Endovascular treatment of ruptured distal anterior cerebral artery aneurysm
Correspondence Address: Source of Support: Key Project from the Shanghai committee of Science and Technology (074119506) and Grant of National Natural Science Foundation (30901556), Conflict of Interest: None DOI: 10.4103/0028-3886.63809
Source of Support: Key Project from the Shanghai committee of Science and Technology (074119506) and Grant of National Natural Science Foundation (30901556), Conflict of Interest: None
Background: Distal anterior cerebral artery (DACA) aneurysms are less common, accounting for 3.1 to 9.2% of all intracranial aneurysms.The clinical characteristics and surgical techniques are quite different from those of other aneurysms of Willis circle. Objective: We aimed to investigate the clinical and radiographic characteristics of ruptured distal anterior cerebral artery (DACA) aneurysms and the efficacy of endovascular treatment for these lesions. Patients and Methods: From 1998 to 2008, 41 patients with 44 DACA aneurysms were treated by endovascular coiling, including parent vessel occlusion using coils or coils combined with n-butyle-2-cyanoacrylate (NBCA) in two, endosaccular coiling alone in 39, and stent-assisted coiling in three. Results: Technical success was achieved in 40 (97.6%) patients. Among the 41 aneurysms successfully treated with endosaccular coiling or stent-assisted coiling, complete occlusion was obtained in 37, neck remnant in two, and partial occlusion in two. Two patients with poor pretreatment conditions died of cerebral vasospasm. The morbidity was 4.87%. One case each of unruptured recurrence and rebleeding were seen in follow-up DSA of 34 patients and MRA in five cases. Conclusion: Our preliminary results show that endovascular treatment for DACA aneurysms is safe and effective. However, the relative high recurrent rate highlights long-term follow-up for its security.
Keywords: Cerebral aneurysm, coil, embolization, endovascular treatment, stent
Distal anterior cerebral artery (DACA) aneurysms, located distally to the anterior communicating artery on the A2-A5 segment of the anterior cerebral artery (ACA) are less common, accounting for 3.1 to 9.2% of all intracranial aneurysms. , The clinical characteristics and surgical techniques are quite different from those of other aneurysms of Willis circle.  With further improvement of flexibility and maneuverability of micro catheter, mini-invasive endovascular embolization for DACA aneurysm is becoming safer and more effective.  Nonetheless, endovascular series on DACA aneurysms published so far are relatively small. This paper reports our experience of endovascular treatment of ruptured DACA aneurysms in 41 patients. We emphasize on the efficacy of endovascular treatment and the management strategy.
From October 1998 to December 2008, endovascular treatment was employed for 44 DACA aneurysms in 41 patients of a series of 1435 consecutive patients with ruptured aneurysms. We retrospectively reviewed the medical records, angiograms, and endovascular procedure reports of these 41 patients to determine the anatomic features, technical result, periprocedural complications, Hunt-Hess Grade, and clinical outcome defined by the Glasgow outcome scale (GOS). The Institutional Review Board at our institution has approved the retrospective review of the data in all patients.
There were 14 men and 27 women with the mean age of 50 years (range 27 to 76). The diagnosis of subarchnoid hemorrhage (SAH) was determined by computed tomography (CT) scan, which showed significant lateralized intraparenchymal hematomas in 12 patients. According to Hunt and Hess Grading, there were 18 patients in Grade 1,13 in Grade 2, five in Grade 3, three in Grade 4 and two in Grade 5. Traumatic pseudo aneurysm was confirmed in two patients. In one patient with SAH the result of digital subtraction angiography examination at 48 hours after onset was negative. However, a tiny DACA aneurysm was found in DSA done one month later.
Morphology of aneurysms
Aneurysm fundus and neck size were taken at the point of maximum width or length. The aneurysms were divided by fundus size into four categories: 13 tiny aneurysms (under 3 mm), 25 small aneurysms (3 to under 10mm), four large aneurysms (10 to under 25mm), and two giant aneurysms (over 25mm). The mean size was 6.3 mm and no branch originated from any of the aneurysms. The wide-necked aneurysms were defined as neck size greater than 4 mm and/or a fundus-to-neck ratio less than 2. There were 14 wide-necked aneurysms, accounting for 31.8%. Partial intrasaccular thrombosis was demonstrated on MR scan in all six patients with large or giant aneurysms. According to the location of aneurysmal neck, there were seven aneurysms in A2 segment, 25 in A3 segment, seven in A4 and five in A5 segment. Variations of the DACA anatomy were noted in 12 patients (29.3%), including azygous ACA in six, common origin of bilateral paracentral artery or superior parietal artery in four, and crossover of branches from one to the other hemisphere in two. Two patients experienced an SAH resulting from posttraumatic DACA aneurysms. Both of them had a severe head injury in two weeks before the SAH. There were multiple aneurysms in 11 patients (26.8%), including two or more DACA aneurysms in three and associated aneurysms in other eight.
