Advances in diagnostic audiology and the creation of early hearing detection and intervention programs in all states and territories have lowered the average age of hearing loss identification to 2-3 months, down from 2½-3 years in the early 1990s. The US Food and Drug Administration's labeled indications for pediatric cochlear implantation, however, have remained unchanged since 2000 despite this significant improvement.
The FDA recommends 12 months as the minimum age for cochlear implantation. This does not mean that infants under 12 months will not benefit from cochlear implantation, but obtaining behavioral hearing estimates for the youngest infants was difficult. This concern may not be as valid today given the audiologic checks and balances at our disposal for behavioral assessments of hearing and physiologic estimates of auditory function. This may also support the argument for lowering the FDA-approved age for cochlear implantation from 12 months to slightly younger, perhaps 6 to 9 months.
Many developmental changes occur in the first year of life that may be missed in an infant with severe to profound hearing loss. This is true even for infants with appropriately fitted hearing aids because audibility is often insufficient to allow consistent auditory access to spoken language, at least for those with bilateral severe to profound sensorineural hearing loss.
Word segmentation — the process of dividing connected discourse into meaningful units such as individual words — has been to shown to develop rapidly between 7½ and 10½ months. (Science 1997;277:1984.) Infants have the capacity for long-term storage of new words by 8 months, which is an important precursor to auditory-based language learning. (Science 1997;277:1984; J Exp Psychol Hum Percept Perform 2003;29:1143.) An infant with severe to profound sensorineural hearing loss who has limited aided audibility may be missing out developing these critical auditory-based, language-learning opportunities.
Cochlear Implantation in the Very Young Child: Issues Unique to the Under-1 Population
Cosetti M, Roland JT Jr. Trends Amplif 2010;14:46
Cosetti and Roland summarized the literature regarding the surgical and anesthetic risks associated with surgery in infants, noting a higher incidence of morbidity, mortality, and life-threatening adverse surgical events for infants younger than 12 months. They explained that the majority of reported concerns and complications were confounded by emergency surgery, for which young and possibly medically fragile patients were unable to fast and thus had a greater risk of aspiration. The authors noted that a number of studies demonstrate no greater anesthetic risk for infants younger than 12 months during cochlear implant surgery.
Surgical issues unique to infants younger than 12 months include intraoperative blood loss, facial nerve anatomy, skull thickness (<1 mm), fixation of the receiver or stimulator package, thin scalp flap, and device migration with skull growth. It was reported, however, that these known variables can be moderated with a highly trained surgical team with extensive pediatric experience.
Word Learning in Deaf Children with Cochlear Implants: Effects of Early Auditory Experience
Houston DM, Stewart J, et al Dev Sci 2012;15:448
A growing body of literature demonstrates higher levels of word and language acquisition, speech perception, speech intelligibility, and vocabulary development for infants implanted under 12 months, even when compared with children implanted at age 2 years. (Dev Sci 2012;15:448; Otol Neurotol 2010;31:1254.) The authors examined whether age at implantation affects a child's word learning and vocabulary development, looking at novel word learning in 25 prelingually deaf children who had been implanted under 24 months (age range 21.7-40.1 months) and 23 children with normal hearing (age range 10.3-20.1 months). The children were evaluated on speech perception, expressive vocabulary, and novel word learning.
Children implanted between 6 and 13 months exhibited significantly better word learning abilities than children implanted between 15 and 20 months. This is interesting because children implanted between 15 and 20 months would generally not be considered as having received “late” implantation. Word learning ability significantly correlated with expressive vocabulary at two years postactivation. Children who spent more time looking at the correct item on the computer monitor corresponding with the auditory stimulus exhibited significantly higher levels of expressive vocabulary.
Children implanted between 6 and 13 months not only exhibited higher word learning abilities, but also did not differ significantly from their normal hearing peers. The children implanted later at 15 to 20 months, on the other hand, exhibited significantly worse word learning abilities than their normal hearing peers.
These data were consistent with previous studies also showing significantly greater language outcomes for children implanted in their first year of life. (Volta Review 2003;103:303; Int J Pediatr Otorhinolaryngol 2011:75:504; Ear Hear 2007;28[2 Suppl]:11S.) The authors suggested that early implantation results in better language outcomes, which is likely related to early auditory experience. (Restor Neurol Neurosci 2010;28:157.) They hypothesized that providing earlier auditory experience to the developing brain affords development of cognitive mechanisms that are known precursors to language learning, such as audiovisual integration. Clearly more research is needed to test these hypotheses. It would have significant clinical, familial, societal, educational, and financial implications if research determined that children implanted under 13 months demonstrate age appropriate language outcomes by just 2 years postactivation.
Given the known benefits of cochlear implantation for children with severe to profound sensorineural hearing loss, a thorough revision of FDA-labeled indications for pediatric implant candidacy is well overdue. It is likely that criteria in the near future will include children as young as 9 months, perhaps even younger. A child under 12 months who is healthy enough and adequately prepared to undergo surgery has no major risks for cochlear implantation. The potential benefits associated with early implantation and recommended early intervention may be the key to closing the gap permanently between children with cochlear implants and their normal hearing peers for speech, language, and academic outcomes.
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