Correlation of electroencephalogram background evolution with the degree of brain injury in neonates with hypoxic-ischemic encephalopathy.

Objectives: To study the correlation of electroencephalogram (EEG) background evolution with the degree of brain injury in neonates with hypoxic-ischemic encephalopathy (HIE).

Methods: A retrospective analysis was performed for 56 neonates with HIE who underwent continuous video electroencephalogram (cVEEG) and brain magnetic resonance imaging (MRI) examinations. According to clinical symptoms, they were divided into a mild group with 3 neonates, a moderate group with 36 neonates, and a severe group with 17 neonates. EEG background grading and MRI score were determined for each group to analyze the correlation of EEG background evolution with the degree of brain injury.

Results: Compared with the moderate group, the severe group had significantly lower gestational age and Apgar score at 5 minutes after birth, a significantly higher resuscitation score, significantly lower base excess in umbilical cord blood or blood gas within 1 hour, a significantly higher proportion of neonates on mechanical ventilation, and a significantly higher incidence rate of short-term adverse outcomes (<0.05). For the neonates in the mild and moderate groups, MRI mainly showed no brain injury (67%, 2/3) and watershed injury (67%, 16/24) respectively, and EEG showed mild abnormality in 62% (13/21) of the neonates on the 3rd day after birth. For the neonates in the severe group, MRI mainly showed basal ganglia/thalamus + brainstem injury (24%, 4/17) and whole brain injury (71%, 12/17), and EEG showed moderate or severe abnormalities on the 3rd day after birth. EEG background grading was correlated with clinical grading, MRI score, and short-term outcome on days 1, 2, 3 and 7-14 after birth (<0.01). The highest correlation coefficient between EEG grading and MRI score was observed on the 3rd day after birth (=0.751, <0.001), and the highest correlation coefficients between EEG grading and clinical grading (=0.592, =0.002) and between EEG grading and short-term outcome (=0.737, <0.001) were observed 7-14 days after birth. Among the neonates with severe abnormal EEG, the neonates without brain electrical activity had the highest MRI score, followed by those with status epileptics and persistent low voltage (<0.05).

Conclusions: There is a good correlation between EEG background grading and degree of brain injury in neonates with HIE, which can help to evaluate the degree and prognosis of brain injury in the early stage.