Long-term histological and scanning electron microscopy results of endovascular and operative treatments of experimentally induced aneurysms in the rabbit

An Improved Surgical Technique to Increase Neck Width of Elastase-Induced Aneurysm Model in Rabbits: A Prospective Study

Background

Rabbit elastase-induced aneurysms have widely been used to test various endovascular materials over the past two decades. However, wide-necked aneurysms cannot be stably constructed.

Objective

The purpose of the study was to increase the neck width of the elastase-induced aneurysm model in rabbits via an improved surgical technique with two temporary clips.

Materials and Methods

Fifty-four elastase-induced aneurysms in rabbits were successfully created. Group 1 was (n = 34) composed of cases in which two temporary aneurysm clips were placed closely medially and laterally to the origin of the right common carotid artery (RCCA), respectively. Group 2 (n = 20) included cases in which a single temporary aneurysm clip was placed crossed the origin of RCCA. Digital subtraction angiography (DSA) was performed before and immediately after elastase incubation and 3 weeks later. The diameter of the origin of RCCA before and immediately after elastase incubation and aneurysm sizes of the two groups were measured and compared. Moreover, the correlation analysis was performed between the diameter of the origin of RCCA immediately after elastase incubation and aneurysm neck width.

Results

The mean aneurysm neck and dome width of group 1 were both significantly larger than that of group 2 (p-value < 0.001 and p-value = 0.005, respectively). Moreover, the proportion of wide-necked aneurysms (neck width ≥4 mm) in group 1 was significantly larger than that in group 2 (p-value = 0.004) and the mean dome to neck ratio (D/N) of group 1 was smaller than that of group 2 (p-value = 0.008). Furthermore, there was a positive correlation between the diameter of the origin of RCCA immediately after elastase incubation and aneurysm neck width.

Conclusion

The improved surgical technique with two temporary clips, focusing on the direct contact of elastase with the origin of RCCA, could increase the neck width of elastase-induced aneurysm models in rabbits.

Braided stents assisted coiling for endovascular management of posterior cerebral artery aneurysms: a preliminary mid-term experience

PURPOSE

Posterior cerebral artery (PCA) aneurysms are rare. This study is to evaluate the preliminary experience of braided stents applied in PCA aneurysms treatment.

METHODS

Angiographic and clinical data of 28 PCA patients treated with braided stents from July 2016 and September 2020 were retrospectively analyzed.

RESULTS

A total of 28 PCA aneurysms were enrolled. 22 (78.6%) aneurysms were dissecting aneurysms, while 6 (21.4%) aneurysms were saccular aneurysms. Thirty-five braided stents were implanted with dual stents implanted in 7 cases. Immediate angiographic results show that Raymond class I was obtained in 13 patients (46.4%), Raymond class II was obtained in 4 patients (14.3%), and Raymond class III was obtained in 11 patients (39.3%). Perioperative hemorrhagic events occurred in 1 patient (3.6%). Twenty-four patients (85.7%) received angiographic follow-up, and the mean follow-up time was 11.2 ± 4.9 months. Two patients (8.3%) were confirmed with IA neck recurrence, and 3 patients (12.5%) were confirmed asymptomatic parent artery occlusion (PAO). The other 19 patients were confirmed promoted occlusion with 18 Raymond class I (75%) and 1 Raymond class II (4.2%). Twenty-seven patients (96.4%) received clinical follow-up, and the mean follow-up time was 32.2 ± 13.5 months. One patient (3.7%) confirmed the death event 2 weeks after discharge. The other 27 patients (96.3%) got favorable clinical outcomes with an mRS score of 0-2.

CONCLUSIONS

Braided stent-assisted coiling with a high occlusion rate and relatively low complication rate provides an alternative strategy in treating PCA aneurysms. Long-term outcomes need further randomized study with larger case numbers.

Preclinical extracranial aneurysm models for the study and treatment of brain aneurysms: A systematic review

Animal models make an important contribution to our basic understanding of the pathobiology of human brain aneurysms, are indispensable in testing novel treatment approaches, and are essential for training interventional neuroradiologists and neurosurgeons. Researchers are confronted with a broad diversity of models and techniques in various species. This systematic review aims to summarize and categorize extracranial aneurysm models and their characteristics, discuss advantages and disadvantages, and suggest the best use of each model. We searched the electronical Medline/PubMed database between 1950 and 2020 to identify main models and their refinements and technical modifications for creation of extracranial aneurysms. Each study included was assessed for aneurysm-specific characteristics, technical details of aneurysm creation, and histological findings. Among more than 4000 titles and abstracts screened, 473 studies underwent full-text analysis. From those, 68 different techniques/models in five different species were identified, analyzed in detail, and then grouped into one of the five main groups of experimental models as sidewall, terminal, stump, bifurcation, or complex aneurysm models. This systematic review provides a compact guide for investigators in selecting the most appropriate model from a range of techniques to best suit their experimental goals, practical considerations, and laboratory environment.

