The Influence Of Neonatal Hyperbilirubinemia On Auditory Function

BACKGROUND AND OBJECTIVE:Neonatal hyperbilirubinemia is defined as a condition of total serum bilirubin level above 220.6μmol/L(12.9mg/dL) in term neonates while above 255μmol/L(15.0mg/dL)in preterm neonates.The prevalence of jaundice in term and preterm infants is approximately 60% and 80%,even nearly in all preterms with some reports.Most jaundice disappear spontaneously,nevertheless,the others may develope into hyperbilirubinemia even kernicterus causing permanent neurologic sequelae, including developmental delay,autism , cerebral palsy and sensorineural hearing loss. Extremely severe cases may die in acute stage.It is possible that builirubin encephalopathy occur when bilirubin level under the traditional stander of hyperbilirubinemia if accompanied by infection, hypercapnia, hypoproteinemia and so on.Since the central auditory nerve is very sensitive to the toxicity of bilirubin.,sensorineural hearing loss happens in children with hyperbilirubinemia with the mobidity about 18%.Cochlear, auditory nerve and cochlear nuclei may be involved.Abnormal auditory function may appear in early stage.Delayed hearing loss may affect the normal language development in children.To some extent,the damage is reversible after appropriate treatment.Therefore, early intervention can reduce the morbidity and motality .However, some studies show that there is no relationship bewteen hyperbilirubinemia and hearing loss.Distortion product otoacoustic emissions (DPOAE) mainly reflects the cochlear function, but can not detect condition of the auditory nerve and brainstem auditory pathway. We can maintain these by using auditory brain stem ( ABR).This study was designed to assess and analyse the auditory function of children with neonatal hyperbilirubinemia by using ABR and DPOAE.We attempt to explore the effects of different bilirubin levels on hearing and the relationship between them. So as to carry out clinical intervention as soon as possible.MATERIALS AND METHODS:1.Subjects:43 Children(total ears=86) with neonatal hyperbilirubinemia ,who were outpatients of ENT department of Guangzhou women and children's medical center ,were selected as study group during 2007 September and 2009 June.According to the total serum bilirubin level(TSB) ,they were divided into two groups .Group 1(n=20,total ears=40) :TSB is below 428μmol/L(25mg/dL).Group 2(n=23,total ears=46):TSB is above 428μmol/L(25mg/dL).30 normal children without neonatal hyperbilirubinemia were enrolled as control group (G0)at the same time.It has no significant difference in age and gender between groups.2.Methods:In the sound shielded room, all subjects were examined with the apparatus of ABR and DPOAE in sleep.Then we compared of ABR threshold ,latency of waveⅠⅢⅤ,inter-peak latencys and abnormal results of DPOAE between groups.3.Statistical analysis:Data was processed by the use of SPSS13.0ccording to the information and types, two independent samples Chi-square test, two independent samples t test were used.P <0.05 means statistically significant difference .RESULTS:1.There is no significant difference between Group1 ( TSB<25mg/dL ) and Group2(TSB≥25mg/dL) on the rate of abnormal DPOAE.(p>0.05)2.On the rate of abnormal ABR, Group2 is higher than Group1. Difference is significant.(p<0.05)3.On the rate of mean ABR threshold,both Group1 and Group2 rise comparing to the control group.While comparing to Group 1,Group 2 is higher.It has significant difference.(p<0.05)4.There are no significant differences between Group1 and Group2 on both the rate of mild and moderate hearing loss(p>0.05).However,Group2 is higher than Group1 with significant difference(p<0.05) on severe hearing loss.5.Comparing on the rate of well differentiated waves of ABR among children with abnormal hearing function,Group2 is lower than Group1.Difference is significant(p<0.05).Nevertheless,there is no significant differences on the rates of other absent waves between two groups (p>0.05). 6.With significant difference(p<0.05),Group2 is higher than Group1 on the rate of occurrence of auditory neuropathy(AN).7.When comparing to the Control Group,both Group1 and Group2 have prolonged not only the latencies of waveⅠ,ⅢandⅤbut also the inter-peaks latencies of waveⅠ～Ⅲ,Ⅲ～Ⅴ,andⅠ～Ⅴ.Differences are significant(p<0.05).But there is no significant differences between Group1 and Group2(p>0.05).CONCLUSIONS:1.Hearing loss is association with the level of total serum bilirubin when neonatal hyperbilirubinemia happens.The higher level of total serum bilirubin(TSB),the greater chance of hearing loss.2.The higher level of total serum bilirubin(TSB),the more severe hearing loss.3.The higher level of total serum bilirubin(TSB),the greater chance of auditory neuropathy(AN).4.As far as the lesions of auditory pathway in neonates with hyperbilirubin is concern, retrocochlear nerve may be mainly involved, with cochlear damaged at the same time.