FIG 1. Initial left internal carotid artery (ICA) arteriograms, anteroposterior (A) and lateral views (B and D).

A and B, Images show a large aneurysm originating from the MCA trifurcation with a short neck from the distal M1 segment (arrow in A). Two major branches arise from the dome of the aneurysm (arrowheads).

C, 3D image obtained at rotational angiography. The cone-shaped short and broad-based neck is better visualized than on the 2D-DSA images.

D, Lateral-oblique projection obtained during test occlusion. The tip of the microcatheter (arrowhead) cannot be advanced into the aneurysmal dome; it is wedged into the narrowed neck (arrow) that is directed anteriorly and cranially. This placement results in subtotal occlusion of the inflow zone and leads to immediate retrograde filling of the distal MCA territory (not shown).