Ann E. Geers
Popular version of 2aPP6. Language emergence in early-implanted children
Presented at the 169th Meeting of the Acoustical Society of America
Before the advent of Cochlear Implants (CI), children who were born profoundly deaf acquired spoken language and literacy skills with great difficulty and over many years of intensive education. Even with the most powerful hearing aids and early intervention, children learned spoken language at about half the normal rate, and fell further behind in language and reading with increasing age. At that time, many deaf children learned to communicate through sign language, though more than 90% of them had parents with normal hearing who did not know how to sign when their deaf child was born.
Following FDA approval in the 1990s, many deaf children began receiving a CI (in one ear) at some point after their second birthday. Dramatic improvements were seen compared to hearing aid users in the ability to hear and produce clear speech, understand spoken language and acquire literacy skills. However many children with CIs still did not reach levels within the range of their age mates with normal hearing in these areas. Over the next 2 decades, with universal newborn hearing screening mandatory in most states, implantation occurred at younger ages (typically 12-18 months) and CI technology offered improved access to speech, especially soft sounds. As implant performance continued to improve for children receiving one CI, receiving a second CI to optimize hearing at both ears was considered.
This study followed 60 children implanted between 12 and 38 months of age when they were 3, 4 and 10 years old. All of them were in preschool programs focused on developing spoken language skills and had no disabilities other than hearing impairment. By age 10, 95% of them were enrolled in regular education settings with hearing age mates.
Three groups, roughly equal in size, were identified from standardized language tests administered at 4 and 10 years of age. 1) Normal Language Emergence – these children exhibited spoken language skills within the normal range by age 4 and continued along this normal course into their elementary school years. They developed above-average reading comprehension. 2) Late Language Emergence – these children were language-delayed in preschool, but caught up by the time they were 10. They developed average reading comprehension for their age. 3) Persistent Language Delay- these children were also language-delayed in preschool, but they did not catch up with hearing age-mates by age 10. They were below-average readers.
Achieving age-appropriate language and reading skills by mid-elementary grades is a remarkable accomplishment for children with profound hearing loss and the fact that two-thirds of the sample reached or exceeded this level attests to the efficacy of early cochlear implantation. In fact, children with normal language emergence were most likely to have received a CI very young – between 12 and 18 months of age. However, age at first CI did not differentiate children with late language emergence from those with persistent delay. In fact, these groups did not differ in nonverbal intelligence, mother’s education, bilateral implantation, age at first intervention or age enrolled in regular education classrooms. As a result, predicting during preschool whether or not a child will catch up with hearing children in the same grade is difficult. We looked for factors distinguishing language-delayed preschoolers who would reach age-appropriate language levels by mid-elementary grades from those who would remain delayed. Early prediction is important for intensifying and individualizing early intervention for children at risk for long-term delay.
Results from a battery of tests and questionnaires revealed a constellation of factors distinguishing children with persistent from those with resolving language delay. Most of these factors were associated with the quality of the audio input provided by the device. For example, odds were 3-4 times greater that children who caught up used more recent CI technology than those who remained delayed. Children who caught up in language had a particular advantage in their ability to detect and understand speech presented at soft levels. This is understandable, because incidental or casual language acquisition depends on the ability to overhear soft speech in addition to speech at normal-conversation levels. In addition, a smaller repertoire of speech sounds, lower vocabulary and poorer grammar skills were evident in the conversational language of persistently delayed children as early as 3 years of age with smaller language gains between 3 and 4 years, foreshadowing slower long-term speech and language development. A somewhat surprising finding was that a much larger percentage (47%) of persistently delayed children had left-ear CIs as compared with those who caught up (14%).
These results have important implications for surgeons, speech-language pathologists, educators and audiologists serving young children with cochlear implants. For the surgeon, right-ear placement of the first CI should be preferred over the left unless cochlear anatomy precludes placement at the right ear. This, along with implantation by 18 months, may help to maximize chances of age-appropriate spoken language development. For the speech language pathologist, the extent of immature speech production and language use during preschool years may foreshadow later language difficulties. For the audiologist, encouraging upgraded speech processor technology and working to ensure the audibility of soft speech when programming the device may positively influence future language development. For the educator, recognition of risk factors for persistent language delay may signal increased intensity of language intervention. Addressing these issues should increase the likelihood that children with CIs will exhibit spoken communication and academic skills in line with expectations for their grade placement.