Introduction Flow diversion stents are effective for treating fusiform and wide-neck aneurysms, but postprocedural complications remain concerning, including parent vessel occlusion, in-stent thrombosis and in-stent stenosis. Macdonald et. al reported that parent vessel occlusion can occur up to 1,5 years after.

Methods We present a case of a patient in their 50s with very delayed parent vessel occlusion after flow diversion treatment for a giant fusiform M2 aneurysm. The occlusion was successfully recanalized, but re-in-stent-thrombosis followed.

Initially, the aneurysm was clipped in 2010, with regular follow-ups. However, due to the increase in its size a decade later, the patient underwent endovascular treatment with placement of a single Derivo-flowdiverter stent in the M1/M2 segments. Follow-up MRI and DSA controls at 3, 9 and 18 months showed decreased aneurysm size. Due to non-response to Clopidogrel, they received 100mg Aspirin and 90 mg Ticagrelor, discontinuing the latter after 6 months.

20 months after the initial treatment, they presented with mild right-sided hemiparesis and aphasia (NIHSS 4, ASPECTS 9) due to the flow diverter occlusion. Recanalization with TICI3 outcome was achieved and a continuous 12-hour Tirofiban therapy was initiated. However, after extubation, five hours following the recanalization, they exhibited global aphasia and right-sided hemiparesis (NIHSS 15). A recurrent flow diverter occlusion along with infarct demarcation were observed, leading to no further endovascular therapy. Since the initial endovascular treatment, continuous regimen of Aspirin has been maintained.

Conclusion Very delayed in-stent thrombosis and subsequent parent vessel occlusion can occur after flow diversion procedures.

Disclosure of Interest AK: Nothing to disclose

MB: Consultant for Microvention, Cerenovus, Acandis, and Rapid

JF: The Co-author reports personal fees from Consultant for Acandis, Cerenovus, Medtronic, Microvention, Phenox, Penumbra, Roche, Tonbridge outside of the submitted work. He is a member of the Executive Board of the scientific societies DGNR and the President of ESMINT and holds Stock in Vastrax LLC and Tegus.