Prevalence of unilateral hearing loss ranges between 1% and 5% in school-aged children1-3 and as high as 6% to 14% with the inclusion of older children.3,4 Children spend much of their day in challenging auditory environments (classroom, school cafeteria, extracurricular activities) where sounds and speech overlap, originate from multiple sources and talkers, and vary in level. Communication deficits and disrupted binaural processing are consequences of unilateral severe to profound hearing loss whether hearing in the contralateral ear has mild to moderate hearing loss (AHL; asymmetric hearing loss) or normal/near-normal hearing (SSD; single-sided deafness). Standardized care for children with bilateral mild/moderate or bilateral severe to profound hearing loss supports restoring auditory input to both ears to facilitate binaural hearing, either with bilateral hearing aids or bilateral cochlear implants (CIs).5,6 In contrast, standardized clinical intervention to restore hearing to both ears has not been established for children with AHL or SSD. A hearing aid in the poor ear provides minimal or no benefit. Contralateral routing of sound (CROS) devices allow detection of sounds originating from the side of the poor ear; however, input remains unilateral and benefit varies depending on the environment.7-9 Cochlear implantation is the only treatment that restores hearing to an ear with severe to profound hearing loss and is therefore the only treatment that can provide AHL/SSD children access to bilateral input and binaural cues. Currently, the field is lacking prospective information on expected CI performance outcomes in these pediatric populations.
MED EL obtained FDA approval in 2019 to implant a subset of children with AHL or SSD. While this advances access to treatment options, the approval was based on extrapolation from adult data and the candidacy criteria are restrictive. Children must be 5 years and have profound hearing loss ( 90 dB HL at .5 - 4 kHz) with 5% aided word recognition in the poor ear. Cochlear Americas received FDA approval in early 2022 for SSD only (not AHL) with similar criteria except for the hearing thresholds in the poor ear (> 80 dB HL at .5 - 4 kHz). These criteria exclude younger children and the large number of children with severe to profound hearing loss in the poor ear. Additionally, cochlear implantation of children with AHL/SSD is relatively new; therefore, guidelines regarding CI candidacy criteria, appropriate assessment tools, and expected outcomes over time are not well defined. Particularly lacking is benchmark evidence of hearing aid performance over time with more recent amplification technology to compare with CI performance. Our current NIH/NIDCD-funded (U01DC018942) and FDA-approved (G190269) multicenter, two-phase, longitudinal clinical trial will determine expected growth in outcomes and inform clinical decision-making, such as whether or when to consider a CI for children with AHL or SSD.
The five study sites and Principal Investigators at each site are: Washington University School of Medicine (Jill B. Firszt, PhD)/St. Louis Children’s Hospital (Jamie Cadieux, AuD), St. Louis, MO; University of Southern California (Laurie S. Eisenberg, PhD), Los Angeles, CA; Children’s Hospital of Philadelphia (John A. Germiller, MD, PhD), Philadelphia, PA; Hearts for Hearing (Jace Wolfe, PhD), Oklahoma City, OK; and Fairview Health Services, University of Minnesota (Margaret Koeritzer, AuD), Minneapolis, MN. The sites have geographic and population diversity, busy clinical pediatric practices to support recruitment, and audiologists and surgeons experienced in rehabilitative treatment of children with AHL and SSD.
Approximately 80 children will participate in the study, 40 with AHL and 40 with SSD. Children in each hearing group are 4-14 years of age, fluent in English, and able to complete the study protocol. Hearing criteria for the poor ear expands the current FDA-approved criteria. Criteria for the poor ear includes a PTA (.5, 1, & 2 kHz) > 70 dB HL and an aided CNC word score < 40% at 60 dB SPL. For children with AHL, the better ear criteria include a PTA (.5, 1, 2, & 4 kHz) > 25 and 60 dB HL, and a CNC word score 55%. For children with SSD, the better ear criteria include a PTA (.5, 1, 2, & 4 kHz) 25 dB HL and a CNC word score 70%. Onset of severe-to-profound hearing loss may be congenital for children 4-5 years of age, whereas children 6 years and older will have evidence of noncongenital onset (e.g., passed newborn hearing screening).
Participants complete an initial Hearing Aid Phase (4 months) followed by a CI Phase (15 months). Multiple test sessions during each phase will allow a comparison between the rate of progress with a CI compared with hearing aids. Many of the study visits can be coordinated with standard clinical visits. Children who complete the Hearing Aid Phase will continue on to the CI Phase if the following criteria are met: hearing in the better ear remains stable, imaging provides evidence of a normal cochlear nerve and of normal cochlear anatomy in the ear to be implanted, parents/participants decide to proceed with a CI, and insurance coverage for a CI is obtained. The primary risk during the Hearing Aid Phase is that a CROS device or a hearing aid in the poor ear may make speech more difficult to understand in some situations (e.g., noise toward the poor ear). For participants who continue with cochlear implantation, the surgical risks are the same as those for children who have bilateral, severe-to-profound hearing loss. Specific to study participation, children may experience boredom or fatigue during the testing. Potential benefits for the participant during the Hearing Aid Phase include the possibility of improved sound detection and speech understanding. During the CI Phase, potential benefits include improved sound -detection and speech understanding in the poor ear, which could improve everyday communication and/or sound localization. From the study, we will learn more about the treatment options for children with AHL and SSD and which options provide the most benefit to everyday communication.
The study protocol uses measures known to address everyday challenges for children with hearing asymmetry, including word understanding at soft levels, speech understanding in noise, and localization/lateralization. Quality-of-life measures address communication in real-world listening situations, general and cognitive fatigue, and social and emotional function. Data analysis will differentiate changes due to development from those due to cochlear implantation. Study results will provide much needed information to inform and improve clinical management and treatment of children with AHL or SSD. Enrollment has recently begun at all five sites. Additional information regarding the study and contact information for each study location is available at ClinicalTrials.gov (NCT04793412). Questions may also be directed to Noël Dwyer at [email protected] or Laura Holden at [email protected] at Washington University School of Medicine, St. Louis.
This work is supported by U01DC018942 from the National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health (NIH).
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