Oxygen deprivation before or around the time of birth often results in hipoxia-ischemia-induced brain damage, which remains a common cause of neonatal injury, and affects 1 to 3 per 1000 live births in developed contries with incidence increased up to 26 per 1000 live births in the developing world.

The pattern of injury depends on the level of the development of the brain and on the severity and duration of the insult.

Neonatal encephalopathy resulting from hypoxic-ischemic injury is characterized by altered consciousness level, seizures and abnormal neurologic examination. An association between moderate or severe neonatal encephalopathy and autism has been reported.

Treatment of hypoxic-ischemic encephalopathy consists largely of supportive care. Prior to the era of hypothermia for neuroprotection, mortality rates were high among infants with severe hypoxic-ischemic encephalopathy. Children who survived neonatal encephalopathy had cognitive deficits even in the absence of functional deficits.

Three of the hypothermia for neonatal hypoxic-ischemic encephalopathy randomized controlled trials have reported on the neonatal MRI as a biomarker of outcome at 18-24 months of age.

- TOBY trial demonstrated a reduction in lesions in the basal ganglia and thalamus (BGT), the white matter (WM) and the posterior limb of the internal capsule (PLIC) among cooled infants compared to control infants.

- ICE trial group noted that WM injury was decreased on the neonatal MRI among cooled infants. BGT and PLIC injury were associated with death or disability at 24 months of age.

- NICHD NRN trial group describe a decrease in areas of infarction in the watershed area among infants in the hypothermia group compared to the control group.

The objectives of this review are the following:

1. To describe the pathophysiological mechanisms involved in hypoxic-ischemic encephalopathy.

2. To establish the differences between hypoxic-ischemic encephalopathy in preterm and term population, older children and adults.

3. To define the utility of conventional and functional MR imaging in the early diagnosis and predicting outcome in hypoxic-ischemic encephalopathy.