Early Hearing and Communication Development

Executive Summary

In the past decade, identification of hearing impairment in early infancy has emerged as an important public health issue. This has been spurred primarily by significant technological advances in hearing screening tests. Population-wide screening of newborns for hearing impairment has been frequently advocated and is now being widely implemented - for example, in Ontario, the United States and the United Kingdom. However, in the health services community, there remains a lack of full consensus about the appropriateness of universal newborn hearing screening.

Given the importance of this issue, as well as evidence of diverse patterns of early identification of hearing impairment throughout Canada, Health Canada established the Canadian Working Group on Childhood Hearing (CWGCH) in 2000. The Working Group was a multidisciplinary expert body that included relevant health professionals and public representatives.

The goal of the Working Group was to provide information that will assist individuals or agencies considering the development of programs for early hearing and communication development (EHCD). The approach selected was to develop and disseminate a summary of the latest scientific information on key aspects of the rationale and methods for EHCD. The Working Group adopted an evidence-based method in order to go beyond clinical opinion and withstand scientific scrutiny. The World Health Organization principles of screening and the conceptual framework of the International Classification of Functioning, Disability and Health guided the evidence reviews and terminology used.

The Working Group addressed the following areas:

- the burden of the disorder, including the number of children affected by hearing impairment (prevalence) and patterns of detection
-hearing screening tests
- audiologic assessment
- medical evaluation and management
- amplification
- effectiveness of different approaches to communication development

For these topics, the Working Group conducted formal evidence reviews by standard scientific methods, to the fullest extent possible within resource and timeline constraints. Working Group members also considered program infrastructure, evaluation and quality improvement, and cost-effectiveness, but did not formally review these topics.

The following are the main findings of this process:

• The burden of the disorder is substantial. The prevalence of permanent childhood hearing impairment is about 1 per 1,000 live births in infancy for impairment greater than 40 dBHL in the better ear. In infants with documented risk factors such as extreme prematurity, congenital facial auricular defects or severe jaundice, this rate is up to 10 per 1,000.

• In the absence of systematic screening, the detection, confirmation, diagnosis and management of hearing impairment are significantly delayed. With universal newborn hearing screening, the median age of diagnosis is less than 3 months.

• Hearing screening is currently based on automated otoacoustic emission testing and automated auditory brainstem response testing. These tests perform well when appropriate protocols are used. Loss to follow-up is the largest single factor limiting the effectiveness of screening.

• Complete audiologic assessment, which can be achieved in healthy children under 6 months of age, is essential to appropriate hearing aid fitting and to family decisions about communication development options. The existing literature is unclear with respect to the audiologic assessment and management of auditory neuropathy.

• Medical evaluation of an infant with hearing impairment should be initiated at less than 3 months of age and management (e.g., amplification) should be started by 6 months of age. Common causes of bilateral sensorineural hearing impairment include:

  • nonsyndromic gene mutations, such as connexin 26 mutations
  • genetic syndromes, such as Waardenburg syndrome
  • nongenetic causes, including preterm birth, asphyxia, meningitis, kernicterus, intrauterine infection and auditory neuropathy

• There is a need for evidence-based rational decision strategies, embracing history taking, physical examination, risk assessment and genetic testing and their interpretation, in children with bilateral sensorineural hearing impairment.

• Between 70% and 90% of children will experience fluctuating conductive hearing impairment secondary to otitis media with effusion, with or without acute otitis media, in the first two years of life. Unilateral otitis media with effusion clears after an average of five weeks with or without a history of acute otitis media. Bilateral otitis media with effusion clears on average after eight to nine weeks. Bilateral myringotomy and ventilation tube placement reduces the mean duration of otitis media with effusion and improves hearing thresholds, as well as some behavioural problems and expressive language scores in some children. Antibiotic therapy and conjugate pneumococcal vaccine should be considered in relation to middle ear disease in children.

• Accurate assessment of otitis media with effusion is important for the diagnosis and treatment of children with sensorineural hearing impairment. Many physicians advocate an aggressive treatment approach to children with otitis media with effusion and underlying sensorineural hearing impairment.

• Hearing aids can improve auditory performance in children with auditory impairment who have some hearing bilaterally. To ensure the accurate fitting of amplification in young infants, highly qualified professionals and paediatric-specific hearing instrument fitting protocols are required.

• Based on existing research, it is not possible to determine the effectiveness of the four most common communication development options for children with permanent congenital hearing impairment: aural-oral, auditory verbal therapy, American Sign Language and total communication.

• Some studies have concluded that early identification and strong family involvement improve the development of speech and language in infants and young children with hearing impairment.

• Public health system models and linkages seem more appropriate than traditional medical models for effective delivery of comprehensive EHCD programs.

• Universal newborn hearing screening must be accompanied by appropriate, accessible services for confirmation, diagnosis and effective hearing and communication development options for all children referred through screening. EHCD programs should reflect demographic and cultural factors as well as existing systems, infrastructure and well-developed collaborative links with other health care, social support and educational systems.

The CWGCH has concluded that newborn hearing screening leads to early identification of hearing impairment. Early identification leads to improved hearing and facilitates communication development. The detailed reviews of evidence underlying this position are available on request.

This document also contains recommendations for further research. For example, the generation of evidence on a broad range of possible outcomes for affected children and families is a high priority.

The issues of ethics and societal values are beyond the scope of this report. Nevertheless, these questions are crucial and should be weighed, along with the available evidence, when considering whether to implement a new EHCD program.

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