From bench to bedside: utility of the rabbit elastase aneurysm model in preclinical studies of intracranial aneurysm treatment

Preclinical studies are important in helping practitioners and device developers improve techniques and tools for endovascular treatment of intracranial aneurysms. Thus an understanding of the major animal models used in such studies is important. The New Zealand rabbit elastase induced arterial aneurysm of the common carotid artery is one of the most commonly used models in testing the safety and efficacy of new endovascular devices. In this review we discuss: (1) the various techniques used to create the aneurysm, (2) complications of aneurysm creation, (3) natural history of the arterial aneurysm, (4) histopathologic and hemodynamic features of the aneurysm, (5) devices tested using this model, and (6) weaknesses of the model. We demonstrate how preclinical studies using this model are applied in the treatment of intracranial aneurysms in humans. The model has similar hemodynamic, morphological, and histologic characteristics to human aneurysms, and demonstrates similar healing responses to coiling as human aneurysms. Despite these strengths, however, the model does have many weaknesses, including the fact that the model does not emulate the complex inflammatory processes affecting growing and ruptured aneurysms. Furthermore, the extracranial location of the model affects its ability to be used in preclinical safety assessments of new devices. We conclude that the rabbit elastase model has characteristics that make it a simple and effective model for preclinical studies on the endovascular treatment of intracranial aneurysms, but further work is needed to develop aneurysm models that simulate the histopathologic and morphologic characteristics of growing and ruptured aneurysms.

Analysis of Multiple Intracranial Aneurysms with Different Outcomes in the Same Patient After Endovascular Treatment

BACKGROUND

Aneurysm recanalization after coiling, with or without stent assistance, is a major issue in the endovascular management of intracranial aneurysms. Multiple intracranial aneurysms with different outcomes after endovascular treatment may represent a useful disease model in which patient-specific risk factors can be balanced to investigate possible features linked to aneurysm recanalization. In the present study, we evaluated the impact of aneurysm-specific, treatment-related, and hemodynamics-related factors on multiple aneurysms and to explore the reason why one aneurysm recanalized and the other did not.

METHODS

Between 2010 and 2015, 763 multiple intracranial aneurysms in 326 patients were diagnosed by digital subtraction angiography. We retrospectively collected and analyzed 13 pairs of multiple aneurysms with different outcomes (recanalized or stable) in the same patient. Patient-specific models were constructed and analyzed by a computational fluid dynamics method. The virtual stent deployment method was used, and the coils were simulated by a porous medium model. Factors were evaluated for significance with respect to recanalization.

RESULTS

Aneurysm size (P = 0.021), neck width (P = 0.027), ruptured aneurysms (P = 0.002), reduction ratio of averaged velocity (P = 0.008), and wall shear stress (P = 0.024) were significantly associated with aneurysm recanalization. By contrast, the aneurysm location, all of treatment-related factors (packing density, duration of follow-up, stent use, initial angiographic result) and the reduction ratio of averaged pressure were not significantly associated (P > 0.05).

CONCLUSIONS

Small aneurysm size and neck width, unruptured aneurysm, and perianeurysmal hemodynamics with marked reduction may be important factors associated with the midterm durability of aneurysm embolization.

Occlusion of canine aneurysms using microporous self-expanding stent grafts: long-term follow-up

PURPOSE

The treatment of large or giant cerebral aneurysms by surgical and/or endovascular techniques is difficult and poses relatively high risks. Therefore, a microporous self-expanding (hybrid) stent graft composed of a thin, expandable, segmented polyurethane (SPU) membrane with micropores and a drug-delivery system was developed.

MATERIALS AND METHODS

A commercially available, self-expanding carotid stent was covered with a thin microporous SPU membrane fabricated by the dip-coating method and the excimer laser ablation technique, with an intraluminal coating of argatroban. Experimentally fabricated lateral-wall aneurysms in canine carotid arteries using venous pouches were occluded with the hybrid stent graft (bale-shaped pore density of 23.6%) on one side and a bare-metal stent on the other side without systemic antiplatelet therapy.

