Perforator Preservation Technologies (PPT) Based on a New Neuro- interventional Classi cation in Endovascular Treatment of Perforator Involving Aneurysms (piAN)

Chen Li The PLA Rocket Force Characteristic Medical Center Ao-Fei Liu The PLA Rocket Force Characteristic Medical Center Han-Cheng Qiu The PLA Rocket Force Characteristic Medical Center Xianli Lv Tsinghua Changgung Hospital, School of Clinical Medicine Ji Zhou The PLA Rocket Force Characteristic Medical Center Yi-Qun Zhang The PLA Rocket Force Characteristic Medical Center Jin Lv The PLA Rocket Force Characteristic Medical Center Ying-Ying Zhang The PLA Rocket Force Characteristic Medical Center Sushan Hu The PLA Rocket Force Characteristic Medical Center Fang Liu The PLA Rocket Force Characteristic Medical Center Yun-e Liu The PLA Rocket Force Characteristic Medical Center Min Jin The PLA Rocket Force Characteristic Medical Center Wei-jian Jiang (  jiangweijian2018@163.com ) The PLA Rocket Force Characteristic Medical Center


Background
The standard methods of treatment for intracranial aneurysms are surgical clipping and endovascular treatment, both of which are very mature 1,2 . However, treatment of perforator involving aneurysm (piAN) remains a challenge to open and endovascular neurosurgeons 3,4 . Because the success of aneurysm surgeries lies in the complete clipping of the aneurysm neck and in the preservation of branching and perforating arteries 3 . The same is true for endovascular treatment of intracranial aneurysms. Injury to perforating arteries has always been one of the major causes of postoperative morbidity in aneurysm treatment 4 . Under the premise of ensuring complete treatment of aneurysm neck, better techniques are needed to protect the perforators. Researchers try to classify piANs and formulate corresponding treatments to improve the success rate of surgery. Satti et al. proposed a three-point classi cation based on the exact anatomical origin of basilar artery perforator aneurysms (BAPAs), and present this unique classi cation system to enable future papers to standardize descriptions: Type I -the aneurysm arises from the basilar trunk adjacent to the perforating arterial branch but not involving a perforating artery; Type IIaaneurysms incorporating the origin of the perforating arteries; Type IIb -aneurysms having the perforating artery arising from the dome of the aneurysm; Type III -fusiform aneurysms arising beyond the parent vessel (basilar artery). 3,4 However, this classi cation method is only applicable to BAPAs, not completely applicable to all intracranial piANs. We improved the classi cation method based on the characteristics and feasibility of interventional therapy and also proposed some perforator preservation technologies (PPT) on basis of this classi cation, which can protect the blood supply of the perforator artery on the premise of ensuring the satisfactory aneurysm packing. Here we report the preliminary treatment results.

