Extremely low birth weight infants are at high risk for auditory neuropathy

Abstract

Auditory neuropathy (AN) is a condition in which transmission of sound to the brain is abnormal. This is reflected as an electrophysiologic profile of normal otoacoustic emissions (OAE), with abnormal auditory brainstem evoked responses (ABR). Functionally speech perception is impaired and management strategies remain controversial. AN can be missed if high-risk newborns are screened for hearing loss with only OAE testing. The rate of sensorineural hearing loss (SNHL) in high-risk nursery infants is 10 times greater compared with normal term newborns. Therefore, we hypothesize that infants from the neonatal intensive care unit (NICU) are at significantly higher risk for AN than normal term infants.Objective: The objective of this study is to establish a prevalence rate and characterize risk factors for NICU graduates who demonstrate the AN electrophysiologic profile.Study Design: This retrospective study examined infants admitted to the NICU at Kapi'olani Medical Center for Women and Children in Honolulu, HI from 1999 through 2003. Infants were screened with automated ABR. Diagnostic testing and OAE were performed before discharge if the ABR was abnormal. Hospital courses of 24 AN, 71 SNHL and 95 gestational age (GA)-matched control infants with normal hearing were reviewed.Result: With a SNHL prevalence of 16.7/1000, the rate for AN was 5.6/1000 NICU infants. Compared to infants with SNHL, infants with AN were significantly younger (GA 28.3±4.8 AN vs 32.9±5.2 weeks SNHL, P<0.0001) and smaller (BW 1318±894 AN vs 1968±1006 g SNHL).Nearly two-thirds of the AN infants were ELBW and had significantly longer hospital stays compared to SNHL infants of the same birth weight group. Exposure to furosemide, aminoglycosides, vancomycin or dexamethasone was associated with increased AN but not SNHL. Peak bilirubin level correlated with SNHL but not AN.Conclusion: Low birth weight NICU infants are at significant risk for AN. ELBW infants are at significantly higher risk for both AN and SNHL.Infants admitted to the NICU should be routinely screened by automated ABR and if abnormal, further evaluation should be started before hospital discharge. Early identification of AN will result in better understanding of this disorder and lead to the development of appropriate intervention strategies.

Selective Inner Hair Cell Loss in Prematurity: A Temporal Bone Study of Infants from a Neonatal Intensive Care Unit

“…These differences between the selective IHC loss group and both other groups were statistically significant (pG 0.05 by unpaired t test). These data mirror those of a recent clinical study finding that infants with AN showed, on average, 4-week shorter gestation periods than those with other forms of sensorineural hearing loss (Xoinis et al 2007). …”

“…The high percentage of ears with hair cell loss of all types is perhaps not surprising given that sensorineural hearing loss is significantly more common in NICU survivors than in babies not requiring such intense hospital care at birth (Xoinis et al 2007) and that the ears analyzed here were from the population that was so seriously ill that they did not survive the NICU stay. Although many of these infants with various forms of sepsis may have been treated with aminoglycosides, such treatment is not highly correlated with hearing loss in NICU survivors (Hess et al 1998).…”

“…The finding was surprising since selective inner hair cell loss is an uncommon pathology in both the human and animal literature. The finding was also intriguing because all three cases were preterm babies and because there are many reports in the literature of an association between AN and prematurity (Rance et al 1999;Madden et al 2002;Beutner et al 2007;Xoinis et al 2007).…”

“…Retrospective clinical studies have suggested that low birth weight and prematurity are risk factors for AN (Madden et al 2002;Beutner et al 2007;Xoinis et al 2007;Teagle et al 2010). Of course, prematurity is associated with a long list of comorbid factors including hyperbilirubinemia, hypoxia, necrotizing enterocolitis, bronchopulmonary dysplasia (Beutner et al 2007;Teagle et al 2010), and other clinical conditions also noted in the NICU charts of the premature infants in this study (Tables 1 and 2).…”

“…Estimates suggest that as many as 1.5% of NICU survivors have a significant hearing loss compared with only 0.3% of those without such serious neonatal health issues (Xoinis et al 2007). Prevalence increases to 3% if the sample is limited to premature infants born G28 weeks' gestation (Robertson et al 2009).…”