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Brainstem Evoked Response Audiometry (BAER) in Neonates With Hyperbilirubinemia P r a m o d Sharma 1, N.P. C h h a n g a n P , K e s h Ram M e e n a 3, R a k e s h Jora ~, Navratan Sharma 3 and B.D. G u p t a 4

1Assistant Professors, ZAssociate Professor, 3Senior Resident, 4Prof and Head, Department of Pediatrics, Umaid Hospital for Women and Children Dr. S.N. Medical College, Jodhpur, Rayasthan, India.

A B S T R A C T . 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-maih drpramodsh@ hotmail, com

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

Neonata l Hyperb i l i rub inemia is an adverse perinatal clinical event that places the affected neona te at an increased risk of hear ing impa i rmen t . 1 Jaundice is a common finding in neonates affecting 70% of term and 80% of preterm neonates during the 1 't week of life. An essential aim is the early identification of infants with deep jaundice or impaired hearing so that rehabilitation can be in i t i a ted w h e n the b ra in is sens i t ive to the development of speech and language.

A number of methods have been evaluated to search for a reliable and effective technique for de te rmin ing audi tory functions in the neonates. Brainstem Evoked Response A u d i o m e t r y (BAER) has e x p a n d e d the possibility of objective testing of hearing functions. This is an effective and s imple 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 inpu t to the cortex. 2 Besides t imely r ecour se to e f fec t ive p h o t o t h e r a p y and exchange transfusion can reverse changes in BAER. The study was thus undertaken to s tudy the initial BAER recordings in icteric term neonates and note its correlation with serum b i l i rub in levels as also its r eve r s ib i l i ty fo l lowing therapeutic interventions.

Correspondence and Reprint requests : Dr. Pramod Sharma, 115, Roop Nagar, Paota 'C' Road, Jodhpur, Rajasthan, India.

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.

N e o n a t e s wi th c o m p l i c a t e d p r e g n a n c y , a d v e r s e neonata l events l ike-severe bi r th a s p h y x i a , p y o g e n i c meningi t is , severe sep t icemia ,congeni ta l craniofacial malformations or babies on mechanical ventilator were excluded. BERA studies were performed between 2 ~ to 6 th days of life. Neonates with hyperbil irubinemia were m a n a g e d as per r e c o m m e n d a t i o n s of Behrman et al. ~ BERA was recorded as per the me thod descr ibed by Taylor 4 after taking an informed consent. Recordings were taken at the t ime of peak h y p e r b i l i r u b i n e m i a , a f ter therapy and again at the age of 2-4 months us ing the Nicolas Compass Meridian Instrument from Biomedical USA using cup shaped silver coated electrodes of 10ram diameter. Facility of automatic artifact rejection was used. Sweep velocity was l0 mm/sec .and click acoustic stimuli at a rate o f l 0 / s e c were p r e s e n t e d to each ear at an intensity of 90dB hearing ]evel. Subsequently stimuli at decreas ing f requencies 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- s t imula t ed ear. Electrical act ivi ty was f i l tered and a v e r a g e d to 2000 responses. Latency, interpeak latencyand ampli tudes of waves were measu red placing cursors on the screen tracings. 5 Therea f t e r r ight and left ears were tes ted

Indian Journal of Pediatrics, Volume 73--May, 2006 413

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Pramod Sharma et al

T a b l e 1. Late , .cy of W a v e I (Msec) at Various I n t e n s i t i e s (dB)

In tens i ty S t u d y g r o u p C o n t r o l g r o u p A Vs B B Vs C N=30 N= 30 p v a l u e s

M e a n • SD M e a n L SD Before T r e a t m e n t After T r e a t m e n t (c)

(A) [B]

A V s C

30 2.96 + i).76 2.08 z 0.73 1.87 _': 0.17 < 0.001 > 0.2

45 2.93 • 0.89 1,98 _+ 0.36 1.84 • U.i2 <l).001 > 0.1

75 2 5 6 • 1.99 • 1 0 6 1.80 +_ 0.18 < 0.02 > 1).4

90 2.65 -+ 0.81 1.75 z 0.44 1.65 *- 0.35 < 0.05 > 0.5

< 0.05

< 0.001

< 0.001

< 0.01

T~,BLL 2. ln terwave I n t e r v a l I - I I I (Msec) at Var ious Intensi t ies (dB)