Patient population
From November 2017 to July 2019, 6 consecutive patients with 6 piANs received endovascular treatment in our center. All of the demographic data, clinical presentation, aneurysm size and location, therapeutic intervention, immediate angiographic and clinical result, as well as clinical and radiological follow-up information were recorded and analyzed.
We proposed a three-point classi cation based on the anatomy relationship between aneurysms and perforating arteries after summarizing the characteristics of these piANs Type I -aneurysm arises from the perforating artery Type IIa -aneurysms having the perforating artery arising from the neck of the aneurysm Type IIb -aneurysms having the perforating artery arising from the dome of the aneurysm Type III -fusiform aneurysms involve all trunk and perforating branches of the parent artery 2.2 Endovascular treatment All patient's pre-medication was given orally doses of aspirin (100 mg) and Clopidogrel (75 mg) every morning for at least 4 days prior to the operation. The post-procedural antiplatelet regimen consisted of aspirin (100 mg once daily) and Clopidogrel (75 mg once daily) continued for 3 months following treatment and aspirin (100 mg once daily) continued for life. All 6 patients received intravascular treatment and all the treatments were performed under general anaesthesia. All procedures were performed via the right common femoral route using a 6Fr access system as standard. All procedures were performed under heparin anticoagulation with a 3000 IU bolus dose at the start of the procedure and subsequent 1000 IU bolus doses every hour to maintain the activated clotting time between 2 and 2.5 times the baseline. The selection of stents and coils was based on operator preference as well as the size of the aneurysms and parent vessels.
Based on the above-mentioned aneurysm classi cation, we summarized two major types of perforator preservation technologies (PPT). It is mainly a coilbasket protection technology, and the other is a stent protection technology. Use different protection techniques to develop a personalized surgical plan.
Type I aneurysms arise from the perforating artery. However, the diameter of the perforator is usually very small, and it is not easy to release the stent in the perforator. We can place a braided stent on the main parent vessel and push the stent when it is adjacent to the perforating artery, which is commonly called the lantern technique to protect the starting lumen of the perforating artery.
Type IIa aneurysms having the perforating artery arising from the neck. If the neck of the aneurysm is densely packed conventionally, the perforating artery will de nitely be affected. We choose different diameters coils to densely embolize the aneurysm cavity, and the aneurysm neck near the perforator originating is loosely lled, leaving a little space to ensure blood supply to the perforating artery.
Type IIb aneurysms have the perforating artery arising from the dome of the aneurysm. If all the aneurysm body is packed densely, it will lead to occlusion of the perforating artery. We still use different diameters coils to embolize the main part of the aneurysm body, leaving a certain space at the dome of the aneurysm.
Type III fusiform aneurysms involve all trunk and perforating branches of the parent artery. We implant multiple stents in dissection to block blood ow as much as possible while protecting the perforating artery.

Procedural assessment and follow-up
Usually the Raymond-Roy Occlusion Classi cation (RROC) qualitatively assesses intracranial aneurysm occlusion following endovascular coil embolization.
The Modi ed Raymond-Roy Classi cation (MRRC) was developed as a re nement of this classi cation scheme(Class I: complete obliteration; Class II: residual neck; Class IIIa: residual aneurysm has contrast within the coil interstices; Class IIIb: contrast along the aneurysm wall). 5,6 However, MRRC does not seem to be suitable for the assessment of satisfactory embolization of perforator involving aneurysms. Here we propose a new de nition of satisfactory obliteration based on our new classi cation and perforator preservation technologies (PPT) for perforator involving aneurysms: Type I: The whole saccular aneurysm body is densely embolized which arises from the perforating artery; Type IIa -The saccular aneurysm body is densely embolized leaving a gap in the neck where the perforating artery arising from; Type IIb -The saccular aneurysm body is densely embolized leaving a gap in the dome where the perforating artery arising from; Type III -Fusiform aneurysm is repaired and has a smooth inner wall; Immediate outcome of aneurysmal obliteration after treatment was evaluated. Patency and ow characteristics within the aneurysm and parent artery were also assessed immediately after treatment of the aneurysms and during follow-up. Successful perforating artery preservation was de ned as keeping good antegrade ow of those perforators on postoperative angiography. All of the complications during the perioperative period, clinical data during follow-up and imaging results were recorded and analyzed. Procedural follow-up was performed initially at 1-3 months, again at 6-12 months and then once per year.
Standard angiographic projections were used to assess the patency of the vessels and the aneurysms. 3. Results 6 patients ranged in age from 43 to 66 years old. Half of the patients were male (n = 3, 50%). Each patient had a single aneurysm and there were no aneurysms identi ed elsewhere in the intracranial circulation. The size of the aneurysms was listed in Table 1. According to the classi cation of our unique classi cation of piAN one aneurysm were classi ed as type I, two as type IIa, two as type IIb and the remaining one aneurysm was classi ed as type III. Two of the piANs were ruptured and the remaining four aneurysms were unruptured. All 6 patients received intravascular treatment and the operations were very successful. Four patients with piANs had used coil-basket protection technology, and the other two patients had used the stent protection technology. All perforating arteries involved by piANs were successfully preserved. All patients had no cerebral hemorrhage or infarction caused by occlusion of perforating artery during perioperative period. Only one patient developed TIA symptoms 4 hours after surgery, mainly manifested as motor aphasia and di culty in expression. Postoperative head MRI revealed no infarcts. The symptoms were completely relieved in 24 hours. There was no evidence of perforator infarction on the follow-up post treatment imaging. The clinical follow-up time distribution of 6 patients ranges from 12 months to 50 months. Clinical follow-up data was available in 6 patients all achieving a good outcome (mRS ≤ 2) (100%).The results are summarised in Table 1.

