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Sound localization acuity in children with unilateral hearing loss who wear a hearing aid in the impaired ear.

BACKGROUND
Disrupted binaural hearing is thought to contribute in part to the academic, social, and communication problems often associated with unilateral hearing loss (UHL) in childhood. It is not known, however, if putting a hearing aid in the impaired ear of a child with UHL will lead to bilateral or binaural benefit. This study seeks to utilize sound localization acuity measurements to assess hearing aid amplification efficacy in children with UHL.


PURPOSE
To measure sound localization ability in children with UHL who use a hearing aid in the impaired ear to determine the extent to which amplification, age, early intervention, and degree of hearing loss affects localization acuity.


RESEARCH DESIGN
A within-subjects experimental design using repeated measures is used to determine the effect of amplification on localization acuity in children with UHL. A between-subjects experimental design is used to compare localization acuity between children with UHL and age-matched controls with normal hearing.


STUDY SAMPLE
Twelve children with UHL who used a hearing aid in the impaired ear and 12 age-matched controls with normal hearing. Children with UHL were divided into two groups based on degree of hearing loss. Children in both groups were divided into two age groups: older children (10-14 yr) and younger children (6-9 yr).


DATA COLLECTION AND ANALYSIS
All testing was done in a sound-treated booth with a horizontal array of 15 loudspeakers (radius of 1 m). The stimulus was a spondee word, "baseball": the level averaged 60 dB SPL and randomly roved (±8 dB). Each child was asked to identify the location of a sound source.


RESULTS
In the experimental study a significant interaction was found between hearing aid amplification and child age. A hearing aid significantly improved localization acuity in younger children with UHL and significantly impaired localization acuity in older children. A significant correlation was found between age at intervention and localization bilateral benefit. Children who were fit earlier showed bilateral benefit whereas children who were fit later showed bilateral interference. Development, however, may play a role in sound localization acuity. When unaided, older children had significantly better localization acuity than younger children with UHL.


CONCLUSIONS
A hearing aid can provide bilateral localization benefit to some children with UHL. Early intervention may increase the likelihood of bilateral benefit. However, developmental factors appear to play a role in improving localization abilities over time for children with UHL. Nonetheless, without a means of establishing bilateral benefit with hearing aid amplification, localization performance in children with UHL will rarely equal that of peers.