Suboptimal postnatal function of brainstem auditory pathway in late preterm infants who do not have major perinatal and postnatal complications.

OBJECTIVES: To examine postnatal functional status of the brainstem auditory pathway in late preterm infants and detect any postnatal auditory abnormality. METHODS: Thirty preterm infants born at 33-36 weeks gestation were studied three months after term. None had major perinatal and postnatal complications to minimize confounding effects. Brainstem auditory evoked responses were recorded with 21-91/s clicks. RESULTS: Compared with postnatal age-matched normal term infants, the late preterm infants did not manifest any major abnormalities in brainstem auditory evoked responses at conventionally used 21/s clicks. At higher click rates, however, the late preterm infants manifested a moderate prolongation in BAER wave V latency. All interpeak intervals tended to be prolonged at higher click rates. The I-V interval was significantly prolonged at 51/s and particularly at 91/s clicks. Both the I-III and III-V intervals were significantly prolonged at 91/s. The late preterm infants also manifested reduced amplitudes of BAER waves III and V at most click rates. CONCLUSION: The central components of the brainstem auditory evoked responses were abnormal at higher click rates three months after term in the late preterm infants. Postnatal brainstem auditory function is suboptimal in late preterm infants without major complications. This suboptimal brainstem auditory function may not be clearly shown at term or an earlier stage, but can be shown later. Late preterm infants, although they may not have major complications, should be followed for later auditory development, providing valuable information for improving postnatal care.

Brainstem auditory abnormality in extremely premature babies and the impact of neonatal bronchopulmonary dysplasia.

INTRODUCTION: Extremely premature babies, particularly those who have neonatal bronchopulmonary dysplasia, are at risk of brain damage and neurodevelopmental impairment. This study aimed to examine functional status of the brainstem auditory pathway in extremely premature babies and assess the impact of bronchopulmonary dysplasia on function. MATERIAL AND METHODS: Brainstem auditory evoked response was studied at term in babies born at ≤27 weeks of gestation with or without neonatal bronchopulmonary dysplasia. The normal controls were term babies without perinatal problems. RESULTS: Compared with the normal controls, the extremely premature babies showed an elevated response threshold, increased latencies of waves I, III and particularly V. They also showed significantly increased I-V and III-V intervals. The amplitudes of waves I and V were moderately reduced. These abnormalities were clearly more significant in those with bronchopulmonary dysplasia than those without bronchopulmonary dysplasia. A direct comparison between the two groups of extremely premature babies revealed that wave V latency, and I-V and particularly III-V intervals were significantly longer in the babies with bronchopulmonary dysplasia than those without bronchopulmonary dysplasia. CONCLUSIONS: Extremely premature babies have functional impairment of the brainstem auditory pathway. The impairment is clearly more significant in those with bronchopulmonary dysplasia than those without bronchopulmonary dysplasia. Neonatal bronchopulmonary dysplasia and associated unfavorable conditions are major contributors to brainstem auditory impairment in extremely premature babies.

Short-term outcome of functional integrity of the auditory brainstem in term infants who suffer perinatal asphyxia.

OBJECTIVES: To assess short-term outcome of impaired functional integrity of the auditory brainstem in term infants who suffer perinatal asphyxia. METHODS: Maximum length sequence brainstem auditory evoked response (MLS BAER) was recorded and analyzed at a mean age of 3months in term infants after perinatal asphyxia. The data were compared with age-matched normal term infants. RESULTS: The infants after asphyxia showed an increase in the latency of MLS BAER wave III at 91, 455 and 910/s, and wave V at all click rates of 91-910/s. The interpeak intervals in the infants after asphyxia were increased at almost all click rates. The IV and I-III intervals were increased at all click rates, and the III-V interval was increased at 455 and 910/s. These increases were generally more significant at higher than at lower click rates. The amplitudes of waves I, III and V in the infants after asphyxia were reduced at all click rates. The V/I amplitude ratio was increased at 91-455/s clicks. The slope of III-V interval-rate function was abnormally increased. 17.1% of the infants after asphyxia had an abnormal increase in IV intervals. CONCLUSIONS: MLS BAER was moderately abnormal at 3months of age in term infants after perinatal asphyxia, suggesting moderate impairment in the functional integrity of the auditory brainstem. The impairment occurs in 17.1% of the infants. Compared with that found at term, the impairment has improved, but not completely recovered.

