Exploring the relationship between case volume and intracranial aneurysm treatments with flow-diverters and flow-disruptors: Insights from the 2020 to 2021 Database of the German Society for Interventional Radiology National Registry in Germany

BACKGROUND AND PURPOSE

Intracranial aneurysm treatment using flow-diverters and flow-disruptors requires a higher level of expertise when compared to more traditional methods. Our hypothesis was that the procedural success and the rate of complications are dependent on the annual case load of a center.

MATERIALS AND METHODS

Conducting a retrospective analysis on the Database of the German Society for Interventional Radiology for the years 2020 to 2021, we examined flow-diverter and flow-disruptor procedures. We categorized centers into four groups according to their annual case load and proceeded to analyze success rates, complication rates, and fluoroscopy times across these centers.

RESULTS

No statistically significant differences were observed among the groups in both flow-diverter and flow-disruptor cases concerning fluoroscopy time and the incidence of technical complications. However, within the subgroup of flow-disruptor cases, centers with lower case load exhibited significantly higher rates of hemorrhagic and clinically relevant complications. Additionally, it was noted that the rate of therapeutic success in the flow-diverter group significantly increased in centers with higher case volumes.

CONCLUSION

Our findings support the intention towards centralization of medical care especially for complex neuroendovascular procedures. Furthermore, our findings are an argument to further develop a standardized educational and procedural algorithm based on defined case numbers and training modules for complex neurovascular procedures as already implemented by the Database of the German Society for Interventional Radiology.

Delayed fatal rupture of vertebral artery after treated with flow-diverter in fibromuscular dysplasia patient: A case report and review of the literature

Fibromuscular dysplasia (FMD) is a noninflammatory arterial diseases that affects predominantly women. Multiple studies have demonstrated an increased prevalence of FMD in patients who experience carotid or vertebral artery dissection (VAD). This case report presents a 57-year-old female who presented with a headache and was diagnosed with partially thrombosed giant aneurysm of vertebral artery. This aneurysm was successfully treated with flow-diverter and coil, but new onset rupture of vertebral artery was detected two weeks later, leading to internal trapping. This case report underscores the need for awareness and understanding of treatment of dissection and aneurysm in patient who is suspected FMD.

Successful use of an LVIS device to treat unruptured distal aneurysm of the superior cerebellar artery at a vascular bifurcation

Background

Aneurysms of the distal superior cerebellar artery (SCA) account for only a small proportion of all cerebral aneurysms. Reports of the use of flow diverters (FDs) started to appear in 2013. We obtained good results from placement of a low-profile visualized intraluminal support device (LVIS) to treat unruptured distal aneurysm of the SCA at a vascular bifurcation.

Case Description

A 65-year-old man presented at our hospital with sudden peripheral facial nerve palsy and suspected subarachnoid hemorrhage. Investigational cerebral angiography revealed an aneurysm at the bifurcation of the caudal and rostral trunks of the SCA. An LVIS was placed with the aim of obtaining flow diversion, and cerebral angiography 6 months after this procedure showed disappearance of aneurysm with preservation of the distal SCA.

Conclusion

Twelve cases of the use of FDs to treat aneurysms of the SCA have been reported previously. However, none of those reports described FD use to treat an aneurysm at a vascular bifurcation, as in the present case. Our results suggested that LVIS placement with the aim of obtaining flow diversion may be useful for the treatment of aneurysms at such sites.

Ruptured blood blister like aneurysm: does the best therapeutic option really exist?

Our study aimed to evaluate the outcome of patients with ruptured blood-blister like aneurysm (BBLA) in our institution by comparing microsurgical selective treatment to endovascular treatment using flow-diverter stent (FD). Our study included 18 consecutive patients treated for BBLA between 2004 and 2020. Until 2014, microsurgery was preferred in all patients with BBLA (n = 10). Significant postoperative morbi-mortality was recorded at this time and led us to change therapeutic strategy and to favor FD as first-line treatment in all patients (n = 8). Postprocedural complications and BBLA occlusion were recorded. High WFNS score (> 2) was noted in 6 patients of microsurgical group and in 2 of endovascular group. In microsurgical group, ischemic lesions were noted in 6 patients and led to death in 3 patients. Immediate BBLA occlusion was obtained in all patients. Favorable outcome after 3 months (mRS < 3) was recorded in 4 of the 7 survivors. In endovascular group, ischemic lesions were noted in 4 patients. One patient died from early postprocedural BBLA rebleeding. Scarpa hematoma was noted in 3 patients with surgical evacuation in 1. Persistent BBLA at 3 months was recorded in 4 patients without rebleeding, but further FD was required in 1 with growing BBLA. Favorable outcome was noted in 6 of the 7 survivors. Although, rate of morbi-mortality appear lower in patients treated with FD, neurological presentation was better and BBLA diagnosis remains questionable in this group. Moreover, persistent BBLA imaging with potential risk of rebleeding after FD deserves to be discussed.

