39

Original Article

Brainstem Evoked Response Audiometry (BAER) in

Neonates With Hyperbilirubinemia
Pramod Sharma1, N.P. Chhangani2, Kesh Ram Meena3, Rakesh Jora1, Navratan Sharma 3 and
B.D. Gupta4
1
Assistant Professors, 2Associate Professor, 3Senior Resident, 4Prof and Head, 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.
[Indian J Pediatr 2006; 73 (5) : 413-416] E-mail: drpramodsh@ hotmail. com

Key words : Brain stem evoked response; Audiometry (BAER), Neonatal Hyperbilirubinemia; Auditory functions

Neonatal Hyperbilirubinemia is an adverse perinatal MATERIAL AND METHODS

clinical event that places the affected neonate at an
increased risk of hearing impairment. 1 Jaundice is a The study was conducted in the Department of Pediatric
common finding in neonates affecting 70% of term and Medicine, Umaid Hospital Jodhpur where 30 term icteric
80% of preterm neonates during the 1 st week of life. An neonates with serum bilirubin >12mg% were enrolled as
essential aim is the early identification of infants with the study group & 30 non-icteric babies were recruited as
deep jaundice or impaired hearing so that rehabilitation control.
can be initiated when the brain is sensitive to the Neonates with complicated pregnancy, adverse
development of speech and language. neonatal events like-severe birth asphyxia,pyogenic
A number of methods have been evaluated to search meningitis,severe septicemia,congenital craniofacial
for a reliable and effective technique for determining malformations or babies on mechanical ventilator were
auditory functions in the neonates. Brainstem Evoked excluded. BERA studies were performed between 2 nd to
Response Audiometry (BAER) has expanded the 6th days of life. Neonates with hyperbilirubinemia were
possibility of objective testing of hearing functions. This is managed as per recommendations of Behrman et al. 3
an effective and simple method that requires less co- BERA was recorded as per the method described by
operation of the patient and measures the specific part of Taylor4 after taking an informed consent. Recordings were
the auditory pathway. It is not significantly altered by the taken at the time of peak hyperbilirubinemia, after
state of consciousness, drugs and environmental factors therapy and again at the age of 2-4 months using the
like the sensory input to the cortex. 2 Besides timely Nicolas Compass Meridian Instrument from Biomedical
recourse to effective phototherapy and exchange USA using cup shaped silver coated electrodes of 10mm
transfusion can reverse changes in BAER. The study was diameter. Facility of automatic artifact rejection was used.
thus undertaken to study the initial BAER recordings in Sweep velocity was 10 mm/sec.and click acoustic stimuli
icteric term neonates and note its correlation with serum at a rate of10/sec were presented to each ear at an
bilirubin levels as also its reversibility following intensity of 90dB hearing level. Subsequently stimuli at
therapeutic interventions. 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
Correspondence and Reprint requests : Dr. Pramod Sharma, 115,
Roop Nagar, Paota ‘C’ Road, Jodhpur, Rajasthan, India.
tracings. 5 Thereafter right and left ears were tested

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Pramod Sharma et al

Table 1. Latency of Wave I (Msec) at Various Intensities (dB)

Intensity Study group Control group A Vs B B Vs C A Vs C

N=30 N= 30 p values
Mean + SD Mean + SD
Before Treatment After Treatment (c)
(A) [B]

30 2.96 ± 0.76 2.08 ± 0.73 1.87 ± 0.17 < 0.001 > 0.2 < 0.05
45 2.93 ± 0.89 1.98 ± 0.36 1.84 ± 0.12 <0.001 > 0.1 < 0.001
75 2.56 ± 0.77 1.99 ± 1.06 1.80 ± 0.18 < 0.02 > 0.4 < 0.001
90 2.65 ± 0.81 1.75 ± 0.44 1.65 ± 0.35 < 0.05 > 0.5 < 0.01

TABLE 2. Interwave Interval I-III (Msec) at Various Intensities (dB)

Intensity Study group Control group Þ Values

(dB) N=30 N=30
Mean + SD Mean + SD
Before Treatment After Treatment (C) A Vs B B Vs C A Vs C
(A) (B)

30 3.16 ± 1.49 2.04 ± 0.45 2.17 ± 0.57 < 0.001 > 0.4 <0.01
45 3.59 ± 1.87 1.84 ± 0.22 2.05 ± 0.61 < 0.001 > 0.1 < 0.001
75 3.34 ± 1.66 1.99 ± 0.13 2.18 ± 0.53 < 0.001 > 0.1 < 0.001
90 2.52 ± 0.70 2.01 ± 0.38 2.15 ± 0.42 < 0.01 > 0.2 < 0.02

TABLE 3. Changes in BAER in Study Group Before and after Exchange Transfusion at 90 dB

