A modified technique for using elastase to create saccular aneurysms in animals that histologically and hemodynamically resemble aneurysms in human

Treatment of intracranial aneurysms is evolving with the development of novel therapies. It is important to have an animal model which simulates human aneurysms. We describe a new modified technique to the elastase aneurysm model which creates aneurysms that histologically and hemodynamically resemble human aneurysms. Twelve New Zealand white rabbits underwent the aneurysm creation procedure, and 2 underwent a control procedure. In the aneurysm creation procedure, the right common carotid artery (RCCA) origin is surgically exposed and temporarily occluded with a temporary aneurysm clip. The RCCA is ligated distally, and the trapped segment is infused with elastase for 20 minutes, after which the clip is removed. In the control procedure, the RCCA is ligated distally with no elastase. Animals were assessed neurologically using a previously described rabbit neurologic grading scale and food intake scale. Intravenous digital subtraction angiography (IVDSA) was performed 21 days after the procedure. Aneurysms were harvested and stained with H&E and Verhoeff's stain. All 14 rabbits had normal neurologic and food intake assessments. All 12 rabbits that underwent aneurysm creation procedures demonstrated saccular aneurysms on IVDSA. Mean aneurysm size was 5.9+/-1.9 mm; range 4.3-10.8 mm. The close proximity of the LCCA to the origin of the RCCA on the aortic arch of the New Zealand white rabbit closely resembles a bifurcation aneurysm. Both rabbits that underwent control procedures showed no aneurysm and retrograde thrombosis of the RCCA. Histologic analysis showed the aneurysms had histology characteristic of true human aneurysms. We have developed a new modified technique to the elastase aneurysm model which creates aneurysms that hemodynamically and histologically resemble human aneurysms. There have been previous elastase models described, however we find our model is easier to perform and highly reproducible. The aneurysms can be accessed transfemorally making the model ideal for testing endovascular therapies.