An angiographic study of incidence and morphology of infundibular dilation of the posterior communicating artery.

In the last 9 years, infundibular dilatation (ID) has been sought in 260 aneurysm (An) cases and 398 carotid angiogram's (CAG) to reveal its incidence and morphology. Findings were as follows: The incidence was about double that so far published. Small ID, usually triangular in shape, tended to become round as it grew larger (P less than 0.01). Large ID favored young age (P less than 0.05). In internal carotid-posterior communicating aneurysm (IC-P com An) cases, a high incidence of ID was noted as compared to other An cases (P less than 0.05), and intermediate or large, round ID accounted for high ratios. Cases with a history of hypertension showed a high large ID ratio (P less than 0.05). Cases with well developed P com A had a high ratio of large, round ID (P less than 0.01). In cases with a large divergent angle of ICA and P com A, intermediate or large, round ID was found in high ratio (P less than 0.05). Aggressive follow-up or treatment was thought necessary in cases which possess the factors mentioned.