Retreatment strategies for recurrent and residual aneurysms after treatment with flow-diverter devices

PURPOSE

The management of residual or persistent intracranial aneurysms after flow-diversion therapy is not well defined in the literature. In this multicentric study, we report clinical and angiographic outcomes of 11 patients that underwent retreatment for 12 aneurysms initially treated with flow-diverter stents.

METHODS

The median patient age was 53 years. Aneurysms (median size, 7.3 mm) were located at the internal carotid artery in 9 cases, and at the posterior circulation in 3. Treatment strategies, complications, and angiographic outcome were retrospectively assessed.

RESULTS

Retreatment was feasible in all cases and performed by overlapping flow-diverter implantation. Overall, 12 side vessels were covered during retreatment, whereof 10 (83.3%) remained patent until mid-term follow-up. There were no further technical or symptomatic complications and no treatment-related morbidity. Angiographic follow-up (median, 17 months) showed improved aneurysm occlusion in all patients. Complete or near-complete aneurysm occlusion was achieved in 11 aneurysms (91.7%).

CONCLUSION

Required retreatment after failed flow-diversion therapy can be performed with adequate safety and efficacy by placement of additional flow-diverter stents.

Evaluation of flow changes after telescopic stenting of a giant fusiform aneurysm of the vertebrobasilar junction

BACKGROUND

The use of flow-diverters for non-saccular cerebral posterior circulation aneurysms requires complex deployment techniques and is associated with high mortality and morbidity. Therefore, further studies are required to clarify the effect of stenting on post-treatment hemodynamics in such aneurysms. In this study, we evaluated flow alterations in a treated giant fusiform aneurysm of the vertebrobasilar junction and correlated them with the clinical outcome.

METHODS

A patient-specific aneurysm model was acquired by rotational angiography, and three SILK flow-diverters (4.5 × 40, 5 × 40 and 5.5 × 40 mm) were virtually deployed in series along the basilar and right vertebral arteries. Image-based blood flow simulations before and after the treatment were performed under realistic pulsatile flow conditions. The flow reduction, velocity and wall shear stress (WSS) distribution, streamlines and WSS-derived parameters were evaluated before and after the treatment.

RESULTS

The computed velocity streamlines showed substantial alterations of the flow pattern in the aneurysm and successful redirection of blood flow along the series of flow-diverters with no flow through the overlapping stents. The obtained flow reduction of 86% was sufficient to create thrombogenic flow conditions. Moreover, a 6.2-fold increase in relative residence time and a decrease by 87% of time-averaged WSS contributed to a successful treatment outcome observed during the follow-up.

CONCLUSIONS

We found a correlation between the numerically predicted flow alterations and the available treatment outcome. This shows the potential of image-based simulations to be used in clinical practice for treatment planning and estimation of possible risk factors associated with a complex stent deployment in fusiform aneurysms of the posterior circulation.

A Virtual Comparison of the eCLIPs Device and Conventional Flow-Diverters as Treatment for Cerebral Bifurcation Aneurysms

PURPOSE

Effective, consistent, and complication-free treatment of cerebral bifurcation aneurysms remains elusive despite a pressing need, with the majority of lesions presenting in such locations. Current treatment options focus either on aneurysm coil retention, supported by a stent-like device positioned in the parent vessel lumen, or intrasaccular devices that disrupt flow within the aneurysm dome. A third alternative, i.e., the use of conventional (intraluminal) flow-diverters to treat such bifurcation aneurysms raises the problem that at least one daughter vessel needs to be jailed in such a deployment. The eCLIPs is a stent-like device that offers the possibility of flow-diversion at the aneurysm neck, without the drawbacks of daughter vessel occlusion or those of intrasaccular deployment.

METHODS

In this study the eCLIPs device was virtually deployed in five cerebral bifurcation aneurysms and compared with a conventional tubular flow-diverter device. Computational fluid dynamics (CFD) simulations of the aneurysm haemodynamic environment pre- and post-implantation were conducted, and focussed on metrics associated with successful aneurysm occlusion. Absolute and relative reductions in aneurysm inflow rate (Q) and time-averaged wall shear stress (TAWSS) were recorded.

