Universal neonatal hearing screening: past, present, and future.

After a brief review of the history of newborn hearing screening including the Downs behavioral testing procedure, the Crib-o-gram and similar devices, and the use of auropalpebral reflex and otoacoustic emissions, there is a discussion of key issues that need to be resolved before universal hearing screening is introduced. Included are questions regarding the target population(s) of screening programs, well baby versus NICU screening, dealing with false-positives and the effects on parent-child relationships, and finally, the availability of resources for screening and follow-up. The results of a recent study in the United Kingdom that assessed the current state of audiology services and found there is a difference between existing standards and what is actually being done in practice, are presented and considered in terms of current trends in the United States to move ahead with universal screening without a solid database of information regarding the preparedness of clinical centers to deal with the need for services that will result from the initiation of universal programs. Caution is urged.

Universal newborn screening: a dream realized or a nightmare in the making?

There is a very strong movement to develop universal newborn hearing screening. This effort is the end product of a long international research effort to determine the most effective means to screen newborns. Now that OAE and ABR together offer a superior mechanism to achieve universal screening, problems related to middle ear effusion, non-high-risk children and adequate resources for all aspects of identification, diagnosis and treatment have come to the fore. Further, what to do in the developing world is also a major problem as audiology embarks on this exciting new frontier. This paper discusses some of the issues, raises some concerns and offers a few small solutions.

Prevalence of sensorineural hearing loss in children in Costa Rica.

There is very limited information available about hearing loss in children in Latin America and in Central America in particular. Costa Rica is a peaceful, well-organized country with an excellent health care system and a very good infrastructure of roads, programs, and services. It served as the site for a four-phase study to determine the incidence and prevalence rate for sensorineural hearing loss in children in that region of the world. The four phases involved (1) screening over 12,500 children in the public schools, (2) examining those enrolled at programs for the hearing impaired, (3) searching the community for children not in schools or special programs, and (4) an extensive questionnaire designed to obtain basic demographic data about hearing-impaired children in the country. Included were questions about age of identification, etiology, and hearing aid use. Results of phases 1 and 2 are reported here. Using a 1.368 per 1,000 live birth average (a figure reported for 36 nations), the projected number of hearing-impaired children in Costa Rica should be about 1,068. After concluding the first two phases of the study, it was determined that the actual number of hearing-impaired children in Costa Rica is between 1,174 and 1,274. That is a ratio of between 1.50 and 1.63 hearing impaired per 1,000 live births, well within the ranges reported elsewhere. Since this is the first national study of a Latin American country, that information is significant, suggesting that the general prevalence of hearing loss in that part of the world is the same as in the developed nations of Europe and North America.

Challenge of epidemiological research in the developing world: overview.

Listing the eight most important aspects of epidemiological research relevant to hearing loss, this paper reviews some of the difficulties encountered in trying to do such research in the developing world. Various research formats are discussed. This paper concludes with a review of what has been reported in the world's literature about the incidence and prevalence of sensorineural hearing loss in children. The average finding from 34 nations is 1.368 hearing impaired per 1,000.

Neonatal asphyxia, definitive markers and hearing loss.

A study of 56 severely asphyxiated infants (8 hearing impaired and 46 normally hearing) was designed to identify specific markers associated with asphyxia which could be related to hearing loss. Sixteen variables, including such items as: one- and five-minute Apgar scores, muscle tone, use of a ventilator, prolonged stay in the NICU, hypoxic-ischemic encephalopathy (HIE), other organ damage, and intra-uterine growth retardation (IUGR) were considered. Results suggested four factors related to asphyxia which are often found in the presence of hearing loss, but none of these was considered a definitive marker or predictor of such a disability. A combination of HIE, seizures, associated organ damage and IUGR should be considered a strong marker for the probability of a sensorineural hearing loss.

Ototoxicity and irradiation: additional etiologies of hearing loss in adults.

A brief review of the effects of the seven groups of substances and chemicals known to affect hearing and/or the vestibular system is followed by a more detailed discussion of cisplatin (cisplatinum). An illustrative case study is included that exemplifies a recent finding of some recovery of hearing following withdrawal of cisplatin chemotherapy. Some suggestions for reducing the potential for ototoxicity are also presented. The article continues with a discussion of the effects of irradiation on hearing and the ear and an illustrative case study. Included are some reported results from patients in the Ukraine who were exposed to excessive radiation as a result of the Chernobyl nuclear disaster. A discussion of the effects on the ear and the vestibular system caused by the interaction between chemotherapy and irradiation treatment is followed by the warning that, with the recent successes these treatments have had in the war against cancer, more patients with hearing loss triggered by these techniques will be seen in audiology clinics. These factors are now one of the newest and more frequent etiologic factors for hearing loss in adults in this decade.

