Delayed hemorrhagic complications after flow diversion for intracranial aneurysms: a literature overview

Delayed aneurysm rupture and delayed intraparenchymal hemorrhages (DIPH) are poorly understood and often fatal complications of flow diversion (FD) for intracranial aneurysms. The purpose of this study was to identify risk factors for these complications.We performed a systematic review on post-FD delayed aneurysm rupture and DIPH. For each reported case, we collected the following information: aneurysm location, size and rupture status, type of flow diverter used, timing of the hemorrhage, and neurological outcome. We reported descriptive statistics of patients suffering DIPH and delayed aneurysm rupture to determine if there were any characteristics consistently present among patients with these complications.We identified 81 delayed aneurysm ruptures and 101 DIPH. Of the delayed ruptures, 76.6% (45/58) occurred within 1 month. The prognosis of delayed ruptures was poor, with 81.3% (61/75) experiencing death or poor neurological outcome. Giant aneurysms accounted for 46.3% of ruptures (31/67). Of these aneurysms, 80.9% (55/68) were initially unruptured. Of the delayed ruptured aneurysms, 17.8% (13/73) had prior or concomitant coiling. DIPHs were ipsilateral to the treated aneurysm in 82.2% (60/73) of cases. Of the DIPH, 86.0% (43/50) occurred within 1 month after FDS. Combined morbidity/mortality rate was 68.5% (50/73) following DIPH. Of DIPHs, 23.0% (14/61) occurred in patients with giant aneurysms.Our study demonstrates that giant aneurysms represent almost 50% of delayed aneurysm ruptures in the flow diverter literature. About 2% of delayed ruptures occurred despite associated coiling. A substantial proportion of DIPHs occur early following FDS treatment of giant aneurysms.