International Journal of Pediatric Otorhinolaryngology
Case reportAuditory neuropathy/auditory dys-synchrony detected by universal newborn hearing screening
Introduction
Objective physiological hearing assessments are used in newborn hearing screening because behavioral testing is unreliable. Two common assessments used are the otoacoustic emissions (OAE) and the automated auditory brainstem response (Auto-ABR). The OAE test is a quick and inexpensive method but it has a high false positive rate; and of more concern is the possibility of false negatives, such as in the case of auditory neuropathy/auditory dys-synchrony (AN/AD).
The term auditory neuropathy was first used by Starr et al. [1] in 1996 to describe 10 patients who had acquired hearing impairment in the presence of normal cochlear outer hair cells. All went on to develop a peripheral neuropathy later in life. Starr et al. [1] attributed the hearing loss to a generalized neuropathic disorder and he suggested that the lesion might be in the auditory nerve. In 1996, Kaga et al. [2] also described two patients with absent auditory brain response (ABR) but almost normal OAE. In addition, one patient had vestibular problems. These patients were diagnosed to have auditory nerve disease due to an unknown cause.
In 1997, Deltenre et al. [3] reported three cases of infants who had hearing loss detected early following major neonatal events. They showed the same pattern of absent auditory brainstem response but with preserved cochlear outer hair cell function. Doyle et al. [4] in 1998 described eight children who had hearing loss disproportionate to the normal OAE and cochlear microphonics. Five had reverse sloping hearing loss, two had predominantly high-frequency hearing loss and one had a mild flat pattern. The pattern of test results suggested neuropathy of the cochlear nerve and implied a neural deafness as opposed to a sensory deafness.
Hood [5] describes auditory neuropathy as being distinguished from other types of auditory abnormalities by the presence of normal OAE, absent middle ear muscle reflex and auditory brain response in the presence of normal radiological results. ABR testing showed that this disorder was distinct from a central deafness and the lesion potentially could be anywhere from the inner hair cells to the auditory cortex. In 2001, Berlin et al. [6] recommended that the term auditory neuropathy/auditory dys-synchrony be used because the presence of poor synchrony of the auditory nerve suggests a more logical connection to viable management options. The pattern of AN/AD has been seen in varied presentations from neonates to adults with acquired hearing loss. Hence, AN/AD is not a diagnosis, but a presentation now readily identified with OAE and ABR screening. It is not a new disease, but an entity, which is recognized because of improvements in hearing assessment.
Since mid 2002, universal newborn hearing screening has been implemented in Kandang Kerbau Women's and Children's Hospital (KKWCH), Singapore with the use of Auto-ABR testing. We present nine cases of newborns detected to have auditory test patterns consistent with AN/AD over 1 year. This pattern consisted of absent ABR in the presence of normal OAE.
Section snippets
Patient demographics (refer to Table 1)
Previous publications on AN/AD have mainly been sporadic case reports and case series from at risk infants. Our cases are from a universal newborn hearing screening program. All newborn infants in our hospital have an Auto-ABR test. Infants with abnormal results are referred to and followed up by the Pediatric Otolaryngology Service. A total of 52 cases of hearing loss were detected out of 14,807 infants screened from April 2002 to March 2003. Nine cases out of 52 had a pattern consistent with
Discussion
The cochlea has inner and outer hair cells. Inner hair cells have mainly an auditory role. Outer hair cells have mainly a modulatory role as a cochlear amplifier. The two systems are biologically distinct and differ in their vulnerabilities to different pathologies. OAE are generated primarily by the outer hair cells and hence may not be a reliable surrogate for the inner hair cell function. Therein lies the limitation of using OAE testing as a screening tool for hearing loss.
The other methods
Conclusion
AN/AD is not as rare as once thought and even infants with no risk factors have been seen to have this presentation. The percentage of AN/AD presentation in newborns at our institution with hearing loss is 17.3%. Unilateral presentation accounts for one-third of the cases. Passing OAE screening does not rule out deafness completely. The use of OAE as a screening technique has its limitations. The use of Auto-ABR enables earlier detection of this condition with less false positives and false
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2014, International Journal of Pediatric OtorhinolaryngologyCitation Excerpt :In one analysis, Wolff et al. [20] found that the reported sensitivity of OAE measurement varied from 50% to 100% and the specificity from 49% to 97% [15]. A weakness of OAE measurement is that it does not detect fluctuating hearing impairments or those due to auditory neuropathy [19–21]. A controlled study carried out in the UK employed two-stage screening: the estimated sensitivity was 91.7% with a 95% confidence interval (95% CI) between 0.742 and 0.977, the specificity 98.5% (95% CI 0.983–0.987) [21–23].