Histopathologic evaluation of aneurysms treated with Guglielmi detachable coils or matrix detachable microcoils

The purpose of this study was to evaluate the degree of organization and fibrocellular tissue development in aneurysms treated with bare platinum or biologically active microcoils.

Twelve aneurysms were removed at autopsy between 1-18 days and another 2 between 2-3 months posttreatment. Four aneurysms were surgically removed between 6 months and 3 years following treatment. One aneurysm removed at 8 days and another at 6 months were treated with bioactive (Matrix) coils; the other 16 with bare platinum (Guglielmi detachable coils; GDCs). All specimens were embedded in plastic, stained with hematoxilin-eosin and elastin and examined by light microscopy.

All specimens removed within 3 weeks demonstrated intra-aneurysmal thrombus, without signs of organization or fibrotic tissue formation over the neck regardless of the type of coils used. In the GDC-treated aneurysms, evidence of early thrombus organization was observed within 2-3 months, and completed yet imperfect fibrocellular reaction together with residual thrombus at 2-3 years. In the Matrix-treated specimens, the aneurysm cavity was completely filled with granulation tissue corresponding to still ongoing fibrocellular reaction at 6 months, including newly formed blood vessels, smooth muscle cells, and collagen deposition without signs of residual thrombus.

Our results indicate that in aneurysms treated with bare platinum coils thrombus organization does not occur until late after treatment and may remain imperfect for years. In one aneurysm studied 8 days following treatment with Matrix coils, no difference was noted compared to aneurysms treated with bare platinum coils. In another aneurysm examined 6 months following packing with Matrix coils, the histologic changes support the hypothesis that the biologically active polymer may accelerate aneurysm healing.