Introduction Fish-mouth deformation of the stent may occur in up to 4% of cases of aneurysm treatment with flow-diverters (FDs).

Case Description Two young females were treated with FDs, which developed an extreme fish-mouth deformation. FDs were Stryker Surpass Evolve in one case and Medtronic Pipeline Vantage in the other case.

Results Patient 1 showed severe fish-mouthing and subsequent high-grade stenosis in the regular MRI-control three months after flow-diverter implantation. Despite good collateralization through the anterior and posterior communicating arteries, balloon angioplasty was performed. The stenosis could be improved only slightly due to recoil. The fish-mouth deformation was reduced at 10 months follow-up and resolved at 15 months follow-up.

Patient 2 showed severe fish-mouthing and subsequent high-grade stenosis of the distal end of the FD one month after emergent treatment. A follow-up CT two weeks later showed complete occlusion of the distal FD. No recanalization attempt was performed due to the lack of symptoms and a long occluded FD-segment. Control-MRI at three-months showed recanalization of the occluded FD-segment with remaining severe stenosis and hypoperfusion. The patient remained asymptomatic and was kept under dual antiplatelet therapy.

Fish-mouth deformation is a rare complication after FD-treatment. However, severe ischemic complications may occur if the deformation progresses to high-grade stenosis or even stent-occlusion. Frequent controls may be required if collateralization is poor and occlusion would result in a severe ischemia. In case of good collaterals, a conservative watch-and-wait approach may be appropriate.

Disclosure of Interest no.