Morphological and Hemodynamic Risk Factors for Middle Cerebral Artery Aneurysm: a Case-Control Study of 190 Patients

Flow Diversion for the Treatment of Middle Cerebral Artery Aneurysms

The invention of flow diverting stents (FDS) is a novel milestone in the field of endovascular aneurysm therapy, promoting physiological healing of the vessel segment contrary to prior deconstructive treatment strategies, such as coiling. The effects of FDS are based on changes in flow patterns, segmental wall stabilization, and the growth of a neointima. Although flow diversion is already well established for cerebral aneurysms in proximal segments, peripheral locations remain challenging. Especially the middle cerebral artery (MCA) with its predominance of non-collateralized perforators and functional end arteries that supply the eloquent areas of the brain is of major concern.The literature was reviewed for flow diversion of the MCA and antiplatelet therapy.Resulting from the special anatomical characteristics of the MCA, FDS implantation in this territory is completely different from the proximal vessel segments. Still, flow diversion represents an effective endovascular strategy, especially in otherwise non-accessible or sufficiently treatable lesions. However, the risk of ischemic adverse events might be increased. Special attention to the individual decision regarding device selection, antiplatelet regimen, and exact definition of the proximal and distal landing zone considering the jailed side branches is essential for a good angiographic and clinical outcome. · MCA aneurysms can be sufficiently treated by FDS.. · The anatomic and hemodynamic characteristics of the MCA result in an increased risk of thromboembolism.. · Individual device selection and antiplatelet regimen are essential for treatment success.. · Schüngel M, Wohlgemuth WA, Elolf E et al. Review: Flow Diversion for the Treatment of Middle Cerebral Artery Aneurysms. Rofo 2025; DOI 10.1055/a-2343-0046.

Drill turn technique for enhanced visualization of wide-neck bifurcation aneurysms in Y-stent-assisted coiling with LVIS EVO stents: technical considerations and mid-term results

BACKGROUND

Crossing Y-stent-assisted coiling (CYSAC) is a feasible yet technically challenging technique for the treatment of wide-neck bifurcation aneurysms (WNBAs).

OBJECTIVE

To present mid-term results of Y-stent-assisted coiling (YSAC) using the LVIS EVO stent and to describe our "drill turn" technique for stent crossing.

METHODS

This retrospective, observational study included 37 consecutive patients treated with YSAC using LVIS EVO stents at five centres between September 2020 and March 2023.

RESULTS

Immediately after treatment, 31 of the 37 patients (83.8%) achieved Raymond-Roy occlusion classification (RROC) Class I occlusion, while 5 patients (13.5%) had Class II and 1 patient (2.7%) had Class III occlusion. The mean follow-up period was 32.8 months (range: 11-41 months), and all patients underwent follow-up imaging after ≥ 6 months. On follow-up imaging, 34 patients (92%), including all those with immediate RROC Class I occlusion, 2 with Class II, and 1 with Class III, showed Class I occlusion. One patient with RROC Class II occlusion demonstrated a gradual decrease in residual filling, while one large partially thrombosed middle cerebral artery aneurysm and one large basilar tip aneurysm (8%) with residual neck filling remained unchanged on the 6-month digital subtraction angiograph.

CONCLUSION

Utilizing the described drill turn technique, CYSAC with LVIS EVO stents was found to be feasible and safe for WNBA treatment, with high and stable occlusion rates observed during mid-term follow-up.

Are There Left-Right Differences in Ruptured Middle Cerebral Artery Bifurcation Aneurysms? A Single-Center Retrospective Study and Review of the Literature

