MRI/MRA - Infarct, bilateral anterior cerebral artery distribution: This 37-year-old man with a history of hypertension presented with the acute onset of difficulty walking. On examination he had bilateral leg paresis and hyperreflexia. The image on the left is a diffusion-weighted axial MR image showing increased signal intensity involving the paramedial frontal lobes bilaterally. The corresponding MRA on the right shows an absence of the A1 segment of the right anterior cerebral artery.