Cochlear implant (CI) technology has evolved dramatically since the U.S. Food and Drug Administration (FDA) approved cochlear implantation for children in 1990. Most of the advancements in internal devices, external sound processors, signal processing, and various preprocessing strategies have occurred in just the past decade. Despite this rapid evolution in technology, FDA-labeled indications for pediatric CI candidacy have been officially unchanged since 2000.
To date, the least restrictive criteria for pediatric cochlear implantation are those of Cochlear Americas, specifying that a child must be 12 months of age and have bilateral profound sensorineural hearing loss. If over 2 years of age, audiometric thresholds may be in the severe-to-profound range. For children old enough to complete speech recognition testing, criterion level performance ranges from 12 to 30 percent correct for aided open-set word recognition (Advanced Bionics, Cochlear, and MED-EL package inserts) and up to 30 percent correct for aided open-set sentence recognition (Advanced Bionics)—depending on which measure is most developmentally appropriate.
Current pediatric CI indications are much more restrictive than adult indications, the latter of which are generally intended for postlingually deafened individuals pursuing cochlear implantation for rehabilitation purposes. The least restrictive criteria for adult cochlear implantation are those of Cochlear Americas, specifying moderate sloping to profound sensorineural hearing loss with aided open-set sentence recognition up to 60 percent correct. Children, on the other hand, are generally being implanted for habilitation purposes and are highly dependent on hearing for development of language (Ear Hear. 2006;27:286 http://bit.ly/2eUeC0T;JAMA. 2010;303:1498 http://bit.ly/2eUc6I2), psychosocial skills (Ear Hear. 2007;28:729 http://bit.ly/2eUhevT;Int J Audiol. 2016 http://bit.ly/2eUioYg), neurocognitive maturity (J Deaf Stud Deaf Educ. 2014;19:456 http://bit.ly/2eUg1oa), and various aspects of academic learning, particularly literacy (Ear Hear. 2007;28:740 http://bit.ly/2eUkGGH). Given the critical importance of hearing for various aspects of a child's neurodevelopmental abilities, having such stringent criteria for pediatric implant candidacy holds considerable potential to negatively impact a child's neural development, academic success, psychosocial skills, and overall quality of life.
In the October 2012 issue http://bit.ly/2eUw05L of The Hearing Journal, this failure of labeled indications to reflect current evidence was discussed. Today, we revisit the issue with more evidence supporting expanded pediatric implant criteria, yet we are now even further from the most recent official change in labeled indications. Despite this, we know that many CI centers, typically those affiliated with large academic medical centers, are routinely implanting children with sensorineural hearing loss who may not meet the conventional implant profile. For many implant programs, this is considered common practice based on the prevalence of evidence in both the clinical medical records and peer-reviewed literature. The need exists for an official expansion of implant criteria for children with significant hearing loss but who are not making expected, month-for-month progress in auditory, speech, and language skills with appropriately fitted amplification and recommended intervention. This topic has garnered considerable attention over the past two decades with our field's thought leaders, principal scientists, and master clinicians who all advocate for the expansion of pediatric CI criteria, including both audiometric thresholds and speech recognition abilities (Am J Otol. 1997;18[6 Suppl]:S125 http://bit.ly/2eUwQiQ;J Speech Lang Hear Res. 2005;48:853 http://bit.ly/2eUtmwK;Ann Otol Rhinol Laryngol Suppl. 2000;185:33 http://bit.ly/2eUxoFp;Int J Pediatr Otorhinolaryngol. 2002;63:91 http://bit.ly/2eUwwk3;Ear Hear. 2002;23:450 http://bit.ly/2eUylgX;Arch Otolaryngol Head Neck Surg. 2004;130:612 http://bit.ly/2eUwzwx;Ear Hear. 2011;32:313 http://bit.ly/2eUxjll;Ear Hear. 2015;36:14 http://bit.ly/2eUxf4L).
