variations in the circulus arteriosus of willis: autopsy findinds in 101 human cadav ers

in order to evaluate the microvascular anatomy and the interconnections, 101 fixed brains from human cadavers with a mean age of 41.3 years were subjected to objective scrutiny. symmetry was visualized with an unaided eye and measurements made under microscopic magnification technique using a micrometer. classic symmetry was observed in only 19 of the specimens, whereas the rest of the 82 specimens revealed considerable variations in the form of diverse anomalies. these anomalies consisted of hypoplasia (45 cases), duplication (40 cases), triplication (6 cases), fenestration (6 cases), aplasia (5 cases), aneurysm (2 cases), common trunk (1 case) and a rare presentation where the internal carotid artery was found to have anastomosis with the posterior cerebral artery. the frequency of anatomic variations and the presence of prevalent anomalies at the circle of willis underscore the difficulty in understanding various cerebral vascular diseases and their anatomical knowledge and information serve to adopt effective strategies in tackling such microvascular diseases.