Hypoxic ischemic injury in adults is usually following cerebral hypoxia commonly as a result of cardiac arrest, drowning and asphyxiation. If ischemia is mild it manifests as watershed zone infarcts. Severe hypoxic injury primarily affects the gray matter structures such as the basal ganglia, thalami, cerebral cortex and hippocampi. Cerebellar injury can also occur. Diffusion-weighted MR imaging shows restricted diffusion in affected areas within the first few hours after a hypoxic-ischemic event. Changes in T1 and T2 images take longer to develop.