CONSIDERATIONS FOR CHILDREN UNDER 12 MONTHS
As mentioned previously, labeled indications for pediatric cochlear implantation include children 12 months of age and older. This age restriction, however, is not due to safety concerns about cochlear implantation for infants (Trends Amplif. 2010;14:46 http://bit.ly/2eUv5lH;Laryngoscope. 2016 http://bit.ly/2eUBD3W), nor lack of efficacy for cochlear implantation in infants with severe-to-profound sensory hearing loss. Rather, there is a rapidly growing body of literature demonstrating that children implanted under 12 months of age exhibit significantly higher word and language acquisition (Restor Neurol Neurosci. 2010;28:157 http://bit.ly/2eUyTDC;Otol Neurotol. 2010;31:1248 http://bit.ly/2eUC7a4;J Am Acad Audiol. 2012;23:446 http://bit.ly/2eUA6e6;JAMA. 2010;303:1498 http://bit.ly/2eUc6I2;Otol Neurotol. 2010;31:1315 http://bit.ly/2eUEfyH;Otol Neurotol. 2013;34:443 http://bit.ly/2eUBQEi;Int J Pediatr Otorhinolaryngol. 2014;78:1327 http://bit.ly/2eUB0Hw), speech perception (Otol Neurotol. 2010;31:1254 http://bit.ly/2eVcGFn), speech production intelligibility (Int J Pediatr Otorhinolaryngol. 2010;74:855 http://bit.ly/2eVeHSa), gross motor development (Ear Hear. 2015;36:e113 http://bit.ly/2eVhDhx), and vocabulary development (Ear Hear. 2009;30:128 http://bit.ly/2eVhA5h;Otol Neurotol. 2010;31:1248 http://bit.ly/2eUC7a4;J Speech Lang Hear Res. 2005;48:853 http://bit.ly/2eUtmwK), even when compared with children implanted in the second year of life.
Language learning opportunities are both critical and fertile in the first year of life. A baby with severe-to-profound sensory hearing loss is missing out on this precious, critical window of auditory- and multisensory-based opportunities for language learning and overall neurocognitive development. For a detailed review of language learning occurring in the first year of life, see Levine and colleagues http://bit.ly/2eUCJfO. They describe infant development of word segmentation, multisensory integration, lexical development, and identification of syntactic patterns. This is an excellent review for those of us in audiology clinics who rarely interact with the typically developing infant population.
EVIDENCE FOR EXPANSION OF CRITERIA
Until we have an official alteration of FDA-approved, labeled indications for pediatric cochlear implantation, the best we can do is to stay on top of the literature so that we can provide data-driven recommendations for our patients and their families. In this month's Journal Club article, we will review two recent articles providing evidence for the expansion of pediatric CI criteria.
Carlson MC, Sladen DP, Haynes DS, Driscoll CL, DeJong MD, Erickson HC, Sunderhaus LW, Hedley-Williams A, Rosenzweig EA, Davis TJ, Gifford RH. (2015). Evidence for the expansion of pediatric cochlear implant candidacy. Otology & Neurotology. 36:43-50 http://bit.ly/2eUD2HJ.
Carlson et al., completed a multi-center retrospective study of 51 pediatric implant recipients who had not met labeled indications for implantation. Their inclusion criteria were as follows:
- less severe hearing loss than specified in the current indications and/or,
- open-set word or sentence recognition scores > 30 percent, and
- recipient of the current generation of internal device and external sound processor (at time of study commencement).
Children with a diagnosis of auditory neuropathy were excluded for the purposes of this study.
Many of the children in this study had asymmetric hearing loss. On average, hearing losses were consistent with a severe-to-profound sensory loss in the implanted ear with a moderate sloping to profound sensory hearing loss in the non-implanted ear. Carlson and colleagues reported an average improvement in speech understanding of 63 percentage points in the implanted ear and 40 percentage points in the best-aided, bimodal condition. This finding was statistically significant for both listening configurations. The authors described that perhaps the most powerful finding in this study was the fact that each of the 51 children demonstrated postoperative benefit. In other words, not one implant recipient exhibited a decrement in performance for speech understanding, auditory skills development, or language development.
