed with ANSD from birth to 14 years of age. Eighty-two participants received CI intervention at ≤5 years of age (range = 21– 68 months), and two participants (one each from Miyamoto et al., 1999, and Santarelli et al., 2006) received a CI at ages 10.9 and 18 years, respectively. Two studies (Lin et al., 2005; Raveh, Buller, Badrana, & Attias, 2007) did not provide information regarding age at intervention. The majority of studies (80%, 12/15) reported unsuccessful trials of acoustic amplification (HA and /or FM systems) prior to CI intervention. Of the remaining three studies, two (Mason, De Michele, Stevens, Ruth, & Hashiasaki, 2003; Shallop, 2002) did not provide previous intervention history, while one (Santarelli et al., 2006) indicated no HA trial prior to CI intervention. Contrary to the heterogeneity among children receiving hearing amplification interventions, 85% of the children who received cochlear implantation exhibited severe to profound hearing loss (n = 75). All 15 studies contributed data to Clinical Question 5 (see Table 1). Six studies reported changes in pure-tone thresholds (Buss et al., 2002; Jeong, Kim, Kim, Bae, & Kim, 2007; Mason et al., 2003; Miyamoto et al., 1999; Trautwein, Sininger, & Nelson, 2000; Vermeire, Brokx, Van de Heyning, Cochet, & Carpentier, 2003), and 12 reported speech perception outcomes (Jeong et al., 2007; Lin et al., 2005; Madden et al., 2002; Miyamoto et al., 1999; Rance & Barker, 2008; Raveh et al., 2007; Rouillon et al., 2006; Santarelli et al., 2006; Shallop, 2002; Shallop et al., 2001; Teagle et al., 2010; Trautwein et al., 2000). Raveh et al. (2007) also reported speech and language outcomes (Clinical Question 6). No studies were found that examined social/emotional or academic outcomes after cochlear implantation (Clinical Questions 7 and 8). Similar to the findings pertaining to HA interventions, all participants with ANSD exhibited improved pure-tone detection thresholds after CI. Six studies reported improvement in PTA thresholds ranging from 40 to 87 dB, five of which assessed PTAs at 0.5, 1, 2, and 3 or 4 kHz (Buss 164 American Journal of Audiology • Vol. 20 • 159–170 • December 2011 Table 4. Studies examining cochlear implantation (CI). Citation N Buss et al. (2002) 4 Jeong et al. (2007) Age at intervention Duration/ compliance Model Clarion 12 months 9 P1 = 25 months P2 = 28 months P3 = 68 months P4 = 62 months M = 4 years Nucleus M = 24 months Lin et al. (2005) 1 NR Clarion NR Madden et al. (2002) 2 P1 = 39 months Clarion 7 months Mason et al. (2003) Miyamoto et al. (1999) 1 P2 = 21 months 32 months Clarion NR 24 months 5 months 1 10.9 years Nucleus 12 months Rance & Barker (2008) Raveh et al. (2007) 10 M = 33 months Nucleus >24 months 4 NR NR NR Rouillon et al. (2006) Santarelli et al. (2006) 2 P1 = 35 months P2 = 48 months 18 years Nucleus Nucleus Nucleus 1 months 18 months NR d 1 Shallop (2002) 10 M = 45 months Shallop et al. (2001)d Teagle et al. (2010) 5 M = 53 months 15 Group B M = 30 months 26 Group C M = 63 months Trautwein et al. (2000) 1 39 months Vermeire et al. (2003) 1 R = 29 months L = 52 months 9 nucleus 1 clarion Nucleus NR Outcomes measured Pre-CI Post-CI 101 dB 101 dB 104 dB 90 dB 83 dB 0 5% 3% 36 dB 31 dB 36 dB 26 dB 29 dB 5 59% 46% 35% 25% 70% 70% 50% 64% 90% 90% 100% 100% 100% 88% 0/40 70–80 dB 27/40 35–40 dB PTAc PBK Words Phonemes MW test 97 dB 4% 4% 12% <40% IT-MAIS Ling Test CAP MUSS MAIS MAIS TIPI Vowel identification Consonant identification MAIS 18% .75 1 3% 4/40 4/40 39 dB 4% 4% 20% >55% M = 59.6% 56% 5 3.5 29% 40/40 31/40 52% 95% 25% 55% 8% 91% 1 4 26% (21%) 79% (16%) 14% 49% 54% (34%) 76% (22%) 22/30 1 104 dB 110 dB 27/30 4 40 dB 23 dB a P1 PTA P2 PTAa P3 PTAa P4 PTAa PTAb (n = 6) CAP MW test Common phrase test MAPTB Spondee Vowel Tone Phrase Sentence Closed-set discrimination IT-MAIS PTAa M = 18 months ESP 10 nucleus 4 HiRes90 1 sonota 5 Nucleus 8 NucleusFreedom 8 HiRes90 3 Clarion 2 Med El Nucleus M = 20 months IT-MAIS M = 50 months PPK Words Phonemes Nucleus 9 months after 2nd CI 12 months Ling Test ESP PTAb (18 months) PTAb Note. CAP = Categories of Auditory Performance (Archbold et al., 1995); MW = monosyllabic word; IT-MAIS = Infant-Toddler Meaningful Auditory Integration Scale (Zimmerman-Phillips, Osberger, & Robbins, 1997); Ling Test = Ling 6 Sound Test (Ling, 1976); MUSS = Meaningful Use of Speech Scale (Robbins & Osberger, 1991); MAIS = Meaningful Auditory Integration Scale (Robbins, 1998); TIPI = Test di Identificazione Parole Infantili (Test of Identification of Words for Children; Arslan et al., 1997); ESP = Early Speech Perception Test (Moog & Geers, 1990); L = left; R = right. a PTA threshold at 0.5, 1, 2, and 4 kHz. PTA threshold at 0.5, 1, 2, and 3 kHz. c PTA threshold at 0.5, 1, and 2 kHz. d Shallop (2002) and Shallop et al. (2001) had overlapping participants. b Roush et al.: ANSD Systematic Review 165 et al., 2002; Jeong et al., 2007; Mason et al., 2003; Trautwein et al., 2000; Vermeire et al., 2003), and one (Miyamoto et al., 1999) that assessed PTA thresholds at 0.5, 1, and 2 kHz. Improvements were also noted across studies examining speech perception outcomes. However, it is important