Relationship Between Circle of Willis Morphology on 3D Time-of-Flight MR Angiograms and Transient Ischemia During Vascular Clamping of the Internal Carotid Artery During Carotid Endarterectomy
Jeong Hyun Leea,
Choong Gon Choia,
Do Kyun Kimb,
Geun Eun Kimb,
Ho Kyu Leea and
Dae Chul Suha
a Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
b Department of Vascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
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FIG 1. Schematic views of anatomic variations of the anterior (A) and posterior (B) parts of the circle of Willis. Only the right side is presented. The left side is a mirror image of the right side.
A, Demonstrable anterior communicating artery (a), approximated both proximal A1 segments without demonstrable anterior communicating artery (b), hypoplastic contralateral A1 segment (c), widely separated both A1 segments with no demonstrable anterior communicating artery (d), absence of contralateral A1 segment (e). The anterior part of the circle of Willis is considered as complete in types a and b, incomplete in types d and e, or indeterminate in type c.
B, Demonstrable ipsilateral posterior communicating artery and P1 segment (a), hypoplastic ipsilateral posterior communicating artery or ipsilateral P1 segment (b1 and b2), no demonstrable ipsilateral posterior communicating artery (c), no demonstrable ipsilateral P1 segment (d). The posterior part of the circle of Willis is considered as complete in type a, incomplete in types c and d, or indeterminate in type b (b1 or b2).
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FIG 2. A 62-year-old man with a history of sudden loss of consciousness immediately after vascular clamping during CEA.
A, Contrast-enhanced MR angiogram shows focal severe stenosis of the left proximal ICA and occlusion of the contralateral ICA.
B, Three-dimensional TOF MR angiogram demonstrates incomplete anterior and posterior patterns of the circle of Willis with absence of the right A1 segment of the anterior cerebral artery and the left posterior communicating artery.
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FIG 3. A 65-year-old man without any neurologic symptoms during CEA.
A, Contrast-enhanced MR angiogram shows short segmental severe stenosis of the left proximal ICA. The contralateral ICA is occluded at the level of the carotid bifurcation.
B, Three-dimensional TOF MR angiogram shows intact both A1 segments, anterior communicating artery, and ipsilateral posterior communicating artery. The circle of Willis is complete in both anterior and posterior parts.
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