Delayed Focal Stenosis and Aneurysmal Dilatation after Flow Diverter Placement Possibly Related to Distal Malapposition

Incomplete expansion or distal malapposition of a flow diverter (FD) can lead to unexpected vascular complications. We report a rare case of focal stenosis with adjacent aneurysmal dilatation after FD placement, which was likely related to distal malapposition and altered local hemodynamics, and was treated successfully with the placement of an additional FD. Hemodynamic alterations were evaluated using 4-dimensional flow MRI.

A woman in her 60s with no significant medical history underwent MRI for persistent diplopia, which revealed an internal carotid artery aneurysm at the C4 segment. FD placement was performed; however, incomplete distal apposition and suboptimal distal edge expansion were observed at the distal edge of the device. The immediate postoperative course was uneventful. At both the 6-month and 1-year follow-up examinations, MRI and DSA demonstrated focal stenosis distal to the FD with aneurysmal dilatation adjacent to the stenotic segment. A 2nd FD was deployed in a telescoping manner from the C2 segment into the initial FD. Follow-up DSA performed 6 months later showed resolution of the stenosis and aneurysmal dilatation, with complete occlusion of the original aneurysm (O'Kelly-Marotta grade D).

Distal malapposition or incomplete expansion of the FD may lead to focal stenosis and secondary aneurysmal dilatation, possibly through altered local hemodynamics and vessel wall injury. Careful attention to distal landing zones and follow-up imaging is essential. Additional FD placement may be an effective treatment option for this rare but clinically important complication.