Auditory impairment in infants with neonatal chronic lung disease is alleviated after term.

AIM: Very premature infants with neonatal chronic lung disease (CLD) have been reported to have major auditory impairment at term, and we examined the outcomes in 30 infants after term age. METHODS: Brainstem auditory evoked response (BAER) was recorded at a postconceptional age of 46-61 weeks in 13 CLD cases and 14 controls from China and 17 CLD cases and 22 controls from the UK. RESULTS: The BAER threshold in the CLD infants was slightly higher. Clicks at the normal hearing level (60 dB) showed no significant differences between the cases and controls in the latencies of BAER waves I, III and V and the I-V interval. However, the CLD infants demonstrated marginal shortening in the I-III interval and a marginal increase in the III-V interval. The amplitudes of BAER waves in the CLD infants were all slightly smaller than the controls. At 70 and 40 dB normal hearing level, the BAER findings were similar to those obtained at 60 dB normal hearing level, with only small variations. CONCLUSION: There were minor BAER abnormalities in the CLD infants, suggesting minor auditory impairment. The auditory impairment previously detected at the term date was later alleviated.

Abnormal findings in brainstem auditory evoked response at 36-37weeks of postconceptional age in babies with neonatal chronic lung disease.

AIM: To examine brainstem auditory function at 36-37weeks of postconceptional age in preterm infants who are diagnosed to have neonatal chronic lung disease (CLD). STUDY DESIGN: Preterm infants, born at 31 and less weeks of gestation, were studied at 36-37weeks of postconceptional age when they were diagnosed to have neonatal CLD. Brainstem auditory evoked response (BAER) was recorded and analyzed at different click rates. RESULTS: Compared with healthy controls at the same postconceptional age, the CLD infants showed a slightly increase in BAER wave V latency. However, the I-V, and III-V interpeak intervals in the CLD infants were significantly increased. The III-V/I-III interval ratio was also significantly increased. The amplitudes of BAER waves III and V in the CLD infants tended to be reduced. These BAER findings were similar at all 21, 51 and 91/s clicks, although the abnormalities tended to be more significant at higher than at low click rates. CONCLUSION: At 36-37weeks of postconceptional age, BAER was abnormal in preterm infants who were diagnosed to have neonatal CLD. This suggests that at time when the diagnosis of CLD is made there is functional impairment, reflecting poor myelination, in the brainstem auditory pathway in preterm infants with neonatal CLD.

Small-for-gestation birth exerts a minor additional effect on functional impairment of the auditory brainstem in high-risk babies born at late preterm.

OBJECTIVE: To address if small-for-gestational-age (SGA) significantly affects the developing auditory brainstem in late preterm babies with perinatal problems (i.e. high-risk), providing valuable information for management of such babies. METHODS: SGA and appropriate-for-gestational age (AGA) babies born at 33-36weeks of gestation were studied at term using maximum length sequence brainstem auditory evoked response in response to 91-910/s clicks. RESULTS: Compared with AGA late preterm babies without perinatal problems (i.e. low-risk), the high-risk SGA babies manifested a significant increase in wave V latency and I-V interval at all 91-910/s clicks, and III-V interval at 455 and 910/s. The amplitude was smaller for wave I at 227 and 910/s, wave III at 910/s and wave V at 227 and 910/s. Compared with low-risk SGA babies, the high-risk SGA babies showed similarly abnormalities. Compared with high-risk AGA babies, the high-risk SGA babies manifested slightly different abnormalities. CONCLUSIONS: Brainstem auditory response was abnormal in high-risk SGA late preterm babies. The abnormalities, suggesting brainstem auditory impairment, were slightly different from high-risk AGA late preterm babies. SIGNIFICANCE: SGA birth exerts a minor additional effect on the impaired auditory brainstem in high-risk babies born at late preterm. For these babies, neuroprotective measures should mainly target at associated perinatal problems, although the relatively minor adverse SGA effect cannot be ignored.