Latency Study group Control Þ Value

Mean + SD Mean + SD
Before Treatment After Treatment (n=30) A Vs B a Vs A a Vs B
(n=14) (n=14) (a)
(A) (B)

I 2.67 + 0.88 2.03 + 0.77 1.65 + 0.35 < 0.05 <0.001 >0.1
II 3.32 + 0.45 2.74 + 0.54 2.72 + 0.32 < 0.01 <0.001 > 0.5
III 4.59 + 0.75 4.25 + 0.75 4.28 + 0.16 < 0.05 < 0.02 > 0.1
IV 5.70 + 0.72 4.75 + 0.80 4.79 + 0.28 < 0.01 < 0.01 > 0.9
V 8.25 + 1.64 6.35 + 1.37 6.25 + 0.39 < 0.01 < 0.01 > 0.9
IP Intervals
I - III 3.08+ 0.57 2.08 + 0.42 2.15 + 0.42 < 0.001 <0.001 > 0.4
I–V 5.06 + 0.56 4.10 + 0.72 3.90 + 0.82 < 0.001 <0.001 > 0.5
III – V 3.12 + 0.12 1.96 + 0.41 2.07 + 0.38 < 0.001 <0.001 > 0.4

TABLE 4. Changes in BAER in Study Group Before and after Phototherapy at 30 dB

Latency Study group Control p value

30 (dB) Mean + SD Mean + SD
Before Treatment After Treatment (n=30) A Vs B a Vs A a Vs B
(n=14) (n=14) (a)
(A) (B)

I 2.57 + 0.50 1.58 + 0.32 1.87 + 0.17 < 0.01 < 0.001 > 0.5
II 3.37 + 0.43 2.84 + 0.45 3.17 + 0.36 < 0.01 > 0.2 > 0.1
III 5.02 + 0.85 4.34 + 0.43 4.44 + 0.78 < 0.001 < 0.05 >0.7
IV 5.67 + 0.67 5.35+0.18 5.20+0.26 < 0.01 <0.02 > 0.3
V 7.35 + 1.35 6.75 + 0.35 7.06 + 0.33 <0.05 >0.5 >0.3
IP
Intervals
I – III 2.49 + 1.26 1.71 + 0.41 2.17 + 0.57 < 0.05 > 0.4 > 0.1
I–V 4.26 + 0.91 3.74 + 0.58 4.02 + 0.67 > 0.20 > 0.4 > 0.3
III – V 2.23 + 0.54 2.11 + 0.16 2.01 + 0.35 > 0.20 < 0.05 > 0.3

414 Indian Journal of Pediatrics, Volume 73—May, 2006

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Brainstem Evoked Response Audiometry (BAER) in Neonates with Hyperbilirubinemia

TABLE 5. Relationship Between Latency, Interwave Interval and Serum Bilirubin at 90 dB Levels

Latency Before treatment Control Þ Value

(Serum bilirubin (mg%) Mean + SD
Mean + SD
12-18 18-25 >25 (a) a/A a/B a/C
(n=5) (n=6) (n=19)
(A) (B) (C)

I 1.71 + 0.15 1.67 + 0.52 2.42 + 0.88 1.65 + 0.35 > 0.6 > 0.9 < 0.01
II 2.61 + 0.08 2.65 + 0.23 3.08 + 0.59 2.72 + 0.32 > 0.7 > 0.9 < 0.02
III 4.71 + 0.25 4.73 + 1.09 5.45 + 0.94 4.28 + 0.16 > 0.3 > 0.8 < 0.02
IV 4.84 + 0.20 5.09 + 0.30 5.05 + 0.71 4.79 + 0.28 > 0.7 > 0.1 <0.001
V 6.09 + 0.35 6.38 + 1.44 7.54 + 1.97 6.25 + 0.39 > 0.4 > 0.9 < 0.01
IP
Intervals
I – III 1.82 + 0.36 2.05 + 0.34 2.86 + 0.64 2.15 + 0.42 > 0.1 > 0.7 <0.001
I–V 3.87 + 0.14 4.01 + 1.18 4.91 + 0.62 3.90 + 0.82 > 0.9 > 0.9 <0.001
III – V 1.86 + 0.44 2.39 + 0.59 2.87 + 0.48 2.07 + 0.38 > 0.3 >0.3 <0.001

TABLE 6. BAER in Follow-up of Cases at 30dB

Latency Initial BAER Follow up Control group Þ Value

30 (dB) Mean + SD BAER group
(A) Mean + SD Mean + SD
(n=7) (B) (n=7) (n=30) (C) A Vs B B Vs C

