Evaluation of auditory brainstem evoked responses and neuron-specific enolase for detection of auditory neuropathy in neonatal hyperbilirubinemia

ABSTRACT

This study was designed to evaluate the correlation between neuron-specific enolase and neonatal hyperbilirubinemia in children diagnosed as having auditory neuropathy by auditory brainstem evoked responses. Thirty infants admitted in neonatology unit of AL-Minya university hospital in the period from July 2002 to January 2004 for treatment from hyperbilirubinemia and 20 neonates as a control group all infants and bilirubin levels above 20mg/dl and had a full work-up hyperbilirubinemia. All study group infants were treated with phototherapy. And 16 infants required blood exchange transfusion as well. Hyperbilirubinemic infants were placed into two groups according to serum bilirubin values group [A] total bilirubin 20-25mg/dl, group [B] total bilirubin >25mg/dl. The control group consisted of 20 healthy full-term neonates with bilirubin levels within physiologic ranges [<13mg/dl]. Serum samples for neuron specific enolase [NSE] determination were taken on the day of admission and stored at-20°C until the time of assayed by a commercial enzyme immunoassay [EIA] kit. All hyperbilirubinemic infants in the study were evaluated with auditory brain stem evoked responses [ABERs] and transient evoked otoacoustic emission [TEOAE] tests. ABERs were recorded using nihon kohden 4 channels equipment, while TEOAEs were obtained by using the quickscreen option of the ILO 92 OAE system. The results showed no significant differences between serum NSE value in hyperbilirubinemic groups [50.19 +/- 34.37] when compared with control infants [44.50 +/- 27.68 ng/ml] [p=0. 253]. A significant difference was detected between serum NSE values of group A [33.29 +/- 16.98 ng/ml] and group B [67.09 +/- 39.33 ng/ml] [p = 0.02]. NSE and total bilirubin levels of patients with absent ABRs but present TEOAEs [36.43 +/- 16.47 ng/ml and 25.06 +/- 4.25 mg/dl, reciprocal] were significantly higher than those of the patients with normal ABRs [70.83 +/- 43.82 ng/ml and 31.29 +/- 7.34 mg/dl, reciprocal], [p=0.001]. no correlation was found between serum NSE and bilirubin values [r-= 0.15, p= 0.33]. there was no relationship between NSE concentration and the duration of the hyperbilirubinemia [r = 0.29, p=0.23]. In this preliminary study, although we could not demonstrate any correlation between serum NSE and bilirubin levels but NSE levels were significantly higher in infants with auditory neuropathy which diagnosed by ABER. Thus, this finding indicated the importance of a close follow-up with dual screening of hearing by ABER and TEOAEs in hyperbilirubinemic newborns to avoid the auditory neuropathy. Biochemical index of neuronal damage [e.g. NSE] and ABERs can be used to evaluate the neurological sequels of neonatal hyperbilirubinemia like auditory neuropathy. For appropriate results to demonstrate the role of NSE and ABER for diagnosis of auditory neuropathy in neonatal hyperbilirubinemia, we must test a much larger sample of subjects in the future