Brainstem evoked response audiometry (BAER) in neonates with hyperbilirubinemia
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《美国医学杂志》
Department of Pediatrics, Umaid Hospital for Women and Children Dr. S.N. Medical College, Jodhpur, Rajasthan, India
Abstract
Objectives : To evaluate Brainstem Evoked Response Audiometry (BAER) as an objective testing of hearing assessment in icteric babies and correlate the abnormalities with serum bilirubin levels. Methods : BAER recordings were taken in 30 icteric ferm neonates at birth, at peak of serum bilirubin levels and on a follw-up visit at 2-4 months of age. Results : Mean latency of waves and interwave intervals on the BAER records were prolonged in icteric babies compared to the control group suggesting early bilirubin encephalopathy. Abnormal records were obtained in 73.3% cases and the abnormality persisted in the follow-up tracings of 23.3% of the study group. Conclusion : BAER is a sample, reliable and effective technique for determining auditory functions in the neonates especially changes of early bilirubin toxicity.
Keywords: Brain stem evoked response; Audiometry (BAER), Neonatal Hyperbilirubinemia; Auditory functions
Neonatal Hyperbilirubinemia is an adverse perinatal clinical event that places the affected neonate at an increased risk of hearing impairment.[1] Jaundice is a common finding in neonates affecting 70% of term and 80% of preterm neonates during the 1st week of life. An essential aim is the early identification of infants with deep jaundice or impaired hearing so that rehabilitation can be initiated when the brain is sensitive to the development of speech and language.
A number of methods have been evaluated to search for a reliable and effective technique for determining auditory functions in the neonates. Brainstem Evoked Response Audiometry (BAER) has expanded the possibility of objective testing of hearing functions. This is an effective and simple method that requires less co-operation of the patient and measures the specific part of the auditory pathway. It is not significantly altered by the state of consciousness, drugs and environmental factors like the sensory input to the cortex.[2] Besides timely recourse to effective phototherapy and exchange transfusion can reverse changes in BAER. The study was thus undertaken to study the initial BAER recordings in icteric term neonates and note its correlation with serum bilirubin levels as also its reversibility following therapeutic interventions.
Material and Methods
The study was conducted in the Department of Pediatric Medicine, Umaid Hospital Jodhpur where 30 term icteric neonates with serum bilirubin >12mg% were enrolled as the study group & 30 non-icteric babies were recruited as control.
Neonates with complicated pregnancy, adverse neonatal events like-severe birth asphyxia,pyogenic meningitis,severe septicemia,congenital craniofacial malformations or babies on mechanical ventilator were excluded. BERA studies were performed between 2nd to 6th days of life. Neonates with hyperbilirubinemia were managed as per recommendations of Behrman et al.[3] BERA was recorded as per the method described by Taylor[4] after taking an informed consent. Recordings were taken at the time of peak hyperbilirubinemia, after therapy and again at the age of 2-4 months using the Nicolas Compass Meridian Instrument from Biomedical USA using cup shaped silver coated electrodes of 10mm diameter. Facility of automatic artifact rejection was used. Sweep velocity was 10 mm/sec.and click acoustic stimuli at a rate of10/sec were presented to each ear at an intensity of 90dB hearing level. Subsequently stimuli at decreasing frequencies i.e. 75,60,45 and 30 dB were presented to each ear and recordings taken. Masking sound of 40dB was used for the non-stimulated ear. Electrical activity was filtered and averaged to 2000 responses. Latency, interpeak latencyand amplitudes of waves were measured placing cursors on the screen tracings.[5] Thereafter right and left ears were tested seperately with rarefaction clicks of 0.1msec duration administered at a rate of 50 per second. 2000 responses were averaged and minimum of two tests performed for reproducibility. 30 dB was taken as the normal threshold of wave V. An infant was considered as passed the test if wave V was present at 30 dB nHL in both ears or in one ear at 30 dB and in the other at 45 dB.
Results
Male female ratio in the study was 1.3:1. Mean age of babies was 4.16 ± 0.77 days, mean weight 3.31 ± 0.41 kg, mean gestational age 38.83 ± 1.26 weeks and mean serum Bilirubin 25.97 ± 7.28 mg/dl. Five patients had Rh incompatibility.