All procedures were performed under general anesthesia. From 1998 to 2001, only conventional intra-arterial DSA was used for aneurysm embolization. Since 2002 rotational DSA and 3D reconstruction have been routinely used in all the patients. After systemic heparinization, a guiding catheter (Envoy, Cordis; Fasguide, Boston Scientific) was placed in the distal internal carotid artery (ICA) to obtain a stable position. Endovascular treatment was carried out utilizing techniques as previously outlined in other publications. When the micro catheter tips were advanced, the aneurysms were packed using softer coils. Beginning in 2003, Neuroform stents (Boston-scientific) were used in three patients to reconstruct the aneurysm neck or reduce the risk of coil protrusion into parent vessels. For neuroform stenting, a 300cm 0.014-inch micro-guidewire was introduced distal to the aneurysm neck, with the help of a suitable micro catheter. The neuroform stents were advanced over the micro-guidewire and deployed when the precisely targeted location was confirmed. At the end of coiling, an image was acquired to confirm adequate coiling.
All patients received systemic heparinization throughout the procedure. The activated clotting time (ACT) is maintained at two to three times the baseline throughout the procedure. After stenting, low-molecular-weight heparin was subcutaneously injected for three days as a matter of routine. In patients who experienced SAH within 72 hours, 300mg clopidogrel and 300mg aspirin were administered rectally at two hours before stenting. All the patients were maintained on aspirin and clopidogrel for six weeks, followed by aspirin alone, which was continued indefinitely.
Clinical and angiographic follow-up
There was no strictly defined follow-up protocol. Patients were advised to come for follow-up visits at the end of 1, 3, 6, and 12 months, and yearly thereafter; angiogram was advised after six months to assess the status of the treated aneurysm. However, for aneurysm with partial or near complete occlusion, the first angiographic follow-up was carried out, one to three months after treatment. Angiographic images were reviewed independently by two authors (HQH and XY) to determine the degree of obliteration of the aneurysm immediately post procedure and at follow-up.
In 40 (97.6%) of the 41 patients, primary occlusion of DACA aneurysm was successful. Among 11 patients with multiple aneurysms, eight were treated in one session; three required two sessions to complete treatment. For a total of 44 endovascular procedures, stent-assisted technique was used in three procedures. One patient could not be successfully coiled because of the broad aneurysmal neck, which was treated by surgical clipping. In two patients with traumatic aneurysms, the aneurysms and parent vessels were occluded using coils alone or combined with glue.
Patients were evaluated by angiography at the end of the procedure to document aneurysm obliteration. Angiographic results were classified as complete occlusion (no contrast filling the aneurysmal sac), neck remnant (residual contrast filling the aneurysmal neck), and incomplete occlusion (residual contrast filling the aneurysmal body). According to modified Raymond scale,  the immediate post procedural angiogram in 41 aneurysms treated by endosaccular coiling showed complete occlusion in 37 (90.3%, 33 of 34 small aneurysms, three of four large aneurysms, and one of two giant aneurysms), neck remnant in two, and partial occlusion in two.
Immediate and follow-up clinical outcome
Two patients died of severe cerebral vasospasm, one with Hunt-Hess Grade 4 and the other with Grade 5. Totally, the mortality and morbidity rates were 4.9%, retrospectively. All 39 patients were evaluated clinically before hospital discharge by use of the GOS. Among these patients, 35 (89.7%) were classified as having a GOS score of 5, 2 (5.1%) as a GOS score of 4, and 2 (5.1%) as a GOS score of 2. Follow-up clinical outcomes were obtained in 38 (97.4%) of the 39 patients. One patient who lost follow-up was classified as having a GOS score of 5 at discharge. During the follow-up period varying from six to 108 months (mean, 27.5 mos), the GOS score was 5 for 34 patients (89.5%), 3 for three patients (7.9%), and 2 for one patient (2.6%). There was one case of new SAH due to rupture of recurrent aneurysms.
Of the 43 embolized aneurysms, including 41 treated with endosaccular coiling and two with parent vessel occlusion, 34 were followed up angiographically for a median of 10.7 months (range 3-28 months). Sustained stable aneurysm occlusion was achieved in 30 patients, further endosaccular thrombosis with partial occlusion or neck remnant in two patients. One aneurysm recanalized at six months follow-up, which was re-embolized using coil packing alone. One patient experienced rebleeding at three years after first embolization. And recanalization was confirmed in DSA. The patient was treated by surgical clipping and hematoma removal. Among the other nine patients unavailable for DSA follow-up, five have contrast-enhanced MRA follow-up (4-36 months) with no obvious recanalization. Totally, the recanalization rate was 5.1% for all followed-up patients.
Two patients experienced aneurysm perforation during the procedure. The bleeding was controlled by further coiling and heparin reversals with protamine sulphate. And one died of severe cerebral vasospasm. For patients treated by endosaccular coiling, there was no procedure-related thrombo-embolic event.
