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

We studied the short- and long-term histological responses induced by conventional and modified electronically detachable coils (GDCs) in experimental aneurysms. Eighteen carotid bifurcation aneurysms were produced microsurgically 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 untreated controls. Follow-up angiograms were obtained immediately and at 3, 6, 9, 12, 17, and 24 weeks after embolization prior to sacrifice of the animals. All aneurysms were studied macroscopically and histopathologically with the coils in situ. Five of six control aneurysms remained patent. Endovascular occlusion rates between > 90% and 100% were achieved in nine of twelve coiled aneurysms. Follow-up angiography demonstrated recanalization and coil compaction in 5 of them. Gross and microscopic histopathological examination revealed a membrane covering the orifice, intra-aneurysmal scar formation, and development of a neo-intima in both treatment groups at 17 and 24 weeks postembolization. The granulation tissue response appeared to be equally distributed in aneurysms treated with either uncoated or coated coils. Further quantitative morphometric studies are needed to prove if a thrombogenic/antithrombolytic coil-coating might be of value in providing a more enduring anatomic result after GDC-treatment of human brain aneurysms.

Gross and microscopic histopathological findings in aneurysms of the human brain treated with Guglielmi detachable coils

OBJECT

The histopathological characteristics of aneurysms obtained at autopsy or surgery 3 days to 54 months after being treated with Guglielmi detachable coils (GDCs) were assessed.

METHODS

Seventeen aneurysms were obtained at autopsy and one was removed at surgery. Fourteen were examined histologically with the coils in situ. Naked coils embedded in an unorganized thrombus were found in those aneurysms that had been treated with coils within 1 week earlier. An incomplete replacement of the intraluminal blood clot by fibrous tissue and a partial membranous covering at the aneurysm orifice were observed in those aneurysms that had been treated with coils between 2 and 3 weeks prior to examination. One small aneurysm treated 6 weeks before harvesting showed formation of an endothelium-lined layer of connective tissue at the orifice. Collagen-rich vascularized tissue surrounding the coils was found in an aneurysm removed at surgery 54 months after coil implantation. Interestingly, six (50%) of 12 aneurysms (two small, three large, and one giant) that had been deemed 100% occluded on initial angiography showed tiny open spaces between the coils at the neck on gross examination.

CONCLUSIONS

Endothelialization of the aneurysm orifice following placement of GDCs can occur; however, it appears to be the exception rather than the rule. In large aneurysms the process of intraaneurysm clot organization seems to be delayed and incomplete; tiny open spaces between the coils and an incomplete membranous covering in the region of the neck are frequently encountered. Further longitudinal studies are required to establish the spectrum of healing profiles that may direct our efforts in modifying the GDC system to produce a more stable long-term result.

Coiling of recurrent and residual cerebral aneurysms after unsuccessful clipping

We treated four patients with 3 recurrent and 1 residual aneurysm after surgical clipping by using Guglielmi detachable coils (GDCs). Three subjects presented after a second subarachnoid hemorrhage (SAH) occurring between 10 and 25 years after the first bleeding. Early postoperative angiography of the fourth patient showed an incompletely clipped aneurysm. In three poor grade patients we observed one good outcome, one fair result and one death due to the sequelae of SAH. One good grade patient remained in excellent condition postoperatively. Three aneurysms were totally occluded and in one a more than 90% occlusion was achieved with GDCs. We consider the treatment with GDC a viable alternative to reoperation in all patients with recurrent or residual aneurysms following failed attempt at surgical obliteration.