Endovascular Management of Distal ACA Aneurysms: Single-Institution Clinical Experience in 22 Consecutive Patients and Literature Review

Evolution of Endovascular Management of Distal ACA Aneurysms

In the 1990s, favorable results from centers experienced with microsurgical clipping, combined with the low incidence of distal ACA aneurysms, discouraged early referrals for endovascular care. Moreover, the peripheral location of distal ACA aneurysms and their small size precluded successful treatment by endovascular means with the use of developing technology.^12,15 Pierot et al¹² pioneered the endovascular management of 8 cases of distal ACA aneurysms in 1996, but embolization was successful in only 25%. Although based on a small series, Menovsky et al¹⁰ first proposed coiling distal ACA aneurysms as an alternative to clipping. Initial complete occlusion was obtained in 91.7% of their 12 cases. At last follow-up, 66.7% of the aneurysms remained completely occluded, no patient had again presented with bleeding, and 91.7% of the patients achieved a GOS score of 5 (Table 1). In a large microsurgical series primarily composed of patients with a good clinical grade, 83% of the patients with a ruptured distal ACA aneurysm had a favorable GOS score, and the mortality rate was 7.7% (Table 2).¹ Although our follow-up was limited, periprocedural occlusion rates in our series compare well against historical controls. Of 22 patients, 11 (50%) experienced complete occlusion and another 10 (45%) had near-complete occlusion. Furthermore, there were no periprocedural deaths and only 1 instance each of intraprocedural rupture and retroperitoneal hematoma formation. Thromboembolic events were treated successfully with abciximab infusion in 4 patients.

Nguyen et al¹⁷ pointed out the caveat that the rate of intraprocedural rupture was higher when these lesions were coiled, compared with coiled aneurysms located elsewhere. They reported 3 perforations in 25 patients undergoing endovascular management of distal ACA aneurysms and suggested that the small size and distal distribution of the aneurysms could explain the high rate of rupture.¹⁷ Overall, in 7 endovascular series that enrolled 160 patients, including the current series, intraoperative rupture occurred in only 5.6%.^{10,13,15⇓⇓–18}

Recurrences

Nguyen et al¹⁷ emphasized the recurrence rate of coiled distal ACA aneurysms, though the rate was not significantly higher than that for intracranial aneurysms coiled elsewhere. The cumulative rate of distal ACA aneurysm recurrence was 52.6%. A major recurrence, an event leading to retreatment, was observed in 21%. Pandey et al¹⁶ reported an 18% recurrence rate at a mean follow-up of 16.5 months. In a similar circumstance, Waldenberger et al¹⁵ identified a recurrence in 17.2% of patients at 6-month follow-up examination. Although it is difficult to draw strong conclusions on the basis of the length of follow up, we observed aneurysm regrowth in 2 patients (15.4%) at a mean follow-up of 15 months. Both of our patients underwent coiling again, and the aneurysms remained completely obliterated.

At a mean follow-up of 12.3 months, Raymond et al²⁰ found recurrences in 33.6% of 381 intracranial aneurysms at various sites after endovascular treatment. They stressed that a main factor involved in recurrence, besides the initial occlusion rate and rupture, is the large size of an aneurysm (an infrequent feature of distal ACA aneurysms).²⁰ Furthermore, the ISAT showed that the clinical implications of recurrences are unknown.^7,21,22 For comparison, Tsutsumi et al²³ found regrowth in 2.3% of 220 patients undergoing initial complete surgical obliteration of an intracranial aneurysm at a mean follow-up of 10 years. A review of 147 consecutive surgically treated aneurysms at our institution revealed a recurrence in 1.5% of completely obliterated aneurysms, but a regrowth occurred in 41.7% of those in which a neck remnant was observed on initial postoperative angiography.²⁴ A neck remnant may lead to aneurysm regrowth, but its presence may not necessarily be indicative or predictive of an aneurysm that is unsecured or is more likely to rupture than a completely occluded aneurysm. The risk for subarachnoid hemorrhage from a neck remnant remains unclear.

Immediate Occlusion Rates in Microsurgical Series and Subsequent Rebleeds

In 1999, de Sousa et al¹ observed an impressive 100% rate of complete occlusion on routine postoperative angiography after treating 74 distal ACA aneurysms with surgery, though their long-term follow-up was limited. Lehecka et al¹⁹ reported a satisfactory occlusion rate of 95% of 362 patients undergoing microsurgical treatment. In microsurgical clipping, recurrent subarachnoid hemorrhage can affect 2.7% of patients with complete occlusion of an intracranial aneurysm.²³ An identical rebleed rate was found in 43 patients in a surgical series focusing specifically on distal ACA aneurysms.² In a large series of 262 clipped distal ACA aneurysms, the rebleeding rate was only 0.4%.²⁵ Although immediate complete occlusion with clipping occurs at an incredibly high rate, the rate of immediate occlusion with coiling, whether complete or near-complete, was more than 95% in this series and compared favorably with previous reports (Table 2).

Clinical Outcomes in Endovascular and Microsurgical Series, Focusing on Distal ACA Aneurysms

In 1999, Vanninen et al²⁶ reported the first randomized prospective study comparing endovascular treatment of ruptured intracranial aneurysms with surgical clipping. A late analysis at 12 months showed no significant difference in the clinical outcomes of both groups managing ACA aneurysms, but the procedure-related mortality rate was higher among patients undergoing surgical clipping.

The endovascular group in the ISAT had better outcomes, even after 7 years of follow-up.²⁷ However, this finding could not be generalized to a specific type of aneurysm such as distal ACA aneurysms.^16,28

Studies have shown that the admission HH grade is a significant predictor of poor clinical outcome.^{8,15,16,19,29} Intracerebral hemorrhage on initial CT also predicted a poor outcome in patients undergoing either endovascular or microsurgical treatment of distal ACA aneurysms.^8,15,19 The large number of distal ACA aneurysms surgically managed by Lehecka et al¹⁹ yielded a longer list of predictors. Intraventricular hemorrhage, severe preoperative hydrocephalus, age, and rebleeding before treatment were associated with unfavorable clinical outcomes in their series.

Periprocedural Morbidity and Mortality Rates

Endovascular management of ACA aneurysms was associated with a mean morbidity rate of 8.8% and ranged from 0%–17.2%.^{10,13,15⇓⇓–18} In 2 surgical series providing satisfactory data, the mean rate of morbidity among 405 patients was 14.3%.^2,19 Finally, the mean mortality rate in patients with distal ACA aneurysms undergoing endovascular treatment was 8.8% in the assessed series, including ours, and ranged from 0%–20.7%.^{10,13,15⇓⇓–18} On analysis of only the cases of patients with ruptured aneurysms (n = 124), the mortality rate for endovascular treatment reached 11.3%. Overall, in 7 endovascular series that enrolled 160 patients, including the current series, intraoperative rupture occurred in only 5.6%.^{10,13,15⇓⇓–18}