Replaced posterior cerebral artery (PCA): origin of all branches of the PCA from the anterior choroidal artery diagnosed by MR angiography.

We present a rare variant of the right posterior cerebral artery (PCA), recently named "replaced PCA," that demonstrates the origin of all its branches from the right anterior choroidal artery (AChA) on magnetic resonance (MR) angiography. In this variation, the right posterior communicating artery (PCoA) is hypoplastic and resembles the transposition of the AChA and PCoA. Detection of such rare arterial variations on MR angiographic images requires careful review of images, including source images, and partial maximum-intensity-projection images aid their identification.