The ability to hear spoken language early in life is critical to development of spoken language. A number of studies have provided evidence that implantation of children younger than age 12 months may improve spoken language (1,4,8,11–13). The largest series of implanted infants was published in 2016 by Dettman et al. (1). They reported the long-term outcomes of congenitally deaf children including 151 implanted by age 12 months and younger. The 12 months and younger group had significantly better language and speech production outcomes than those implanted at 13 to 18 months and 19 to 24 months, when evaluated at school entry and late primary school.
Unlike many studies, this series does not exclude children with additional disabilities and conditions associated with language delay. These children are included because they are a growing proportion of CI candidates (10). Taking advantage of neuroplasticity by early implantation and providing effective auditory habilitation may be more important for maximizing the outcomes of this population than those having only an auditory deficit. Our results demonstrate that a significant number of complex children achieve measurable open-set skills and oral communication as their primary mode of communication, especially when implanted at a younger age.
The most striking finding in our series is the relationship between oral-only communication mode and younger age of first CI. The decline in rate of oral-only communication was particularly striking for all children implanted over age 24 months. Because communication mode in this study was determined at last follow up when the average age was 7.5 years, this reflects communication mode as many of the children entered grade school. In our locale, the vast majority of children who use sign in addition to oral communication are placed in total communication classrooms. Placement in total communication rather than oral-only or mainstream classrooms for most children requiring sign is, in our experience, influenced by these children often having lower oral language ability.
Although children implanted in the younger group (<12 mo) and the older group (12–36 mo) had similar preoperative hearing thresholds, the cause of hearing loss was variable and often unknown. It is likely that some children had hearing at birth and, therefore, more access to sound before CI. Earlier residual hearing would more likely advantage those in the older group. However, the children implanted below 12 months developed auditory skills more rapidly and were more likely to develop oral-only communication.
Comparisons using level of speech perception ability were not possible in this study due to the young ages and range of developmental status which required clinical use of different test measures and procedures. This is a significant limitation of the study as achieving a low but greater than zero level on a test can represent a considerable difference in ability from achieving a score near the high end of a test. In addition, only information regarding communication mode(s) rather than comprehensive information about receptive and expressive language at last follow up was available. We also note that there may be unknown differences such as parenting and socioeconomic status between children who receive an implant under age 12 months and those who do not, that might influence performance outcome. For example, the finding of a lower rate of Medicaid funding in the younger age group suggests the possibility that those who received CIs at this younger age came from families likely to have more financial resources and higher education level which may have benefited the child's learning and development. These are all areas for future study.
Regarding outcomes of the complex children, it was not possible to grade the relative severity of complicating conditions. Therefore, complex children in the older group may have been more severely affected and for reasons beyond age of first CI, less likely to develop open-set ability and oral-only communication outcomes in comparison to those in the younger group.
Growing evidence of the advantages of implantation below age 12 months must be balanced against potential increased anesthetic and surgical risk (14). Previous series describing surgical complications in children under 12 months reported complication rates similar to those found in older children and adults (13,15–18). An additional publication focused solely on soft tissue complications in 94 ears of 66 children implanted below 12 months reported only one minor wound infection that was successfully treated without surgery (19). Our series is similar, with a low rate of major surgical complications even in the children under 12 months of age. Most were related to intra-cochlear CSF and were anticipated.
Yeh et al. (20) previously published the most comprehensive study of anesthesia outcomes in 123 children implanted under age 18 years, of which 12 were below age 12 months. Few events requiring intervention occurred and all but one were respiratory. Other authors have concluded anesthesia risk of implanting infants and young children is acceptable (13,15–18). However, ASA status or occurrence of respiratory critical events was often not reported (15–18).
