Multichannel EEG abnormalities during the first 6 hours in infants with mild hypoxic–ischaemic encephalopathy

Abstract

Background Infants with mild HIE are at risk of significant disability at follow-up. In the pre-therapeutic hypothermia (TH) era, electroencephalography (EEG) within 6 hours of birth was most predictive of outcome. This study aims to identify and describe features of early EEG and heart rate variability (HRV) (<6 hours of age) in infants with mild HIE compared to healthy term infants. Methods Infants >36 weeks with mild HIE, not undergoing TH, with EEG before 6 hours of age were identified from 4 prospective cohort studies conducted in the Cork University Maternity Services, Ireland (2003–2019). Control infants were taken from a contemporaneous study examining brain activity in healthy term infants. EEGs were qualitatively analysed by two neonatal neurophysiologists and quantitatively assessed using multiple features of amplitude, spectral shape and inter-hemispheric connectivity. Quantitative features of HRV were assessed in both the groups. Results Fifty-eight infants with mild HIE and sixteen healthy term infants were included. Seventy-two percent of infants with mild HIE had at least one abnormal EEG feature on qualitative analysis and quantitative EEG analysis revealed significant differences in spectral features between the two groups. HRV analysis did not differentiate between the groups. Conclusions Qualitative and quantitative analysis of the EEG before 6 hours of age identified abnormal EEG features in mild HIE, which could aid in the objective identification of cases for future TH trials in mild HIE. Impact Infants with mild HIE currently do not meet selection criteria for TH yet may be at risk of significant disability at follow-up. In the pre-TH era, EEG within 6 hours of birth was most predictive of outcome; however, TH has delayed this predictive value. 72% of infants with mild HIE had at least one abnormal EEG feature in the first 6 hours on qualitative assessment. Quantitative EEG analysis revealed significant differences in spectral features between infants with mild HIE and healthy term infants. Quantitative EEG features may aid in the objective identification of cases for future TH trials in mild HIE.

Cerebral Oxygenation and Metabolism After Hypoxia-Ischemia

“…This pattern is very different from the typical overall suppression seen in moderate-severe HIE at term ( 20 ). However, interestingly a small cohort study in term infants with mild HIE found that early EEG recordings (3–6 h after birth) showed disruption of the sleep cycle, excessive sharp and slow waves and changes in spectral measures in the low-frequency bands compared to healthy term infants ( 21 ). We speculate that these maturation and severity related differences may reflect relative sparing of the cortex in this setting.…”

Prognostic Neurobiomarkers in Neonatal Encephalopathy

“…Evoked potentials have been noted for their usefulness in improving prognosis in small cohorts of infants that received TH [82], and can be measured with standard aEEG setups [83]. Other EEG features of recent interest for prediction are cortical power bursts [84], spectral power and micro-scale transients [85][86][87], and neurovascular coupling [88] in moderateto-severe NE, and sharp and diffuse delta waves, mild asymmetry, and spectral edge frequency in mild NE [7,80].…”

“…Moreover, aEEG monitoring has limited predictivity <6 h for mild NE [9]. Continuous and Discontinuous Normal Voltage were the predominant background patterns [73, 79], although excessive discontinuity and disrupted sleep-wake cycling are also common in these infants [79, 80]. By contrast, conventional EEG has higher accuracy, but requires resources and expertise that may not always be available in NICUs [81].…”

Biomarker und Neuromonitoring zur Entwicklungsprognose nach perinataler Hirnschädigung

“…Daher wird seit vielen Jahren in der Neonatologie eine zeitlich komprimierte, kontinuierliche Ableitung, das aEEG, eingesetzt; dieses sollte aber das konventionelle EEG bei Auffälligkeiten nicht ersetzen. Nur wenige Zentren verfügen über ein kontinuierliches EEG-Monitoring für Neonaten [ 35 ].…”