to note that studies varied greatly in type of speech perception measure reported, making it difficult to interpret the results across studies. Two studies (Rance & Barker, 2008; Shallop et al., 2001) reported significant differences in speech perception ability after cochlear implantation. Rance and Barker (2008) examined the speech perception skills of 10 children with a mean age at CI of 33 months, nine of whom were diagnosed with ANSD at ≤3 months of age. The authors reported significant improvement in consonant-nucleus-consonant (CNC) phoneme scores ( p = .006) after CI. Additionally, 10 participants in the Shallop (2002) study who completed pre- and posttesting demonstrated significant improvement on the Meaningful Auditory Integration Scale (MAIS; Robbins, 1998; p < .0001). These participants were diagnosed with ANSD at 14 months of age, receiving CI at a mean age of 45 months. Although pre-CI data were not provided, Shallop et al. (2001) also reported significant improvements in speech awareness thresholds and/or speech reception thresholds of five participants with auditory neuropathy-type hearing loss. In this study, mean age of implantation was 53 months, and mean diagnosis was 38 months of age. Mean duration of CI use was reportedly 18 months. Additionally, the authors reported that participants were unable to discriminate speech (Early Speech Perception Test [ESP] Category 1; Moog & Geers, 1990) prior to CI intervention and demonstrated consistent ability to discriminate words (ESP Category 4) postimplantation. Lastly, the recent longitudinal study by Teagle et al. (2010) followed the largest cohort of participants receiving CI interventions to date (n = 52). In this study, participants were identified with ANSD through newborn hearing screening protocols. The mean preoperative PTA threshold was 88 dB HL, and the mean duration of HA use prior to CI was reportedly 26 months. Of the 52 participants studied, 11 (Group A) did not have sufficient pre- and postdata for analyses; however, the remaining 41 were included and demonstrated improved speech perception abilities. One cohort (Group B) consisted of 15 participants with CI use for >6 months who were unable to participate in open-set speech perception testing due to young age or development delays; however, 13 of 15 participants in this group provided preand postdata on the Infant-Toddler Meaningful Auditory Integration Scale (Zimmerman-Phillips, Osberger, & Robbins, 1997) with a mean improvement of 53% postimplantation. The other cohort (Group C) had 26 CI users who could perform open-set measures. Although pre-CI data were not reported for all 26 participants who completed PBK testing, the authors reported a mean improvement of 40% and 27%, respectively, for PBK words and phonemes, with mean PBK phoneme and word scores postimplantation of 76% (SD = 22%, range = 24%–100%) and 54% (SD = 34%, range = 4%–100%), respectively.2 2 The first author was a coauthor on Teagle et al. (2010) and provided the PBK data for Cohort C. The findings detailed in Table 4 suggest that children with ANSD with thresholds in the severe to profound range may benefit from CI interventions. Interestingly, Rance and Barker (2008) found no significant difference in performance on CNC phoneme scores between children with ANSD who received CI intervention compared to a group who received HA intervention, d = 0.20, 95% CI [–0.69, 1.07]. They did note that children in their cohort who were among the poorer performers with HAs had already been referred for CI. Furthermore, the authors went on to report that 10 age-matched CI users with SNHL performed significantly better than both the CI and HA users with ANSD ( p = .0006). Finally as mentioned above, only one study (Raveh et al., 2007) examined the effect of CI intervention on speech and language outcomes of children with ANSD. Of the 18 participants with severe to profound loss initially included in the study, only four had sufficient follow-up testing post-CI using the Meaningful Use of Speech Scale (Robbins & Osberger, 1991) allowing for inclusion in the review. Mean performance was 3% preimplantation and 29% postimplantation. Although sufficient pre- and postdata were not provided by Buss and colleagues (2002) for inclusion in Clinical Question 6 (see Table 1), the authors noted that participants with ANSD using CI performed comparably to age-matched CI users with SNHL on a speech production test (Paden–Brown Test; Paden & Brown, 1992). The authors stated that three of the four participants performed “within or slightly above the confidence interval one standard deviation around the control group mean” (Buss et al., 2002, pp. 330–331). Methodological Quality The methodological quality of the included studies is outlined in Table 5. Level of interrater agreement between authors for appraisal of study quality was good (K = .742; Landis & Koch, 1977). All studies were case series reports or single case studies. While the majority of studies (67%, 12/18) provided an adequate description of the treatment protocol, all 18 studies recruited participants using a method of convenience sampling and did not report blinding of