International Journal of Neuroscience
ISSN: 0020-7454 (Print) 1543-5245 (Online) Journal homepage: http://www.tandfonline.com/loi/ines20
Differential Maturation of Brainstem Auditory Evoked Potentials in Preterm Infants According to Birthweight I. Soares, L. Collet, V. Desreux And, A. Morgon & B. Salle To cite this article: I. Soares, L. Collet, V. Desreux And, A. Morgon & B. Salle (1992) Differential Maturation of Brainstem Auditory Evoked Potentials in Preterm Infants According to Birthweight, International Journal of Neuroscience, 64:1-4, 259-266, DOI: 10.3109/00207459209000553 To link to this article: http://dx.doi.org/10.3109/00207459209000553
Published online: 07 Jul 2009.
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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ines20 Download by: [McMaster University]
Date: 14 April 2016, At: 15:57
fnrern. J . Neuroscience, 1992, VoI. 64,pp. 259-266
0 1992 Gordon and Breach Science Publishers S.A.
Reprints available directly from the publisher Photocopying permitted by license only
Printed in the United States of America
Brief Communication DIFFERENTIAL MATURATION OF BRAINSTEM AUDITORY EVOKED POTENTIALS IN PRETERM INFANTS ACCORDING TO BIRTHWEIGHT I. SOARES, L. COLLET, V. DESREUX and A. MORGON
Downloaded by [McMaster University] at 15:57 14 April 2016
Laboratoire de Physiologie Sensorielle: Audition et Voix. CNRS URA I447 Hdpital Edouard Herriot, Pavillon U , 3 Place dArsonva1, 69437 LYON Ce'dex 03 France and
B. SALLE Service de Neonatalogie, Hdpital Edouard Herriot, Pavillon J , 69437 LYON Ce'dex 03 France. (Received January 10. 1992) Brainstem auditory evoked potentials (BAEPs) were recorded from 39 preterm infants, divided into 3 groups: small-for-gestational-age, with a birthweight less than or equal to 1500 g (SGA); appropriatefor-gestational-age, with a birthweight less than or equal to 1500 g (AGA1); and appropriate-for-gestational-age, with a birthweight higher than 1500 g (AGA2). A significant shortening of the I-V interval due to an increase in wave I latency was found in the SGA group. The lower-weight AGA group (AGA1) was never significantly different from the SGA group. Although there was no correlation between conceptional age and weight at the time of the examination for the studied population, negative correlations were found between wave I latency and weight at the time of the examination. These findings confirm previous research and suggest the existence of a link between weight and basal cochlear maturation. Keywords: Brainstem auditory evoked potentials, small-for-gestational-age neonates, birthweight. auditory maturation, cochlea.
Among preterm infants, immaturity and its consequences are closely related to a higher incidence of cerebral lesions, the true effect of intrauterine growth retardation being difficult to assess. In very-low-birthweight neonates, a greater incidence of impaired intellectual functioning, as well as learning retardation and perceptual and linguistic disturbances have been found. Verbal acquisition is dependent upon proper functioning of peripheral and central auditory pathways and the role of auditory integrity in cognitive development is now recognized (Kurtzberg et al., 1984). Small-for-gestational-age (S.G.A.) children are defined as having a discrepancy between gestational age and birthweight (gestational age being determined according to chronological, morphological, neurological criteria (Rumiere et al., 1973). Children's low weight remains a criterion of nonmaturity; the 1500 g or less S.G.A. infants have a severe prognosis for mortality and morbidity, due to physiological disturbances associated with immaturity of vital body system (Kurtzberg et al., 1984). They show neurological maturation retardation in comparison to appropriate-for-gestational-age (A.G.A.) infants. (Pettigrew & Edwards, 1985). 259
