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|Year : 2019 | Volume
| Issue : 5 | Page : 1264-1265
Management of A1 Aneurysm: A Critical Appraisal
Consultant Neurosurgeon, Manipal Hospitals, Old Airport Road, Bangalore, Karnataka, India
|Date of Web Publication||19-Nov-2019|
Dr. Paritosh Pandey
Consultant Neurosurgeon, Manipal Hospitals, Old Airport Road, Bangalore, Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Pandey P. Management of A1 Aneurysm: A Critical Appraisal. Neurol India 2019;67:1264-5
Aneurysms arising from the pre-bifurcation (A1) segment of the anterior cerebral artery are rare aneurysms, often presenting with subarachnoid hemorrhage or intracerebral hemorrhage of smaller sizes, and having a myriad of etiologies. These are a unique group of aneurysms, because there are very few branches in this segment of ACA, some of these aneurysms are related to lenticulostriate arteries or small perforators, and some of the aneurysms are of blister or dissecting variety. Many factors are associated with the treatment of these aneurysms, mainly the type of aneurysm, angio-architecture, relationship with branches, presence of contralateral ACA and A com artery, and availability of facilities, especially endovascular. Surgical clipping, coiling, parent vessel occlusion, bypass and trapping, and flow diversion are the options for different kinds of A1 segment aneurysms, depending on the morphology and the location of aneurysm.,,, The author's publication of their experience of 7 patients with A1 aneurysms is a welcome addition to the existing body of literature in these rare lesions.
The authors present their experience of 7 patients with A1 aneurysms, which were clipped. All these patients presented with SAH/ICH, while one of the patients presented with neurological deficit secondary to vasospasm. Most of these aneurysms were small in size, and directing posteriorly. All of them were clipped uneventfully, and 6 out of 7 patients did well at follow-up. Notably, none of these patients were treated by endovascular route, the cause of which is not mentioned in the paper. As expected, there were morphological variations in the form of contralateral A1 hypoplasia, azygos ACA and fenestration of the A1 segment. Contralateral A1 hypoplasia is a common anatomical finding though, and is also commonly seen in patients with A com aneurysm. As expected, clipping of posteriorly pointing, or postero-inferiorly aneurysms was technically challenging, because the parent vessel would come in the way of clipping the neck of the aneurysm. In many instances, a clip parallel to the parent vessel is the best clipping technique, to avoid kinking of the vessel. Most importantly, the perforators arising from the ACA should not be caught in the clip, or else there is a risk of lenticulostriate territory infarct. Once clipped, these patients have the usual risk of vasospasm, which was there in one patient.
As mentioned by the authors, there have been many other reports of A1 aneurysms in the literature. One of the largest series was reported by Ding. et al., where they reported 42 patients with A1 aneurysm who were treated either with open surgery or coil embolization. They classified the aneurysms into three types. Type I was in the proximal segment, pointing postero-inferiorly (IA), postero-superiorly (IB) or anteriorly (Ic). These aneurysms were both clipped or coiled, with good results. Type II aneurysms arose from the distal trunk of the A1 segment, type IIA being from an abnormal cortical branch or a fenestration, while IIb from anywhere in distal segment. Type III aneurysms were dissecting or fusiform aneurysms, and were better treated with endovascular techniques. This classification is useful for management of these aneurysms. In this series, 6 of the aneurysms were of Type 1, while one was of type II, according to this classification.
As with surgery, there have been advances in endovascular treatment in aneurysms of all the locations, and A1 segment is no exception. There are legitimate concerns regarding the treatment of A1 aneurysms by coiling. Some of these concerns are involvement of lenticulostriate arteries in the aneurysm, broad neck, small size, usage of stents and others. However, there is an increasing body of literature of endovascular treatment of A1 segment aneurysms with good results. Alurkar, et al., presented their experience of 5 patients with A1 segment aneurysm. Four of them were treated with simple coiling, while the fifth patient had a dissecting fusiform A1 aneurysm and was treated with stent-assisted coiling. Chang, et al., described their experience with 12 patients (3 ruptured, 9 unruptured) with A1 aneurysm, all of which were treated with coil embolization. Despite having peri-procedural complications in 3 patients, all of them had good outcome without any neurological deficits. Xiaochuan, et al., described their experience with 15 unruptured A1 aneurysms, who were treated with coil embolization. Five of these were treated with balloon or stent assistance. All the patients had an excellent outcome with coil embolization. Hence, it is prudent to offer endovascular treatment to patients with A1 aneurysm, and would have good results in well selected patients. There are some occasions when parent vessel sacrifice is done through endovascular route, with good outcomes. Krafft, et al., reported a patient with a giant serpentine A1 segment aneurysm, presenting with visual deficits. Angiographic cure, and good visual outcome was achieved with parent vessel occlusion through endovascular route, because there was a good A1 and robust A com artery on the contralateral side.
Blister and dissecting aneurysms are rarely reported in the A1 segment, and can be devastating, owing to the high incidence of rebleed in them, and difficulty in treating them by either surgical or endovascular route. Different methods have been described to treat these aneurysms. Rajah, et al., described a case of blister aneurysm of the A1 segment, which was treated with surgical clipping. In these patients, it is prudent to put a clip parallel to the artery, preferably after reinforcing it with muscle or muslin. In today's endovascular era, a short flow diverter is also a good alternative for these aneurysms, though the placement without covering the MCA and A com might be difficult. Parent vessel occlusion is also an option, if there is a robust ACA and A com on the other side. Mitsuhara et al., presented 3 patients with ruptured dissecting aneurysms, 2 of which were clipped, while one of them rebled before any intervention could be done. Uozomi et al., however advocated revascularization, with STA to ACA bypass, and trapping of dissecting aneurysms, citing high incidence of rebleeding after simple clipping in these diseased vessels. Both these examples of complicated aneurysms, and should be managed in a comprehensive cerebrovascular center, with the availability of all kinds of expertise.
In conclusion, A1 segment aneurysms are a separate category of aneurysms, which can be treated either by open surgery, or endovascular coiling. The angiographic morphology, pathophysiology of the aneurysm, ruptured versus unruptured status, and presence of branches and contralateral A1/A com are important decision making factors for choosing the treatment.
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