Distal internal carotid artery pseudoaneurysms: technique and pitfalls of surgical management: two technical case...

Small, irregular aneurysms of the internal carotid artery (ICA) that are not related to arterial divisions are rare and have characteristics similar to pseudoaneurysms: they do not appear to have well-formed sacs, they are surrounded by clot, and they avulse readily. We report two patients whose treatment demonstrates the surgical technique and important points concerning the management of distal ICA pseudoaneurysms.

Both patients presented with diffuse subarachnoid hemorrhage. The initial angiographic results were unremarkable in each case. A week after presentation, however, a growing outpouching in the distal ICA was seen.

At surgery, the aneurysms were found to be on the medial wall of the ICA and were not related to arterial divisions. Quantitative blood flow measurements of the efferent vessels at risk (ICA, M1 and A1 segments) were obtained using a perivascular microflowprobe before and after clipping. In each patient, the aneurysm avulsed entirely during clip application, despite careful placement of the clip parallel to the parent vessel. An encircling clip was then used. Pathological sectioning of the aneurysms revealed loose connective tissue and/or clot with no defined aneurysmal sac.

Aneurysms of the distal ICA that are not related to arterial divisions are difficult to visualize on angiograms immediately after subarachnoid hemorrhage. They are frail, avulse easily, and may be pseudoaneurysms, necessitating the use of encircling clips. The base of the aneurysm or clot must be trimmed to prevent it from buckling inside the clip sleeve and compromising the ICA lumen. Measuring distal blood flow quantitatively provides valuable information about the patency of the ICA inside the metallic sleeve, since this segment cannot be demonstrated with angiography.