Policy-makers have struggled to define the minimum degree of hearing impairment at which children should be offered cochlear implants rather than the less invasive alternative of acoustic hearing aids. This study compared outcomes for children with bilateral cochlear implants and children with bilateral hearing aids, to determine a criterion of candidacy for pediatric bilateral cochlear implantation.
This observational study measured the listening skills of children who received routine audiological care in the United Kingdom. Participants were recruited from hospitals, educational services, and charities. Eligibility criteria included a diagnosis of hearing impairment before 31 months of age and pure-tone thresholds greater than or equal to 50 dB HL at 2 and 4 kHz bilaterally. Seventy-one children participated, aged 46 to 86 months (mean 64 months). Twenty-eight children used bilateral implants provided in a simultaneous surgery; 43 used bilateral digital hearing aids. The two groups of children were demographically similar in variables that predict outcomes for children with hearing impairment. Children’s ability to understand speech was measured using closed-set tests of word discrimination in three conditions: in quiet, in pink noise, and in two-talker babble. For each listening test, an actuarial method was used to compare the distribution of scores from children with cochlear implants and children with hearing aids. The aim was to calculate the unaided pure-tone average (PTA) hearing level at which a child has odds of 4:1 of a better outcome with implants than with hearing aids. The PTA associated with odds of 4:1 has been used previously to define criteria of candidacy for implantation. The main analyses used a four-frequency PTA (mean of unaided thresholds at 0.5, 1, 2, and 4 kHz in the better-hearing ear). Additional analyses used a three-frequency PTA (0.5, 1, and 2 kHz) and two-frequency PTA (2 and 4 kHz).
Odds of 4:1 of a better outcome with implants were associated with a four-frequency PTA of 79, 86, and 76 dB HL for tests of word discrimination in quiet, noise, and babble, respectively. The mean of these three estimates is 80 dB HL. It can be difficult to measure a four-frequency PTA in young children, but a two-frequency PTA typically can be measured. Odds of 4:1 were associated with a two-frequency PTA of 83, 92, and 80 dB HL for tests of word discrimination in quiet, noise, and babble, respectively. The mean of these three estimates is 85 dB HL.
Children with an unaided four-frequency PTA of 80 dB HL or poorer in both ears should be considered candidates for bilateral cochlear implantation. In cases where a four-frequency PTA cannot be measured, the criterion of candidacy should be a two-frequency PTA of 85 dB HL or poorer in both ears. If adopted by policy-makers, these recommendations would expand the provision of cochlear implants among children in England and Wales.