Hearing health care professionals differ in their opinions about appropriate intervention options for children with auditory neuropathy/auditory dys-synchrony (AN/AD). Some experts have suggested that hearing aids offer little to no benefit for children with AN/AD (Berlin, 1999), while others have suggested that in some cases, hearing aid use has proven beneficial (Rance et al., 1999; Rance et al., 2004; Tharpe, 2004; Buchanan et al., 2005). Rance et al. (2004) showed that some children with AN/AD obtain open-set speech recognition performance that is poorer than expected for their degree of hearing loss, while other children with AN/AD performed up to expectations in open-set speech recognition.

Unfortunately, confounding reports provide limited definitive evidence of cochlear implant (CI) benefit for children with AN/AD. Several reports indicate that children who have AN/AD and receive a CI perform similarly to children who have cochlear hearing loss and receive a CI (Shallop et al., 2001; Trautwein et al., 2001; Peterson et al., 2003). Other reports, however, suggest that variable performance is observed when evaluating large groups of pediatric CI recipients with AN/AD (Gibson & Halit, 2007; Runge-Samuelson et al., 2007). The authors' experience has indicated that some children with AN/AD may develop age-appropriate speech and language with hearing aids, while others receive limited benefit from hearing aids but perform relatively well with a CI.

Case Study

"Will" is a 4-year-old boy with a positive medical history of severe hyperbilirubinemia who required an exchange transfusion at age 2 weeks. Electrophysiologic assessment of auditory function conducted after discharge from the NICU revealed an absent auditory brainstem response with a present cochlear microphonic, resulting in an audiological diagnosis of AN/AD. At 6 months, hearing aids were fitted bilaterally for behavioral thresholds in the moderate hearing loss range as determined via pure tone thresholds obtained by visual reinforcement audiometry (Figure 1 [PDF]).

The prescribed hearing aid output was determined using simulated real-ear probe microphone assessment and the DSL-I/O 4.1 prescribed output for his behavioral thresholds. Will demonstrated good aided detection for speech and environmental sounds as evidenced by parental report and aided soundfield warble-tone thresholds near 20 dB HL. His parents reported that he wore the hearing aids during all waking hours but often seemed to have difficulty understanding speech. Will did show modest improvements in developing auditory skills, but a speech and language assessment conducted at age 2 suggested that his speech and language abilities lagged significantly behind chronological age expectations.

When Will was 2, after much discussion with his family regarding poor speech development, the cochlear implant team determined that a CI would be beneficial for his right ear. With use of the CI, Will improved considerably in his speech, language, and auditory skills (Table 1 [PDF, 1.8MB]). Assessments conducted at one-year post-cochlear implantation indicated Will's speech and language skills approached his chronological age; more recent testing conducted at age 4 revealed his speech and language skills exceeded chronological age expectations. More recently, Will's mother reports that he refuses to use a hearing aid for his left ear, especially in the presence of competing noise. She also has noted that his hearing appears to be worse in noise when he uses the hearing aid bimodally with the CI.

Speech Recognition

Interestingly, the mother's report was consistent with her son's most recent audiometric assessment. Speech recognition was conducted in quiet and indicated excellent performance with the CI alone (100% correct) and with the hearing aid alone (92% correct). It should be noted that Will took a considerably longer amount of time to respond to stimuli when using the hearing aid.

Speech recognition was assessed in noise by determining the signal-to-noise ratio (SNR) required for Will to identify correctly spondee stimuli in the presence of steady-state speech noise presented at 45 dB HL. With the CI, Will could correctly identify 50% of spondee stimuli at an SNR of -8 dB. With the hearing aid alone, Will could not identify any spondee stimuli, even at a very favorable SNR. Furthermore, when assessment was conducted with bimodal use of both the CI and the hearing aid, Will was still unable to correctly identify spondee stimuli in the presence of competing noise and became very frustrated with the evaluation.

Will's inability to understand speech in noise while using the hearing aid and the CI is suggestive of binaural interference and is consistent with his mother's report that use of the hearing aid is not beneficial in noise. She expressed reluctance to consider bilateral cochlear implantation, noting that Will hears without the CI while taking a bath when she speaks loudly into his ear. She specified that she must turn off the bath water when doing this, because any competing noise impedes his comprehension.

Recommendations

This case study exemplifies the complicated nature of providing intervention for children with AN/AD and offers several insights:

Children with AN/AD—in fact, all children with hearing loss—should be followed closely by an auditory-verbal therapist or speech-language pathologist well-versed in normal speech and language development so the child can receive habilitative services and to ensure that speech and language are developing at the expected rate. If the child's speech and language age lags behind his or her chronological age (adjusted for prematurity), then the effectiveness of the intervention provided for the child should be evaluated.

Some published reports (Rance et al., 2004; Buchanan et al., 2005; Rance et al., 2007) and the authors' experience have suggested that some children with AN/AD may receive considerable benefit from hearing aids. However, Will's case demonstrates that limited open-set speech recognition capacity in quiet may be insufficient to support adequate speech and language development. Children with AN/AD should be afforded the opportunity to excel with hearing aids, but with aggressive monitoring of speech, language, and auditory skill development by a multi-disciplinary team. If hearing aid use does not support age-appropriate speech and language, then alternative intervention strategies, such as cochlear implantation, should be considered.

Will clearly demonstrated difficulty with speech understanding in noise. The authors have followed other children with AN/AD who excelled with hearing aids but experienced difficulty with communication in noise. Rance and colleagues (2007) also demonstrated that children with AN/AD may experience substantial difficulty understanding speech in the presence of competing noise.

Pediatric audiologists should make evaluation of speech in noise a universal component of their standard protocol along with standardized parent report questionnaires and/or speech-in-noise testing to identify situations in which considerable communication difficulty exists in noise. Furthermore, use of a personal FM system should be considered for all children who have AN/AD and wear hearing aids.