Cochlear Implantation for Young Single-sided Deaf Children

Overview

Children with profound sensorineural unilateral hearing loss (UHL) lag behind in spoken language, cognition, spatial hearing, and academic performance compared to normal hearing (NH) children. Until recently children with UHL were not remediated, thereby assuming that the normal ear would provide sufficient sensory cues for speech understanding. However, this is not true. Because of the difference between the two ears they have difficulty localizing sounds and understanding speech in noise. Such auditory deprivation leads to more global changes in neurocognitive function. It is expected that a cochlear implant in the deaf ear will provide the necessary cues for hearing with two ears. The main objective of this research project is to fundamentally investigate language, cognitive, and spatial/binaural hearing longitudinally in children with unilateral deafness who receive a cochlear implant and age-matched peers.

The main objective of the research project is to fundamentally investigate spatial and binaural hearing in a group of children with a normal hearing ear (NH) and a cochlear implant (CI) longitudinally in order to understand the relationship between sensory experience and auditory cortex plasticity. This relationship is most striking during infancy when changes in sensory input can have profound effects on the functional organization of the developing cortex. Recent studies in the auditory system have revealed the remarkably adaptive nature of sensory processing and provided important insights into the way in which cortical circuits are shaped by experience and learning. The binaural system processes and integrates differences in phase (low frequencies) or intensity (high frequencies) between sounds arriving at the left and right ear and this process goes on from birth up to adulthood. It is expected that cochlear implantation will promote normal or near-normal spatial-hearing skills in children with UHL and that intervention at 2 years of age yields the best conditions for (near-) normal development of cognition, spoken language, balance, and psychopathology, outcomes which will be monitored annually too. Fifteen NH-CI children, aged 2 or younger, will receive a cochlear implant. This device has already been provided to over 400.000 bilaterally profoundly deaf persons worldwide and is considered a standard treatment. The novelty of the present studies lies in the treatment of unilaterally deaf children with a cochlear implant. Because of the cost of this device, the Belgian government does not reimburse a CI for children with unilateral hearing impairment, which is why a study is done to demonstrate its effectiveness. The 15 devices are provided by Cochlear. While the sample size may seem small, providing the device (25.000€ a piece) and some follow-up (mapping and/or remediation) are a large investment for Cochlear Ltd. The children will act as their own control (tested with and without CI) when possible. In addition, at the start of the research project the NH-CI children will be age-matched with 15 normal hearing children (NH-NH), and with 15 children with unilateral hearing loss without a CI (NH - x). Care will be taken to control for as many other factors as possible (e.g. other disabilities, parental and socioeconomic characteristics, ..). It is hypothesized that the children with UHL and a CI (NH-CI) will outperform children without intervention (NH-x) because of access to bilateral input, and that provision at a very young age will result in near-normal binaural processing in the following years and hence better auditory/neuro/cognitive processing and learning in general. After cochlear implantation, the children will be followed up in terms of language development, cognitive development, binaural hearing, and academic achievements.