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

Nutrition and management of glycemia in neonates with neonatal encephalopathy treated with hypothermia

Adequate nutrition and glycemic homeostasis are increasingly recognized as potentially neuroprotective for the developing brain. In the context of hypoxia-ischemia, evidence is scarce regarding optimal nutritional support and administration route, as well as the short- and long-term consequences of such interventions. In this review, we summarize current knowledge on disturbances of brain metabolism of glucose and substrates by hypoxia-ischemia, and compound effects of these mechanisms on brain injury characterized by specific patterns on EEG and MRI. Risks and benefits of nutrition delivery via parenteral or enteral routes are examined. Nutrition could mitigate adverse neurodevelopmental outcomes, and the impact of nutritional strategies and specific nutritional interventions are reviewed. Limited literature highlights the need for further studies to understand the changes in energy metabolism during and after hypoxic-ischemic injury, to optimize nutritional regimens and glucose management, and to inform the neuroprotective role of nutrition.

Brainstem shape is affected by clinical course in the neonatal intensive care unit

The brainstem, critical for motor function, autonomic regulation, and many neurocognitive functions, undergoes rapid development from the third trimester. Accordingly, we hypothesized it would be vulnerable to insult during this period, and that a difficult clinical course in the neonatal intensive care unit (NICU) would affect development, and be reflected through atypical shape. Our study population consisted of 66 neonates - all inpatients from the NICU at Victoria Hospital, London Health Sciences Centre, ON, Canada, of which 45 entered the final analysis. The cohort varied in gestational age (GA) and ranged from neurologically healthy to severely brain-injured. Structural MRI was used to quantify brainstem shape at term-equivalent age. From these images, brainstems were semi-automatically segmented and co-registered across subjects. The anterior-posterior dimensions on a sagittal maximum intensity projection were used as the basis for shape comparison. Factor analysis was used to summarize variation in shape and in clinical course to determine three shape factors and three clinical factors, and their relationship assessed using correlation. A factor driven by low GA and associated complications correlated with alterations in the posterior medulla, while a factor driven by complications independent of GA correlated with alterations in the midbrain. Additionally, single clinical measures most representative of their respective clinical factor (days in NICU; days on ventilation) predicted the changes. Thus, different clinical courses in the NICU may have different effects on the shape of the brainstem, and may mediate some of the distinct neurodevelopmental profiles observed in premature and brain-injured neonates.

Reduced wave amplitudes of brainstem auditory response in high-risk babies born at 28-32week gestation

OBJECTIVE

To examine brainstem auditory electrophysiology in high-risk babies born at 28-32week gestation by analysing the amplitudes of wave components in maximum length sequence brainstem auditory evoked response (MLS BAER).

METHODS

94 preterm babies, ranging in gestation 28-32weeks, with perinatal problems (high-risk) were recruited. The amplitudes of MLS BAER wave components were studied at term age (37-42weeks postconceptional age).

RESULTS

Compared with normal term controls, the amplitude in the high-risk preterm babies was significantly smaller at the highest click rate 910/s for wave I (p<0.01), at all 91-910/s for wave III (all p<0.01) and at 455 and 910/s (p<0.05 and 0.01) for wave V. Compared with age-matched low-risk preterm controls, the amplitude was significantly smaller at 455 and 910/s for wave I (p<0.05 and 0.05), 91-910/s for wave III (p<0.05-0.001), and 227-910/s (p<0.05 and 0.01) for wave V. No differences in the V/I and V/III amplitude ratios were found between the high-risk preterm babies and the controls.

CONCLUSIONS

The amplitudes of MLS BAER wave components, mainly more central components, were reduced in the high-risk preterm babies born at 28-32week gestation. Electrophysiological activity of the brainstem auditory neuron in such babies is depressed, mainly attributed to or related to the associated perinatal problems.

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.

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.