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. 2012 Nov 14;33(3):365–371. doi: 10.1038/jcbfm.2012.171

Figure 4.

Figure 4

Distribution of incomplete/hypoplastic circle of Willis in the study population stratified by site of occlusion. In 11 patients with intracranial internal carotid artery (ICA) occlusions, only 2 patients had an incomplete anterior circle of Willis as a potential explanation for dominant posterior cerebral artery (PCA)–middle cerebral artery (MCA) leptomeningeal collateral pattern. In 14 patients with isolated M1 MCA occlusions, only 1 patient had an hypoplastic ipsilateral A1 anterior cerebral artery (ACA) as a potential explanation for dominant posterior PCA–MCA leptomeningeal collateral pattern.