Background: The challenges associated with auditory neuropathy spectrum disorder (ANSD) are due
primarily to temporal impairment and therefore tend to affect perception of low- to
midfrequency sounds. A common treatment option for severe impairment in ANSD is cochlear
implantation, and because the degree of impairment is unrelated to degree of hearing
loss by audiometric thresholds, this population may have significant acoustic sensitivity
in the contralateral ear. Clinically, the question arises as to how we should treat
the contralateral ear in this population when there is acoustic hearing—should we
plug it, amplify it, implant it, or leave it alone?
Purpose: The purpose of this study was to examine the effects of acute amplification and plugging
of the contralateral ear compared to no intervention in implanted children with ANSD
and aidable contralateral hearing. It was hypothesized that due to impaired temporal
processing in ANSD, contralateral acoustic input would interfere with speech perception
achieved with the cochlear implant (CI) alone; therefore, speech perception performance
will decline with amplification and improve with occlusion.
Research Design: Prospective within-subject comparison. Adaptive speech recognition thresholds (SRTs)
for monosyllable and spondee word stimuli were measured in quiet and in noise for
the intervention configurations.
Study Sample: Nine children treated at the Medical College of Wisconsin Koss Cochlear Implant Program
participated in the study. Inclusion criteria for this study were children diagnosed
with ANSD who were unilaterally implanted, had aidable hearing in the contralateral
ear (defined as a three-frequency pure-tone average of ≤80 dB HL), had at least 1
yr of cochlear implant experience, and were able to perform the speech perception
task.
Intervention: We compared SRT with the CI alone to SRTs with interventions of cochlear implant
with a contralateral hearing aid (CI+HA) and cochlear implant with a contralateral
earplug (CI+plug).
Data Collection and Analysis: SRTs were measured and compared within subjects across listening conditions. Within-subject
comparisons were analyzed using paired t-tests, and analyses of predictive variables for effects of contralateral intervention
were analyzed using linear regression.
Results: Contrary to the hypothesis, the bimodal CI+HA configuration showed a significant
improvement in mean performance over the CI-alone configuration in quiet (p = .04). In noise, SRTs were obtained for six subjects, and no significant bimodal
benefit was observed (p = .09). There were no consistent effects of occlusion observed across subjects and
stimulus conditions. Degree of bimodal benefit showed a significant relationship with
performance with the CI alone, with greater bimodal benefit associated with poorer
CI-alone performance (p = .01). This finding, however, was limited by floor effects.
Conclusions: The results of this study indicate that children with ANSD who are experienced cochlear
implant users may benefit from contralateral amplification, particularly for moderate
cochlear implant performers. It is unclear from these data whether long-term contralateral
hearing aid use in real-world situations would ultimately benefit this population;
however, a hearing aid trial is recommended with assessment of bimodal benefit over
time. These data may help inform clinical guidelines for determining optimal hearing
configurations for unilaterally implanted children with ANSD, particularly when considering
candidacy for sequential cochlear implantation.
Key Words
Auditory neuropathy - bimodal - cochlear implant - hearing aid