RESULTS

Angiography at 1, 6, and 12 months of stenting revealed that all arteries were patent without marked stenosis without systemic antiplatelet therapy. All aneurysms treated with hybrid stent grafts remained occluded throughout the 12-month period, while among those treated by bare-metal stents, 2 of 3 aneurysms were occluded at 6 months (67%) and only 1 of 3 aneurysms were occluded at 12 months (33%). Histology revealed that the novel hybrid stent graft had less intimal hyperplasia than the bare-metal stent. The hybrid stent graft was useful for the successful occlusion of these canine carotid aneurysms, even at 12 months.

CONCLUSIONS

The novel hybrid stent grafts are expected to overcome the disadvantages of fully covered stent grafts and simple bare-metal stents, while combining both their merits, and appear to be useful in the treatment of large or giant cerebral aneurysms.

A novel tissue engineering approach using an endothelial progenitor cell–seeded biopolymer to treat intracranial saccular aneurysms

Object

Recurrence after endovascular coiling of intracranial aneurysms is reported in up to 42% of cases and is attributed to the lack of endothelialization across the neck. In this study the authors used a novel tissue engineering approach to promote endothelialization by seeding endothelial progenitor cells (EPCs) within a fibrin polymer injected endovascularly into the aneurysm.

Methods

Experimental aneurysms were created in New Zealand White rabbits and were left untreated, surgically clipped, or embolized with platinum coils, fibrin biopolymer alone, or fibrin combined with autologous cultured EPCs.

Results

In aneurysms treated with EPCs, a confluent monolayer of endothelial cells with underlying neointima was demonstrated across the neck at 16 weeks posttreatment, which was not observed with aneurysms treated using the other methods.

Conclusions

This novel technique may address reasons for the limited durability of standard coil embolization and provides further avenues for the development of improved devices for the care of patients with aneurysms.

Development of microporous self-expanding stent grafts for treating cerebral aneurysms: designing micropores to control intimal hyperplasia

Treatment of large (diameter 12-25 mm) or giant (diameter >25 mm) cerebral aneurysms with a broad neck in the cranio-cervical area is difficult and carries relatively high risks, even with surgical and/or endovascular methods. To this end, we have been developing a high-performance, self-expanding stent graft which consists of a commercially available NiTi stent (diameter 5 mm, length 20 mm) initially covered with a thin microporous segmented polyurethane membrane fabricated by the dip-coating method. Micropores are then created by the excimer laser ablation technique, and the outer surface is coated with argatroban. There are 2 types of micropore patterns: circular-shaped pore type (pore: diameter 100 μm, opening ratio 12.6%) and the bale-shaped pore type (pore: size 100 × 268 μm, opening ratio 23.6%). This self-expanding stent graft was tested on side-wall aneurysms of both canine carotid arteries that were experimentally induced using the venous pouches from the external jugular veins, with the self-expanding stent graft on one side and a bare self-expanding stent on the other side. All carotid arteries were patent and free of marked stenosis after 1 month. All aneurysms were occluded by stent grafts, while patent in those treated with bare stents. Histologically, the stent grafts with bale-shaped micropores and a high opening ratio were associated with less intimal hyperplasia (187 ± 98 μm) than the bare stents (341 ± 146 μm) or the stent grafts with circular micropores and a low opening ratio (441 ± 129 μm). A pore ratio of 23.6% was found to control intimal growth.

Microsurgery for Previously Coiled Aneurysms: Experience With 81 Patients

BACKGROUND:

Residual and recurrent intracranial aneurysms after endovascular treatment with Guglielmi detachable coils may necessitate a microsurgical occlusion.

OBJECTIVE:

To analyze the microsurgical technique and describe how the location, morphology, and appearance of the coiled aneurysm affect the technique.

METHODS:

We retrospectively analyzed 81 patients with 82 previously coiled aneurysms treated microsurgically at 2 Finnish neurosurgical university hospitals in Helsinki and Kuopio between July 1995 and August 2009. Seven videos were selected to demonstrate the microsurgical strategy in various locations.

