Use of 2-channel bedside electroencephalogram monitoring in term-born encephalopathic infants related to cerebral injury defined by magnetic resonance imaging.

OBJECTIVE: Single-channel amplitude-integrated electroencephalography has been shown to be predictive of neurodevelopmental outcome in term infants with hypoxic-ischemic encephalopathy. We describe the relationship of quantifiable electroencephalogram (EEG) measures, obtained using a 2-channel digital bedside EEG monitor from term newborn infants with encephalopathy and/or seizures, to cerebral injury defined qualitatively by MRI.

METHODS: Median values of minimum, mean, and maximum EEG amplitude were obtained from term-born encephalopathic infants during a 2-hour seizure-free period obtained within 72 hours of admission. Infants underwent MRI with images qualitatively scored for abnormalities of cortex, white matter, deep nuclear gray matter, and posterior limb of the internal capsule. Eighty-six infants had EEG measures related to qualitative MRI outcomes.

RESULTS: The most common diagnosis was hypoxic ischemic encephalopathy (n = 40). For all infants there was a negative relationship between EEG amplitude measures and MRI abnormality scores assessed on a scale from 4 to 15, with a higher score indicating more abnormalities. This relationship was strongest for the minimum amplitude measures in both hemispheres; that is, for every unit increase in score there was a mean drop of 0.41 microV for the left cerebral hemisphere, with 35% of variance explained. This relationship persisted on sub-group analyses for infants with hypoxic-ischemic encephalopathy, infants with other diagnoses and infants monitored after the first 24 hours of life. Using an MRI abnormality score cutoff of 8 or worse for cerebral injury in infants with hypoxic-ischemic encephalopathy, a minimum amplitude of 4 microV showed a higher specificity (80%: left hemisphere), whereas a minimum amplitude of 6 muV showed a higher sensitivity (92%: left hemisphere).

CONCLUSIONS: Bedside EEG measures in term-born encephalopathic infants are related to the severity of cerebral injury as defined by qualitative MRI. A minimum amplitude of <4 microV appears useful in predicting outcome.