The Degree of Hearing Loss Moderates the Benefit of Amplification in Preventing Children’s Cortical Structural Changes

Importance: Children with bilateral sensorineural hearing loss (SNHL) benefit from binaural amplification provided by hearing aids (HA) to develop auditory skills, language and social abilities. However, few studies have examined the effect of amplification on brain structure in children with SNHL. This study evaluates a group of children with bilateral SNHL who were cochlear implant candidates.Objective/Design/Setting: To investigate whether the extent of HA use before cochlear implantation (CI) modulates neuroanatomical structural changes in the brain. A cross-sectional, population-based study was conducted.Participants: One hundred and three children with bilateral SNHL who were candidates for CI. Seventy-eight children with normal hearing were selected from the NIH MRI Study of Normal Brain Development.Exposures: The length of HA use was obtained. Moreover, the unaided speech-frequency pure-tone average (PTA) was measured to represent residual hearing.Main Outcomes and Measures: Multivoxel pattern similarity analysis was used to examine the similarity of gray matter (GM) density in the local spatial morphological pattern of the auditory cortex for children with SNHL in comparison with age expectations (children with normal hearing).Results: One hundred and three children with hearing loss were included (55 females and 48 males). The mean (SD) age was 15.84 (11.53) months. Children’s GM preservation in the left Heschl’s gyrus was nonlinearly affected by their experience of HA use (β = -0.380, p = 0.03). During the first year of HA use, children who had longer experience of HA use showed higher GM preservation, while further use of HA attenuated their GM preservation. Such effect was moderated by the degree of HL (β = -0.347, p = 0.03). Children with worse residual hearing benefited more from HA use compared to those with better residual hearing. Conclusions and Relevance: Amplification may prevent auditory structural changes which result from a lack of auditory input in children with HL, especially those whose loss is in the profound range. Although HA does not provide adequate audibility of spoken language for children who are cochlear implant candidates, pre-CI use of HA serves to preserve the auditory cortex during the first year of HA use. After the first year, this effect disappears, which reinforces the need for early cochlear implantation as the main treatment modality for hearing loss.