Minimum and Maximum Age for Implantation and Hearing Aid Benefit

The minimum age for implantation is currently set at 2 years in the United States, with compassionate exemptions granted for children younger than age 2 who are deafened by meningitis, with the threat of cochlear ossification possibly preventing adequate electrode insertion. Data regarding a small sample of early implanted infants (before 2 years of age) show a lack of surgical complications,2 whereas others report improved communication outcomes on children with early implantation.3 The controversy arises when considered with the second issue of how to show hearing aid benefit.

There are both national initiatives and regional efforts to establish universal hearing screening in the United States.4'5 The stated goal of these initiatives is to identify all infants with early onset of hearing loss by 3 months of age and to accomplish hearing aid fitting by 6 months of age for those infants identified with significant hearing loss. The point of these initiatives is to take advantage of the child's natural facility for the acquisition of speech and language during the first year(s) of life, a facility that does not depend on exposure to spoken language but that applies across any mode of language expression. If spoken language is the goal, we know that the sooner sensory evidence from the aided auditory channel is incorporated into learning for the child with congenital deafness, the better the outcomes will be. According to this argument, implantation during the first year of life, but certainly before 2 years of age, seems logical. If this approach is taken, however, there is the real risk that insufficient time for hearing aid use, inadequate hearing aid fitting, and inadequate definition of the infant's residual hearing will mask the child's aided auditory potential. Infants and toddlers with severe hearing loss who are identified early, and who have the benefits of properly fit hearing aids, as well as family and professional support show clear advantage in the area of communication development.6

Children with severe hearing loss (90 to 100 dB bilaterally) who have the advantage of early intervention outperform children who are congenitally deaf and receive implants, particularly in terms of interpersonal communication development.7 In addition, although accurate and reliable evaluation of hearing sensitivity can be accomplished in infants and toddlers through electrophysiologic and behavioral tests administered by experienced pediatric audiologists, the same cannot be said about the quality of hearing evaluations and habilitation processes everywhere in the United States. Despite the criterion of a minimum of 6 months of hearing aid use before an implant is chosen, children more typically need 1 to 2 years of quality input through a well-fit hearing aid before aided hearing benefits are realized. Implant signal processing is improving, as is hearing aid technology. Because implanted cochleas will be unable to take advantage of present or future hearing aid advances, careful definition of residual hearing, informed fitting of hearing aids, and early intervention that includes appropriate use of amplification must precede any consideration of implantation.

With regard to maximum age for implantation, the data suggest that most children with congenital deafness implanted after age 5, and particularly during or after puberty, will be parttime or nonuser 1 to 2 years postimplant.8'9

Some data are available regarding adolescents and adults who are congenitally deaf who, after further progression of hearing loss, elect to switch from hearing aid use to a cochlear implant. The individuals in this subset who were long-term dedicated hearing aid users and possessed spoken language before implantation, seem to derive substantial benefit. These persons would likely resemble typical learners in that audition has played a role in their communication development in the first place.10 As suggested, evidence regarding implant outcomes in adolescents and adults who were not hearing aid users and/or who were primarily sign language users suggests far less satisfaction. Implantation in persons in this latter category should be approached very carefully, if it is performed at all.

Hearing Aids Inside Out

Hearing Aids Inside Out

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