RESULTS:

Fifty-eight aneurysms (71%) were located at anterior circulation and 24 (29%) at posterior circulation. Fifteen patients were operated on within the first month (early surgery) after coiling, whereas 66 were treated later (late surgery). Complete or partial removal of coils during surgery may facilitate clipping, but is significantly (P &lt; .001) more difficult to accomplish in late surgery. Removal of coils may also increase the chance of poor outcome. Chance of poor outcome also increased with intraoperative aneurysm rupture, size of the aneurysm, and posterior circulation location. Good clinical outcome (same or better clinical condition 3 months after surgery) was achieved in 71 patients (88%). After microsurgery, 4 patients were severely disabled and 6 patients died, 3 of them because of poor clinical condition.

CONCLUSION:

Complete microsurgical occlusion of the residual aneurysm is possible. However, in large or giant aneurysms direct microsurgery is a challenging high-risk procedure, and we recommend that these patients be referred to a dedicated neurovascular center to minimize surgical complications. Even in experienced hands, use of different bypass procedures may be the best option for demanding growing lesions, especially those in the posterior circulation.

Bare, bio-active and hydrogel-coated coils for endovascular treatment of experimentally induced aneurysms. Long-term histological and scanning electron microscopy results

Endovascular treatments of cerebral aneurysms with bare platinum coils have a higher rate of recurrence compared to surgical clipping. This may be related to failed vessel wall reconstruction since histological and scanning electron microscopy results following embolization failed to demonstrate neoendothelialization over the aneurysm neck. The present study tried to elucidate whether the use of modified coils resulted in a better rate of reconstructing the vessel wall over the aneurysm neck in experimental aneurysms. Aneurysms were created in 20 rabbits by intraluminal elastase incubation of the common carotid artery. Five animals each were assigned to the following groups: untreated, bare platinum coils, bioactive coils with polyglycolic/polylactic acid coating, and hydrogel-coated platinum coils. After 12 months, angiography, histology and scanning electron microscopy was performed. No neoendothelial layer was visualized in the bioactive and bare coil groups with a tendency to an increased layering of fibroblasts along the bioactive coils at the aneurysm fundus. However, at the aneurysm neck perfused clefts were present and although a thin fibrinous layer was present over some coils, no bridging neointimal or neoendothial layer was noted over different coils. Following loose Hydrogel coiling, a complete obliteration of the aneurysm was present with neoendothelialization present over different coil loops. The study demonstrates that with surface coil modifications complete and stable aneurysm obliteration may become possible. A smooth and dense surface over the aneurysm neck may be necessary for endothelial cells to bridge the aneurysm neck and to lead to vessel wall reconstruction.

In vivo experimental intracranial aneurysm models: a systematic review

Animal models are necessary to develop and test innovations in aneurysm therapy before clinical introduction. This review aims at identifying the most likely candidates for standardizing preclinical testing of aneurysm devices. We systematically searched electronic databases for publications on animal aneurysm models from 1961-2008 to assess the methodologic quality of the studies and collect data on the patency and angiographic and pathologic outcomes of treatments. There has been a steady increase in the annual number of publications with time. Species that were most frequently used were dogs, rabbits, and rodents, followed by swine. Most publications are single-laboratory studies with variables and poorly validated outcome measures, a small number of subjects, and limited standardization of techniques. The most appropriate models to test for recurrences after endovascular occlusion were the surgical bifurcation model in dogs, and the elastase-induced aneurysm model in rabbits. A standardized multicenter study is needed to improve the preclinical evaluation of endovascular devices in aneurysm therapy.

Techniques of reoperation for a giant regrown anterior communicating artery aneurysm harboring long-implanted clips and compacted coil mesh

A 57-year-old woman presented with a progressive deterioration of vision. She had previously undergone clipping for a ruptured small anterior communicating artery (Acom) aneurysm 7 years prior to admission and additional coiling for recurrence 2 years prior to admission. Angiography showed regrown out-pouching of the sac, which measured 27 x 18 mm. A decision was made to perform surgical treatment to alleviate the mass effect of the aneurysm. Unique techniques for revision of the scarred surgical corridor, removal of old clips, resection of the coiled mass, thrombectomy, and intra-aneurysmal endarterectomy were required to allow placement of the final clips. The patient recovered uneventfully, and her vision was satisfactorily restored.

