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.

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.

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 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.

Maximum length sequence brainstem auditory evoked response in low-risk late preterm babies.

OBJECTIVES: Recent research indicates that there is delayed development in the more central part of the auditory brainstem in very preterm babies. We aimed to study whether this is also the case for late preterm babies. METHODS: The maximum length sequence brainstem auditory evoked response (MLS BAER) was used to study functional status of the auditory brainstem. Babies born at 33-36 week gestation and without any major perinatal complications were recruited. MLS BAER was recorded and analyzed at term age. RESULTS: No significant correlation was found between most MLS BAER variables and physiological factors (gender, postconceptional age, bodyweight, and head circumference obtained at time of testing). Wave latencies and amplitudes, and I-V and I-III intervals in the preterm babies were essentially similar to those in the term controls at all click rates. However, III-V interval increased significantly at 227-910/s clicks (p<0.05-0.01). All latencies, amplitudes and intervals correlated significantly with click rates (all p<0.001). No differences were found in the slopes of MLS BAER variables-rate functions between the later preterm babies and term controls. CONCLUSIONS: Babies born at 33-36 weeks gestation without major complications had an increased III-V interval at high-rate stimulation. This suggests that late preterm babies have a mild delay in neural conduction in the more central part of the auditory brainstem.

Depressed brainstem auditory function in children with cerebral palsy.

Brainstem auditory evoked responses were studied to examine brainstem auditory function in 80 children with cerebral palsy. The response waveform, particularly later waves, tended to be depressed. Thirty-three (41.3%) showed abnormal results. The main abnormality was reduced wave V amplitude. Other abnormalities were decreased V/I amplitude ratio, missing waves, prolonged I-V interval, and increased interaural difference in I-V interval. The abnormalities were persistent during the follow-up. In contrast to common findings in the responses in progressive neurologies, abnormalities in interpeak intervals were rare in children with cerebral palsy. There were some characteristic changes in the responses in certain etiologies. These results suggest that brainstem auditory function in children with cerebral palsy is depressed, which may be owing to decreased or altered neural firing or synchrony in the auditory brainstem. A detailed analysis of central components of the responses is valuable in detecting central auditory dysfunction in children with cerebral palsy.

Impairment of perinatal hypoxia-ischemia to the preterm brainstem.

Hypoxia-ischemia is a major perinatal problem that results in severe damage to the newborn brain. This study assessed functional integrity of the brainstem at term in preterm infants after perinatal hypoxia-ischemia to shed light on the influence of hypoxia-ischemia on the preterm brainstem. We recruited sixty-eight preterm infants after perinatal hypoxia-ischemia, ranging in gestation 28-35 weeks. Brainstem evoked response was studied at term age (37-42 weeks postconceptional age) with 91-910/s clicks using the maximum length sequence technique. Compared with healthy preterm infants, the preterm infants after perinatal hypoxia-ischemia showed a significant increase in I-V interval at very high rates 455 and 910/s of clicks (P<0.05, 0.05). III-V interval and III-V/I-III interval ratio also increased significantly at 455 and 910/s (P<0.05-0.01). The slope of III-V interval-rate function was significantly steeper than in the healthy preterm infants (P<0.05). Compared with normal term controls, the preterm infants after hypoxia-ischemia showed similar, but slightly more significant, abnormalities. The differences between the preterm infants after hypoxia-ischemia and the healthy preterm and term infants generally increased with increasing click rate. These results demonstrated that central components of brainstem auditory evoked response were abnormal at very high click rates in the preterm infants after perinatal hypoxia-ischemia. Click rate-dependent change in the more central part of the brainstem is also abnormal. Apparently, functional integrity of the brainstem, mainly in the more central part, is impaired. Hypoxic-ischemic damage to the preterm brainstem is unlikely to completely recover within a relatively short period after the insult, which is of clinical importance.

Brainstem response amplitudes in neonatal chronic lung disease and differences from perinatal asphyxia.

OBJECTIVE: To examine neuronal function of the auditory brainstem in neonatal chronic lung disease (CLD) and detect any differences from perinatal asphyxia. METHODS: Infants with CLD and infants after perinatal asphyxia were studied at term (37-42 weeks postconceptional age). Wave amplitudes of maximum length sequence brainstem auditory evoked response (MLS BAER) were recorded and compared between CLD and asphyxia. RESULTS: The amplitudes of waves I, III and V, and V/I and V/III amplitude ratios in CLD infants did not differ from those in normal term controls at all click rates 21-910/s. The slopes of amplitude-rate functions were all similar to those in the controls. In infants after asphyxia, however, wave III and V amplitudes were smaller than those in both the controls and CLD infants, particularly at high-rate stimulation. The intercepts of amplitude-rate functions for waves III and V were smaller than in both the controls and CLD infants, although there were no significant differences in the slopes of these functions. CONCLUSIONS: No abnormalities in MLS BAER amplitudes were found in CLD infants but the amplitudes were significantly reduced in asphyxiated infants, resulting in major differences between CLD and perinatal asphyxia. SIGNIFICANCE: There is no major neuronal impairment in the auditory brainstem in CLD but there is in perinatal asphyxia. This difference may be, at least partly, related to the difference in the nature of hypoxia associated with the two problems; the hypoxia is chronic and sublethal in CLD, but is often acute, lethal and associated with ischaemia in perinatal asphyxia.

Sustained depression of brainstem auditory electrophysiology during the first months in term infants after perinatal asphyxia.

