Cochlear Implantation for Young Single-sided Deaf Children (CICADE)

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.

A cochlear implant is standard care for profoundly deaf persons. It enables hearing through electrical stimulation of the auditory nerve.

The Schlichting Test for Receptive Language is a language comprehension test for children aged 2 to 7 years. Results are reported as an age-referenced language comprehension quotient based on the total score.

The Schlichting Test for Expressive Language is a language production test for children aged 2 to 7 years. Results are reported as age-referenced language quotients for each subtest, namely (1) expressive vocabulary, (2) morphosyntactic skills, (3) auditory memory, (4) pseudoword repetition, (5) story telling.

The Clinical Evaluation of Language Fundamentals (CELF-4-NL) is a language test for children aged 5 to 18 years. Results are reported as age-referenced scores for some of the subtests, namely (1) word structure, (2) sentence repetition, (3) sentence production, (4) word categories, (5) phonologic awareness.

Speech perception in noise is measured for three spatial conditions using the LittleLINT speech material (numbers 1-10). Results are reported for each condition as the speech reception threshold, i.e. the level (in decibel signal-to-noise ratio, dB SNR) at which 50% of the speech is understood. Children with a CI are tested both with and without their device.

Sound localization is assessed in a 9-loudspeaker setup with 15° degrees spacing between the loudspeakers. The stimulus is a 1-second broadband telephone sound. Results are reported as the mean absolute error, i.e. the average difference (in degrees) between the active loudspeaker and the child's response. Children with a CI are tested both with and without their device.

The Bayley Scales of Infant and Toddler Development (Bayley-III-NL) is a developmental test for children aged 0 to 4 years and includes cognitive, language, and motor assessment scales. Results are reported as an age-referenced cognitive quotient for the cognitive scale.

The Wechsler Preschool & Primary Scale of Intelligence (WPPSI-III-NL) is a cognitive development test for children aged 2 to 8 years. Results are reported as age-referenced composite scores or intelligence quotients (IQs), namely (1) full IQ, (2) verbal IQ, (3) performance IQ, (4) processing speed.

The Balance scale of the Bruininks-Oseretsky Test of Motor Proficiency (BOT-2) provides a nine-item screening for balance problems, for children aged 4 to 22 years. Results are reported as an age-referenced standard score.

In the group of single-sided deaf children with a cochlear implant, speech perception using only the implant is measured using the Lilliput speech materials. The sound is streamed directly to the implant to avoid contribution from the normal hearing ear. Results are reported as speech perception scores (in percentages).

At clinical visits after the age of 3, on average 2 times per year, until study completion (average period: 4 years)

Using electroencephalography (EEG), the cortical reorganization effect of single-sided deafness is assessed in a subsample of children with compared to without cochlear implant. Cortical onset responses and bilateral auditory steady-state responses (ASSRs) are used to derive a measure for both cortical symmetry and binaural integration.

Inclusion Criteria: profoundly hearing impaired in one ear normal hearing in contralateral ear Exclusion Criteria: none