assessors. Approximately one third of the studies (39%, 7/18) reported effect size or probability data. Two quality indicators (evidence of treatment fidelity and use of intention-to-treat analysis) were not applicable to the types of studies included in this review and therefore not considered. Discussion The purpose of this EBSR was to investigate the impact of two hearing technologies, acoustic amplification and cochlear implantation, on outcomes in children with ANSD. A systematic review of the literature from 1990 to 2010 yielded 18 studies that met the predetermined inclusion criteria. Only four studies contributed data to address the impact of acoustic amplification on auditory outcomes, while the majority of studies (83%, 15/18) employed cochlear implantation. Only one study (Raveh et al., 2007) provided data on speech and language outcomes after cochlear 166 American Journal of Audiology • Vol. 20 • 159–170 • December 2011 Table 5. Methodological quality of included studies. Citation Study design Adequate description of protocol Assessors blinded Sampling/ allocation Significance ( p values) Precision (ES/CI) Clinical question(s) Buss et al. (2002) Deltenre et al. (1999) Jeong et al. (2007) Lin et al. (2005) Madden et al. (2002) Mason et al. (2003) Miyamoto et al. (1999) Rance & Barker (2008) Rance et al. (1999) Rance et al. (2002) Raveh et al. (2007) Rouillon et al. (2006) Santarelli et al. (2006) Shallop (2002) Shallop et al. (2001) Teagle et al. (2010) Trautwein et al. (2000) Vermeire et al. (2003) Case study Case study Case series Case study Case study Case study Case study Case series Case series Case series Case series Case study Case study Case series Case series Case series Case study Case study + – + + + – + + – – – – + + + + + + – – – – – – – – – – – – – – – – – – Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience Convenience – – – + – – + + + + – – – – + + – – – – – – – – – + – – – – – – – + – – 5 1 5 1, 5 5 5 5 5 1 1 5, 6 5 5 5 5 5 5 5 Note. ES = effect size; CI = confidence interval. implantation. No studies reported social, academic, or parent outcomes for either technology. For both the CI and the HA groups, the majority of participants studied (75%, 86/115) had pure-tone thresholds in the severe or profound range. Yet, Sanyelbhaa Talaat, Kabel, Samy, and Elbadry (2009) found that only 13% of children diagnosed with ANSD exhibited severe to profound hearing loss. The majority of participants (93%, 26/28) studied with HAs were from two studies by Rance et al. (1999, 2002). Two case studies compose the remainder of reports on outcomes with amplification (Deltenre et al., 1999; Lin et al., 2005). Although not directly addressed in this review, Rance et al. (2002) found no correlation between pure-tone thresholds and performance on speech perception tasks for participants with ANSD. This suggests that degree of pure-tone hearing loss may not be a useful predictor of aided speech perception abilities. That is, some children with greater pure-tone hearing loss may experience improved speech perception with amplification, while others with milder degrees of pure-tone loss may not. This finding is in contrast to studies of children and adults with cochlear hearing loss who have been shown to demonstrate poorer speech perception ability with increasing degree of pure-tone hearing loss (Bamford, Wilson, Atkinson, & Bench, 1981; Boothroyd, 1997; Walden, 1984; Yellin, Jerger, & Fifer, 1989). In this EBSR, most of the children with ANSD who received CIs had at least a severe hearing loss (85%, 75/88); only nine with mild or moderate degrees of pure-tone hearing loss were implanted. The majority of CI studies were with children who had reportedly experienced a failed attempt with acoustic amplification; however, information was often limited regarding type of amplification, prescriptive fitting method, verification strategy employed, or tests used to evaluate aided benefit. Although most studies reported improved auditory outcomes for both pure-tone detection thresholds and speech perception scores following cochlear implantation, as is typical in children with cochlear hearing loss, a broad range of postimplantation speech perception abilities was observed. For example, in the Teagle et al. (2010) study, of the 41 of 52 implanted children who had speech perception measures, only 26 were able to perform open-set word recognition testing despite >2 years of device use. Twenty-seven percent of those able to perform open-set testing achieved a score of <30% on PBK word testing, which is below the current level of performance established by CI manufacturers in cooperation with the U.S. Food and Drug Administration as criteria level for determining implant candidacy (U.S. Department of Health and Human Services, 2009). The findings from this review do not resolve the controversies surrounding the audiologic treatment of ANSD in children. The review indicates that some children with ANSD benefit from acoustic amplification, while others benefit from cochlear implantation. Furthermore, the methodological limitations of the studies, the heterogeneity of the participants, and the varied