Comparison of maturational process of hearing threshold in early life between at-risk and low-risk preterm infants.

AIM: To detect any abnormality in the maturational process of hearing threshold during the early life in at-risk preterm infants. STUDY DESIGN: The threshold of brainstem auditory evoked response was recorded and analyzed longitudinally from 30 to 42weeks of postconceptional age in 357 at-risk infants born at 23-36weeks of gestation. The results were compared with those in 82 low-risk infants born at 30-42weeks at various postconceptional ages. RESULTS: From 31 to 42weeks, the response threshold in the at-risk infants was consistently slightly higher than that in the low-risk infants. No statistically significant difference was found between the two groups of infants at any designated postconceptional ages. The threshold in the at-risk infants born at 23-29weeks of gestation tended to be higher than those born at 30-36weeks at various postconceptional ages, but the difference did not reach statistical significance. There was also no significant difference in the slope of BAER threshold-age function between the at-risk infants, irrespective of gestational ages, and the low-risk infants. CONCLUSION: During the early life, hearing threshold in at-risk preterm, mainly very preterm, infants is marginally elevated, but the maturational process of the threshold is generally similar to that in low-risk infants, without notable abnormality.

Functional integrity of rostral regions of the immature brainstem is impaired in babies born extremely preterm.

OBJECTIVE: Babies born extremely preterm are predisposed to brain damage. We test the hypothesis that functional integrity of the auditory brainstem, particularly the rostral regions, is impaired in extremely preterm babies. METHODS: We recruited 68 babies who were born at 23-27 weeks of gestation. At term date, these babies were studied by recording and analysing maximum length sequence brainstem auditory evoked response (MLS BAER) with click rates 91-910/s. Detailed data analysis was performed in 65 babies from whom reliable MLS BAER measurements were obtained. RESULTS: Compared with normal term controls, the extremely preterm babies showed a significant increase in wave V latency, and I-V interval at all rates 91-910/s (p<0.01-0.001). Of two small intervals, I-III interval showed no apparent abnormality, but III-V interval was significantly increased at all rates, which was supported by a significant increase in III-V/I-III interval ratio (all p<0.001). These abnormalities were more significant at higher than at lower rates. The slopes of wave V latency-, I-V interval- and particularly III-V interval-rate functions were all increased. The same was true for the slope of III-V/I-III interval ratio-rate function. CONCLUSIONS: MLS BAER variables that mainly reflect central neural conduction in the extremely preterm babies were abnormally increased. The most important abnormality was a significant increase in III-V interval and its click rate-dependent change. The abnormalities tended to be more significant than those previously reported in late and very preterm babies. SIGNIFICANCE: Babies born extremely preterm have a major impairment or maturational delay in functional integrity of the rostral regions of the immature brainstem, which is more significant than in less preterm babies.

Changes in hearing threshold between 28 and 42 weeks of age in babies born at under 30 weeks of gestation.

AIM: This study aimed to describe changes in hearing thresholds in babies born below 30 weeks of gestation at 28-42 weeks of postconceptional age, detect differences between gestational ages and explore the prevalence of hearing impairment. METHODS: The threshold of brainstem auditory evoked response (BAER) was obtained longitudinally at 28-42 weeks of postconceptional age in 71 babies born at 23-29 weeks of gestation. RESULTS: The BAER threshold was 28 decibels above normal hearing level (dB nHL) at 28 weeks of postconceptional age and decreased to 13 dB nHL at 39-42 weeks. The threshold was slightly higher in babies born at 23-26 weeks of gestation than in those born at 27-29 weeks at most postconceptional ages studied. From 28 to 36 weeks, the threshold decreased at 0.98 dB/week. At term, BAER threshold elevation (>20 dB nHL) occurred in 12 (16.9%) of the 71 babies. CONCLUSION: The hearing threshold of babies born at 23-29 weeks of gestation decreased from 28 dB at 28 weeks of postconceptional age to 13 dB at 42 weeks. There were no major differences between gestational ages. During the preterm period, the threshold changed at around 1 dB/week. At term, one in six babies had hearing impairment.

