Subacute Stent Deformities as an Underlying Reason for Vessel Stenosis after Flow Diversion with the p64 Stent: Review and Discussion of Biologic Mechanisms and Consequences.

Background and purpose: Flow-diverter stents are a potent and efficient tool in the instrumentarium of neurointerventional radiologists for the treatment of intracranial aneurysms. With their implementation, some adverse effects and complications such as hemorrhagic and ischemic ones, have been seen as a potential downfall of the method. In-stent stenosis is one such complication, which until now has not received enormous attention due to its seemingly benign characteristic. In our study we propose a different point of view on this matter and aim to establish a potential mechanism for its development: a subacute postprocedural stent deformation, due to segmental vessel constriction as a reaction to the implant.

Materials and methods: We enrolled 48 patients between the ages of 31 and 71 (8 men) with aneurysms on the distal portions of the ICA, all of whom were treated with the p64 flow-diverter stent, to assess the incidence of this phenomenon, as well as establish a correlation between it and subsequent clinical symptoms. A protocol for short-term follow-up, consisting only of a high-dose fluoroscopy image of the implant (conducted on the 14th postprocedural day) was implemented to assess the state of the implant before endothelization was to be expected.

Results: Stent deformities were seen in 58% of cases. One patient with an observed stent deformity presented with several episodes of acute contralateral 1-sided weakness of the limbs. Seventy-one percent of those patients presented with a mild/moderate unilateral headache postprocedurally. A correlation between the deformity and a subsequent narrowing of the parent vessel diameter was established on follow-ups. Notable in-stent stenosis was reported in 35% of all cases.

Conclusions: Cases with subacute stent deformities are presented in a nonnegligible percent of flow-diversion therapies with the p64 stent. A statistically significant association between the observed deformation and subsequent in-stent stenosis was observed on follow-up.