Fetal PCA

• Fetal PCA origin: common variant, seen in ~20-30% of pts
• Posterior Communicating Artery (PCom) size > P1 seg of PCA, provides most of blood supply → known as “fetal PCom”
• P1 seg can be hypoplastic or absent → influences stroke pattern, as PCA functions as part of anterior circulation
• PCom, larger than P1, allows for collateral circulation
• Fetal PCA positioning: superior or superolateral to oculomotor nerve; non-fetal PCA: PCom superomedial to oculomotor nerve

Potential complications

• Occlusion of fetal PCom can → occipital lobe infarction
• Large aneurysm alone not necessarily problematic for PCom occlusion, but parent arteries preservation preferred
• Multiple aneurysms: not independently assoc. w/ PCom dominance
• Vertebral artery hypoplasia: can be assoc. w/ fetal circulation, especially if bilateral, but not necessarily
• Persistent trigeminal artery: congenital anastomosis b/w internal carotid artery & basilar artery proximal to PCA

If bilateral:

• Basilar artery significantly smaller than normal.