Neural conduction impairment in the auditory brainstem and the prevalence in term babies in neonatal intensive care unit.

OBJECTIVE: To detect neural conduction abnormality in the auditory brainstem in term babies in the neonatal intensive care unit (NICU), determine prevalence of the abnormality, and assess if maximum length sequence (MLS) technique improves early detection of the abnormality. METHODS: One hundred and six term babies were recruited, and studied by recording and analysing MLS brainstem auditory evoked response (BAER). Interpeak intervals were analysed in detail, which were then compared with those in normal term babies. RESULTS: Wave V latency and I-V and III-V intervals in MLS BAER were increased in the NICU term babies at all click rates 91-910/s, particularly at 455 and 910/s (p<0.05-0.001). No major abnormalities were found in wave I and III latencies and I-III interval. The abnormal increase in I-V and III-V intervals were seen in significantly more cases at 455 and 910/s in MLS BAER than at 21/s in conventional BAER (X(2)=10.92-13.88, all p<0.01). As a whole, 38 (35.8%) of the NICU babies had abnormal III-V and/or I-V intervals in MLS BAER, which was significantly more than 13 (12.2%) in conventional BAER (X(2)=16.14, p<0.01). CONCLUSION: There is neural conduction impairment in the auditory brainstem in NICU term babies, which occurs in one-third of these babies. SIGNIFICANCE: Term babies in NICU are at risk of neural conduction impairment in the auditory brainstem. High click rates in MLS BAER enhance early detection of the impairment.

Comparison of brainstem auditory evoked response at different click rates between preterm babies after neonatal necrotizing enterocolitis and healthy preterm babies.

BACKGROUND: Neonatal necrotizing enterocolitis (NEC) is associated with an increased incidence of poor neurodevelopment. The knowledge of underlying neurophysiology is very limited, and the influence of NEC on the preterm brainstem is very poorly understood. OBJECTIVE: To assess the effect of NEC on the immature auditory brainstem by excluding any possible confounding effect of preterm birth. METHODS: We recorded and analyzed brainstem auditory evoked response (BAER) at different click rates in preterm babies (30-34 weeks gestation) after NEC. The results were compared with those in age-matched healthy preterm babies who had no NEC. RESULTS: At click rate 21/s, the latencies of BAER waves I and III in the preterm NEC babies were similar to those babies without NEC. However, wave V latency was longer in the NEC babies than in those without NEC. The I-V interpeak interval was also longer in the NEC babies than in those without NEC. These abnormalities were persistent at higher click rates 51 and 91/s. Wave I amplitude in the preterm NEC babies did not differ significantly from that in those without NEC, but wave III and V amplitudes were smaller than in those without NEC at all 21-91/s clicks. CONCLUSIONS: Compared with healthy preterm babies, preterm babies after NEC showed a major increase in wave V latency and I-V interval at all 21-91/s clicks. Brainstem auditory function is impaired in preterm NEC babies after excluding the possible confounding effect of preterm birth. Neonatal NEC and associated perinatal conditions adversely affect the premature brainstem.

Neonatal necrotizing enterocolitis adversely affects neural conduction of the rostral brainstem in preterm babies.