In t ens i ty S t u d y g r o u p Con t ro l g r o u p b Va lues (dB) N=30 N=30

M e a n • SD M e a n • SD Before T r e a t m e n t Af te r T r e a t m e n t (C) A Vs B B Vs C

(A) (B)

A V s C

30 3.16 +_ 1.49 2.04 _-!- 0.45 2 1 7 + I).57 < 0.001 > 0.4 <0.01

45 3.59 z 1.87 1.84 _+ 0.22 2.05 +_ 0.61 < 0.1101 > t).l < 0.091

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 < 0.111 > 0.2 < 0.02

TABL~ 3. Changes in BAER in S tudy Group Before and after Exchange Transfus ion at 90 dB

I,atenc), S t u d y g r o u p C o n t r o l M e a n • SD M e a n _+.. SD

Before T r e a t m e n t After T r e a t m e n t (n=30) (n=14) (n=14) (a)

(A) (B)

b Va lue

A Vs B a Vs A a Vs B

i 2.67 + 11.88 2.03 _+ 0.77 1.65 • 0.35

II 3.32 • 0,45 2.74 + 0.54 2.72 z 0.32

I11 4,59 • 11.75 4.25 +_0.75 4.28 + 0.16

IV 5.71) +_ 0.72 4.75 + 0.80 4.79 _+ 0.28

V 8.25 + 1.64 6.35 • 1.37 6.25 +_ 0.39 1P I n t e r v a l s l - 111 3.08+ 0.57 2.08 • 0.42 2.15 + 1/.42

I - V 5.{)6 + 0.56 4,111 +_ {).72 3.90 i 0.82

111 - V 3.12 • 0.12 1.96 • {).41 2.07 +_0.38

< 0.05 <O.[X/1 >0.1

< 0.01 <0.001 > 0.5

< 0.05 < 0.02 > 61.1

< 0.01 < 0.01 > 0.9

< 0.01 < 0.01 > 0.9

< 0.001 <0.001 > 0.4

< 0.00l <0.001 > 0.5

< 0.001 <0.001 > 0.4

T.~SrE 4. Changes in BAER in Study Group Before and after Phototherapy at 30 dB

l , a t ency S t u d y g r o u p Con t n ~l 3t) (dB) M e a n • SD M e a n + SD

Before T r e a t m e n t Af te r T r e a t m e n t (n=30) (n=14) (n=14) (a)

(A) (B)

p v a l u e

A V s B a V s A a V s B

I 2.57 • 0.50 1.58 • 0.32 1.87 • I).17

11 3.37 - 0.43 2.84 • 0.45 3.17 + 0.36

Ill 5.02 • 0.85 4.34 +0 .43 4.44 +_ 0.78

IV 5.67 • 0.67 5.35z0.18 5.20•

V 7.35 • 1.35 6.75 • 0,35 7.06 + 0.33 If' I n t e r v a l s 1 - 11I 2.49 + 1.26 1.71 ~0 ,41 2.17 • 0.57

I - V 4.26 +--0.91 3.74 • 0.58 4.02 +_ 0.67

l II - V 2.23 • 0.54 2.11 • 0.16 2.01 • 0.35

< 0.01 < 0.001 > 0.5

< O.Oi > 0.2 > 01

< 0.00! < 0.05 >0.7

< 0.01 <0.02 > 0.3

<0.05 >0.5 >03

< 0.05 > 0.4 > 0.1

> 0.20 > 0.4 > 0.3

> 0.22) < 0.05 > 0.3

4 1 4 ~ndian J o u m a t o f Ped ia t r i cs , V o l u m e 7 3 - - M a y , 2 0 0 6

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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 P Value (Serum bilirubin (rag%) Mean + SD

Mean + SD 12-18 18-25 > 25 (a) a / A a / B (n=5) (n=6) (n:=19)

(A) (B) (C)

a /C

l 1.71 : 0.15 1.67 + 0.52 2.42 .~ 0.88 1.65 : 0.35 > 0.6 > 0.9 II 2.6l - 0.{}8 2.65 • 0.23 3.08 L 0.59 2.72 + 0.32 > 0.7 > 0.9 III 4.71 + 0.25 4.73 + 1.09 5.45 • 0.94 4.28 + 0.16 > 0.3 > 0.8 IV 4.84 • 0.20 5.09 + 0.30 5.05 Z 0.71 4.79 + 0.28 > 0.7 > {}.1 V 6.09 • 0.35 6.38 + 1.44 7.54 ~ 1.97 6.25 + 0.39 > 0.4 > 0.9 IP Intervals 1 - I I l 1.82 + {).36 2.05 + 0.34 2.86 +_ 0.64 2.15 + 0.42 > 0.1 > 0.7 I - V 3.87 +_ 0.14 4.01 + 1.18 4.91 _~ 0.62 3.90 + 0.82 > 0.9 > (}.9 III - V 1.86 • 0.44 2.39 _+ 0.59 2.87 -[ 0.48 2.07 • 0.38 > 0.3 >0.3