Background  The left (Lt) and right (Rt) middle cerebral artery bifurcation (MCAB) aneurysms have mostly been regarded as identical. Considering substantial Lt-Rt differences in hemispheric infarction, however, the presence of Lt-Rt differences may not be denied totally in patients with ruptured MCAB aneurysms. We herein investigated whether such Lt-Rt differences existed by a single-center retrospective study. Materials and Methods  Clinical data prospectively acquired between 2011 and 2021 on 99 patients with ruptured MCAB aneurysms were analyzed. They were dichotomized based on the laterality, and demographic and outcome parameters were compared. Additionally, a literature review was conducted to elucidate possible Lt-Rt differences in the frequency of ruptured MCAB aneurysms (Rt/Lt ratio). Results  Among the 99 patients, 42 had Lt and 57 had Rt ruptured MCAB aneurysms, with the Rt/Lt ratio of 1.36. Neither demographic, radiographic, nor outcome variables differed significantly between the two groups. A total of 19 studies providing information on the laterality of the ruptured MCAB were retrieved by literature search. A sum total for the Lt and Rt MCAB aneurysms was 671 and 940, making the Rt/Lt ratio of 1.40. After adding our data, a sum total for the Lt and Rt MCAB aneurysms was 713 and 997, making the Rt/Lt ratio of 1.40. Conclusion  The Rt ruptured MCAB aneurysms were 1.40 times more frequent than the Lt-sided counterpart. While there may be some Lt-Rt differences in the MCA anatomy, it remains to be seen whether such anatomical differences are truly responsible for the disproportionately higher frequency of Rt MCAB aneurysms.

Combining Machine-Measured Morphometric, Geometric, and Hemodynamic Factors to Predict the Risk of Aneurysm Rupture at the Middle Cerebral Artery Bifurcation

BACKGROUND

Middle Cerebral Artery Bifurcation Aneurysm (MbifA) is associated with a high risk of rupture and poor overall prognosis in patients once it ruptures. Morphological, geometric, and hemodynamic parameters have been identified as factors contributing to the rupture of intracranial aneurysms. However, there are no studies that combine these 3 types of parameters to specifically target MbifA rupture.

METHODS

This study enrolled all patients with MbifAs diagnosed at our treatment center from 1 April 2021 to 31 July 2023 who met the study criteria. All patients underwent digital subtraction angiography examination to obtain 3D rotational angiography data. We imported the complete image data into the Aneurysm/Artery Reconstruction and Analysis machine to obtain 13 morphological parameters (Dneck, Ddome, Height, Dmax, Dartery, aspect ratio [AR], size ratio, dome-neck-ratio [DNR], height-artery-ratio, bottleneck factor, Inflow Angle, Incline Angle, Arterial Angle), 5 geometric parameters (V,S,undulation index [UI], ellipticity index [EI],nonsphericity index [NSI]), and 5 hemodynamic parameters (wall shear stress [WSS], the maximum WSS, the parent artery WSS, the normalized WSS [NWSS], oscillatory shear index [OSI]). All the above significant parameters were tested by univariate and multivariate analyses to find out the independent discriminatory factors.

RESULTS

A total of 49 MbifAs (16 ruptured and 33 unruptured) from 44 patients were included in the study. Height (P = 0.033), AR (P = 0.007), DNR (P = 0.011), EI (P = 0.042), NSI(P = 0.030), UI(P = 0.027), WSS(P = 0.033), and NWSS(P = 0.002) were all associated with MbifA rupture in univariate analyses, but only NWSS was an independent risk factor (P = 0.036, OR = 0.046, 95% CI: 0.003-0.815) in multivariate logistic regression analysis.

CONCLUSIONS

Height, AR, DNR, EI, UI, NSI, WSS, and NWSS may be correlated with MbifA rupture, but only NWSS was an independent risk factor. A lower NWSS was associated with a higher risk of MbifA rupture. No significant differences were observed in the angle parameters, including the Inflow Angle, between ruptured and unruptured MbifAs. OSI was significantly increased at the dome of the aneurysm but the mean OSI was not found to be associated with MbifA rupture.

Anatomical variations in the circle of Willis are associated with increased odds of intracranial aneurysms: The Tromsø study

PURPOSE

Studies on patients suggest an association between anatomical variations in the Circle of Willis (CoW) and intracranial aneurysms (IA), but it is unclear whether this association is present in the general population. In this cross-sectional population study, we investigated the associations between CoW anatomical variations and IA.

METHODS

We included 1667 participants from a population sample with 3 T MRI time-of-flight angiography (40-84 years, 46.5% men). Saccular IAs were defined as protrusions in the intracranial arteries ≥2 mm, while variants of the CoW were classified according to whether segments were missing or hypoplastic (< 1 mm). We used logistic regression, adjusting for age and IA risk factors, to assess whether participants with incomplete CoW variants had a greater prevalence of IA and whether participants with specific incomplete variants had a greater prevalence of IA.