OBJECTIVE: Necrotizing enterocolitis (NEC) is a devastating neonatal disease, often leading to long term neurodevelopmental impairment. The effect of NEC on the immature brain remains not fully understood. We test the hypothesis that NEC adversely affects functional integrity, particularly neural conduction, of the preterm brainstem. METHODS: Thirty-two preterm NEC babies (30-36weeks gestation) were recruited at term age. Maximum length sequence brainstem auditory evoked response was recorded and analysed with click rates 91-910/s at term age. The results were compared with normal term babies and age-matched healthy preterm babies. RESULTS: Wave V latency, I-V and III-V intervals, and III-V/I-III interval ratio differed significantly among the three groups of babies at all click rates 91-910/s. Compared with normal term babies, preterm NEC babies showed significant increase in all these MLS BAER variables at all rates, with no apparent abnormalities in wave I and III latencies and I-III interval. All these abnormalities were more significant at higher than at lower click rates. No notable abnormalities were seen in wave amplitudes. Compared with age-matched healthy preterm babies, NEC babies showed similar abnormalities, although the abnormalities were relatively less significant. CONCLUSIONS: MLS BAER components that mainly reflect neural conduction in the more central regions of the auditory brainstem were abnormal in preterm NEC babies, although those components that mainly reflect peripheral function were generally normal. SIGNIFICANCE: Neonatal NEC adversely affects myelination of the more rostral or central regions of the immature brainstem, resulting in delayed or impaired neural conduction, but spares the more peripheral regions.

Impaired neural conduction in the auditory brainstem of high-risk very preterm infants.

OBJECTIVE: To test the hypothesis that neural conduction in the auditory brainstem is impaired in high-risk very preterm infants. METHODS: Eighty-two very preterm infants (gestation 28-32 weeks) with various perinatal problems or complications were studied at term using maximum length sequence (MLS) brainstem auditory evoked response (BAER) with click rates 91-910/s. The data were compared with those in 31 age-matched low-risk very preterm infants and 44 normal gestation (term) infants. RESULTS: High-risk very preterm infants showed a general increase in MLS BAER wave latencies and interpeak intervals. Wave V latency, and III-V and I-V intervals in high-risk very preterm infants were significantly longer than in normal term infants at all click rates, particularly higher rates. I-III interval was significantly longer, and III-V/I-III interval ratio was significantly greater at higher rates. These latency and intervals in high-risk very preterm infants were also longer, though relatively less significantly, than in low-risk very preterm infants. Click rate-related changes in major MLS BAER variables in high-risk infants were more significant than in the two groups of controls. CONCLUSIONS: There were major abnormalities in MLS BAER variables that mainly reflect central neural conduction in high-risk very preterm infants. The abnormalities were relatively less significant when compared with low-risk very preterm infants than with normal term infants. SIGNIFICANCE: Neural conduction in the auditory brainstem, mainly the more central regions, is impaired in high-risk very preterm infants. The impairment is largely attributed to the associated perinatal problems, and partially related to very preterm birth.

Brainstem auditory electrophysiology is supressed in term neonates with hyperbilirubinemia.

BACKGROUND: Whether hyperbilirubinemia suppresses electrophysiological activity of the neonatal auditory brainstem remains to be investigated. AIM: To determine whether hyperbilirubinemia suppresses the brainstem auditory electrophysiology in term neonates. METHODS: Maximum length sequence brainstem auditory evoked response (MLS BAER) was recorded shortly after confirming hyperbilirubinemia in 58 term neonates. Wave amplitudes of the response were analyzed in detail. RESULTS: Compared with age-matched term controls, the neonates with hyperbilirubinemia showed a significant reduction in the amplitudes of MLS BAER waves III and particularly V at all click rates 91-910/s. The reduction tended to be more significant at higher than lower rates. Wave I amplitude was reduced at 910/s. V/I amplitude ratio was decreased at all click rates. Therefore, the amplitudes of MLS BAER, particularly later, waves were all reduced. The amplitudes of all MLS BAER waves tended to be reduced with the increase in total serum bilirubin level. All wave amplitudes were correlated with the level of total serum bilirubin at some or most click rates. CONCLUSIONS: Brainstem auditory electrophysiology is suppressed in neonates with hyperbilirubinemia, which related to the severity of hyperbilirubinemia. Wave amplitudes are valuable BAER variables to detect functional impairment of the brainstem and auditory pathway in neonatal hyperbilirubinemia, and are recommended to be used in assessing bilirubin neurotoxicity to the neonatal brain.