Downloaded by [McMaster University] at 15:57 14 April 2016
260
I. SOARES er al.
The incidence of sensory hearing deficit in very-low-birthweight infants (or S .G.A.) is significantly greater than in the normal full-term population (2 to 12.4% hearing disorders compared to .26% for controls) (Kurtzberg, 1982). Electrophysiological equipment has proved very useful in identifying and evaluating these disorders. The incidence of persistent abnormal BAEPs in very-low-birthweightinfants remains around 11% (Kurtzberg, 1982). Among these BAEP alterations, a shortening of central conduction time (I-V interval) has been found in SGA newborns (Pettigrew et al., 1985; Kesson et al., 1985; Soares et al., 1988). The interpretation of this shortening is controversial: we have hypothesized that this shortening is associated with latency lengthening of wave 1 in SGA subjects, and, thus, with an immaturity of the basal part of the cochlea (Soares et al., 1988) rather than with a precocious auditory brainstem neural function development, as other authors claim (Pettigrew & Edwards, 1985; Kesson et al., 1985). The aims of the present study were to verify our previous findings (Soares et al., 1988) for a larger sample of SGA subjects, and to examine a possible influence of the birthweight of the children on the maturation of the BAEPs. For this purpose we tested 3 groups of subjects of less than 37 weeks of conceptional age at the time of examination: a SGA group, with weight less than or equal to 1500 g (called “SGA.” group); an AGA group with birthweight less than or equal to 1500 g (called “AGA1” group); an AGA group with birthweight higher than 1500 g (called ‘AGA2” group). METHODS Subjects
This study involved 39 preterm neonates (23 male, 16 female), of gestational age between 28 and 36 weeks ( m = 32.72; S . D . = 1.75). The subjects were less than 37 weeks of conceptional age at the time of the examination. All the subjects were healthy, with Apgar scores over 7 at 5 minutes, an absence of a family or personal history of deafness or major pathology, and an absence of hyperbilirubinemia. All the infants had normal cranial ultrasound examination. The presence of BAEPs responses (especially wave V) was examined for decreasing itensities (by 10 dB steps). The presence of responses at 30 dB HL or less for all the subjects was chosen as a criterion of auditory threshold normality. The weights of the AGA infants (groups AGAl and AGA2) were within normomature values as defined by Usher et al., Usher & Mc Kean, 1969); the weights of the SGA infants were lower than these normative values. Conceptional ages (or postmenstrual ages) were calculated from the mothers’ last menses. In case of doubt, gestational and conceptional ages were calculated using the Dubowitz Neonate Maturity Scale (Dubowitz et al., 1970). Following a full explanation of the procedure to be undertaken, the informed consent of the subjects parents was obtained in every case. BAEPs Recordings The neonate recordings were carried out in a neonatal intensive care unit (Edouard Herriot Hospital - Lyon, France), without removing the baby from its bassinet or incubator, and without sedatives. Each ear was studied independently. The clicks were generated by passing 100 microseconds duration pulses through the right ear-
MATURATION, BIRTHWEIGHT AND BAEPs
26 1
phone, then through the left earphone. During the testing of one ear, we did not use white noise masking for the nonstudied ear. Unfiltered clicks were used. The sound came through a 2 cm diameter earphone held in very close contact with the external auditory canal. The click rate was 20 Hz. Recordings were made with disc electrodes on the forehead and ipsilateral mastoid, the other mastold electrode serving as ground. Responses were amplified with a MEDELEC A.A.6 M.K.3, at a filter setting of 140-1600 Hz (with 6 and 12 dB/octave), and averaged with a MEDELEC D.A.V.6 (1024 points). The analysis period was 20 ms and the responses were recorded after 2500 sweeps. The infants were studied during their physiological sleep. The right ear curves were chosen arbitrarily for this study, at intensity levels of 80 and 60 dB HL .
