Anterior choroidal artery supply to the posterior cerebral artery distribution: embryological basis and clinical implications.

OBJECTIVE AND IMPORTANCE: We report four cases of anomalous anterior choroidal artery supply to the temporal, parietal, and occipital cortical regions normally supplied by branches of the posterior cerebral artery. Three of these cases were associated with significant intracranial vascular pathology. We examine the embryological basis for the anomalous vascular anatomy to emphasize the potential variability of the anterior choroidal artery distribution and illustrate the spectrum of this variability angiographically. These variants may also have significant implications for surgical and endovascular treatment. CLINICAL PRESENTATION: One patient was diagnosed with an arteriovenous malformation, and two patients were diagnosed with aneurysms, one of which presented with a subarachnoid hemorrhage. INTERVENTION: The patient with the arteriovenous malformation underwent preoperative embolization and surgical resection, one patient with an aneurysm was treated via surgical clipping, and the other aneurysm underwent endovascular coiling. CONCLUSION: This group of patients illustrates an underemphasized but potentially important vascular anomaly. Phylogeny and embryology of the intracerebral vessels suggest a mechanism related to transposed distributions. Careful attention must be directed to the microvascular anatomy of the intracerebral circulation so that these anomalies are recognized and, if necessary, factored into surgical and interventional planning.