Leigh JR, Dettman SJ, Dowell RC. (2016). Evidence-based guidelines for recommending cochlear implantation for young children: Audiological criteria and optimizing age at implantation. International Journal of Audiology. 55:S9–S18 http://bit.ly/2eUD42p.
Leigh and colleagues completed a retrospective study of 140 children with sensory hearing loss (78 CI recipients, 62 hearing aid [HA] users) in an attempt to determine the degree of hearing loss and optimal age for pediatric CI candidacy. For the first experiment investigating the audiometric thresholds determining implant candidacy, all CI recipients were implanted before turning 3 years old and the HA users had a wide range of pure tone averages (PTAs) ranging from 25 to 120 dB HL. Both groups of patients completed open set word recognition testing and their postoperative scores were stratified into one of four groups: CI, profound HA, severe HA, and moderate HA. The CI recipients’ word recognition scores were significantly higher than both the severe and profound HA groups; however, there was no difference between scores obtained for the CI group and the moderate group.
For the second experiment investigating the optimal age for pediatric CI candidacy, a subset of 27 CI recipients was assessed on measures of expressive and receptive language. All participants were implanted at 2.5 years of age or younger and all 27 children exhibited significant language delay at one-year post-activation. In fact, both receptive and expressive language delay were significantly correlated with the age at implantation. However, all children demonstrated significant progress for language development with a mean rate of growth equivalent to one year per year of CI use—even for children implanted at 2.5 years of age. Important to consider here, however, is that the older the child is at the time of surgery, the greater language delay that the child will exhibit. Furthermore, it is possible that children implanted beyond 2 to 2.5 years may not close the language gap. Thus, the authors concluded that younger was most definitely better, though they were unable to provide a definitive lower age recommendation based on the limited dataset. Leigh and colleagues proposed that children under 3 years of age should be considered CI candidates provided that the PTA is 65 dB HL or poorer. This recommendation, if followed, would essentially equate the candidacy criteria for adults and children regarding preoperative audiometric thresholds. Further research is needed with larger sample sizes to determine the optimum lower age range for pediatric CI candidacy.
REVISION OF FDA-LABELED INDICATIONS
Noting the known benefits of cochlear implantation for children—now with moderate to profound sensory hearing loss (Otol Neurotol. 2015;36:43 http://bit.ly/2eUHF4v;Int J Audiol. 2016;55 Suppl 2:S9 http://bit.ly/2eUD42p), a thorough revision of FDA-labeled indications for pediatric implant candidacy is desperately needed to bring this technology to children who could truly benefit from it. Several large implant programs are making data-driven recommendations for CI candidacy for children who are under 12 months of age and/or with moderate sloping to profound hearing loss, provided that an appropriate hearing aid trial has been completed and the child is not making month-for-month progress on auditory, speech, and language skills. While this practice is already ongoing, conventional wisdom and direct professional and clinical evidence tell us that for each progressive implant center, there are more implant centers with practicing clinicians who are uncomfortable with making recommendations for children who do not meet the conventional auditory profile for CI candidacy.
Hearing health care professionals have a long way to go to bring this technology to infants, toddlers, and all children who could derive significant benefit. Indeed, the point of diminishing returns has not been identified, even for children with moderate hearing loss in the lower frequency region (Otol Neurotol. 2015;36:43 http://bit.ly/2eUHF4v;Int J Audiol. 2016;55 Suppl 2:S9 http://bit.ly/2eUD42p). Looking to the future, I remain hopeful that the next time we revisit this issue, we will be able to report that (1) CI indications officially specify candidacy for children less than 12 months of age, and (2) hearing losses ranging from moderate sloping to profound will be indicated, provided that the child is not exhibiting significant benefit from conventional acoustic amplification. The benefits associated with early implantation and expansion of implant criteria may just be the key to permanently close the gap between children with CIs and their normal-hearing peers for speech, language, psychosocial, and academic outcomes.