OBJECTIVE: To gain further insights into the pathophysiological processes of neuronal impairment in neonatal brainstem after perinatal asphyxia. METHODS: Maximum-length sequence brainstem auditory-evoked response (MLS BAER) was recorded with clicks at 91, 227, 455 and 910/s on days 1, 3, 5, 7, 10, 15 and 30 after birth in 108 term infants who suffered perinatal asphyxia. Wave amplitude variables in the MLS BAER were analysed in detail at 40 dB above BAER threshold in 86 infants who had no peripheral hearing impairment. RESULTS: On day 1 the amplitudes of MLS BAER waves I, III and V were all reduced significantly at all click rates, especially at higher ones (91-910/s, ANOVA P<0.05-0.001). On day 3 these amplitudes were reduced further. On days 5 and 7, the amplitude reduction persisted and did not show any significant further changes. On days 10 and 15 the reduced amplitudes were increased slightly. On day 30 all amplitudes were still reduced significantly (P<0.05-0.0001). During the first month, the reduction of wave amplitudes was more significant for the later MLS BAER components than for the earlier ones, and occurred most significantly at 455 and 910/s clicks. By comparison, the amplitude reduction in conventional BAER was much less significant. CONCLUSIONS: During the first month after perinatal asphyxia the amplitudes of MLS BAER waves were reduced significantly and persistently, which was more significant at higher rates of clicks than at lower rates. The reduction is much more persistent than the increase in wave latencies and intervals we previously reported. SIGNIFICANCE: There is sustained depression of brainstem auditory electrophysiology, indicating neuronal damage of the auditory brainstem, in infants after perinatal asphyxia. This may have important clinical implications.

Sub-optimal function of the auditory brainstem in term infants with transient low Apgar scores.

OBJECTIVES: To assess functional integrity of the auditory brainstem in neonates with transient low Apgar scores. METHODS: Forty-two term infants were studied with brainstem auditory evoked response (BAER) using the maximum length sequence during the first month of life. All had transient low Apgar scores but no clinical signs of hypoxic-ischaemic encephalopathy (HIE). RESULTS: The latencies of BAER waves I and III in these infants were similar to those of age-matched normal controls at all click rates (91/s, 227/s, 455/s and 910/s) during the period studied. Wave V latency was increased at 910/s on day 1 (P<0.01), but did not differ from that in the controls on any other days. I-V interval was increased significantly at 455/s and 910/s on day 1 (P<0.01 and 0.001) and day 3 (P<0.05 and 0.01). On days 5 and 7, BAER wave latencies and intervals were similar to those in the controls. On day 30, all latencies and intervals reached the values in the controls. No abnormalities were seen in BAER wave amplitude variables on any days. CONCLUSIONS: Neonates with transient low Apgar scores but without HIE had a significant increase in I-V interval at very high click rates on the first three days of life. SIGNIFICANCE: Brainstem auditory function is sub-optimal during the first few days in neonates with transient low Apgar scores.

Brainstem auditory evoked responses in very low birthweight infants with chronic lung disease.

UNLABELLED: Very low birthweight (VLBW) infants who had prolonged oxygen dependence due to chronic respiratory problems, typically neonatal chronic lung disease (CLD), are at high risk of neurodevelopmental impairment. To assess the effect of CLD on neonatal auditory function we studied brainstem auditory evoked response (BAER) in VLBW infants who suffered CLD but no other major perinatal complications or problems. At 37-42 week postconceptional age, the latencies of waves I, III and V in CLD infants were all significantly longer than in normal term infants (all p<0.001). The differences between CLD infants and the term controls were greater for the later waves than for the earlier waves. Abnormally prolonged wave latency (>2.5 SD of the mean measurement) was seen in 7 (21.2%) CLD infants for wave I, suggesting peripheral auditory impairment, 8 (24.2%) for wave III and 14 (42.4%) for wave V. I-V interval in CLD infants was significantly longer than in the term controls (p<0.001). Seven (21.2%) infants had abnormally prolonged I-V interval, suggesting brainstem or central auditory impairment. Of these infants, 2 had both prolonged wave latencies and prolonged I-V interval, suggesting both peripheral and central auditory impairment. Similar abnormalities were found in CLD infants when compared with the BAER in birthweight- and age-matched healthy VLBW infants without CLD. CONCLUSION: Neonatal auditory function is impaired, both peripherally and centrally, at term age in VLBW infants who suffer neonatal CLD.

Distortion product otoacoustic emissions during the first year in term infants: a longitudinal study.

Understanding of any age-related differences in distortion product otoacoustic emissions (DPOAEs) during infancy is important for the use of DPOAEs in detection of cochlear impairment in infants. We studied DPOAEs at 10 frequencies of f2 primary tone between 500 Hz to 10 kHz longitudinally during the first year of life in 70 ears of 35 normal term infants. On days 3-5 after birth DPOAE pass rates ranged between the highest 98.6% at f2 frequencies 6-10 kHz and the lowest 22.9% at 750 Hz. The higher the frequency, the higher was the pass rate. At 6 months the pass rates at various frequencies were generally similar to those on days 3-5, and were greater than 91% across the frequencies of 3-10 kHz. At 12 months the pass rates were 100% or near 100% across 3-10 kHz. During the first year the pass rate was always very low at 750 Hz (<40%) and tended to decrease at 1 kHz with the increase in age. DPOAE level at f2 frequencies 4kHz increased from birth to 6 months but then reduced slightly at 12 months. At lower frequencies the age-related DPOAE levels change was less significant. These results indicate that there are no major changes in DPOAE or cochlear function during the first year of life at most frequencies. However, the interpretation of DPOAE results in infants need to take into account the age-related difference in DPOAE pass rate at low-frequency and in DPOAE level at high-frequency.

Changes in BAER amplitudes after perinatal asphyxia during the neonatal period in term infants.

We recorded serially brainstem auditory evoked response (BAER) during the neonatal period in term infants who suffered perinatal asphyxia. The amplitudes of BAER components was analysed at 40 dB above BAER threshold of each subject who had a threshold