Fetal PCA

FETAL POSTERIOR CEREBRAL ARTERY (PCA)

• In this anomaly, the Posterior Communicating artery(PCom) is prominent, with hypoplastic / Absent P1. Original Fetal PCA has absent P1, which is very rare.   

• Unilateral right OR Unilateral left PCA has an incidence of ~10% each. Bilateral Fetal PCA has an incidence of ~8%.

• The calibre of the PCom can be same as or greater than the PCA, and thereby the blood supply to the occipital lobes will be derived from the ICA through the PCom. The importance of this comes when ICA gets occluded, and will involve the ACA, MCA and PCA territories altogether (which will be difficult to explain by embolization). 

• Fetal origin of the posterior cerebral artery occurs when the embryonic posterior cerebral artery fails to regress.

Following are Axial Sections of NECT Brain of a middle aged female, which shows possible bilateral fetal PCAs. Here the Basilar artery bifurcation is not visualized and bilateral PComs are seen prominent (fig.3).

Small Basilar Artery anterior to Pons	Prominent bilateral PComs
Prominent bilateral PComs
P2 starts here!	Further continuation of PCAs(P2)