Circle of Willis anatomy as a predictor of posterior cerebral artery territory infarction in the presence of tentorial herniation

Abstract

Twenty-two brains in which tentorial herniation was present were examined to see whether the circle of Willis anatomy was a predictor of posterior cerebral artery territory infarction. This factor was considered in the context of the patients' known survival interval. Three brains in which tentorial herniation was not present were included as negative controls. Of the 22 brains in which tentorial herniation was present, 12 showed posterior communicating arteries smaller than the P1 segments of the posterior cerebral arteries; posterior cerebral artery territory infarction occurred in 8 of these. In these cases the survival interval was greater than 24 h (40 h to 2 months). In the 4 cases in which no infarction was seen the survival interval was less than 14 h. In 10 of the 22 cases the posterior communicating arteries were larger than, or equal in size to, the P1 segments of the posterior cerebral arteries and no infarction was seen in the posterior cerebral artery territories. No infarction was seen in the three control brains. These were trauma cases with no tentorial herniation. Statistical analysis indicated there was a true relationship between the sizes of the arteries and the occurrence of infarction. It cannot be excluded that other factors may have relevance in terms of whether infarction occurs. However, from the results of this study it appears that one can predict whether infarction in the posterior cerebral artery territory will occur as a complication of tentorial herniation by consideration of the anatomy of the circle of Willis in relation to the survival interval. The reasons for the presence or absence of posterior cerebral artery territory infarction have not previously been satisfactorily explained.