RESULTS

Participants with an incomplete CoW had an increased prevalence of IA (OR, 2.3 [95% CI 1.05-5.04]). This was mainly driven by the variant missing all three communicating arteries (OR, 4.2 [95% CI 1.7-1 0.3]) and the variant missing the P1 segment of the posterior cerebral artery (OR, 3.6 [95% CI 1.2-10.1]). The combined prevalence of the two variants was 15.4% but accounted for 28% of the IAs.

CONCLUSION

The findings suggest that an incomplete CoW is associated with an increased risk of IA for adults in the general population.

Cerebrovascular Pulsatility Index Is Reduced in Autosomal Dominant Polycystic Kidney Disease

INTRODUCTION

Cerebrovascular dysfunction, characterized by increased brain pulsatile flow, reduced cerebrovascular reactivity, and cerebral hypoperfusion precedes the onset of dementia and is linked to cognitive dysfunction. Autosomal dominant polycystic kidney disease (ADPKD) may increase the risk of dementia, and intracranial aneurysms are more prevalent in ADPKD patients. However, cerebrovascular function has not been previously characterized in patients with ADPKD.

METHODS

Using transcranial Doppler, we compared middle cerebral artery (MCA) pulsatility index (PI, cerebrovascular stiffness) and MCA blood velocity response to hypercapnia (normalized for blood pressure and end-tidal CO2, cerebrovascular reactivity) in patients with early-stage ADPKD versus age-matched healthy controls. We also administered the NIH cognitive toolbox (cognitive function) and measured carotid-femoral pulse-wave velocity (PWV, aortic stiffness).

RESULTS

Fifteen participants with ADPKD (9F, 27 ± 4 yrs, eGFR: 106 ± 22 mL/min/1.73 m2) were compared to 15 healthy controls (8F, 29 ± 4 yrs, eGFR: 109 ± 14 mL/min/1.73 m2). MCA PI was unexpectedly lower in ADPKD (0.71 ± 0.07) versus controls (0.82 ± 0.09 AU; p < 0.001); however, normalized MCA blood velocity in response to hypercapnia did not differ between groups (2.0 ± 1.2 vs. 2.1 ± 0.8 %Δ/mm Hg; p = 0.85). Lower MCA PI was associated with a lower crystalized composite score (cognition), which persisted after adjustment for age, sex, eGFR, and education (β = 0.58, p = 0.007). There was no association of MCA PI with carotid-femoral PWV (r = 0.01, p = 0.96), despite greater carotid-femoral PWV in ADPKD, suggesting MCA PI reflects vascular properties other than arterial stiffness (such as low wall shear stress) in ADPKD.

DISCUSSION/CONCLUSION

MCA PI is lower in patients with ADPKD. Follow-up research on this observation is merited as low PI has been associated with intracranial aneurysm in other populations.

Rupture pressure values of cerebral arteries in the presence of unruptured intracranial aneurysm

Cerebral arteries (CAs) are prone to the saccular aneurysm formation. Since aneurysms may be considered as balloon-like dilations of the locally weakened arterial wall, it should be determined whether the presence of intracranial aneurysm is related to the generalized weakening of CAs. Among 184 consecutive forensic autopsies, eight brains with a single unruptured saccular aneurysm were identified. Aneurysms with adjacent CAs and specific CA segments were excised, namely: the anterior communicating artery complex, and bifurcations of the basilar artery, internal carotid arteries, and middle cerebral arteries. Then, aneurysm and CA specimens were subjected to pressure-inflation tests until rupture occurred at the arterial bifurcation or at the wall of the CA or aneurysm. The same protocol was applied to the control group composed of CAs excised from eight brains without aneurysm. No significant differences were noted between the experimental and control groups, depending on the mean rupture pressure (1054 vs. 1048 mmHg) and rupture site (bifurcation vs. wall) of the analyzed specimens. These findings indicate that the presence of unruptured saccular aneurysm is not related to generalized weakening of CAs among autopsy subjects. Moreover, the CA bifurcations do not represent regions of decreased wall strength.

