2.1 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 classification 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 classification, we summarized two major types of perforator preservation technologies (PPT). It is mainly a coil-basket 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 definitely be affected. We choose different diameters coils to densely embolize the aneurysm cavity, and the aneurysm neck near the perforator originating is loosely filled, 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 flow as much as possible while protecting the perforating artery.
2.3. Procedural assessment and follow-up
Usually the Raymond–Roy Occlusion Classification (RROC) qualitatively assesses intracranial aneurysm occlusion following endovascular coil embolization. The Modified Raymond–Roy Classification (MRRC) was developed as a refinement of this classification 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 definition of satisfactory obliteration based on our new classification 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 flow 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 defined as keeping good antegrade flow 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.