There is great variability in the normal configuration of the circle of Willis (Alpers, Berry, Paddison).1 Relatively little information is available concerning its structure in cerebral softening due to thrombosis and embolism and in cerebral hemorrhage and aneurysm. The present study was undertaken in order to determine the incidence and nature of the anomalies of the circle of Willis in the various forms of cerebral vascular disorder, particularly in occlusive vascular disease, where the factor of collateral circulation appears to have greater significance than in cerebral or meningeal hemorrhage.
Material and Methods
The basis of the present study is formed by 194 gross brain softenings. Of these 56 were found to be the result of thrombosis; 53 were due to embolism; and the cause of the softening was unidentified in 85 cases. The high incidence of an unidentified source is due to the fact that many of the