Mean latency of all waves was prolonged before treatment and reverted back to normal after phototherapy and /or exchange and this difference was statistically significant at all decibels. Similarly interwave intervals I-III-, I-V and III-V were also prolonged before treatment and reverted back to normal after therapy. A total of fourteen neonates with hyperbilirubinemia required exchange transfusion. In 7 neonates BAER remained abnormal on follow-up tracings in that the interwave interval reverted back to normal but latency of various waves did not decrease significantly.
Discussion
BAER was abnormal in 22/30 neonates (73.3%), which is comparable to figures derived in other studies[6],[7] Prolongation of latency of wave I as observed in our study was similar to findings of Agarwal and Perlman but other authors[6],[8] observed that in hyperbilirubinemia wave I is not prolonged due to non-involvement of the cochlear nerve. Prolongation of latencies of other waves (II-V) were observed in our study which showed a tendency to come close to normal following therapeutic interventions.This is in consonance to findings of other authors.[6],[7][8]
Mean latency of various waves and interpeak distance was compared at different serum bilirubin levels viz.12-18, 18-25 and more then 25 mg% and statistically significant correlation in prolongation of latency and the inter wave intervals was obtained with serum bilirubin levels more then 25 mg%. Agarwal et al[6] also found correlation with serum bilirubin more then 25 mg and but Gupta et al found such correlation only at serum bilirubin > 30%.[7]
After treatment BAER abnormalities in form of prolonged interwave interval persisted only in 7 cases while the latencies of various waves had normalised showing that in most cases with hyperbilirubinemia the deafness induced is transient and improves if treated in time and appropriately. Further follow up tracing obtained 2 to 4 months after discharge from the hospital revealed that responses improved in 2 more cases while 5 infants continued to show persistent abnormalities. Similar findings were reported by Deorari et al[9] while other authors[10] reported that on follow-up all neonates with abnormal BAER showed a reversion back to normal. Improved brain functions may be due to removal of bilirubin from the brainstem because of phototherapy and/or exchange transfusion thus postulating the hypothesis of transient bilirubin toxicity or the transient brainstem encephalopathy. But persistence of abnormalities in some cases may be due to permanent damage caused by axonal degeneration and loss of myelin rather than hair cell loss.[11]
References
1. American Academy of Pediatrics. Joint Committee on infant hearing: Position statement. Pediatrics 1982; 70; 496-497.
2. Wood S, Marcormick B, Marson S.Auditory brainstem response in Pediatric audiology. Arch Dis Child 1988; 63 : 565-567.
3. Berhman Richard E, Kliegman Robert M, Jenson Hal B. Jaundice and hyperbilirubinemia in the newborn. Nelson Text Book of Pediatrics . 16th ed. 2001; Part XI; 513-519.
4. Taylor MJ, Evoked potential in Pediatrics In Halliday AM Ed Edinburg. edn. Evoked Potential in Clinical Testing 2nd eds. Churchill Livingstone, 1993; 489-521.
5. Deurieux SA. Introduction. Brainstem evoked response audiometry in neonates. J Otolaryngol 1985; 14(suppl.14) : 5-6.
6. Agarwal VK, Shukla Rakesh, Misra PK, Kapoor RK, Malik GK.Brainstem auditory evoked response in newborn with hyperbilirubinemia. Ind J Peditr 1998: 35; 513-518.
7. Gupta AK,Anand NK,Hans Raj. BAER-a diagnostic tool in neonatology. Ind Pediatr 1990; 27 : 1039-1044.
8. Perlman M, Fainmesses P, Shohmer H, Tameris H, Wazy Persmer B. Auditory nerve brainstem evoked response in hyperbilirubinemia. Pediatr 1983; 72: 703-708.
9. Deorari AK, Singh M, Ahuja GK, Bisht MS, Verma A. One Year outcome of babies with severe neonatal hyperbilirubinemia and reversible abnormality in brainstem auditory evoked responses. Ind Pediatr 1994; 31 : 915-921.
10. Kramer SJ, Vertes DR, Condon M. Auditory brainstem response and clinical follow-up of high-risk infants. Pediatr 1989; 83 : 385-392.