Efficacy and safety of endovascular therapy versus surgical clipping for patients with unruptured middle cerebral artery bifurcation aneurysms

This study aims to evaluate the efficacy and safety of endovascular therapy versus neurosurgical clipping carried out for patients with unruptured middle cerebral artery bifurcation aneurysms (MCABAs). Patients diagnosed with MCABAs were enrolled in this prospective study according to the inclusion and exclusion standard. Enrolled patients were divided into a study group (endovascular therapy) and a control group (neurosurgical clipping), with 65 cases in each group. In terms of efficacy, we found that the proportion of Glasgow Outcome Scale (GOS) grade 1 after treatment in the study group was significantly higher than in the control group (p<0.001), while the proportion of GOS grades 2, 3, and 4 after treatment was significantly lower in the study group than in the control group (p<0.05). The postoperative brain injury indicators neuron-specific enolase and S100β in the study group were significantly lower than in the control group (p<0.001), and the postoperative life activity score of patients in the study group was significantly higher than in the control group (p<0.001). In terms of safety, the postoperative hospital stay of patients in the study group was significantly shorter than in the control group (p<0.001), and the incidence rate of postoperative pulmonary and intracranial infections in the study group was significantly lower than in the control group (p<0.05). Endovascular therapy for patients with unruptured MCABAs may be effective in improving outcomes and has better safety profile compared with neurosurgical clipping, but may increase the risk of postoperative recurrence.

Outflow angle: a risk factor for thromboembolic complications in coil embolisation for treating unruptured middle cerebral artery bifurcation aneurysms

BACKGROUND

Thromboembolic complications are a relevant risk in coil embolisation of cerebral aneurysms. This retrospective study aimed to assess the treatment outcomes of unruptured middle cerebral artery (MCA) bifurcation aneurysms and the predictors for thromboembolic complications based on the aneurysm morphological characteristics. We examined the following three features: inflow angle, outflow angle (OA), and bifurcation angle, formed by the aneurysm and neighbouring blood vessels.

METHODS

A total of 32 MCA bifurcation aneurysms were retrospectively investigated in 32 patients treated consecutively at our institute between April 2008 and March 2019. The predictors for thromboembolic complications were analysed in two groups: patients with and without thromboembolic complications.

RESULTS

Perioperative thromboembolic complications were detected in six patients (18.8%), including two and six intra- and post-procedural thromboembolic complications, respectively; all cases were resolved. Regarding the aneurysms' morphological characteristics, the group with thromboembolic complications showed a significantly smaller OA (55.58° ± 14.05° vs. 86.04° ± 28.58°, P = 0.01) than the group without complications. Multivariate analysis revealed that smoking habits and OA < 70° were significant predictors of thromboembolic complications (smoking habits: P = 0.01, odds ratio [OR]: 6.89, 95% confidence interval [CI]: 3.78-12.62; OA < 70°: P = 0.04, OR: 3.19, 95% CI: 1.52-6.56).

CONCLUSIONS

Our findings indicate significant pre-procedural predictors of thromboembolic complications to consider for safe treatment; clipping should be preferred to coil embolisation in high-risk patients. The method of choice should be considered in each case to allow the safe treatment of unruptured MCA aneurysms.

Morphometry of cerebral arterial bifurcations harbouring aneurysms: a case-control study

Background

Conclusions from studies evaluating vessel dimensions and their deviations from values resulting from the principle of minimum work (PMW) on the formation of intracranial aneurysms (IAs) are still inconclusive. Our study aimed to perform a morphometric analysis of cerebral arterial bifurcations harbouring aneurysms.

Methods

The study comprised 147 patients with basilar artery (BA) and middle cerebral artery (MCA) aneurysms and 106 patients constituting the control group. The following morphometric parameters were evaluated: the radii of vessels forming the bifurcation, the junction exponent, the values of the bifurcation angles (Φ₁ and Φ₂ angles between the parent vessel trunk axis and the larger or smaller branches, respectively; α angle, the total bifurcation angle) and the difference between the predicted optimal and observed branch angles.

Results

The analysed parameters for internal carotid artery (ICA) bifurcations were not significantly different among the groups. The MCA and BA bifurcation angles and the radii of the parent MCA and BA vessels with aneurysms were significantly higher than those of the control group. The differences between the predicted optimal and observed branch angles were significantly higher for BA and MCA bifurcations with aneurysms compared to the control group. The mean junction exponent for bifurcations in the circle of Willis (i.e., ICA and BA bifurcations, respectively) and MCA bifurcations with aneurysms was significantly lower than the theoretical optimum and did not significantly differ among the groups. In a multilevel multivariate logistic regression analysis, the branch angles and the radius from the parent vessel were significant independent predictors of the presence of an IA. The ROC analysis indicated that the α angle was the best performer in discriminating between aneurysmal and nonaneurysmal bifurcations.

