Therapeutic Hypothermia in Neonates and Selective Hippocampal Injury on Diffusion-Weighted Magnetic Resonance Imaging

BACKGROUND: Hippocampal injury is most often observed in conjunction with basal ganglia injury after hypoxia-ischemia in term newborns. Objective was to determine perinatal characteristics leading to selective hippocampal injury vs basal ganglia injury on diffusion-weighted imaging in term encephalopathic infants following intrapartum hypoxia-ischemia treated with selective head cooling and to correlate specific injury to subsequent neurodevelopmental outcome. METHODS: Retrospective chart review of obstetric and/or perinatal risk factors and patient characteristics in term infants treated with selective head cooling. All infants met standard enrollment criteria for cooling. MRI was obtained at a median of 7 days of life. Abnormal outcome was defined as spastic quadriplegia, cognitive delay, both, or death. RESULTS: Fifty-seven infants were included for analysis. Diffusion-weighted imaging findings included normal (n = 31), basal ganglia injury (n = 16), and selective hippocampal injury (n = 10). No differences in gestational age, birth weight, sex, or labor complications between groups. More infants in the, basal ganglia vs hippocampal group required delivery room cardiopulmonary resuscitation (P = 0.05), exhibited persistent severe acidosis, severe amplitude electroencephalography suppression, and encephalopathy at birth (P < 0.05). Abnormal neurodevelopmental outcome or death was observed in 88% vs 10% of infants in the basal ganglia vs the hippocampal group, respectively (P = 0.0001). CONCLUSIONS: Infants with hippocampal injury on diffusion-weighted imaging recovered from an intrapartum asphyxial insult more rapidly as reflected by an earlier correction of acid-base status, were less likely to need cardiopulmonary resuscitation, and were less severely encephalopathic. These findings highlight the exquisite vulnerability of the hippocampus to acute hypoxia unaffected by selective head cooling, whereas the normal appearance of the basal ganglia in these infants suggests a neuroprotective effect of cooling.