Replaced posterior cerebral artery

Purpose Replaced posterior cerebral artery (PCA), defined as a hyperplastic anterior choroidal artery (AChA) supplying all branches of the PCA, is an extremely rare anatomical variation. To the best of our knowledge, there are only a few reports of replaced PCA. Methods Herein, we report a case of replaced PCA diagnosed by digital subtraction angiography. Results A 76-year-old woman visited a neurosurgical clinic because of headache and vertigo. Magnetic resonance imaging and magnetic resonance angiography incidentally revealed a left internal carotid artery aneurysm. She was referred to our hospital for further examination and treatment of the unruptured intracranial aneurysm. Left internal carotid angiography revealed a paraclinoid aneurysm. We also incidentally found an anomalous hyperplastic AChA distal to the aneurysm. This hyperplastic AChA supplied not only the AChA territory but also the entire PCA territory. No vessels that could be a normal AChA or posterior communicating artery were identified along the left internal carotid artery. Vertebral angiography demonstrated that the left PCA was not visualized. With these findings, we diagnosed anomalous hyperplastic AChoA in this case as replaced PCA. Conclusion Careful imaging assessment is important to identify replaced PCA. Both direct findings of a hyperplastic AChA course and perfusion territory and indirect findings of the absence of the original PCA are useful in the diagnosis of replaced PCA.