Conclusions

The dimensions of the arteries forming the circle of Willis do not follow the PMW. Deviation from the energetically optimum geometry for bifurcations beyond the circle of Willis (particularly, a larger radius of the parent artery and a wider total bifurcation angle) may lead to the formation of IAs. Further studies are warranted to investigate the significance of vessel dimensions and the bifurcation angle on the magnitude of shear stress in the walls of arterial bifurcations.

Geometric Features Associated with Middle Cerebral Artery Bifurcation Aneurysm Formation: A Matched Case-Control Study

OBJECTIVES

The pathogenesis of intracranial aneurysms is multifactorial and includes genetic, environmental, and anatomic influences. We aimed to identify image-based morphological parameters that were associated with middle cerebral artery (MCA) bifurcation aneurysms.

MATERIALS AND METHODS

We evaluated three-dimensional morphological parameters obtained from CT angiography (CTA) or digital subtraction angiography (DSA) from 317 patients with unilateral MCA bifurcation aneurysms diagnosed at the Brigham and Women's Hospital and Massachusetts General Hospital between 1990 and 2016. We chose the contralateral unaffected MCA bifurcation as the control group, in order to control for genetic and environmental risk factors. Diameters and angles of surrounding parent and daughter vessels of 634 MCAs were examined.

RESULTS

Univariable and multivariable statistical analyses were performed to determine statistical significance. Sensitivity analyses with smaller (≤ 3 mm) aneurysms only and with angles excluded, were also performed. In a multivariable conditional logistic regression model we showed that smaller diameter size ratio (OR 0.0004, 95% CI 0.0001-0.15), larger daughter-daughter angles (OR 1.08, 95% CI 1.06-1.11) and larger parent-daughter angle ratios (OR 4.24, 95% CI 1.77-10.16) were significantly associated with MCA aneurysm presence after correcting for other variables. In order to account for possible changes to the vasculature by the aneurysm, a subgroup analysis of small aneurysms (≤ 3 mm) was performed and showed that the results were similar.

CONCLUSIONS

Easily measurable morphological parameters of the surrounding vasculature of the MCA may provide objective metrics to assess MCA aneurysm formation risk in high-risk patients.

Imaging markers of intracranial aneurysm development: A systematic review

BACKGROUND

Imaging markers of intracranial aneurysm (IA) development are not well established.

PURPOSE

To provide an overview of imaging markers of IA development.

METHODS

A systematic search of PubMed and Embase up to December 1st 2020 using predefined criteria. Thirty-six studies met our inclusion criteria. We performed a quantitative summary of the included studies.

RESULTS

We found converging evidence for A1 segment asymmetry as an anatomical marker of anterior communicating artery (Acom) aneurysm development, and moderate evidence for several other markers. No hemodynamic markers yielded converging or moderate evidence. There was large heterogeneity across studies, especially in the definitions of imaging markers and study outcomes used. Due to the poor methodological quality of many studies and unavailability of effect sizes or crude data to calculate effect sizes, a formal meta-analysis was not possible. Many studies had poor methodological quality and varied inmarkerdefinitions and outcome measuresused, which prevented us from performing a formal meta-analysis.

CONCLUSIONS

We only identified A1 segment asymmetry as an imaging marker of Acom aneurysm development with converging evidence. A meta-analysis was not possible due to the heterogeneity of marker definitions and outcomes used, and poor methodological quality of many studies. Future studies should use robust study designs and uniformly defined imaging markers and outcome measures.

Wall shear stress gradient is independently associated with middle cerebral artery aneurysm development: a case-control CFD patient-specific study based on 77 patients

Background

Previously published computational fluid dynamics (CFD) studies regarding intracranial aneurysm (IA) formation present conflicting results. Our study analysed the involvement of the combination of high wall shear stress (WSS) and a positive WSS gradient (WSSG) in IA formation.

Methods

We designed a case-control study with a selection of 38 patients with an unruptured middle cerebral artery (MCA) aneurysm and 39 non-aneurysmal controls to determine the involvement of WSS, oscillatory shear index (OSI), the WSSG and its absolute value (absWSSG) in aneurysm formation based on patient-specific CFD simulations using velocity profiles obtained from transcranial colour-coded sonography.