Downloaded by [McMaster University] at 15:57 14 April 2016
Measurements
The wave latencies were measured for peaks I, 111 and V at 80 dB HL. The interpeak intervals 1-111, 111-V and I-V were also measured at this intensity. After the recordings, their values were assessed by two independent observers. The neonates were included in this study only if identical values were found for each subject for waves I, I11 and V and intervals 1-111, I-V, and 111-V by the 2 observers, and if the patterns had an excellent intrasubject reproducibility at 80 dB HL. If discrepancies occurred, the subject was excluded from the study. Statistics
Gestational ages, conceptional ages, birthweights and weights at the time of the examination were compared across the 3 groups of infants (SGA., AGA 1 and AGA 2) by one-factor analysis of variance. Then, statistical analysis (one-way Anova) was performed on the latency variations for waves I, 111 and V , and for the 1-111, IIIV , and I-V intervals, at intensity levels of 80 and 60 dB. RESULTS Intergroup Comparability
The subjects were divided into 3 groups (Table 1): Group I comprised 14 SGA subjects. Mean conceptional age was 35.3 weeks (S.D. = .95), and weight lower than or equal to 1500 g, both at birth and at the time of the examination. Group 2 comprised 10 AGA subjects (called “AGA.l group”), but nevertheless of low birthweight. Weight at birth and at the time of the examination was lower than or equal to 1500 g and mean conceptional age was 34.4 weeks ( S . D . = 1.08). Group 3 comprised 15 AGA subjects (called ”AGA2 group”) with weight at birth and at the time of the examination higher than 1500 g.; the mean conceptional age was 34.8 weeks (S.D. = 1.25). The 3 groups did not present any significant difference according to the gestational age of the subjects (F = .47; p > .05) or to their conceptional age (F = 1.93; p > .05). This homogeneity allowed intergroup comparison. In contrast, the 3 groups presented a significant difference according to the average birthweight of the subjects (F = 35.57; p < .0001), and their average weight at the time of the examination ( F = 49.87; p < .0001).
I. SOARES et al.
262
TABLE 1 The 3 Groups of Neonates: Intergroup Comparison Conceptional Birthweight
Group 1 : S.G.A. (n = 14) Group 2: A.G.A., (n = 10) Group 3: A.G.A., (n = 15) I.'
Downloaded by [McMaster University] at 15:57 14 April 2016
P
Gestational Age (weeks)
Age (weeks)
(g)
Weight at the Time of the Examination (g)
m : 32.5 S . D . : 2.2
m: 35.3 S.D.: .91
m : 1108 S . D . : 195
m: 1335 S.D.: 162
m: 32.5 S.D.: 1.2
m: 34.4 S . D . : 1.08
m: 1401 S.D.: 81
in: 1426 S.D.: 68
m: 33 S . D . : 1.6 0.47 N.S.
m: 34.8 S . D . : 1.25 1.92 N.S.
m : 1935 S . D . : 380 35.57 < .0001
m: 2003
S . D . : 262
49.87
ISSN: 0020-7454 (Print) 1543-5245 (Online) Journal homepage: http://www.tandfonline.com/loi/ines20
Differential Maturation of Brainstem Auditory Evoked Potentials in Preterm Infants According to Birthweight I. Soares, L. Collet, V. Desreux And, A. Morgon & B. Salle To cite this article: I. Soares, L. Collet, V. Desreux And, A. Morgon & B. Salle (1992) Differential Maturation of Brainstem Auditory Evoked Potentials in Preterm Infants According to Birthweight, International Journal of Neuroscience, 64:1-4, 259-266, DOI: 10.3109/00207459209000553 To link to this article: http://dx.doi.org/10.3109/00207459209000553
Published online: 07 Jul 2009.
Submit your article to this journal
Article views: 1
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ines20 Download by: [McMaster University]
Date: 14 April 2016, At: 15:57
fnrern. J . Neuroscience, 1992, VoI. 64,pp. 259-266
0 1992 Gordon and Breach Science Publishers S.A.
Reprints available directly from the publisher Photocopying permitted by license only
Printed in the United States of America
Brief Communication DIFFERENTIAL MATURATION OF BRAINSTEM AUDITORY EVOKED POTENTIALS IN PRETERM INFANTS ACCORDING TO BIRTHWEIGHT I. SOARES, L. COLLET, V. DESREUX and A. MORGON
Downloaded by [McMaster University] at 15:57 14 April 2016
Laboratoire de Physiologie Sensorielle: Audition et Voix. CNRS URA I447 Hdpital Edouard Herriot, Pavillon U , 3 Place dArsonva1, 69437 LYON Ce'dex 03 France and
B. SALLE Service de Neonatalogie, Hdpital Edouard Herriot, Pavillon J , 69437 LYON Ce'dex 03 France. (Received January 10. 1992) Brainstem auditory evoked potentials (BAEPs) were recorded from 39 preterm infants, divided into 3 groups: small-for-gestational-age, with a birthweight less than or equal to 1500 g (SGA); appropriatefor-gestational-age, with a birthweight less than or equal to 1500 g (AGA1); and appropriate-for-gestational-age, with a birthweight higher than 1500 g (AGA2). A significant shortening of the I-V interval due to an increase in wave I latency was found in the SGA group. The lower-weight AGA group (AGA1) was never significantly different from the SGA group. Although there was no correlation between conceptional age and weight at the time of the examination for the studied population, negative correlations were found between wave I latency and weight at the time of the examination. These findings confirm previous research and suggest the existence of a link between weight and basal cochlear maturation. Keywords: Brainstem auditory evoked potentials, small-for-gestational-age neonates, birthweight. auditory maturation, cochlea.