Neck injury is critical to elastase-induced aneurysm model

We modified the elastase-induced aneurysm model by use of a simple surgical technique in rabbits. A temporary arcuated aneurysm clip was placed at the origin of the right common carotid artery (RCCA), ascertaining the inner edge of the clip blade on the juncture of the RCCA and right subclavian artery (RSCA), and the elastase-induced aneurysm procedure was undertaken. We found elastase and location of the temporary arcuated aneurysm clip are critical to the success of this aneurysm model.

Early Rebleeding of Small Anterior Communicating Artery Aneurysm with Presumed Extrusion of Coil Loop to Outside the Aneurysmal Wall during Endovascular Treatment. A Report of Two Cases

SUMMARY

Although endovascular treatment has been proved to be as effective as surgical clipping in the prevention of rebleeding of ruptured aneurysm, early rebleeding after coil embolization has seldom been reported. We experienced early rehemorrhage in two patients of ruptured small anterior communicating artery aneurysms of complete treatment with coil-embolization initially. In both cases what interested us was not early rebleeding itself but how the presumed extrusion of the first part of coil loop beyond aneurysmal wall developed. However, there was no evidence of intraprocedural rupture and moreover complete occlusion with only one or two coils was obtained. Our two patients underwent successful second treatment. We discovered the presumed extruded first part of the coil loop initially was located inside the enlarged aneurysmal sac in retreatment stage. In case of coil embolization of ruptured small anterior communicating aneurysm, the phenomenon we experienced with no evidence of intraprocedural rupture in spite of obvious extrusion of coil loop beyond the aneurysmal wall can be a sign of necessity for early follow-up study including plain radiography to track the change in the presumed extruded coil loop.

A compartmentalized volumetric system for outcome analysis of coiled cerebral aneurysms: aneurysm-coil mass-neck outcome assessment system

OBJECTIVE

Current methodologies for outcome assessment of coiled cerebral aneurysms are based on rough estimations. The aim of this study was to develop a system of quantitative analysis for objective and accurate assessment of the outcome of cerebral aneurysms treated with coil embolization.

METHODS

The quantitative analysis system is based on a concept of a perfect vessel tube and compartmentalized analysis of a coiled aneurysm. Based on the volumetric data of 3-dimensional radiographic angiography of the aneurysm and its associated parent vessel, a 2-step volume extraction method, including a global thresholding method and an augmented vessel method, is used for volume calculation. The coiled aneurysm (A) is compartmentalized into 2 volumetric components for quantitative analysis: 1) the volume of the coil mass (C), and 2) the volume of the uncoiled neck of the aneurysm (N). Changes in the volumetric data of the compartments A, C, and N at the time of follow-up provide a basis for outcome analysis. To test the clinical applicability of the system, the volumetric data for 21 consecutive cases of cerebral aneurysms in which a residual or recurrent cavity at the neck region was noted at the time of the 6-month follow-up evaluation were assessed with the aneurysm-coil mass-neck (ACN) outcome assessment system.

RESULTS

The results of the outcome analysis of the 21 cases according to the ACN system correlated well with angiographic assessment of treatment outcome.

CONCLUSION

The ACN outcome assessment system is a useful diagnostic instrument for objective and accurate assessment of the outcome of cerebral aneurysms treated with coil embolization.

Angiographic analysis of animal model aneurysms treated with novel polyurethane asymmetric vascular stent (P-AVS): feasibility study

Image-guided endovascular intervention (EIGI), using new flow modifying endovascular devices for intracranial aneurysm treatment is an active area of stroke research. The new polyurethane-asymmetric vascular stent (P-AVS), a vascular stent partially covered with a polyurethane-based patch, is used to cover the aneurysm neck, thus occluding flow into the aneurysm. This study involves angiographic imaging of partially covered aneurysm orifices. This particular situation could occur when the vascular geometry does not allow full aneurysm coverage. Four standard in-vivo rabbit-model aneurysms were investigated; two had stent patches placed over the distal region of the aneurysm orifice while the other two had stent patches placed over the proximal region of the aneurysm orifice. Angiographic analysis was used to evaluate aneurysm blood flow before and immediately after stenting and at four-week follow-up. The treatment results were also evaluated using histology on the aneurysm dome and electron microscopy on the aneurysm neck. Post-stenting angiographic flow analysis revealed aneurysmal flow reduction in all cases with faster flow in the distally-covered case and very slow flow and prolonged pooling for proximal-coverage. At follow-up, proximally-covered aneurysms showed full dome occlusion. The electron microscopy showed a remnant neck in both distally-placed stent cases but complete coverage in the proximally-placed stent cases. Thus, direct flow (impingement jet) removal from the aneurysm dome, as indicated by angiograms in the proximally-covered case, was sufficient to cause full aneurysm healing in four weeks; however, aneurysm healing was not complete for the distally-covered case. These results support further investigations into the treatment of aneurysms by flow-modification using partial aneurysm-orifice coverage.