Auditory brain stem responses to air- and bone-conducted clicks in the audiological assessment of at-risk infants.

Auditory brain stem responses (ABRs) to air- and bone-conducted clicks were used to assess the auditory status of 170 at-risk neonates. During the perinatal period, 20.6% (35/170 cases) of the at-risk infants failed ABRs to air-conducted clicks at 30 dB nHL in at least one ear. Ear-specific results indicated an initial failure rate of 15.0% (51/340 ears). Approximately two-thirds (32/51 ears) of these initial failures showed purely conductive deficits, whereas the remaining one-third (19/51 ears) involved suspected sensorineural components. Follow-up audiological evaluations were performed for 87.1% (148 cases) of these at-risk infants at 4 mo and/or 1 yr corrected age. Based on the initial tests and follow-up assessments, the tentative operating characteristics of ABRs to both air- and bone-conducted clicks for identification of sensorineural deficits in at-risk neonates were calculated. It was found that the ABR to bone-conducted clicks yielded better specificity, predictive value of positive results, and overall efficiency. It is suggested that the ABR to bone-conducted stimuli should be viewed as a valuable addition in the assessment of cochlear reserve in infants who fail a newborn auditory screening to air-conducted stimuli.

Maturation of behavioral response.

The level of maturation of the auditory system markedly affects the results of all forms of infant hearing screening. The same test repeated in two weeks may yield significantly different results. The paper reviews some of the maturational changes which occur, considers male/female differences, and offers some normative developmental information about the preterm infant.

Hearing loss and congenital rubella in Atlantic Canada.

There were 41 children born between 1973-1976 in Atlantic Canada who were victims of a severe rubella epidemic. This paper investigates prevalent audiometric patterns, incidence of middle ear disease, evidence regarding progressivity of hearing loss and any relationship between presence of middle ear disease and progressivity. Both surgical and audiological records were utilized in a combined retrospective-prospective study. Results indicate a typically flat audiogram for our group, with possible errors in the analysis of high frequency data accounting for differences between our center and those audiograms reported by other centers. Most of our children have a type A (normal) tympanogram (72.9%), but three have a type As which may be indicative of possible middle ear malformations. Six children (11 ears) have demonstrated only type AD and/or type B tympanograms. These may represent ongoing disease, middle ear malformation, or both. A number of variables (i.e., poor reliability, maturational effects, sound field compared to ear phone results) have contributed to a general feeling that progressivity of the hearing loss of rubella children may be a common phenomenon. A careful examination of our data found progressivity clearly documented in three cases. There was no relationship between presence of middle ear pathology and progressivity.

Intensive care nursery noise and its influence on newborn hearing screening.

Numerous studies have recently reported the possible damaging effects noise exposure may have on premature infants. While noise levels appear to be within established damage risk criteria for an adult, there is little evidence to support the assumption that intensity levels and duration are similar for an infant population. It was the purpose of this study to measure sound pressure levels within an intensive care nursery and a series of isolettes and to report the behavioral pass/fail screening status of infants who were confined to those settings immediately after birth. It is suggested from the results of our study that due to the stimulus parameter used in behavioral testing, noise exposure is not an influencing factor in infant hearing screening.

Identifying deafness in the newborn.

The necessity of early identification of hearing loss has long been urged by otolaryngologists, pediatricians, audiologists, and others working with the deaf. Yet there have been difficulties in implementing accurate and cost-effective newborn hearing screening programs. This article reviews some of the history of infant screening programs, discusses various areas of research related to stimulus and response parameters, and outlines a screening program, designed to fit new recommended procedures, currently under way in Halifax.

Observer bias as a factor in neonatal hearing screening.

To evaluate observer bias as a possible factor influencing neonatal hearing testing, two trained observers were asked to evaluate the behavior of 200 neonates at a moment the observers thought a stimulus was being presented. Observers were receiving masking noise, and when the stimulus button was pressed a stimulus might or might not be delivered to the child. Results suggest that observer bias is not a factor when arousal is the only acceptable response and is clearly defined, and the observers are limited to a yes-no decision. Sequential analysis of infant response patterns is presented and a specific test scoring protocol is outlined.

White noise as a pretest sensitizer for neonatal hearing screening.

To determine the effects of white noise as a pretest sensitizer in neonatal hearing screening, 450 neonates were tested under 18 test conditions which also permitted examination of infant state and criterion stimuli (warble tone versus narrow band noise) as variables. There were three pretest conditions: No pretest sensitizer; 90 dB pretest sensitizer, and 100 dB pretest sensitizer. Each pretest condition was followed by either a 90 or a 100 dB criterion stimulus. Analysis concerned an increase in the number and in the strength of the responses. Generally, there was no benefit associated with the use of white noise as a pretest sensitizer.