The cisternal segment of the anterior choroidal artery: an anatomical study using magnetic resonance imaging

Purpose The topography of the anterior choroidal artery (AChA) has infrequently been delineated on neuroimages. The present study aimed to explore the cisternal segment of the AChA using magnetic resonance imaging. Methods A total of 50 sides of the AChA obtained from 25 patients were included in this study. A constructive interference in steady-state (CISS) sequence was performed in thin-sliced axial sections. Furthermore, the cisternal AChA and relevant neurovascular structures were observed through cadaveric dissections in two heads. Results In the cadaveric dissections, all the AChAs were exposed only in the proximal part even after extensive arachnoid dissections and cerebral retraction. In the examinations with the CISS sequence, the original site of the AChA was identified on the right side in 88% and on the left side in 96%. In 70% of the 50 sides, the AChA arose from the posterolateral wall of the internal carotid artery, distally to that of the posterior communicating artery. The cisternal course of the AChA was delineated on the right side in 96% and on the left side in 100%; it crossed over the optic tract in variable manners with the middle third as the most frequent site found in 60% of the sides. Conclusions The cisternal AChA shows a morphological variability. The CISS sequence is useful for delineating the cisternal AChA.