Distal anterior cerebral artery is an uncommon location of intracranial aneurysms. However, for surgical clipping or endovascular treatment of DACA aneurysms, they show some unique features compared with other aneurysms in the cerebral circulation, including small size, broad base with originating branches, association with anterior cerebral artery (ACA) anomalies, and multiple aneurysms. ,,, The surgical clipping for DACA aneurysms is difficult, because of narrow operative field, protection of bridge veins, and interhemispheric adhesions.  Although some authors advocated open surgery for DACA aneurysms with intraparenchymal hematoma, most associated aneurysms cannot be reached simultaneously from one approach, so we tried to treat all DACA aneurysms with endovascular interventions, except extremely wide-neck small aneurysms. However, the neck was wider than the parent artery in 68% of the aneurysms in our series. And the fundus-to-neck ratio was less than 2 in 14 patients. The size was smaller than 5 mm in 50% of the aneurysms. At the same time, ACA anomalies were found in 29.3% of all patients. All these findings suggest that it will be difficult to occlude DACA aneurysms completely without compromising the patency of either the parent artery. In addition, in patients with ACA anomalies, damage to the parent artery of occlusion of the branches at the neck is likely to result in large, bilateral, ischemic complications.
Endovascular embolization using detachable coils has emerged as a safe and effective treatment option for intracranial aneurysms.  However, the endovascular treatment for DACA aneurysms was thought to be very difficult.  The technical difficulties include micro catheter navigation resulting from distal position of aneurysms, and higher proportion of small and wide-necked complex which makes it difficult for dense packing without neck remodeling technique. With the development of devices and techniques, successful treatment of DACA using coil embolization was reported in some literature. The success rate was 97.6% in our series, with a dense packing rate of 90.3%. Pandey et al. report their single center experience of endovascular treatment for DACA aneurysm in 28 cases. Their success rate was 89%, lower than that of our cases. This may be related to the sole coiling technique used in their series. 
In terms of embolization techniques, it is very important to place the guiding catheter further distal into the internal carotid artery for increasing stability of the micro catheter because of the distal location and tortuous vascular pathways. Since the majority of DACA aneurysms are small and fragile, the microcatheters with extremely fine tips should be shaped based on the morphology of aneurysms and parent vessels. Accurate shaping of micro catheter is the key to a satisfactory embolization. And soft or ultrasoft coils were used to avoid uncontrolled changes of the position of the catheter tip during the coiling procedure [Figure 1].
The application of a variety of assistive techniques has made it possible to obtain satisfactory embolization for the majority of wide-necked aneurysms. However, the endovascular treatment for such lesions in DACA still remains technical challenging. Because of the concerns about whether the stent can be advanced to distally targeted position and the long-term safety of stenting in small vessels, there were very limited reported lectures of stent-assisted embolization for DACA aneurysms.  Currently, the self-expanding nature, micro-delivery property and low profile of Neuroform make it more flexible and easier to be navigated to target lesions farther in the smaller and distal cerebral vessels.  As demonstrated in our cases, the Neuroform stent was successfully navigated to the targeted location. And during the long-term angiographic follow-up, further thrombosis in aneurysm sac and no in-stent stenosis were confirmed [Figure 2].
Although the literature published in recent years show that surgical treatment of DACA aneurysms can achieve satisfied clinical outcomes, for cases in a critical condition, the mortality rate is still high.  As showed in this series, two of five patients with Hunt-Hess grade IV-V died after treatment. For DACA aneurysms, there are still two issues to be determined, including the surgical timing and the impact of ICH on clinical outcomes. The success rate of endovascular treatment depends on the vascular approach. Cerebral vasospasm may be mild or moderate in early stage after SAH, which may facilitate the access of microcatheters. In addition, early treatment to control aneurysmal rebleeding allows more positive prevention and management of cerebral vasospasm. From this point of view, all the ruptured DACA aneurysms should be treated in acute stage. However, the outcomes of DACA aneurysms management are closely related to preoperative clinical status. And the neurological results depend on the combined intracerebral hematoma, especially the preoperative neurological symptoms and lower limb paralysis. Unlike surgical clipping, endovascular treatment can't directly remove the intracranial hematoma and eliminate the symptoms of increased intracranial pressure. And whether this will affect the clinical curative efficacy of endovascular treatment for DACA aneurysms needs further study.
It is worth noting that rebleeding rate after treatment of distal anterior cerebral was higher than in other aneurysms, regardless of surgical clipping or endovascular treatment. , In our series, no early rebleeding occurred after endovascular coiling. Although some reports in the literature showed the probability of rebleeding after partial embolization which is similar to the natural history of unruptured aneurysms, we still emphasize the necessity to achieve the maximal coil packing in order to prevent rebleeding or recanalization. Both the recurrence rate and retreatment rate in our cases are 5.1%. It is thought to be related to misjudgment of the size of aneurysms caused by hematoma around the aneurysms, as well as technical difficulty in dense embolization resulting from a higher proportion of small, wide-necked aneurysms. This also highlights the importance of close long-term radiographic follow-up after interventional therapy of DACA aneurysms. There are some limitations to this study, including the retrospective nature of the study and single-arm design, limited cases in one institution and the inadequate angiographic follow-up.
[Figure 1], [Figure 2]