Results

Among the analysed parameters, only the WSSG had significantly higher values compared to the controls (11.05 vs − 14.76 [Pa/mm], P = 0.020). The WSS, absWSSG and OSI values were not significantly different between the analysed groups. Logistic regression analysis identified WSS and WSSG as significant co-predictors for MCA aneurysm formation, but only the WSSG turned out to be a significant independent prognosticator (OR: 1.009; 95% CI: 1.001–1.017; P = 0.025). Significantly more patients (23/38) in the case group had haemodynamic regions of high WSS combined with a positive WSSG near the bifurcation apex, while in the control group, high WSS was usually accompanied by a negative WSSG (14/39). From the analysis of the ROC curve for WSSG, the area under the curve (AUC) was 0.654, with the optimal cut-off value −0.37 Pa/mm. The largest AUC was recognised for combined WSS and WSSG (AUC = 0.671). Our data confirmed that aneurysms tend to form near the bifurcation apices in regions of high WSS values accompanied by positive WSSG.

Conclusions

The development of IAs is determined by an independent effect of haemodynamic factors. High WSS impacts MCA aneurysm formation, while a positive WSSG mainly promotes this process.

A retrospective longitudinal study of age-related shifts and deformations in the basilar artery bifurcation

PURPOSE

Previous studies have indicated that cerebral arterial morphology is linked to aging and some cerebrovascular diseases. However, the mechanisms of morphological changes remain unclear. This study evaluated age-related positional changes in the basilar artery (BA) bifurcation based on longitudinal computed tomography angiography (CTA) data.

METHODS

This retrospective study evaluated clinical and imaging data from 72 subjects who underwent two CTA scans between July 2011 and August 2019. Three-dimensional (3D) models were reconstructed for each subject based on the two CTA scans with the longest separating interval. Skull landmarks were used to fuse the two models, and the fused model was used to evaluate positional changes in the BA bifurcation. Univariable and multivariable analyses were used to identify variables that were correlated to BA bifurcation shifting. Pearson's correlation test was used to analyze the correlation between the shifting distance and change in the BA bifurcation angle.

RESULTS

Significant differences between aneurysm and non-aneurysm cases were observed in terms of sex (p = 0.004), CTA scan interval (p = 0.023), and BA bifurcation shifting distance (p = 0.007). Multivariable linear regression analysis revealed that the BA bifurcation shifting distance was significantly correlated with the CTA scan interval (p = 0.038) and the presence of aneurysms (p < 0.001). Furthermore, the shifting distance was positively correlated with widening of the BA bifurcation angle (p = 0.002).

CONCLUSIONS

Aging-related widening of the BA bifurcation angle may be related to distal shifting of the BA bifurcation's position, and larger distal shifting of the BA bifurcation may be associated with the risk of aneurysm formation.

Geometric variations associated with posterior communicating artery aneurysms

BACKGROUND

Hemodynamic stress, conditioned by the morphology of the surrounding vasculature, plays an important role in aneurysm formation. Our goal was to identify image-based location-specific parameters that are associated with posterior communicating artery (PCoA) aneurysms.

METHODS

Three-dimensional morphological parameters obtained from CT angiography or digital subtraction angiography from 187 patients with unilateral PCoA aneurysms, diagnosed at the Brigham and Women's Hospital and Massachusetts General Hospital between 1990 and 2016, were evaluated. In order to control for genetic and clinical risk factors, we chose the contralateral unaffected PCoA as a control group. We examined diameters and angles of the surrounding parent and daughter vessels. Univariable and multivariable statistical analyses were performed to determine statistical significance. Sensitivity analyses with small aneurysms (≤5 mm) only and an unmatched analysis of 432 PCoA aneurysms and 197 control patients without PCoA aneurysms were also performed.

RESULTS

In a multivariable conditional logistic regression model we showed that smaller diameter size ratio (OR 1.45×10^-5, 95% CI 1.12×10^-7 to 1.88×10^-3) and larger daughter-daughter angle (OR 1.04, 95% CI 1.02 to 1.07) were significantly associated with PCoA aneurysm presence after correcting for other variables. In subgroup analyses of small aneurysms (≤5 mm) and in an unmatched analysis the significance and direction of these results were preserved.

CONCLUSIONS

Larger daughter-daughter angles and smaller diameter size ratio are significantly associated with the presence of PCoA aneurysms. These simple parameters can be utilized to guide the risk assessment for the formation of PCoA aneurysms in high risk patients.