Figure 14b. (a) Sagittal contrast-enhanced T1-weighted MR image shows a large, irregularly enhancing mass (arrow) with retroclival extension that encases the left internal carotid artery (arrowhead). (b) Left carotid arteriogram shows narrowing of the distal left internal carotid artery (arrow) and upward displacement of the left middle cerebral artery (arrowhead).