< 0.01 < 0.02 < 0.02 <0.001 < 0.01

<0.001 <0.001 <0.001

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

Latency Initial BAER Follow up Control group b Value 30 (dB) Mean + SD BAER group

(A) Mean • SD Mean +_ SD (n=7) (B) (n=7) (n=30) (C) A Vs B B V s C

I 2.63 +0.26 1.88 + 0.01 1.87 • 0.17 > 0.8 It 3.40+0.11 3.17+ 0.01 3.17+ 0.36 > 0.3 III 4.87 + (}.16 4.70 __+ 0.22. 4.44 + 0.78 > 0.4 IV 5.73 + 0.23 5.21 +_ 0.01 5.20 + 0.26 > 0.4 V 7.95 + 0.91 7.21 + 1.23 7.06 + 0.33 > 0.3 IP Intervals I - lII 2.44 +_ 0.45 2.07 _+ 0.11 2.17 + 0.57 < 0.05 1 - V 4.31 + 0.37 4.01 • 0.01 4.02 + 0.67 < 0.05 I I I - V 2.44,0.36 2.01 _- 0.01 2.01 + 0.35 < 0.05

< 0.001 < 0.02 < 0.05 <0.001 < 0.05

> 0.6 > 0.9 > 0.9

s e p e r a t e l y w i t h r a r e f a c t i o n c l i cks of 0 . 1 m s e c d u r a t i o n

a d m i n i s t e r e d a t a r a t e of 50 p e r s e c o n d . 2000 r e s p o n s e s w e r e a v e r a g e d a n d m i n i m u m of t w o tes ts p e r f o r m e d for

r e p r o d u c i b i l i t y . 30 dB w a s t a k e n as t he n o r m a l t h r e s h o l d of w a v e V. A n i n f a n t w a s c o n s i d e r e d as p a s s e d lhe tes t if

w a v e V w a s p r e s e n t a t 30 dB nHi_ in b o t h ea r s or in o n e ea r at 30 dB a n d in the o t h e r a t 45 dB.

RESULTS

M a l e f e m a l e r a t i o in t h e s t u d y w a s 1.3:1. M e a n a g e of b a b i e s w a s 4.16 -+ 0.77 days , m e a n w e i g h t 3.31 +_ 0.41 kg,

m e a n g e s t a t i o n a l age 38.83 • 1.26 w e e k s a n d m e a n s e r u m B i l i r u b i n 2 5 . 9 7 • 7 .28 m g / d l . F i v e p a t i e n t s h a d R h

i n c o m p a t i b i l i t y . M e a n l a t e n c y of a l l w a v e s w a s p r o l o n g e d b e f o r e

t r e a t m e n t a n d r e v e r t e d b a c k to n o r m a l a f te r p h o t o t h e r a p y

a n d / o r e x c h a n g e a n d t h i s d i f f e r e n c e w a s s t a t i s t i c a l l y s i g n i f i c a n t at all dec ibe l s . S i m i l a r l y i n t e r w a v e i n t e r v a l s l-

IIl-, I -V a n d III-V w e r e a l so p r o l o n g e d b e f o r e t r e a t m e n t

a n d r e v e r t e d b a c k to n o r m a l a f t e r t h e r a p y . A t o t a l o f

f o u r t e e n n e o n a t e s w i t h h y p e r b i l i r u b i n e m i a r e q u i r e d

e x c h a n g e t r a n s f u s i o n . In 7 n e o n a t e s B A E R r e m a i n e d

a b n o r m a l o n f o l l o w - u p t r a c i n g s in t h a t t h e i n t e r w a v e

i n t e r v a l r e v e r t e d b a c k to n o r m a l b u t l a t e n c y of v a r i o u s

w a v e s d i d n o t d e c r e a s e s i gn i f i c an t l y .

