Identification of neonatal hearing impairment: Infants with hearing loss

Objective: This article describes the audiologic findings and medical statu s of infants who were found to have hearing loss, detected as part of the I dentification of Neonatal Hearing Impairment (INHI) project. In addition, t he neonatal and maternal health variables for the group of infants who coul d not be tested with visual reinforcement audiometry (VRA) due to developme ntal and visual disability are presented. Design: The overall goal of the INHI project was to evaluate the test perfo rmance of auditory brain stem response and evoked otoacoustic emission (OAE ) tests given in the newborn period. These tools were evaluated on the basi s of the infants' hearing when tested behaviorally with VRA at 8 to 12 mo c orrected age. The neonatal test results, VRA results, medical history infor mation and a record of intercurrent events occurring between the neonatal p eriod and the time of VRA were collated and reviewed. The purpose of this a rticle is to review the characteristics of those infants who were found to have hearing loss. Results: Of 2995 infants who had VRA tests judged to be of good or fair rel iability, 168 had a finding of hearing loss far at least one ear, an incide nce of 5.6%. Sixty-six infants had bilateral losses, an incidence of 2%, an d 22 infants had bilateral hearing losses in the moderate to profound range , an incidence 0.7%. The prevalence of middle ear problems was greater than 50% among these infants with hearing loss. From the larger group of 168 in fants with hearing loss, a group of 56 infants (86 ears) was chosen as thos e with a low probability that the hearing loss was due to transient middle ear pathology and was more likely hearing loss of a permanent nature. These were the infants used for the analyses of neonatal test performance (Norto n et al., 2000). In this selected group there were 30 infants with bilatera l impairment of at least mild degree, which is an incidence of 1%. There we re approximately equal numbers of ears in the mild, moderate, severe and pr ofound range of hearing loss. Risk factors associated with hearing loss were reviewed for the total sampl e of infants tested with VRA and for those infants with hearing loss. A his tory of treatment with aminoglycosides was the risk factor most often repor ted in the entire sample; however, there was no difference in prevalence of this risk factor for the normal-hearing and hearing-impaired groups. The r isk factor associated with the highest incidence of hearing loss was stigma ta of syndromes associated with sensorineural hearing loss and other neuros ensory disorders. Sixty-seven infants who returned for follow-up could not be tested with VRA due to severe developmental delay or visual disability. Many of these infa nts had medical histories indicating the sequelae of extreme prematurity an d/or very low birthweight. Conclusions: Most of the hearing losses found in this study were mild and, based on clinical history and tympanometry tests, many of the mild and some of the moderate impairments may have been acquired in early infancy due to middle ear effusion. In the group of infants used for determination of neo natal test performance there were approximately equal numbers of mild, mode rate, severe and profound lasses. Only a small percentage of infants with a conventional risk indicator for hearing loss actually had a hearing loss, and there were a significant number of infants with hearing loss who did no t have a risk indicator. These findings support the need for an early ident ification program based on universal neonatal hearing screening rather than by targeted testing of those with risk indicators.