Impaired function of the auditory brainstem in term neonates with hyperbilirubinemia.

OBJECTIVE: We studied maximum length sequence brainstem auditory evoked response in term neonates with hyperbilirubinemia to further our understanding of hyperbilirubinemia on the neonatal auditory brainstem and to determine if maximum length sequence technique improves detection of brainstem auditory impairment due to bilirubin neurotoxicity. METHODS: Maximum length sequence brainstem auditory evoked response was recorded and analysed shortly after confirming total serum bilirubin levels greater than 15mg/dL in fifty-seven term neonates with hyperbilirubinemia. RESULTS: Most wave latencies and interpeak intervals in maximum length sequence brainstem auditory evoked response in the neonates with hyperbilirubinemia were correlated with the level of total serum bilirubin at some or most click rates used. Compared with age-matched normal term controls, wave V latency in these neonates was increased significantly at all 91-910/s click rates (p<0.05-0.001). The I-V and I-III interpeak intervals were also increased significantly at all these rates, and the III-V interval increased at 227-910/s clicks (p<0.05-0.001). The differences between the neonates with hyperbilirubinemia and the controls were more significant at higher than at lower click rates. The slopes of wave V latency-rate function and I-V and III-V interval-rate functions were all significantly increased. By comparison, the abnormalities in conventional BAER were less significant, with only I-III and I-V intervals were increased (both p<0.05). CONCLUSIONS: Functional status of the auditory brainstem is impaired in neonatal hyperbilirubinemia. Maximum length sequence technique at high click rates improves detection of bilirubin neurotoxicity to the neonatal auditory brainstem, particularly for the more rostral regions.

Changes in brainstem auditory response threshold in preterm babies from birth to late term.

CONCLUSION: The hearing threshold in preterm infants was 23 dB above adult hearing level at 30 weeks gestation, and decreased to around 13 dB at term date. There was no major difference in the threshold for infants born at different gestations. At term, 9% had hearing threshold elevation. OBJECTIVE: To examine changes in hearing threshold from preterm to term in infants born at 30-36 weeks gestation and to detect the prevalence of threshold elevation. METHODS: The threshold in brainstem auditory evoked response (BAER) was obtained 656 times from postconceptional age (PCA) 30 to 42 weeks in 268 infants born at 30-36 weeks gestation. RESULTS: The BAER threshold was 23 dB nHL at the youngest age (PCA 30 weeks), and then decreased to around 13 dB nHL at later preterm and term dates (PCA 35-42 weeks). The threshold was decreased with increasing age at a rate of 1.24 dB per week from PCA 30 to 36 weeks and 0.65 dB per week from PCA 30 to 42 weeks. At PCA 33-42 weeks, there were no significant differences in BAER threshold between the infants born at gestational age (GA) 30-32 weeks and those at GA 33-36 weeks. At term, 9% had threshold elevation (>20 dB nHL).

Amplitude reduction in brainstem auditory response in term infants under neonatal intensive care.

OBJECTIVE: To examine brainstem auditory electrophysiology in term neonates under intensive care due to perinatal conditions other than hypoxia-ischemia. METHODS: Maximum length sequence brainstem auditory evoked response was studied in term neonates in an intensive care unit. The amplitudes of wave components of the response were analysed to assess brainstem auditory electrophysiology. RESULTS: The amplitudes of all wave components in the neonates under intensive care tended to be smaller than in those in normal term controls. Wave I amplitude was significantly reduced at all 91-910/s clicks (p < 0.05-0.01). The amplitudes of waves III and V were also reduced, respectively, at 227-910/s (all p < 0.05) and at 455 and 910/s (both p < 0.01). The amplitude reduction was slightly more significant at higher than lower click rates, but there were no significant differences in the slopes of wave I, III and V amplitude-rate functions between the neonates under intensive care and the controls. CONCLUSIONS: Wave amplitudes of maximum length sequence brainstem auditory evoked response were reduced in term neonates under intensive care due to perinatal conditions other than hypoxia-ischemia. SIGNIFICANCE: Brainstem auditory electrophysiology is depressed in term neonates under intensive care, possibly due to collective adverse effects of perinatal conditions. The impairment to the neonatal, particularly rostral, brainstem due to other perinatal conditions is less severe than that due to hypoxia-ischemia previously reported.

