This study evaluated the incidence of recurrence and risk factors for recurrence and retreatment of anterior communicating artery aneurysm after endovascular treatment. We found that the recurrence rate of AcomA after EVT was 14.6%, and its associated factors were younger age, rupture status, bigger aneurysm size, and anterior dome direction. The rate of retreatment, which signifies major recurrence, was 3.8%. Patients with AcomA with a large inflow angle, ruptured status, large aneurysm size, and incomplete aneurysm occlusion may be at a high risk of retreatment.
Many studies have shown that surgical procedure for AcomA can lead to post-operative deficits such as memory impairment and personality changes.13,14 Ramos et al also reported that gyrus rectus resection can cause cognitive and psychiatric dysfunction caused by orbital prefrontal cortex lesion or a disconnection in the ventromedial circuits.15 Another key problem of this surgery is olfactory nerve injury. In some cases of clipping of AcomA, the frontal lobe inevitably is retracted to some degree in order to access the aneurysm. During frontal lobe retraction, the olfactory nerve is also retracted from the cribriform plate. Park et al reported objective olfactory dysfunction rate of 10.8% in their study.16 Because of the risks of these complications, minimal invasive surgery like keyhole approach with eyebrow or palpebral incision was introduced in AcomA surgery.17–19 These approaches reduced the amount of brain retraction and rectus gyrectomy. Some authors even advocated for use of orbitotomy approach,20,21 and recently, endoscopic endonasal approach was reported for AcomA surgery.22
Vascular anomalies such as multiple, fenestrated, or azygous artery are common in Acom.23–26 These anomalies originate during embryologic development. The prevalence of duplication of Acom is 18% and that of fenestration of Acom is 12–21%.27 Surgical clipping of Acom is difficult when anomalies are present.2 Because of these factors, endovascular treatment is becoming a good alternative for AcomA treatment.
O’Neill et al reported that coiling was significantly related to lower rate of treatment-related morbidity compared with clipping (0.8% vs 4.4% for coiling and clipping respectively; P = 0.001), whereas clipping was significantly related to lower angiographic recurrence (4.9% vs 0% for coiling and clipping respectively; P = 0.001) in systemic analysis.7 Many other studies reported that EVT is associated with a high rate of recurrence and retreatment.28–30
Recurrence
Large aneurysm, rupture status, incomplete occlusion, posterior circulation, and incorporating artery with aneurysm are the well-known risk factors for aneurysm recurrence after EVT.12,31 Park et al reported that total recurrence and retreatment rates were 25.7% (44/171) and 10.5% (18/171), respectively after EVT of saccular aneurysm larger than 8 mm.32 They revealed that large size, rupture status, low dome-to-neck ratio, and initial incomplete occlusion status were independent risk factors for recurrence. In this present study, age, rupture status, large aneurysm size, and anterior dome direction were the significant factors for recurrence.
Corns et al reported that younger age predisposed to a higher risk of recurrence in ruptured aneurysm.33 However, their study did not give definite explanation for this observation. In some studies, younger age was a predictor of growth of aneurysm after clipping,34,35 but this age effect is difficult to understand. Our study also showed that younger patients had more recurrence than older patients. This age effect can be explained in two ways. One, there was a bias toward more frequent surveillance imaging in younger patients. Second, is the correlation with other factors that signify recurrence. We therefore performed a correlation analysis, after which correlation between age and maximal diameter was not statistically significant at the significance level of 5%, although the P-value of 0.068 was close to being statistically significant. Therefore, we cannot completely ignore the association (correlation coefficient = 0.114).
Anterior dome direction is known to reflect aneurysm hemodynamics, including wall shear stress and flow velocity, which play important roles in the growth and rupture of aneurysm.36 This may explain its significant association with recurrence in this study.
Retreatment
In ISAT study, younger age, large lumen size, and incomplete occlusion were risk factors for late retreatment after EVT.6 Smoking is known as one of the most important risk factors for formation and rupture of intracranial aneurysm,37–39 and that association was explained by inhibitory effect of cigarette smoke on alpha 1-antitrypsin (A1AT).40 Brinjikji however reported that smoking was not an independent risk factor for aneurysm recurrence (OR = 1.04, P = 0.87) and retreatment (OR = 0.82, P = 0.50) for patients receiving EVT for aneurysm.41 Recently, Futchko found that history of smoking—whether current or former—was associated with a significantly increased risk of aneurysm recurrence. The odds ratios for aneurysm recurrence in current and former smokers were 2.73 and 2.69, respectively, compared with never smokers. The author accounted for the difference between the Brinjikji’s study and their study. The former study exclusively used balloon-assisted coiling, whereas the latter study used stent-assisted coiling.42 Our study showed no association between smoking and recurrence.
Using computational fluid dynamic (CFD) analysis, Merih et al identified inflow angle as an independent and robust rupture status differentiator in intracranial aneurysm.9 CFD showed that increasing inflow angle led to deeper migration of flow with higher peak flow velocities and a greater transmission of kinetic energy into the dome. Wenjun et al also revealed that an inflow angle of over 90° and incomplete occlusion were associated with aneurysm recurrence in unruptured aneurysm after EVT. Our study showed that inflow angle was not related with recurrence, but associated with retreatment.
Rupture status and large aneurysm size were not only associated with recurrence, but also with retreatment. On the other hand, incomplete coil packing status was associated with retreatment but not with recurrence.
Limitation
This study had several limitations. First, the decision to retreat relied on the clinician’s decision, so it was highly subjective. This could have led to bias. Second, recurrence and retreatment cases were few compared with the other group which showed no recurrence and retreatment. This could be a factor in lowering the statistical reliability of the results. Third, inflow angle was not accurate. Even though we used 3D rotation image, there could be inter-observer difference in measurement. Fourth, inflow angle could change after EVT especially in SAC. However, in this study, only 52 patients (20%) were treated with SAC.