outcomes reported provide insufficient clinical evidence to guide the practicing clinician. Especially lacking are HA performance data for children with ANSD whose pure-tone thresholds are in the mildto-moderate range. Of the four studies that evaluated HA outcomes, only 12 participants had pure-tone thresholds in this range. These findings do, however, provide a foundation for further study. Most of the studies reviewed in this report focus on auditory outcomes obtained from measures of audibility for speech, and the ability to perceive and recognize sounds or words. Further research is needed to address other functional aspects including speech, language, learning, social/ emotional development, and psycho-educational performance. Moreover, considering the heterogeneity of this population and the varied etiologies associated with ANSD (e.g., prenatal, genetic, and neurological), there is a need for additional studies with more homogeneous grouping Roush et al.: ANSD Systematic Review 167 of children to assess the impact of various comorbidities on auditory, speech, language, and learning outcomes. It is important to note that the reports we have cited, and indeed many of those not included in this review, have made important contributions to the existing body of knowledge regarding ANSD. Considering the relatively recent discovery of this clinical population and its low prevalence, it is not surprising that most of the studies investigating ANSD in children represent exploratory research from case series or case study reports. To determine the efficacy of acoustic amplification and cochlear implantation with this population, wellcontrolled, prospective, longitudinal studies are needed on larger groups of children with detailed descriptions of participants. It is important to remember that predicting benefit from cochlear implantation or amplification in young children is difficult, not only for the population of children with ANSD but also for young children with non-auditory neuropathytype hearing loss of varying degrees. Several factors appear to affect outcomes: age at identification and device fitting, quality of the fitting, consistency of use, type of intervention, and degree of parental involvement. Furthermore, there are numerous barriers to obtaining accurate outcome measures in the pediatric population, including age at time of assessment, attention span, speech and language abilities, and cognitive status (Boothroyd, 1997). Despite these challenges, the application of age-appropriate, evidence-based measures should make it possible to acquire additional knowledge regarding the benefits and limitations of currently available hearing technologies for children with ANSD. Other factors needing further investigation include risk factors for ANSD and the role of electrophysiological measures such as cortical event-related potentials and electrocochleography to predict the benefit from various interventions. Key points in this EBSR are summarized as follows: • As many as 10% of children born with permanent hearing loss present with clinical evidence of ANSD, yet few studies are available to guide clinicians in the management of this disorder or to guide families in the decisionmaking process. • Most of the children studied to date have severe or profound hearing loss. Further research with children who have milder degrees of sensitivity loss is needed. • Group studies often include children with a variety of medical histories and etiologies. There is a need for well-controlled, longitudinal prospective studies that provide homogeneous grouping of participants (i.e., genetic, neurological, prematurity/low birth weight, and hyperbilirubinemia). • For children who use amplification and for those using CIs, there is a need for studies that combine electrophysiological measures (i.e., cortical evoked potentials, electocochleography, and ABR) with medical/radiologic evaluation and performance. • Studies of children with CIs who were implanted based on a history of failed attempts using amplification must include a detailed description of the fitting method, verification strategies, and outcome measures employed. This information is needed to assist clinicians and researchers with interpretation of the data and evaluation of the criteria for unsuccessful HA use. • There is a need for studies that go beyond auditory performance to include a full range of developmental outcomes. Although our understanding of ANSD and its management is at an early stage, we hope this EBSR will be useful to clinicians and researchers. Until further scientific evidence is available to direct the clinical decision-making process, audiologists should be guided by the peer-reviewed literature and by the recommendations of national and international professional organizations, in combination with clinical experience, empirical observation, and family preference. Acknowledgments This work was supported by the ASHA National Center for Evidence-Based Practice in Communication Disorders. We thank the authors of the articles studied for their contributions to the research on ANSD. 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