Magnetic Resonance Imaging of Hypoxic-Ischemic Brain Injury in the Neonatal Rat

Abstract

Magnetic resonance (MR) imaging was used for the in vivo evaluation of bihemispheric hypoxic-ischemic (HI) injury in the neonatal rat. Seven-day-old rats underwent sham surgery (n = 7) or bilateral carotid artery ligation and hypoxia (30-45 min) (n = 8). T2-weighted imaging was used to study the temporal evolution of injury. Histopathology was used to correlate injury with MR signal changes. T2-weighted images exhibited considerable anatomic detail (0.2 mm resolution in-plane). The cortex, dorsolateral striatum and thalamus were affected, while the hippocampus was spared. Magnetic resonance signal change was seen as early as 1.5 hrs post-HI (lesion extent, 27%-39%), and reached a maximum at 48 hrs (37%-49%). Magnetic resonance imaging estimation of injury at 72 hours after HI was compared with histopathology and correlated well (r = 0.98). The study demonstrates the feasibility of magnetic resonance imaging for in vivo evaluation of neonatal brain injury and that vulnerability in the neonatal hippocampus is strikingly different than in adult HI models.