11. Stockhard JJ, Rossiter VS. Clinical and pathological correlates of brainstem auditory response abnormalities. Neurology 1977; 27: 316-325.(Sharma Pramod, Chhangani )
Abstract
Objectives : To evaluate Brainstem Evoked Response Audiometry (BAER) as an objective testing of hearing assessment in icteric babies and correlate the abnormalities with serum bilirubin levels. Methods : BAER recordings were taken in 30 icteric ferm neonates at birth, at peak of serum bilirubin levels and on a follw-up visit at 2-4 months of age. Results : Mean latency of waves and interwave intervals on the BAER records were prolonged in icteric babies compared to the control group suggesting early bilirubin encephalopathy. Abnormal records were obtained in 73.3% cases and the abnormality persisted in the follow-up tracings of 23.3% of the study group. Conclusion : BAER is a sample, reliable and effective technique for determining auditory functions in the neonates especially changes of early bilirubin toxicity.
Keywords: Brain stem evoked response; Audiometry (BAER), Neonatal Hyperbilirubinemia; Auditory functions
Neonatal Hyperbilirubinemia is an adverse perinatal clinical event that places the affected neonate at an increased risk of hearing impairment.[1] Jaundice is a common finding in neonates affecting 70% of term and 80% of preterm neonates during the 1st week of life. An essential aim is the early identification of infants with deep jaundice or impaired hearing so that rehabilitation can be initiated when the brain is sensitive to the development of speech and language.
A number of methods have been evaluated to search for a reliable and effective technique for determining auditory functions in the neonates. Brainstem Evoked Response Audiometry (BAER) has expanded the possibility of objective testing of hearing functions. This is an effective and simple method that requires less co-operation of the patient and measures the specific part of the auditory pathway. It is not significantly altered by the state of consciousness, drugs and environmental factors like the sensory input to the cortex.[2] Besides timely recourse to effective phototherapy and exchange transfusion can reverse changes in BAER. The study was thus undertaken to study the initial BAER recordings in icteric term neonates and note its correlation with serum bilirubin levels as also its reversibility following therapeutic interventions.
Material and Methods
The study was conducted in the Department of Pediatric Medicine, Umaid Hospital Jodhpur where 30 term icteric neonates with serum bilirubin >12mg% were enrolled as the study group & 30 non-icteric babies were recruited as control.
Neonates with complicated pregnancy, adverse neonatal events like-severe birth asphyxia,pyogenic meningitis,severe septicemia,congenital craniofacial malformations or babies on mechanical ventilator were excluded. BERA studies were performed between 2nd to 6th days of life. Neonates with hyperbilirubinemia were managed as per recommendations of Behrman et al.[3] BERA was recorded as per the method described by Taylor[4] after taking an informed consent. Recordings were taken at the time of peak hyperbilirubinemia, after therapy and again at the age of 2-4 months using the Nicolas Compass Meridian Instrument from Biomedical USA using cup shaped silver coated electrodes of 10mm diameter. Facility of automatic artifact rejection was used. Sweep velocity was 10 mm/sec.and click acoustic stimuli at a rate of10/sec were presented to each ear at an intensity of 90dB hearing level. Subsequently stimuli at decreasing frequencies i.e. 75,60,45 and 30 dB were presented to each ear and recordings taken. Masking sound of 40dB was used for the non-stimulated ear. Electrical activity was filtered and averaged to 2000 responses. Latency, interpeak latencyand amplitudes of waves were measured placing cursors on the screen tracings.[5] Thereafter right and left ears were tested seperately with rarefaction clicks of 0.1msec duration administered at a rate of 50 per second. 2000 responses were averaged and minimum of two tests performed for reproducibility. 30 dB was taken as the normal threshold of wave V. An infant was considered as passed the test if wave V was present at 30 dB nHL in both ears or in one ear at 30 dB and in the other at 45 dB.
Results
Male female ratio in the study was 1.3:1. Mean age of babies was 4.16 ± 0.77 days, mean weight 3.31 ± 0.41 kg, mean gestational age 38.83 ± 1.26 weeks and mean serum Bilirubin 25.97 ± 7.28 mg/dl. Five patients had Rh incompatibility.