The asymmetric vascular stent: efficacy in a rabbit aneurysm model

BACKGROUND AND PURPOSE

Development of hemodynamic modifying devices to treat intracranial aneurysms is an active area of research. The asymmetrical vascular stent (AVS), a stent containing a low-porosity patch, is such device. We evaluate AVS efficacy in an in vivo intracranial aneurysm model.

METHODS

We created 24 elastase rabbit model aneurysms: 13 treated with the AVS, 5 treated with standard coronary stents, and 6 untreated controls. Four weeks after treatment, aneurysms underwent follow-up angiography, cone-beam micro-CT, histological evaluation, and selective electron microscopy scanning.

RESULTS

Four rabbits died early in the study: 3 during AVS treatment and 1 control (secondary to intraprocedural vessel injury and an unrelated tumor, respectively). AVS-treated aneurysms exhibited very weak or no aneurysm flow immediately after treatment and no flow in all aneurysms at follow-up. Standard stent-treated aneurysms showed flow both after treatment (5/5) and at follow-up (3/5). All control aneurysms remained patent during the study. Micro-CT scans showed: 9 of 9 scanned AVS aneurysms were occluded, 6 of 9 AVS were ideally placed, and 3 of 9 low-porosity region partially covered the aneurysm neck; standard stent-treated aneurysms were 1 of 5 occluded, 2 of 5 patent, and 2 of 5 partially patent. Histology results demonstrated: for AVS-treated aneurysms, advanced thrombus organization in the (9/9); for standard stent-treated aneurysms, (1/4) no thrombus, (2/4) partially thrombosed, and (1/4) fully thrombosed; for control aneurysms (4/4), no thrombus.

CONCLUSIONS

The use of AVS shows promise as a viable new therapeutic in intracranial aneurysm treatment. These data encourage further investigation and provide substantial support to the AVS concept.

A novel endovascular clip system for the treatment of intracranial aneurysms: technology, concept, and initial experimental results

Object

The authors describe a novel device for the endovascular treatment of intracranial aneurysms, the endovascular clip system (eCLIPs). Descriptions of the device and its delivery system as well as the results of flow model tests and the treatment of experimental aneurysms are provided.

Methods

The eCLIPs comprises a flexible hybrid implantable device (an anchor and a covered leaf) and a balloon catheter delivery system, designed to be positioned and activated in the parent vessel in such a way that the covered portion will abut the aneurysm neck. The eCLIPs was subjected to testing in glass, elastomeric, and cadaveric flow models to determine its navigability, orientation, and activation compared with commercially available stents. In a second experiment, 8 carotid artery sidewall aneurysms in swine were treated using eCLIPs. The degree of occlusion was observed on angiography immediately following and 30 days after device activation, and a histological analysis was performed at 30 days.

Results

The device could navigate tortuous glass models and human cadaveric vessels. Compared with commercially available stents, the eCLIPs performed well. It could be navigated, oriented, and activated easily and reliably. With regard to the 8 porcine experimental aneurysms, immediate postactivation angiograms confirmed complete occlusion of 4 lesions and near occlusion of the other 4. Angiographic follow-up at 30 days postactivation showed occlusion of all 8 aneurysms and patency of all parent vessels. Histopathological analysis revealed aneurysm healing, with smooth-muscle cells growing across the lesion neck to allow reendothelialization.

Conclusions

Aneurysm occlusion with a single extrasaccular endovascular device has potential advantages. The authors believe that eCLIPs may prove to be a useful tool in the endovascular treatment of cerebral aneurysms. The system should reduce risks associated with coiling, procedure time, costs, and radiation exposure. The device satisfactorily occluded 8 experimental sidewall aneurysms. The observed healing pattern is similar to that seen after microsurgical clipping.

Combined covered stent and onyx treatment for complex dural arteriovenous fistula involving the clivus and cavernous sinus

BACKGROUND

Complex DAVFs involving both the clivus and cavernous sinus are rare, especially when associated with brainstem compression from a large varix. In this report, we describe the use of a covered stent in combination with a liquid embolic agent to cure a complex clival-cavernous DAVF.

