Children with hearing loss are at high risk for delays in acquiring and advancing speech and language, and achieving psycho-educational success. This fact, well known for decades, escapes clear guidelines for treatment when the hearing loss is unilateral, sensorineural, and “unaidable.” The traditional definition of “unaidable” is challenged by modern cochlear implants, which provide a potential—albeit “off-label” solution—to provide bimodal or binaural hearing in cases of unilateral hearing loss. Unilateral hearing loss (UHL) is known to be handicapping, particularly in young children who are acquiring language and speech. Its consequences include difficulty with localization, difficulty understanding speech-in-noise, and difficulty when speech originates from the deaf/impaired side. Negative educational impact of UHL is common, and children are known to be at higher-risk for speech, language and social-emotional difficulties than children with normal hearing in both ears. Sub-optimal signal-to-noise ratios in classrooms, a common occurrence, exacerbate listening and learning difficulties for all children, but particularly those with hearing loss and unidentified/untreated unilateral hearing loss.
The prevalence of UHL in newborns and young children is largely unknown. And when present at birth, it may be late to be identified unless the infant does not pass newborn hearing screening. With the advent of newborn hearing screening, it is apparent that hearing loss in children may not be identified in the birth-screen for a variety of reasons. The proportion of this group having severe-profound unilateral SNHL was not estimated. Unilateral hearing loss, if not present at birth, is often late to be identified.
It is common that physicians, and perhaps to a lesser extent, audiologists, assume that UHL is an inconvenience, but not a significant factor in acquiring language or achieving successful learning in the classroom. Yet the preponderance of research over the past 30 plus years shows this not to be the case for all children. While some children with UHL are able to achieve at grade-level (often with greater listening effort), many children with UHL experience academic challenges.
Listening effort is also a consideration—at what cost does a child with a UHL achieve success in the classroom? Stress and exhaustion associated with increased listening demands are known to be byproducts of classroom listening for children with UHL. Additionally, children with UHL may experience psycho-social impact (e.g., embarrassment) when they “mis-hear” casual conversation at school, or turn the wrong direction when their name is called out in the noisy school cafeteria.
Options for UHL
For the sake of simplicity, “UHL” is defined here as a severe-profound sensorineural hearing loss, where radiographic studies indicate a normal or adequate eighth nerve. UHL can be congenital, or can occur after birth for known or unknown reasons.
Amplification options for children with congenital UHL are limited. If a child is identified as having a UHL and if audiologic treatment is pursued, three approaches are common:
- Contralateral routing of signal (CROS) hearing aid—i.e., delivering sounds from the deaf side of the head into the normal-hearing ear,
- Bone-anchoring hearing (BAH)—i.e., using a bone-anchored device worn on a headband that stimulates the normal hearing ear, by bone-conduction, with the device microphone on the deaf side of the head,
- FM technology coupled to the normal-hearing ear, and FM transmission of the desired speech signal to the normal-hearing ear.
Often there is a perception that a UHL is not handicapping, and no intervention is necessary. This may take the form of waiting until a child begins to demonstrate difficulty in academic performance, and then considering intervention. In school-aged children, often the only approach is to offer “preferential seating” in the classroom.
Increasingly, unilateral cochlear implantation for UHL is considered and performed (“off-label”) for adults with UHL. Why not children? When there is a viable cochlear nerve, early stimulation of the deaf ear via a cochlear implant (CI) could result in achieving bilateral, if not binaural, hearing. Indeed, this is the only approach that holds any possibility for achieving binaural function at all. Absent early direct stimulation of the deaf ear...there is no reference—just common sense and common knowledge. It is well-known that children who do not receive stimulation (via hearing aid or cochlear implant) at a young age fail to develop optimal auditory skills at older ages.
In a recent study in Germany, 20 children with UHL were studied after they received a cochlear implant (Arndt et al, 2015). Older age at implantation portended poorer outcomes, and four years or younger was suggested as an optimal age for implantation. These authors note that a CI presents the only opportunity to restore binaural hearing.
Significant considerations currently impede the consideration of cochlear implantation for infants and children with UHL. First, it is not a Food and Drug Administration (FDA)-approved indication. Without FDA approval, a child with UHL can only be implanted if parents self-pay, or if a child is enrolled in a research study. Second, it is difficult (or at least time-consuming) to do prospective research. Lacking such research, which necessarily takes a significant number of years to complete, it is unlikely that the FDA indications will change. Long-term outcomes are needed in order to impact practice and regulations. But it remains clear that a unilateral CI is the only way to potentially create binaural cues. And it is probable (though unproven) that this approach could help to overcome the known impairments and challenges faced by children with UHL.
Increasingly, cochlear implants for UHL in adults are being sought and performed, with good outcomes. Investigational studies are on-going, and are generally considered “off-label” for insurance reimbursement. Nonetheless, patients may opt for implantation, and in some circumstances, private insurance may pay.
When to Implant?
Should children with severe-profound UHL who do not show benefit from a hearing aid be offered a cochlear implant? In selected circumstances, yes.
If a child has a progressive UHL, and formerly had some degree of hearing and speech perception in the “deaf” ear, a CI might prove to be beneficial. In a very young child with congenital hearing loss, a CI (when implanted early) might also provide benefit.
Sladen et al (2016) found that children with short-duration UHL were benefited in listening in quiet and in noise with a unilateral cochlear implant. These authors noted that “current treatments” for UHL have not proven to be satisfactory for the child in a classroom situation. The CROS hearing aid provides benefit only when a desired signal originates from the deaf side of the head. The CROS hearing aid, conversely, creates detriment when noise originates from the deaf side of the head (effectively introducing noise into the normal and only-hearing ear). The bone-anchored hearing device creates the same outcome—it provides benefit only when the desired signal is on the side of deafness.
Dornhoffer and Dornhoffer (2016) note that there is a “burgeoning accumulation of research on cochlear implantation for the treatment of unilateral sensorineural hearing loss in children.”
A cochlear implant was found to “potentially improve” development of intelligence in deaf children when implanted prior to six years of age (Chen et al, 2016).
Unilateral hearing loss is a disabling condition for people of all ages. Its significance is often minimized by the medical and audiological communities, however, when one considers the advantages of binaural hearing, it is not difficult to understand the challenges experienced by people who have UHL.
With our understanding of the disabling effects of UHL in children, and with the increased consideration and use of CI in adults with UHL, research is needed to determine efficacy of CI in pediatric populations for auditory and psycho-educational success. The FDA criteria can expand when carefully designed, prospective, longitudinal studies confirm what many believe—the advantages of CI for UHL in children at least mirrors, if not exceeds, those seen in adults, when implantation occurs at a young age.
It is time to consider the potential benefit of CI for children with unilateral SNHL, much as we currently consider CI for children with bilateral severe-profound SNHL. The handicap associated with UHL is different from that of bilateral SNHL; yet for the child with UHL, the impact on learning and psychosocial well-being can be profound. We have a tool that can potentially address this condition far better than the tools we have been using for the past 40-plus years.