Brainstem auditory response findings in preterm infants after necrotizing enterocolitis.

AIM: To examine brainstem auditory function and detect any abnormality at term in preterm infants after neonatal necrotizing enterocolitis (NEC). METHODS: Brainstem auditory evoked response (BAER) was recorded at 21/sec and 60 dB nHL in 37 preterm infants who had NEC. The data obtained at term equivalent age were analyzed and compared with those in normal term infants. RESULTS: The threshold of BAER in infants after NEC, though slightly elevated, did not differ significantly from that in the controls. The latencies of waves I and III were slightly longer than in the controls, without any statistical significance. However, wave V latency was prolonged and differed significantly from the controls (p < 0.01). I-V interpeak interval was also prolonged (p < 0.05). The data point distribution of wave V latency and I-V interval was higher in the infants after NEC than in the controls. The amplitudes of BAER wave components in the infants after NEC did not differ significantly from those in the controls. CONCLUSION: Preterm infants after NEC have no major abnormality in peripheral auditory function. However, neural conduction in the brainstem auditory pathway is abnormal, suggesting that NEC adversely affects brainstem auditory conduction.

Brainstem auditory response findings in term neonates in intensive care unit.

OBJECTIVES: Whether term infants in neonatal intensive care unit (NICU) have brainstem auditory abnormalities remains to be determined. This study aimed to detect any abnormality in brainstem auditory function in term neonates who are admitted to NICU. METHODS: From a NICU, we recruited 55 term neonates with various perinatal problems. They were studied during the first week after birth using brainstem auditory evoked response (BAER), and the results were compared with normal term controls. RESULTS: Wave I and III latencies and I-III interpeak interval of the evoked response in the NICU term neonates were similar to those in the controls. Wave V latency and I-V and III-V interpeak intervals tended to be increased at 21/s clicks. The increase was more obvious at higher rates 51 and 91/s. Analysis of variance revealed that at 21/s clicks only III-V interval was significantly increased (p < 0.05). At 51 and 91/s clicks, wave V latency and III-V and I-V intervals were significantly increased (p < 0.05-0.01). The rates of the abnormalities were seen more at higher than at lower click rates. The amplitudes of waves I, III, and V in the NICU neonates were all slightly reduced, but none differed significantly from the controls. CONCLUSIONS: There are some abnormalities in BAER in term neonates in NICU, suggesting functional abnormality in the auditory brainstem in NICU infants.

Functional abnormality of the auditory brainstem in high-risk late preterm infants.

OBJECTIVE: To examine whether late preterm infants with perinatal problems are at risk of brainstem auditory impairment. METHODS: 68 high-risk late preterm infants (gestation 33-36 weeks) with perinatal problems or conditions were studied at term using maximum length sequence brainstem auditory evoked response. The controls were 41 normal term infants and 37 low-risk late preterm infants. RESULTS: Compared with normal term infants, the high-risk late preterm infants demonstrated a significant abnormal increase in MLS BAER variables that mainly reflect more central function of the brainstem auditory pathway, including wave V latency, III-V and I-V interpeak intervals, and III-V/I-III interval ratio. The abnormalities were more significant at higher than at lower click rates. The slopes of MLS BAER-rate function for these variables were increased. Compared with low-risk late preterm infants, the high-risk infants showed similar, though slightly less significant, abnormalities, mainly a significant increase in III-V and I-V intervals. CONCLUSIONS: Maximum length sequence brainstem auditory evoked response components that mainly reflect central function of the auditory brainstem were abnormal at term in high-risk late preterm infants. SIGNIFICANCE: More central regions of the auditory brainstem are impaired in high-risk late preterm infants, which is mainly caused by associated perinatal problems or conditions.