What is the typical MRI pattern seen after neonatal hypoxic-ischemic encephalopathy?

• A. Watershed cortical-subcortical injury with diffusion restriction
• B. Focal basal ganglia lesion
• C. Hemorrhagic transformation
• D. Normal MRI

Answer: (A)

Global hypoxic-ischemic injury in the newborn most often shows a watershed pattern on MRI, reflecting vulnerability of the border zones between major cerebral arteries. Diffusion-weighted imaging reveals restricted diffusion in the cortex and the underlying subcortical white matter, typically in parasagittal regions and often in a bilateral, symmetric distribution. This diffusion restriction signifies cytotoxic edema from energy failure and is most evident in the days after birth. While more severe injury can involve deep gray structures like the basal ganglia and thalami, the classic pattern after neonatal HIE is this cortical–subcortical watershed injury. Hemorrhagic transformation can occur in severe cases but is not the hallmark pattern, and a normal MRI would be unlikely in clinically evident HIE.