Infundibular dilation: an anatomical variant or a pre-aneurysm? Advantages of assessment with three-dimensional...

Whether an infundibular dilation (ID) is an anatomical variant or a pre-aneurysm has not been clearly determined. The aim of the present study was to evaluate the anatomical change of IDs by use of three-dimensional rotational angiography (3DRA) with volume rendering (VR).

One-hundred thirty-eight patients with known or suspected aneurysms, treated consecutively, underwent both two-dimensional digital subtraction angiography (2DDSA) and 3DRA with VR. Two readers evaluated the IDs or aneurysms blindly, using 2DDSA and 3DRA, according to the same diagnostic criteria. A 5-point scale of observer confidence was used to determine the presence of IDs or aneurysms. For 3DRA with VR, the relationship between IDs and aneurysms was classified as one of the three types: type I, protrusion or bulge from side wall of IDs; type II, aneurysms involving or enclosing IDs; or type III, aneurysms and IDs coexisting near each other but with some distance between them.

The number of IDs found by 2DDSA and 3DRA with VR was 41 and 48, respectively. Five anterior choroidal arteries and two posterior communicating arteries IDs were missed by 2DDSA. According to 3DRA with VR, there were five IDs of type I, nine of type II, and 22 of type III.

The 3DRA with VR appears superior to 2DRA for both diagnosing IDs and displaying the anatomical relationship between IDs and aneurysms. The findings also suggest that some IDs might progress to aneurysms or become a part of them, which should be carefully evaluated prior to operation.