RESULTS

The eCLIPs device was found to perform in a similar qualitative fashion to tubular flow-diverters, with overall reduction of metrics being somewhat more modest however, when compared to such devices. Aneurysm inflow reduction and TAWSS reduction were typically 10-20% lower for the eCLIPs, when compared to a generic flow diverter (FD_BRAIDED) similar to devices currently in clinical use. The eCLIPs was less effective at diffusing inflow jets and at reducing the overall velocity of the flow, when compared to these devices. This result is likely due to the larger device pore size in the eCLIPs. Notably, it was found that the eCLIPs provided approximately equal resistance to flow entering and exiting the aneurysm, which was not true for the FD_BRAIDED device, where high-speed concentrations of outflow were seen at the aneurysm neck along with local TAWSS elevation. The clinical implications of such behaviour are not examined in detail here but could be significant.

CONCLUSIONS

Our findings indicate that the eCLIPs device acts as a flow-diverter for bifurcation aneurysms, with somewhat diminished occlusion properties comparing to tubular flow diverters but without the jailing and diminished flow evident in a daughter vessel associated with use of conventional devices.

Effect of flow diversion with silk on aneurysm size: A single center experience

Alterations in aneurysm size and mass effect can result in alleviation or aggravation of symptoms. We assessed the effects of flow diversion with SILK stents on aneurysm sac size and associated factors. A retrospective evaluation of 14 aneurysms treated with SILK stents alone with MRI follow-up was performed. Aneurysm sac size was measured using the sequence best demonstrating the sac. Aneurysm characteristics and flow-related enhancement on time of flight images were documented. Clinical histories were reviewed for evolution of symptoms. Complete collapse of the aneurysm sac was demonstrated at three and 18 months in 2/14 aneurysms. Increase in size was observed in 2/14 aneurysms with associated persistent flow on time of flight MRA. Blister formation with aggravation of symptoms was observed in one aneurysm, and subsequent decrease in size occurred after treatment with a second SILK. The other aneurysm which increased in size initially continued to enlarge asymptomatically despite retreatment with a second SILK, however at 24 months thrombosis of the sac and decrease in size was observed. The remaining 10/14 aneurysms decreased in size. Nine had corresponding MRA occlusion and the tenth demonstrated decreased but persistent flow on the time of flight MRA. No aneurysm with MRA occlusion increased in size. Decrease in sac size was associated with MRA occlusion in our study. Persistence of flow and blistering were associated with increased sac size. As previously demonstrated flow diversion may be effective in the treatment of large aneurysms presenting with mass effect, however rates of sac obliteration in this small series were not as high as previously reported.

Flat detector CT and its applications in the endovascular treatment of wide-necked intracranial aneurysms-A literature review

Flat detector CT (FDCT) provides cross sectional imaging within an angiographic suite and is increasingly gaining popularity in various areas of interventional radiology, as an alternative imaging modality. Its relatively high spatial resolution improves visualization of intraluminal devices such as intracranial stents or flow-diverters. Device deployment and positioning, in relation to the parent vessel and surrounding structures, are easily assessible with FDCT. Furthermore, with contrast agent administration, it expands the diagnostic capabilities of this new imaging tool. However, beam-hardening artifacts is a major limitation in some cases. The examination can be performed both during the endovascular procedure and for pre- and post-treatment imaging. Intravenous contrast agent injection reduces the risk of complications, making it possible to perform this examination in the outpatient settings. The aim of this paper is to present an overview of published studies reporting experience with FDCT in the field of endovascular neurosurgery and in particular, FDCT's contribution in treatment of wide-necked intracranial aneurysms. The authors have focused specifically on stent-assisted coiling and flow-diverter implantation, since obtaining proper parent vessel wall apposition of these devices is essential for short- and long-term procedural outcomes.

Towards Predicting Patient-Specific Flow-Diverter Treatment Outcomes for Bifurcation Aneurysms: From Implantation Rehearsal to Virtual Angiograms

Despite accounting for the majority of all cerebral aneurysm cases, bifurcation aneurysms present many challenges to standard endovascular treatment techniques. This study examines the treatment of bifurcation aneurysms endovascularly with flow-diverting stents and presents an integrative computational modeling suite allowing for rehearsing all aspects of the treatment. Six bifurcation aneurysms are virtually treated with 70% porosity flow-diverters. Substantial reduction (>50%) in aneurysm inflow due to device deployment is predicted in addition to reductions in peak and average aneurysm wall shear stress to values considered physiologically normal. The subsequent impact of flow-diverter deployment on daughter vessels that are jailed by the device is investigated further, with a number of simulations conducted with increased outlet pressure conditions at jailed vessels. Increased outlet pressures at jailed daughter vessels are found to have little effect on device-induced aneurysm inflow reduction, but large variation (13–86%) is seen in the resulting reduction in daughter vessel flow rate. Finally, we propose a potentially powerful approach for validation of such models, by introducing an angiographic contrast model, with contrast transport modeled both before and after virtual treatment. Virtual angiograms and contrast residence curves are created, which offer unique clinical relevance and the potential for future in vivo verification of simulated results.