Quantitative Angiographic and Histopathologic Evaluation of Experimental Aneurysms

Abstract

The article of Bouzeghrane et al 1 is a timely and surely important contribution to reaching standardized quality criteria for experimental aneurysm models and evaluation techniques. Nevertheless, the following comments should be added.The authors of the above-mentioned article state that the lack of correlation between angiographic and histopathologic results is a major limitation to the validity of experimental aneurysm studies. This statement holds true if subjective estimation of aneurysm occlusion is used as in most of the cited literature. However, our studies have shown good correlation of angiographic and histopathologic occlusion rates by applying a new method of computerized quantification, first on 8 venous pouch bifurcation aneurysms in rabbits. 2 Because this correlation reached statistical significance in a subsequent large postmortem series of 14 human aneurysms, 3 the superior precision of computer-assisted quantification for evaluating angiograms and corresponding surface-stained ground sections from polymethylmethacrylate-embedded aneurysms has been validated.Concerning the best suitable specimen preparation for histopathologic evaluation, the authors stated that cutting-grinding techniques with the devices in situ preclude advanced histotechniques such as immunohistochemistry. This limitation applies only to the past because currently several resin-embedding techniques and materials (eg, Technovit 9100 New; Heraeus Kulzer, Wehrheim, Germany) are available, in which denaturation of proteins is avoided by low polymerization temperatures (at Ϫ20°C). Therefore, the major advantage of histotechniques preserving the implants in situ to evaluate cell reactions at implant-tissue interfaces can now be combined with immunocytohistochemistry.As a critique of the rabbit venous pouch bifurcation model, Bouzeghrane et al 1 showed, in Table 4, that neck endothelialization was not described and thrombus organization in the aneurysm sac was not properly followed because only uncovered coils were found in the lumen and no fibrosis was visible between the loops of coils. However, all these features of aneurysm healing have been described in detail by our group 2 and also by several other authors in rabbit venous pouch aneurysms. Bouzeghrane et al also concluded that the rabbit venous pouch bifurcation aneurysm model resulted so far in lower rates of aneurysm patency and higher rates of morbidity, making it less appropriate for embolic device evaluations as in, for example, the rabbit elastase model. However, the rabbit venous pouch model could be substantially improved. 4,5 It now offers equivalent patency and morbidity rates compared with the rabbit elastase and canine bifurcation models. Additionally, the unaltered vein transplant aneurysm walls of venous pouch bifurcation models show many similarities to the walls of human intracranial aneurysms. With proper technique, the foreign body reactions to the sutures are only located outside the aneurysms and, thus will not interfere with reactions to embolic devices...

Microsurgical Venous Pouch Arterial-Bifurcation Aneurysms in the Rabbit Model: Technical Aspects

“…These shortcomings could be overcome with improved surgical procedures and modified peri-and postoperative analgetic management and anticoagulation. [14][15][16] Our techniques reported in this paper demonstrate this optimized technique for microsurgical creation of arterial bifurcation aneurysms.…”

Computerized Occlusion Rating: A Superior Predictor of Aneurysm Rebleeding for Ruptured Embolized Aneurysms

“…This methodologic oversimplification of complex angioarchitecture is also a major shortcoming of SOR. 7,8 Another possible source of bias may be the selection of the ideal time point of the DSA acquisition. In our experience, it is best to analyze the entire arterial DSA acquisition.…”

“…[5][6][7][8] In the present study, COR was retrospectively applied to a large human series for assessment of its clinical value as a more objective predictor of aneurysm rebleeding when compared with SOR as described in the Raymond classification.…”

3D Computerized Occlusion Rating of Embolized Experimental Aneurysms Using Noninvasive 1.5T MR Imaging

“…As reported previously, this methodologic oversimplification of complex angioarchitecture is prone to subjective evaluation biases. [4][5][6] To minimize this subjective estimation bias, COR was introduced for 2D images, and its validity was proved first on experimental and then on human cerebral aneurysms. 4,5,7 These methods have now been transferred to 3D imaging, to eliminate the remaining bias of indirect 2D evaluations.…”