I 2.63 + 0.26 1.88 + 0.01 1.87 + 0.17 > 0.8 < 0.001
II 3.40 + 0.11 3.17 + 0.01 3.17 + 0.36 > 0.3 < 0.02
III 4.87 + 0.16 4.70 + 0.22 4.44 + 0.78 > 0.4 < 0.05
IV 5.73 + 0.23 5.21 + 0.01 5.20 + 0.26 > 0.4 < 0.001
V 7.95 + 0.91 7.21 + 1.23 7.06 + 0.33 > 0.3 < 0.05
IP
Intervals
I - III 2.44 + 0.45 2.07 + 0.11 2.17 + 0.57 < 0.05 > 0.6
I–V 4.31 + 0.37 4.01 + 0.01 4.02 + 0.67 < 0.05 > 0.9
III – V 2.44 + 0.36 2.01 + 0.01 2.01 + 0.35 < 0.05 > 0.9

seperately with rarefaction clicks of 0.1msec duration abnormal on follow-up tracings in that the interwave
administered at a rate of 50 per second. 2000 responses interval reverted back to normal but latency of various
were averaged and minimum of two tests performed for waves did not decrease significantly.
reproducibility. 30 dB was taken as the normal threshold
of wave V. An infant was considered as passed the test if
DISCUSSION
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.
BAER was abnormal in 22/30 neonates (73.3%), which is
comparable to figures derived in other studies 6,7
RESULTS
Prolongation of latency of wave I as observed in our study
was similar to findings of Agarwal and Perlman but other
Male female ratio in the study was 1.3:1. Mean age of authors6,8 observed that in hyperbilirubinemia wave I is
babies was 4.16 ± 0.77 days, mean weight 3.31 ± 0.41 kg, not prolonged due to non-involvement of the cochlear
mean gestational age 38.83 ± 1.26 weeks and mean serum nerve. Prolongation of latencies of other waves (II-V) were
Bilirubin 25.97 ± 7.28 mg/dl. Five patients had Rh observed in our study which showed a tendency to come
incompatibility. close to normal following therapeutic interventions.This is
Mean latency of all waves was prolonged before in consonance to findings of other authors.6-8
treatment and reverted back to normal after phototherapy Mean latency of various waves and interpeak distance
and /or exchange and this difference was statistically was compared at different serum bilirubin levels viz.12­
significant at all decibels. Similarly interwave intervals I­ 18, 18-25 and more then 25 mg% and statistically
III-, I-V and III-V were also prolonged before treatment significant correlation in prolongation of latency and the
and reverted back to normal after therapy. A total of inter wave intervals was obtained with serum bilirubin
fourteen neonates with hyperbilirubinemia required levels more then 25 mg%. Agarwal et al 6 also found
exchange transfusion. In 7 neonates BAER remained correlation with serum bilirubin more then 25 mg and but

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Pramod Sharma et al

Gupta et al found such correlation only at serum bilirubin hearing: Position statement. Pediatrics 1982; 70; 496-497.
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prolonged interwave interval persisted only in 7 cases 3. Berhman Richard E, Kliegman Robert M, Jenson Hal B.
while the latencies of various waves had normalised Jaundice and hyperbilirubinemia in the newborn. Nelson Text
showing that in most cases with hyperbilirubinemia the Book of Pediatrics. 16th ed. 2001; Part XI; 513-519.
deafness induced is transient and improves if treated in 4. Taylor MJ, Evoked potential in Pediatrics In Halliday AM Ed
Edinburg. edn. Evoked Potential in Clinical Testing 2 nd eds.
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Churchill Livingstone, 1993; 489-521.
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revealed that responses improved in 2 more cases while 5 audiometry in neonates. J Otolaryngol 1985; 14(suppl.14) : 5-6.
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Similar findings were reported by Deorari et al9 while GK.Brainstem auditory evoked response in newborn with
other authors10 reported that on follow-up all neonates hyperbilirubinemia. Ind J Peditr 1998: 35; 513-518.
7. Gupta AK,Anand NK,Hans Raj. BAER-a diagnostic tool in
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Improved brain functions may be due to removal of 8. Perlman M, Fainmesses P, Shohmer H, Tameris H, Wazy
bilirubin from the brainstem because of phototherapy Persmer B. Auditory nerve brainstem evoked response in
and/or exchange transfusion thus postulating the hyperbilirubinemia. Pediatr 1983; 72: 703-708.
hypothesis of transient bilirubin toxicity or the transient 9. Deorari AK, Singh M, Ahuja GK, Bisht MS, Verma A. One
Year outcome of babies with severe neonatal
brainstem encephalopathy. But persistence of
hyperbilirubinemia and reversible abnormality in brainstem
abnormalities in some cases may be due to permanent auditory evoked responses. Ind Pediatr 1994; 31 : 915-921.
damage caused by axonal degeneration and loss of 10. Kramer SJ, Vertes DR, Condon M. Auditory brainstem
myelin rather than hair cell loss.11 response and clinical follow-up of high-risk infants. Pediatr
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416 Indian Journal of Pediatrics, Volume 73—May, 2006