Fig 1. A, Patient 1. Right carotid arteriography. Both cerebral hemispheres are supplied by the right internal carotid artery. Enlarged anterior cerebral artery (arrowhead). B, Same patient. Axial T2-weighted (200/100) image shows an abnormal small left hemisphere with a round gray matter mass (arrow), which is criss-crossed by several large vessels. C, Coronal MRA of the neck shows absence of the left internal carotid artery and hyperplasia of the right internal carotid artery (arrow). Normal size of both vertebral arteries (arrowheads).