Among preterm infants, immaturity and its consequences are closely related to a higher incidence of cerebral lesions, the true effect of intrauterine growth retardation being difficult to assess. In very-low-birthweight neonates, a greater incidence of impaired intellectual functioning, as well as learning retardation and perceptual and linguistic disturbances have been found. Verbal acquisition is dependent upon proper functioning of peripheral and central auditory pathways and the role of auditory integrity in cognitive development is now recognized (Kurtzberg et al., 1984). Small-for-gestational-age (S.G.A.) children are defined as having a discrepancy between gestational age and birthweight (gestational age being determined according to chronological, morphological, neurological criteria (Rumiere et al., 1973). Children's low weight remains a criterion of nonmaturity; the 1500 g or less S.G.A. infants have a severe prognosis for mortality and morbidity, due to physiological disturbances associated with immaturity of vital body system (Kurtzberg et al., 1984). They show neurological maturation retardation in comparison to appropriate-for-gestational-age (A.G.A.) infants. (Pettigrew & Edwards, 1985). 259
Downloaded by [McMaster University] at 15:57 14 April 2016
260
I. SOARES er al.
The incidence of sensory hearing deficit in very-low-birthweight infants (or S .G.A.) is significantly greater than in the normal full-term population (2 to 12.4% hearing disorders compared to .26% for controls) (Kurtzberg, 1982). Electrophysiological equipment has proved very useful in identifying and evaluating these disorders. The incidence of persistent abnormal BAEPs in very-low-birthweightinfants remains around 11% (Kurtzberg, 1982). Among these BAEP alterations, a shortening of central conduction time (I-V interval) has been found in SGA newborns (Pettigrew et al., 1985; Kesson et al., 1985; Soares et al., 1988). The interpretation of this shortening is controversial: we have hypothesized that this shortening is associated with latency lengthening of wave 1 in SGA subjects, and, thus, with an immaturity of the basal part of the cochlea (Soares et al., 1988) rather than with a precocious auditory brainstem neural function development, as other authors claim (Pettigrew & Edwards, 1985; Kesson et al., 1985). The aims of the present study were to verify our previous findings (Soares et al., 1988) for a larger sample of SGA subjects, and to examine a possible influence of the birthweight of the children on the maturation of the BAEPs. For this purpose we tested 3 groups of subjects of less than 37 weeks of conceptional age at the time of examination: a SGA group, with weight less than or equal to 1500 g (called “SGA.” group); an AGA group with birthweight less than or equal to 1500 g (called “AGA1” group); an AGA group with birthweight higher than 1500 g (called ‘AGA2” group). METHODS Subjects
This study involved 39 preterm neonates (23 male, 16 female), of gestational age between 28 and 36 weeks ( m = 32.72; S . D . = 1.75). The subjects were less than 37 weeks of conceptional age at the time of the examination. All the subjects were healthy, with Apgar scores over 7 at 5 minutes, an absence of a family or personal history of deafness or major pathology, and an absence of hyperbilirubinemia. All the infants had normal cranial ultrasound examination. The presence of BAEPs responses (especially wave V) was examined for decreasing itensities (by 10 dB steps). The presence of responses at 30 dB HL or less for all the subjects was chosen as a criterion of auditory threshold normality. The weights of the AGA infants (groups AGAl and AGA2) were within normomature values as defined by Usher et al., Usher & Mc Kean, 1969); the weights of the SGA infants were lower than these normative values. Conceptional ages (or postmenstrual ages) were calculated from the mothers’ last menses. In case of doubt, gestational and conceptional ages were calculated using the Dubowitz Neonate Maturity Scale (Dubowitz et al., 1970). Following a full explanation of the procedure to be undertaken, the informed consent of the subjects parents was obtained in every case. BAEPs Recordings The neonate recordings were carried out in a neonatal intensive care unit (Edouard Herriot Hospital - Lyon, France), without removing the baby from its bassinet or incubator, and without sedatives. Each ear was studied independently. The clicks were generated by passing 100 microseconds duration pulses through the right ear-
MATURATION, BIRTHWEIGHT AND BAEPs
26 1
phone, then through the left earphone. During the testing of one ear, we did not use white noise masking for the nonstudied ear. Unfiltered clicks were used. The sound came through a 2 cm diameter earphone held in very close contact with the external auditory canal. The click rate was 20 Hz. Recordings were made with disc electrodes on the forehead and ipsilateral mastoid, the other mastold electrode serving as ground. Responses were amplified with a MEDELEC A.A.6 M.K.3, at a filter setting of 140-1600 Hz (with 6 and 12 dB/octave), and averaged with a MEDELEC D.A.V.6 (1024 points). The analysis period was 20 ms and the responses were recorded after 2500 sweeps. The infants were studied during their physiological sleep. The right ear curves were chosen arbitrarily for this study, at intensity levels of 80 and 60 dB HL .