DISCUSSION

B A E R w a s a b n o r m a l in 2 2 / 3 0 n e o n a t e s (73.3%), w h i c h is c o m p a r a b l e t o f i g u r e s d e r i v e d in o t h e r s t u d i e s 6'7

P r o l o n g a t i o n of l a t ency of w a v e I as o b s e r v e d in o u r s t u d y

w a s s i m i l a r to f i n d i n g s of A g a r w a l a n d P e r l m a n b u t o t h e r a u t h o r s ~.~ o b s e r v e d t h a t in h y p e r b i l i r u b i n e m i a w a v e I is n o t p r o l o n g e d d u e to n o n - i n v o l v e m e n t of t h e c o c h l e a r

ne rve . P r o l o n g a t i o n of l a tenc ies of o t h e r w a v e s (H-V) w e r e o b s e r v e d i n o u r s t u d y w h i c h s h o w e d a t e n d e n c y to c o m e close to n o r m a l f o l l o w i n g t h e r a p e u t i c i n t e r v e n t i o n s . T h i s is

in c o n s o n a n c e to f i n d i n g s of o t h e r a u t h o r s . '~s M e a n l a t e n c y of v a r i o u s w a v e s a n d i n t e r p e a k d i s t a n c e

w a s c o m p a r e d a t d i f f e r e n t s e r u m b i l i r u b i n l e v e l s v iz .12- 18, 1 8 - 2 5 a n d m o r e t h e n 25 m g % a n d s t a t i s t i c a l l y

s i g n i f i c a n t c o r r e l a t i o n in p r o l o n g a t i o n of l a t e n c y a n d t he

i n t e r w a v e i n t e r v a l s w a s o b t a i n e d w i t h s e r u m b i l i r u b i n

l e v e l s m o r e t h e n 25 m g % . A g a r w a l et al ~ a l s o f o u n d

c o r r e l a t i o n w i t h s e r u m b i l i r u b i n m o r e t h e n 25 m g a n d b u t

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Pramod Sharma et al

Gupta et al found such correlation only at serum bil i rubin > 30,0/0. 7

Af t e r t r e a t m e n t BAER a b n o r m a l i t i e s in fo rm of p ro longed in t e rwave in te rva l pers is ted on ly in 7 cases whi le the la tenc ies of va r i ous waves had n o r m a l i s e d showing that in most cases with hyperb i l i rub inemia the deafness induced is t ransient and improves if treated in t ime a n d a p p r o p r i a t e l y . F u r t h e r fo l low u p t r a c i n g obtained 2 to 4 months after discharge from the hospital revealed that responses improved in 2 more cases while 5 i n f a n t s c o n t i n u e d to s h o w p e r s i s t e n t a b n o r m a l i t i e s . Similar f i nd ings were repor ted by Deorar i et aI ~ while other au thors ~" repor ted that on fo l low-up all neona tes with abnormal BAER showed a reversion back to normal. I m p r o v e d b r a i n f u n c t i o n s m a y be due to r emova l of b i l i r ub in f rom the b r a i n s t e m because of pho to the rapy a n d / o r e x c h a n g e t r a n s f u s i o n t h u s p o s t u l a t i n g the hypothesis of t ransient b i l i rubin toxicity or the t ransient b r a i n s t e m e n c e p h a l o p a t h y . But p e r s i s t e n c e of abnorma l i t i e s in some cases may be due to p e r m a n e n t d a m a g e c a u s e d by a x o n a l d e g e n e r a t i o n a n d loss of myel in rather than hair cell loss. ~

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. Ndson Text Book of Pediatrics. 16 'h ed. 20~)1; Part X1; 513-519.

4. Taylor MJ, Evoked potential in Pediatrics In Halliday AM Ed Edinburg. edn. Evoked Potential in Clinical Testing 2 ~ eds. Churchill Livingstone, 1993; 489-521.

5. Deurieux SA. Introduction. Brainstem evoked response audiometry in neonates. J Otola~,ngrd 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 ] Peditr 1998: 35; 513-518.

7. Gupta AK, Anand NK,Hans Ra}. BAER-a diagnostic tool in nc~matology. Ind Pediatr 1990; 27: 1039-1044.

8. Perlman M, Fainmesses P, Shohmer tt, Tameris H, Wazy Persmer B. Auditory nerve brainstem evoked respcmse 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, lnd Pediatr 1994; 31 : 915-921.

10. Kramer SJ, Vertes DR, Cnndon 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.

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