METHODS

A 46-year-old man presented with 6 months of dizziness, dysphagia, and progressive dysarthria. Magnetic resonance imaging showed tortuous and enlarged right cavernous and preclival flow voids. There were also bilateral prepontine varices compressing the ventral pons, which led to marked dorsal pontine edema. A cerebral angiogram revealed a clival DAVF supplied by multiple branches of the right ECA, as well as the MHT of the right ICA.

RESULTS

An endovascular cure was achieved by deploying a covered stent in the right cavernous ICA, followed by transarterial embolization of the feeding arteries originating from the ECA with Onyx (ev3, Irvine, Calif). This combined approach resulted in complete occlusion of the fistula. His 1-month follow-up angiogram confirmed persistent occlusion of the fistula and preserved patency of the right ICA. The patient made a full recovery without any new symptoms, and he remained neurologically intact at 18-month follow-up.

CONCLUSION

The combined technique of covered stent placement and Onyx transarterial embolization is valuable for the management of complex DAVFs supplied by branches of both the external and internal carotid arteries.

Endovascular image-guided treatment of in-vivo model aneurysms with asymmetric vascular stents (AVS): evaluation with time-density curve angiographic analysis and histology

In this study, we compare the results obtained from Time-Density Curve (TDC) analysis of angiographic imaging sequences with histological evaluation for a rabbit aneurysm model treated with standard stents and new asymmetric vascular stents (AVS) placed by image-guided endovascular deployment. AVSs are stents having a low-porosity patch region designed to cover the aneurysm neck and occlude blood flow inside. To evaluate the AVSs, rabbits with elastase-induced aneurysm models (n=20) were divided into three groups: the first (n=10) was treated with an AVS, the second (n=5) with a non-patch standard coronary stent, and third was untreated as a control (n=5). We used TDC analysis to measure how much contrast media entered the aneurysm before and after treatment. TDCs track contrast-media-density changes as a function of time over the region of interest in x-ray DSA cine-sequences. After 28 days, the animals were sacrificed and the explanted specimens were histologically evaluated. The first group showed an average reduction of contrast flow into the aneurysm of 95% after treatment with an AVS with fully developed thrombus at 28 days follow-up. The rabbits treated with standard stents showed an increase in TDC residency time after treatment and partial-thrombogenesis. The untreated control aneurysms displayed no reduction in flow and were still patent at follow-up. The quantitative TDC analysis findings were confirmed by histological evaluation suggesting that the new AVS has great potential as a definitive treatment for cerebro-vascular aneurysms and that angiographic TDC analysis can provide in-vivo verification.

Mechanisms of occlusion and recanalization in canine carotid bifurcation aneurysms embolized with platinum coils: an alternative concept

BACKGROUND AND PURPOSE

Endovascular treatment of aneurysms may result in complete or incomplete occlusions or may be followed by recurrences. The goal of the present study was to better define pathologic features associated with so-called healing or recurrences after coiling and to propose an alternative concept to the currently accepted view.

MATERIALS AND METHODS

Experimental canine venous pouch aneurysms were created by using a T-type (group A, N = 29) or a Y-type constructed bifurcation (group B, N = 37) between the carotid arteries. Coil embolization was performed 2 weeks later; and angiography, immediately after and at 12 weeks. Angiographic results, neointima formation at the neck, endothelialization, and organization of thrombus were compared between groups by using qualitative scores and immunohistochemistry.

RESULTS

Angiographic results at 3 months were significantly better in group A than in group B (P = .001). Macroscopic neointimal scores were also better (P = .012). Only 10/32 aneurysms with satisfactory results at angiography were completely sealed by neointima formation. Animals with residual or recurrent aneurysms had significantly worse neointimal scores than those with completely occluded ones (P = .0003). On histologic sections, the neointima was constantly present in "healed" and in recurrent aneurysms. This neointima was a multicellular layer of alpha-actin+ cells in a collagenous matrix, covered with a single layer of nitric oxide synthetase (NOS+) endothelial cells, whether it completely occluded the neck of the aneurysm or dived into the recurring or residual space between the aneurysm wall and the coil mass embedded in organizing thrombus.

CONCLUSION

Complete angiographic occlusions at 3 months can be associated with incomplete neointimal closure of the neck at pathology. Thrombus organization, endothelialization, and neointima formation can occur concurrently with recurrences.