Reason: evaluate for intracranial stenosis MRI of the brainNo diffusion weighted abnormalities are appreciated.The CSF spaces are appropriate for the patient's stated age with no midline shift. No abnormal enhancing mass lesions are appreciated intracranially. No intracranial hemorrhage is identified. No edema is identified within the brain parenchyma.Normal vascular flow voids are present in the distal carotid and vertebral arteries, the basilar artery and the proximal anterior, middle and posterior cerebral arteries as well as the internal cerebral veins and superior sagittal sinus.The visualized portions of the paranasal sinuses are clear. The visualized portions of the mastoid air cells are clear. The visualized portions of the orbits are intact.MRA brain:Antegrade flow is present in the distal internal carotid arteries, the distal vertebral arteries, the basilar artery and the proximal anterior, middle and posterior cerebral arteries. No aneurysms are appreciated.There is opacification of the entire left internal artery which changes caliber at the level of the posterior communicating artery due to posterior communicating artery collateral supply. There appears to be a high grade stenosis at the opthalmic segment.The anterior communicating artery and the posterior communicating arteries are identified and are intact. The right posterior communicating artery is tiny. The anterior communicating artery is medium-sized. The left A1 segment is not readily identified. There is some supply to lenticulostriate originating from the left A1/A2 junction which receives supply from the right anterior circulation.The right vertebral artery is slightly larger than the left vertebral artery.MRA neck:There is opacification of the aortic arch, great vessels from the aortic arch and carotid arteries and vertebral arteries. There is no stenosis identified of the great vessels from the aortic arch. There is high-grade stenosis present at the left internal carotid artery origin with associated string sign which would effectively represent a 99% stenosis by NASCET criteria. It is not clear whether the string sign is due to distal ICA or proximal ICA stenosis or both based on this exam, however, the general morphology suggests distal stenosis. There is opacification of the entire left internal carotid artery which changes caliber at the level of the posterior communicating artery due to posterior communicating artery collateral supply.On the basis of NASCET criteria there is no significant stenosis at the right carotid bifurcation. There is no significant stenosis along the course of the vertebral arteries.
1.There is a left internal carotid artery string sign present with left internal carotid artery stenosis. It is suspected that there are tandem stenosis, however, the more significant stenosis is not readily identified. The left middle cerebral artery territory is supplied from via the posterior communicating artery. The left anterior cerebral artery territory is supplied via the anterior communicating artery. 2.The left A1 segment is not readily identified.