Use of Amplification in Children With Unilateral Hearing Loss

Unilateral hearing loss (UHL) is defined as decreased hearing in one ear, with normal hearing thresholds in the contralateral ear. Approximately 0.83/1000 newborn children are found to have UHL. It is estimated that about 3-5% of all children in the United States are eventually diagnosed with UHL. When the cutoff for normal hearing is placed at 15 decibels (dB), this incidence is as high as 6.3%, which corresponds to a prevalence of 6.2 million children nationally. The management of UHL continues to be an area of debate, as the handicap associated with UHL is often underestimated. In fact, those with UHL often go without assistance due to lack of recognition of the disability by some health and educational professionals, who have claimed that this hearing loss "attracts little attention from either patient or parent" and that "these children experience few communicational or educational problems." However, in evaluation of children with permanent hearing loss, rates of children who need speech/language intervention and aural rehabilitation are not significantly different between those with bilateral permanent hearing loss and those with unilateral permanent hearing loss. Unfortunately, children with UHL are half as likely to be referred for hearing testing as those with bilateral hearing loss.

Studies have demonstrated the negative impact of unilateral hearing impairment in children. Educational and behavioral difficulties have been clearly shown, with a number of studies demonstrating increased rates of failure of at least one grade in children with UHL when compared to their classmates with normal hearing (24-35% vs. 3.5%). Additionally, increase in special educational needs (12-41%) and frequent problems with behavior have also been noted in this population. In several studies, Lieu and colleagues have shown poorer performance for children with UHL. In a study looking at oral and written language scores, children with UHL did significantly worse than their siblings, who served as matched controls, on language comprehension, oral expression, and oral composite scores. In addition, these children were four times more likely to have Individualized Education Plans (IEPs) and twice as likely to have received speech-language therapy.

Despite these findings regarding the impact of UHL on children, there is a paucity of literature to support or refute the efficacy of hearing aid use in improving measurable academic, behavioral, or quality-of-life (QOL) outcomes. While hearing related disease-specific quality of life measures for children were not developed until very recently, previous studies in adults with UHL reported decreased quality of life, with increased frustration and shame due to hearing disability. The Hearing Environments and Reflection on Quality of Life questionnaire, or HEAR-QL, an instrument developed and validated at Washington University in St. Louis for young children with hearing loss initially (2011) and then later for adolescents (2013), examined effects on environments, activities, and feelings of children with both unilateral and bilateral hearing loss. Significantly lower scores, indicating poorer quality of life, were seen in patients with both UHL and bilateral hearing loss. Interestingly, differences in quality of life between children with UHL and children with bilateral hearing loss were found to be significant in only 1 out of 3 subdomains.

A 2010 study by Johnstone et al. demonstrated that children with UHL who used amplification at a young age (6-9 years) had improvement in localization acuity, while those who received amplification at an older age (10-14 years) noted impairment in localization. This may indicate that the timing of initiation of amplification in UHL may play an important role in whether the intervention is beneficial. In addition, Noh and Park's study in 2012 demonstrated that children with UHL needed to sit 3.5 meters closer to the teacher to obtain the same speech discrimination scores as children with binaural hearing. While this can be accomplished in a small room setting, this may not be possible at all times in all classes, and it is certainly not translatable to hearing environments outside of the classroom. It is not clear whether adding amplification to would eliminate this handicap and improve quality of life, behavior, or academic performance.

Current interventions: Multiple options exist for management of UHL. Preferential seating in the classroom is often the first line of treatment utilized, placing the child at the front of the classroom with the better hearing ear toward the teacher. Evaluation of the classroom by an educational audiologist or other specialist in the education of children with hearing loss in order to optimize the listening environment is another commonly utilized modality for managing UHL. Interventions such as carpeting, tennis balls placed on the legs of chairs, and selection of a classroom with lower ambient noise levels from outside traffic or air handling equipment can reduce significantly improve signal to noise ratios for the student. Another modality for improving signal to noise ration is use of a frequency-modulated (FM) system in the classroom, which specifically amplifies the teacher's voice via a microphone worn by the teacher. This increases the signal-to-noise ratio for the teacher's voice as it does not amplify background noise. Differentiating relevant sound signals from background noise a particularly challenging problem for children with UHL. Other options for management of UHL include various forms of amplification including a unilateral hearing aid, contralateral routing of sound (CROS) systems, and potentially cochlear implantation (though this practice has not been widely adopted in children with UHL in the United States).