Onyx in an experimental aneurysm model: histological and angiographic results

Object: The use of liquid embolic agents for endovascular treatment of cerebral aneurysms is evolving. The authors' aim was to evaluate the use of Onyx HD-500 in an experimental aneurysm model and to obtain histological and angiographic long-term results.

Methods: Ten aneurysms were created using an elastase model in rabbits. The aneurysms were embolized using Onyx in combination with an inflated balloon. One animal died 1 day after embolization. The animals were divided into 2 different groups. The animals in the first group (4 rabbits) were killed at 3 months and those in the second group (5 rabbits) were killed at 6 months after embolization. A venous control angiogram was obtained, and the aneurysms were examined histologically.

Results: In both groups control angiograms demonstrated that all aneurysms were completely occluded. There were no signs of recanalization. Migration of Onyx was seen in 4 animals, leading to the death of 1. Histological examination not only proved the aneurysms to be occluded but also demonstrated a thin layer of endothelium at the neck of the aneurysm. The histological result was identical in both groups.

Conclusions: This is the first study reporting the formation of a neointima over the neck of aneurysms embolized with Onyx in a rabbit model. Although the technique is challenging and migration of the liquid embolic agent cannot always be prevented, Onyx has a great potential to achieve a durable occlusion of aneurysms.