From a pediatric anesthesia perspective, risk of morbidity and mortality is highest for infants with severe comorbid conditions and for children undergoing emergent surgery (9). Study of major morbidity requires thousands of patients because these complications are exceedingly rare. One of the first reliable studies of cardiac arrest in the perioperative setting was published in 2000 and evaluated 289 cardiac arrests in over one million episodes of pediatric anesthesia (21). More than half occurred in infants of who two-thirds had significant comorbidities placing them in ASA status III–V (Table 1). Halothane played a causal role in two-thirds of cardiac arrests. Cardiovascular events caused the majority of anesthesia-related arrests in patients without underlying heart disease and were often related to blood loss and/or inappropriate fluid therapy. The next most common cause of anesthesia-related arrests was respiratory arrests, most commonly caused by laryngospasm and problems managing a difficult airway. By 2000 in the United States, Halothane was replaced by safer agents. Modern monitoring equipment and new approaches to proactively minimize risk have dramatically improved safety. The unique anesthetic needs of children, especially those who are very young and/or have comorbid conditions, has become widely recognized and resulted in pediatric anesthesia becoming a board certified subspecialty in 2013. For these reasons, major morbidity for children, including those less than 12 months, has declined.
Today, for children less than 36 months of age undergoing CI surgery, anesthetic management and risk does not differ from other elective procedures. Although the incidence of cardiovascular and respiratory critical events is significantly lower compared with previous decades, infants under 12 months, especially those with underlying systemic comorbidities or difficult airways, remain at heighten risk (22,23). These risks, however, are minimal in the otherwise healthy ASA I or II child undergoing CI.
Studies have demonstrated more favorable outcomes of elective surgery in children at highest anesthetic risk, namely those with congenital heart disease, craniofacial anomalies and syndromes such as CHARGE (commonly ASA status II or III), who are managed by a specialized pediatric anesthesiologist in a well-resourced setting, rather than the occasional pediatric anesthesiologist or trainee (21,22).
In our series, 236 episodes of anesthesia for CI surgery were reviewed for laryngospasm, desaturation, bradycardia and hypotension requiring intervention, in addition to major morbidity. There were no major morbidities despite implantation of children with complex medical histories and comorbid conditions, an expected finding given the rarity of these types of complications. However, lesser anesthetic events, such as laryngospasm or cardiovascular events requiring management were also uncommon in our series. The paucity of even minor anesthetic events in our series may be due to the nature of our practice within a tertiary care children's hospital staffed by board certified pediatric anesthesiologists.
The two PICU admissions were for monitoring due to concerns about increased risk for complications. The vast majority of children were discharged on the day of surgery, including most that underwent bilateral simultaneous implantations under 12 months of age. Most of the 28 children who were observed overnight in the hospital (Table 8) were ASA status II or above, while only five were ASA status I. A difference in anesthetic-related problems, including pain control and nausea and vomiting, did not account for overnight versus same day discharge. Longer surgery duration, which may be associated with more complex surgery, was related to overnight observation. Although reasons for overnight stay may reflect parental anxiety and geographic distance from the hospital, overnight stay of many of these children may have been influenced by higher ASA status, and longer surgery, especially for children with longer bilateral procedures such as those with ossified cochleae.
Despite decades of research demonstrating the benefits of early implantation, many children are not implanted below age 2 years. There are many barriers to implantation, often based on socioeconomic status, including lack of referral for evaluation and insurance benefits, especially for children under age 12 months. Commercial insurance and Medicaid plans often deny coverage based upon outdated Food and Drug Administration audiological and age guidelines created when commercial approval for use in children 12 months and older was granted almost two decades ago. Despite significant evidence of benefit, CI before age 2 years is not a goal of federal early intervention legislation nor does the Joint Committee on Infant Hearing, an influential multidisciplinary group, promote early implantation (24).
There is a significant body of literature indicating that young age of CI is advantageous. Despite this knowledge, implantation of infants remains relatively uncommon in the US. Our study adds to the growing literature that implantation below age 12 months results in more rapid auditory skill development and exclusively oral communication. In addition, the outcomes of this study provide evidence that CI is also safe and effective for infants and children with complex medical problems, including conditions known to cause language delay. It is likely that significant improvement in language would result if changes in public policy reduced barriers to early implantation for all children.
The authors thank Karen I. Berliner, Ph.D. for data analysis and manuscript editing.
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Keywords:Copyright © 2019 by Otology & Neurotology, Inc. Image copyright © 2010 Wolters Kluwer Health/Anatomical Chart Company
American Society of Anesthesiology physical status; Children with additional conditions associated with language delay; Cochlear implant; Communication mode; Infants; Open-set speech perception; Oral communication; Pediatric anesthetic safety; Spoken language; Surgical and anesthetic complications