Downloaded by [McMaster University] at 15:57 14 April 2016
Measurements
The wave latencies were measured for peaks I, 111 and V at 80 dB HL. The interpeak intervals 1-111, 111-V and I-V were also measured at this intensity. After the recordings, their values were assessed by two independent observers. The neonates were included in this study only if identical values were found for each subject for waves I, I11 and V and intervals 1-111, I-V, and 111-V by the 2 observers, and if the patterns had an excellent intrasubject reproducibility at 80 dB HL. If discrepancies occurred, the subject was excluded from the study. Statistics
Gestational ages, conceptional ages, birthweights and weights at the time of the examination were compared across the 3 groups of infants (SGA., AGA 1 and AGA 2) by one-factor analysis of variance. Then, statistical analysis (one-way Anova) was performed on the latency variations for waves I, 111 and V , and for the 1-111, IIIV , and I-V intervals, at intensity levels of 80 and 60 dB. RESULTS Intergroup Comparability
The subjects were divided into 3 groups (Table 1): Group I comprised 14 SGA subjects. Mean conceptional age was 35.3 weeks (S.D. = .95), and weight lower than or equal to 1500 g, both at birth and at the time of the examination. Group 2 comprised 10 AGA subjects (called “AGA.l group”), but nevertheless of low birthweight. Weight at birth and at the time of the examination was lower than or equal to 1500 g and mean conceptional age was 34.4 weeks ( S . D . = 1.08). Group 3 comprised 15 AGA subjects (called ”AGA2 group”) with weight at birth and at the time of the examination higher than 1500 g.; the mean conceptional age was 34.8 weeks (S.D. = 1.25). The 3 groups did not present any significant difference according to the gestational age of the subjects (F = .47; p > .05) or to their conceptional age (F = 1.93; p > .05). This homogeneity allowed intergroup comparison. In contrast, the 3 groups presented a significant difference according to the average birthweight of the subjects (F = 35.57; p < .0001), and their average weight at the time of the examination ( F = 49.87; p < .0001).
I. SOARES et al.
262
TABLE 1 The 3 Groups of Neonates: Intergroup Comparison Conceptional Birthweight
Group 1 : S.G.A. (n = 14) Group 2: A.G.A., (n = 10) Group 3: A.G.A., (n = 15) I.'
Downloaded by [McMaster University] at 15:57 14 April 2016
P
Gestational Age (weeks)
Age (weeks)
(g)
Weight at the Time of the Examination (g)
m : 32.5 S . D . : 2.2
m: 35.3 S.D.: .91
m : 1108 S . D . : 195
m: 1335 S.D.: 162
m: 32.5 S.D.: 1.2
m: 34.4 S . D . : 1.08
m: 1401 S.D.: 81
in: 1426 S.D.: 68
m: 33 S . D . : 1.6 0.47 N.S.
m: 34.8 S . D . : 1.25 1.92 N.S.
m : 1935 S . D . : 380 35.57 < .0001
m: 2003
S . D . : 262
49.87
