Left vertebral artery and proximal basilar artery occlusion. Right sided weakness. Acute brainstem stroke.IMAGE ACQUISITIONS: Precontrast head CT followed by dynamic bolus contrast enhanced CTA of the head 0.9-mm source images. Sagittal and coronal and 3-D reformats were also obtained. There is complete occlusion of the dominant left vertebral artery. Right vertebral artery is congenitally small and predominantly supplies PICA with minimal if any contribution to basilar flow. Right V4 segment is very small. There is questionably a very thin lumen along the right side of the proximal basilar artery, possibly supplied by the right V4 segment. Most of the flow to the mid and distal basilar artery appears to be from posterior communicating arteries from the carotid arteries.There is intraluminal thrombus of indeterminate age in the left vertebral artery to the level of the proximal basilar artery.There is no other evidence of intracranial arterial stenosis. There is no evidence of intracranial aneurysm or intracranial pseudoaneurysm. There is no acute intracranial hemorrhage. Brain stem and corpus callosum infarcts that were demonstrated on MRI are not yet demonstrable on CT.
Complete occlusion and thrombosis of dominant left vertebral artery to the level of the proximal basilar artery, with minimal if any antegrade flow from the distal right vertebral artery and likely substantial retrograde collateral flow from posterior communicating arteries.Findings were discussed by telephone with Dr. Yallapragada on 06/06/2009 approximately 1930 hrs.