Brainstem auditory evoked response in normal term neonates

Abstract

-Brainstem auditory evoked response (BAER) is a reliable test for neonatal auditory and neurological dysfunction and it permits early diagnosis and rehabilitation. The purpose of this study is to demonstrate latencies of BAER in normal term neonates in order to obtain reference values in a university hospital. BAER was performed in the second day of life in 47 normal newborns (25 male, 22 female) which gestational ages were higher than 37 and lower than or equal to 40 weeks that did not present familial history of deafness. The exam was performed with 80 dBHL alternating polarity 10/sec clicks presented monaurally. Two thousand stimulus trials were averaged and duplicated for each ear. Potencial evocado auditivo de tronco cerebral em recém-nascidos normais a termoRESUMO -O estudo do potencial evocado auditivo de tronco cerebral (PEA-TC) é um teste diagnóstico útil de disfunção auditiva e neurológica neonatal permitindo reabilitação precoce. O objetivo deste estudo é obter dados normativos das latências do PEA-TC em recém-nascidos normais a termo em hospital universitário. PEA-TC foi registrado no segundo dia de vida em 47 recém-nascidos normais (22 femininos e 25 masculinos) com idades gestacionais superiores a 37 e inferiores ou iguais a 40 semanas, que não apresentassem antecedentes familiares de déficit auditivo. O tempo de latência de 2.000 estímulos promediados e uma replicação foram estudados para cada ouvido, utilizando-se clicks monoaurais alternantes de 80 dBHL a 10/s. A média em milisegundos da latência das ondas foi: I, 1,79 (DP 0,20); II, 2,88 (DP 0,28); III, 4,54 (DP 0,31); IV, 5,86 (DP 0,36); V, 6,75 (DP 0,38); latências interpico (LIP) I-III, 2,75 (DP 0,36); LIP III-V, 2,22 (DP 0,22); e LIP I-V, 4,97 (SD 0,43).

Potencial Evocado Auditivo de Tronco Encefálico: padrão de respostas de lactentes termos e prematuros

“…Other studies have not reported any significant absolute and interpeak latency differences between ears. [7][8][9][10]25 These authors found that in subjects with normal peripheral hearing, the responses of both ears in brainstem audiometry are similar, as the anatomical structures are part of the brainstem itself, which are used by both ears when a sound stimulus occurs. Munhoz 26 stated that waves I and II arise ipsilaterally to the stimulus and reflect the action potential of the auditory nerve, whereas waves III, IV and V receive contralateral inputs probably in a greater number than ipsilateral inputs.…”

“…18 The mean values and standard deviation of waves I, III and V absolute and interpeak latencies concurred with other published studies of term and premature newborn and similar reference values. 2,9,[18][19][20]30,31 However, values in premature neonates differed from those in a single study where more prolonged absolute values were found at 80 dBHL in preterm newborn that were evaluated at age 4 months. 7 The latency differences in some of the BAEP components in the abovementioned studies may be due to device differences.…”

“…A few authors have also described this finding in term and premature newborn and in older children. 8,9,30,34 Such variability may be due to individual auditory pathway maturation differences, as well as difficulties in defining the conception date (gestational age plus post-natal age) versus the gestational age of the newborn with a greater than two weeks margin of error; 35,36 during this interval, maturation levels of the auditory transmission time in neonates change rapidly, especially in premature infants. 16 BAEP may be used to assess the integrity of auditory pathways from the auditory nerve to the brainstem.…”

“…7,15,19,20 In relation to interpeak intervals, delays in central conduction times in adults may also be related to changes in myelinization-associated neural conduction velocities and/or changes in synaptic efficiency across the auditory pathway nuclei. 7,9 The brainstem portion that contains auditory pathways triples in length between the 21 st fetal week and the first year of life; the auditory pathway continues to grow until about the third year of life as the brainstem diameter increases. 15 However, interpeak intervals decrease as pathways grow longer and specialize after birth, which increases conduction velocity at a rate that precisely compensates their physical growth.…”

“…9,17,18 The purpose of this study was to analyze the response pattern of premature and term neonates and nursing infants to the BAEP, considering the factors gender and ear, and to check the effect of auditory pathway maturity on the electrophysiological responses in a Brazilian population.…”