Mean latency of all waves was prolonged before treatment and reverted back to normal after phototherapy and /or exchange and this difference was statistically significant at all decibels. Similarly interwave intervals I-III-, I-V and III-V were also prolonged before treatment and reverted back to normal after therapy. A total of fourteen neonates with hyperbilirubinemia required exchange transfusion. In 7 neonates BAER remained abnormal on follow-up tracings in that the interwave interval reverted back to normal but latency of various waves did not decrease significantly.
Discussion
BAER was abnormal in 22/30 neonates (73.3%), which is comparable to figures derived in other studies[6],[7] Prolongation of latency of wave I as observed in our study was similar to findings of Agarwal and Perlman but other authors[6],[8] observed that in hyperbilirubinemia wave I is not prolonged due to non-involvement of the cochlear nerve. Prolongation of latencies of other waves (II-V) were observed in our study which showed a tendency to come close to normal following therapeutic interventions.This is in consonance to findings of other authors.[6],[7][8]
Mean latency of various waves and interpeak distance was compared at different serum bilirubin levels viz.12-18, 18-25 and more then 25 mg% and statistically significant correlation in prolongation of latency and the inter wave intervals was obtained with serum bilirubin levels more then 25 mg%. Agarwal et al[6] also found correlation with serum bilirubin more then 25 mg and but Gupta et al found such correlation only at serum bilirubin > 30%.[7]
After treatment BAER abnormalities in form of prolonged interwave interval persisted only in 7 cases while the latencies of various waves had normalised showing that in most cases with hyperbilirubinemia the deafness induced is transient and improves if treated in time and appropriately. Further follow up tracing obtained 2 to 4 months after discharge from the hospital revealed that responses improved in 2 more cases while 5 infants continued to show persistent abnormalities. Similar findings were reported by Deorari et al[9] while other authors[10] reported that on follow-up all neonates with abnormal BAER showed a reversion back to normal. Improved brain functions may be due to removal of bilirubin from the brainstem because of phototherapy and/or exchange transfusion thus postulating the hypothesis of transient bilirubin toxicity or the transient brainstem encephalopathy. But persistence of abnormalities in some cases may be due to permanent damage caused by axonal degeneration and loss of myelin rather than hair cell loss.[11]
References
1. American Academy of Pediatrics. Joint Committee on infant hearing: Position statement. Pediatrics 1982; 70; 496-497.
2. Wood S, Marcormick B, Marson S.Auditory brainstem response in Pediatric audiology. Arch Dis Child 1988; 63 : 565-567.
3. Berhman Richard E, Kliegman Robert M, Jenson Hal B. Jaundice and hyperbilirubinemia in the newborn. Nelson Text Book of Pediatrics . 16th ed. 2001; Part XI; 513-519.
4. Taylor MJ, Evoked potential in Pediatrics In Halliday AM Ed Edinburg. edn. Evoked Potential in Clinical Testing 2nd eds. Churchill Livingstone, 1993; 489-521.
5. Deurieux SA. Introduction. Brainstem evoked response audiometry in neonates. J Otolaryngol 1985; 14(suppl.14) : 5-6.
6. Agarwal VK, Shukla Rakesh, Misra PK, Kapoor RK, Malik GK.Brainstem auditory evoked response in newborn with hyperbilirubinemia. Ind J Peditr 1998: 35; 513-518.
7. Gupta AK,Anand NK,Hans Raj. BAER-a diagnostic tool in neonatology. Ind Pediatr 1990; 27 : 1039-1044.
8. Perlman M, Fainmesses P, Shohmer H, Tameris H, Wazy Persmer B. Auditory nerve brainstem evoked response in hyperbilirubinemia. Pediatr 1983; 72: 703-708.
9. Deorari AK, Singh M, Ahuja GK, Bisht MS, Verma A. One Year outcome of babies with severe neonatal hyperbilirubinemia and reversible abnormality in brainstem auditory evoked responses. Ind Pediatr 1994; 31 : 915-921.
10. Kramer SJ, Vertes DR, Condon M. Auditory brainstem response and clinical follow-up of high-risk infants. Pediatr 1989; 83 : 385-392.
11. Stockhard JJ, Rossiter VS. Clinical and pathological correlates of brainstem auditory response abnormalities. Neurology 1977; 27: 316-325.(Sharma Pramod, Chhangani )