Discussion
In this study, we proposed a unique three-classi cation method of piAN and perforator preservation technology. 6 patients with piANs were received endovascular therapy based on this new classi cation method and perforator preservation technology. All of 6 aneurysms obtained satisfactory obliteration; and all of their perforating arteries were successfully preserved. In terms of safety, only one patient developed ischemic event in the territory of involving perforators 4 h after operation, and completely resolved within 24 h. Follow-up angiography also showed patency of the parent artery and perforating arteries of treated aneurysms, with no aneurysmal recurrence.
Usually, treatment for intracranial aneurysms is done to achieve complete occlusion of the aneurysm without a remnant sac 7 . However, a large part of the complications in the treatment of aneurysms are due to the excessive pursuit of complete occlusion of the aneurysm and neglect of the protection of the peripheral perforating artery 8 . Such perforator involving aneurysms (piAN) are not uncommon in intracranial aneurysms due to the anatomical characteristics of intracranial vessels. 1 Pritz. et al found that perforators were present in 7% of basilar artery (BA) bifurcations, 17% of internal carotid artery (ICA) bifurcation aneurysms, 12% of middle cerebral aneurysms, and 11% of anterior communicating aneurysms 2 . Thus, preserving blood ow in the branches and perforators of a parent artery is very important for successful treatment of piAN without postoperative morbidity and mortality 9,10 . How to avoid this kind of situation is paid more and more attention by surgeons, and constantly improve the surgical skills and methods to protect the blood supply of the perforating artery [11][12][13] .
Sung-Pil Joo. et al discussed the consequences of perforator injury and how to avoid this phenomenon in aneurysm surgeries using intraoperative monitoring devices 1 . For surgical open craniotomy, the perforating artery can be observed under direct vision, and the damage to the perforating artery can be avoided by improving the shape of the aneurysm clip or the direction of the aneurysm clip.
However, there are still few scholars conducting research to propose how to protect the perforating artery in interventional treatment of intracranial aneurysms. [14][15][16] The advantage of interventional therapy is that it can intuitively observe the blood supply of the perforating artery. Our three-point classi cation is based on the anatomical relationship between the perforator artery and aneurysm which was rst proposed. This classi cation method is more suitable for the endovascular treatment of piANs. We proposed two major perforator preservation technologies (PPT) based on this classi cation for the rst time to help neurointerventional doctors to develop better surgical plans.
However, the classi cation and technologies we proposed still have certain aws. Because we are still in the exploratory stage and the number of piAN cases enrolled in our center is still small, the two types of perforator preservation technology (PPT) based on our unique classi cation may not necessarily meet all piANs. Perhaps there are some complex piANs that cannot be classi ed in our proposed classi cation. Maybe some piANs need to combine two protection technologies, and even need to design new perforator preservation technology to treatment. We proposed a unique three-classi cation method of piAN and perforator preservation technology and hoped to provide new ideas for the neurointerventionists. In the future case expansion and exploration, we hope to continuously improve the new classi cation method and perforator preservation technology to treat piANs.

Conclusion
Page 5/8 The primary results showed that, our perforator preservation technologies on basis of the new neuro-interventional classi cation seems to be feasible, safe and effective for endovascular treatment of perforator involving aneurysm. It helps to evaluate the surgical risk and design an appropriate surgical plan, and new ideas are provided for the interventional treatment of the perforator involving aneurysms.  Figure 1 Our unique three-point classi cation based on the anatomy relationship between aneurysms and perforating arteries Type I -aneurysm arises from the perforating artery; Type IIa -aneurysms having the perforating artery arising from the neck of the aneurysm; Type IIb -aneurysms having the perforating artery arising from the dome of the aneurysm; Type III -fusiform aneurysms involve all trunk and perforating branches of the parent artery