Histopathological findings in experimental aneurysms embolized with conventional and thrombogenic/antithrombolytic Guglielmi coils

We studied the short- and long-term histological responses induced by conve ntional and modified electronically detachable coils (GDCs) in experimental aneurysms. Eighteen carotid bifurcation aneurysms were produced microsurgi cally in rabbits. Six animals each were treated either with conventional or with GDCs coated with a mixture of tissue-thromboplastin to enhance intra- aneurysmal thrombus formation and of plasminogen activator inhibitor type-1 (PAI-1) in inhibit intra-aneurysmal clot fibrinolysis. Six served as untre ated controls. Follow-up angiograms were obtained immediately and at 3, 6, 9, 12, 17, and 24 weeks after embolization prior to sacrifice of the animal s. All aneurysms were studied macroscopically and histopathologically with the coils in situ. Five of six control aneurysms remained patent. Endovascu lar occlusion rates between > 90 % and 100 % were achieved in nine of twelv e coiled aneurysms. Follow-up angiography demonstrated recanalization and c oil compaction in 5 of them. Gross and microscopic histopathological examin ation revealed a membrane covering the orifice, intra-aneurysmal scar forma tion, and development of a neo-intima in both treatment groups at 17 and 24 weeks postembolization. The granulation tissue response appeared to be equ ally distributed in aneurysms treated with either uncoated or coated coils. Further quantitative morphometric studies are needed to prove if a thrombo genic/antithrombolytic coil-coating might be of value in providing a more e nduring anatomic result after GDC-treatment of human brain aneurysms.