Hello, and welcome, everyone, to my talk on experience with the pipeline immobilization device for posterior circulation aneurysms, a multicenter cohort study. My name is Christoph Griesenauer, and I am an endovascular and open vascular neurosurgeon at Geisinger in Pennsylvania. This abstract was accepted as part of the American Academy of Neurological Surgeons meeting 2020 and is presented in the virtual. I do not have any disclosures or conflicts of interest related to this topic. For details on conflicts of interest of our co-authors, please see the upcoming publication of this research in neurosurgery accepted currently and expected to be published later this year. We started this project as a follow-up to an initial study, which we had published in Journal of Neurosurgery in 2018, where we assembled a cohort of neurovascular centers to provide their experience with pipeline immobilization of posterior circulation aneurysms. 131 aneurysms were included. This was the largest study on aneurysms in this location treated with pipeline at the time. And what we noted is that only a small amount of aneurysms were actually the classic saccular aneurysms that were treated with this device. A significant number of lesions were either dissecting and fusiform in nature. What was also interesting is that a large number of patients presented with neurological deficits due to their lesions. This included all locations of posterior circulation aneurysms as seen in this table, and those aneurysms were quite large with a median diameter of 12 mm. These were the aneurysms included, classic saccular aneurysms, but also dissecting aneurysms and fusiform aneurysms as shown on these illustrations. What is interesting is that, in general, non-saccular aneurysms make up approximately 10% of all aneurysms. In our posterior circulation series, about 60% of aneurysms were non-saccular. These aneurysms represent very challenging lesions because conventional treatment techniques, both open and endovascular, are not ideal for these morphologies. This is one example of a large dolichoctatic aneurysm that responded very well to a pipeline embolization as shown here on a six-month follow-up engram. In terms of outcome measures in this initial study, we saw that the number of pipelines used differed significantly based on the lesion morphology treated. There was a relationship between aneurysm occlusion and aneurysm morphology that was not statistically significant, but dissecting aneurysms had the highest complete occlusion rate. In terms of complications, you can see the numbers here. Hemorrhagic complications were quite common and occurred mostly in the brainstem and the cerebellum, and we also had a fair number of hemorrhagic complications listed here. So the purpose of this present study was to see whether the findings of this initial work could be replicated in an independent cohort. None of the original centers were included in this follow-up study. We decided to exclude cases treated at a very early time period when flow diversion and pipeline embolization first became available. We used similar aneurysm characteristics classification and similar outcome measures for this study to allow comparison to the previously published results. We assembled a multicentric collaboration on posterior circulation flow diversion. This included a number of centers that are shown here from the United States, Canada, Europe, the Middle East, and also from China. As I said earlier, this paper was recently accepted in neurosurgery. There were 149 aneurysms treated in 146 patients. Most common location was the intracranial vertebral artery followed by the basilar artery. Other locations such as PCA, SCA, PICA, or vertebrobasilar junction were less common. Again, only a minority or a minor portion of these aneurysms were saccular. There was a significant number of fusiform and dissecting or blister aneurysms just as we had seen in prior publications. Aneurysms had a median diameter of 9 millimeters and about 20% were associated with intraaneurysmal aneurysm. Here are two examples of cases shown. The first patient is a 70-some-year-old female with a history of prior subarachnoid hemorrhage of this complex left PCA aneurysm that had been treated with coil embolization. She initially wasn't in very good neurological condition, but over time improved, so the decision was made to coil that superior projecting PCA lobe and then place a pipeline device from the left PCA into the basilar trunk. She initially did very well, but unfortunately around three months from her procedure, she came back in and had suffered a left PCA stroke as shown on the far left. At last follow-up, she was an MRS of 5. A second case is this patient who presented with a dissecting right vertebral artery aneurysm that presented with a pica stroke and Wallenberg syndrome that was treated with a pipeline embolization. This patient did very well and had an MRS of 1 at the last follow-up. You can also see the complete occlusion of the aneurysm in the lower image. The vast majority of these aneurysms in this series were treated with one pipeline device. Platelet function testing was performed in about two-thirds of cases and adjunctive coiling was used fairly deliberately in about 20% of procedures. In terms of complications, the symptomatic complication rate was 7.5% with infarctions most commonly occurring in the brain stem. It is important to note that there were differences in terms of the imaging follow-up protocols at the different institutions, whereas some institutions got follow-up imaging on those patients regardless of symptomatologies, others did not. Symptomatic complication rates may be more reflective of the true complication rate associated with this procedure. Hemorrhagic complication rates that were symptomatic were seen in 2% of procedures. What was important is that symptomatic complications were associated with patients that had experienced subarachnoid hemorrhage and were treated in that setting, or patients who had presented with brain stem compression, cranial nerve deficits, stroke, or larger aneurysm damage. In terms of the occlusion upon follow-up, the median duration of follow-up was 12 months. Complete occlusion was achieved in 73%, greater than 90% occlusion or near-complete occlusion was achieved in another 17%. Clinical follow-up is reported here also at a median of 12 months, 86% had an MRSA 0 to 2, 3 to 5 was present in 9.7% and a 4% mortality. Now dissecting and blister aneurysms were most likely to occlude, which mirrors our initial study and complete occlusion was also associated with longer aneurysm follow-up as we know that aneurysm occlusion after flow diversion is a progressive process that improves as time goes on. In summary, if we look at these papers on posterior circulation flow diversion, we can make some important conclusions. This is the very first paper that was published in JNS. I had referenced that at the beginning of the presentation. What you could see is that complete occlusion rate was less than desirable, thromboembolic complications were also fairly significant compared to our most recent paper that included aneurysms between 2012 and 2019 and did not include very early aneurysm treated with pipeline immobilization device. You can see that the morphology of these aneurysms is fairly equivalent, but the complete occlusion rate already pretty significantly had improved and the complication rate had significantly decreased. When we compare this to another paper that we had worked on and published recently looking at the FRET device in the posterior circulation, we can also see that complication rates decreased and occlusion rates increased, which provides additional evidence that this treatment has gotten safer as time has gone. In terms of the summary, I would like to say that there are some important aspects for successful flow diversion of posterior circulation aneurysms. That includes the treatment of not acutely symptomatic lesions using as few devices as possible, deliberate use of adjunctive coiling, and the role of platelet function testing still remains to be determined. I would like to acknowledge and thank our contributors from the other sites and thank you for your attention.

Christoph Griesenauer

pipeline immobilization device

posterior circulation aneurysms

multicenter cohort study

saccular and non-saccular aneurysms