Aspirin associated with decreased rate of intracranial aneurysm growth

J Neurosurg 133:1478–1485, 2020

Aspirin has emerged as a potential agent in the prevention of rupture of intracranial aneurysms (IAs). In this study, the authors’ goal was to test if aspirin is protective against aneurysm growth in patients harboring multiple IAs ≤ 5 mm.

METHODS The authors performed a retrospective review of a prospectively maintained database covering the period July 2009 through January 2019. Patients’ data were included if the following criteria were met: 1) the patient harbored multiple IAs; 2) designated primary aneurysms were treated by surgical/endovascular means; 3) the remaining aneurysms were observed for growth; and 4) a follow-up period of at least 5 years after the initial treatment was available. Demographics, earlier medical history, the rupture status of designated primary aneurysms, aneurysms’ angiographic features, and treatment modalities were gathered.

RESULTS The authors identified 146 patients harboring a total of 375 IAs. At the initial encounter, 146 aneurysms were treated and the remaining 229 aneurysms (2–5 mm) were observed. During the follow-up period, 24 (10.48%) of 229 aneurysms grew. All aneurysms observed to grow later underwent treatment. None of the observed aneurysms ruptured. Multivariate analysis showed that aspirin was significantly associated with a decreased rate of growth (odds ratio [OR] 0.19, 95% confidence interval [CI] 0.05–0.63). Variables associated with an increased rate of growth included hypertension (OR 14.38, 95% CI 3.83–53.94), drug abuse (OR 11.26, 95% CI 1.21–104.65), history of polycystic kidney disease (OR 9.48, 95% CI 1.51–59.35), and subarachnoid hemorrhage at presentation (OR 5.91, 95% CI 1.83–19.09).

CONCLUSIONS In patients with multiple IAs, aspirin significantly decreased the rate of aneurysm growth over time. Additional prospective interventional studies are needed to validate these findings.

Size Ratio Performance in Detecting Cerebral Aneurysm Rupture Status Is Insensitive to Small Vessel Removal

Siza Ratio as rupture discriminant

Neurosurgery 72:547–554, 2013 

The variable definition of size ratio (SR) for sidewall (SW) vs bifurcation (BIF) aneurysms raises confusion for lesions harboring small branches, such as carotid ophthalmic or posterior communicating locations. These aneurysms are considered SW by many clinicians, but SR methodology classifies them as BIF.

OBJECTIVE: To evaluate the effect of ignoring small vessels and SW vs stringent BIF labeling on SR ruptured aneurysm detection performance in borderline aneurysms with small branches, and to reconcile SR-based labeling with clinical SW/BIF classification.

METHODS: Catheter rotational angiographic datasets of 134 consecutive aneurysms (60 ruptured) were automatically measured in 3-dimensional. Stringent BIF labeling was applied to clinically labeled aneurysms, with 21 aneurysms switching label from SW to BIF. Parent vessel size was evaluated both taking into account, and ignoring, small vessels. SR was defined accordingly as the ratio between aneurysm and parent vessel sizes. Univariate and multivariate statistics identified significant features. The square of the correlation coefficient (R2) was reported for bivariate analysis of alternative SR calculations.

RESULTS: Regardless of SW/BIF labeling method, SR was equally significant in discriminating aneurysm ruptured status (P , .001). Bivariate analysis of alternative SR had a high correlation of R2 = 0.94 on the whole dataset, and R2 = 0.98 on the 21 borderline aneurysms.

CONCLUSION: Ignoring small branches from SR calculation maintains rupture status detection performance, while reducing postprocessing complexity and removing labeling ambiguity. Aneurysms adjacent to these vessels can be considered SW for morphometric analysis. It is reasonable to use the clinical SW/BIF labeling when using SR for rupture risk evaluation.

Dichotomy between bifurcation and sidewall aneurysms

J Neurosurg 116:871–881, 2012.

Prediction of aneurysm rupture likelihood is clinically valuable, given that more unruptured aneurysms are being discovered incidentally with the increased use of imaging. The authors set out to evaluate the relative performance of morphological features for rupture status discrimination in the context of the divergent geometrical and hemodynamic characteristics of sidewall- and bifurcation-type aneurysms.

Methods. Catheter 3D rotational angiographic images of 271 consecutive aneurysms (101 ruptured, 135 bifurcation type) were used to assess the following parameters in 3D: maximum diameter (Dmax), height, height/width ratio, aspect ratio, size ratio, nonsphericity index, and inflow angle. Univariate statistics applied to the bifurcation, sidewall, and combined (bifurcation + sidewall) sets identified significant features for inclusion in multivariate analysis yielding area under the curve (AUC) and optimal thresholds in the receiver-operating characteristic. Furthermore, a computational fluid dynamics analysis was performed to evaluate the flow and wall shear stress conditions inside sidewall and bifurcation aneurysms at different inflow angles.

Results. The mean Dmax, height, and inflow angle were significantly greater in ruptured sidewall aneurysms than in unruptured sidewall aneurysms, but showed no difference between ruptured and unruptured bifurcation lesions. There was a statistically significant difference between ruptured and unruptured aneurysms for all measured features in the combined set. Multivariate analysis identified the following: 1) nonsphericity index as the only rupture status discriminator in bifurcation lesions (AUC = 0.67); 2) height/width ratio, size ratio, and inflow angle as strong discriminators in sidewall lesions (AUC = 0.87); and 3) height/width ratio, inflow angle, and size ratio as intermediate discriminators in the combined group (AUC = 0.76). Computational fluid dynamics analysis showed that although increasing inflow angle in a sidewall model led to deeper penetration of flow, higher velocities, and higher wall shear stress inside the aneurysm dome, it produced the exact opposite results in a bifurcation model.

Conclusions. Retrospective morphological and hemodynamic analysis point to a dichotomy between sidewall and bifurcation aneurysms with respect to performance of shape and size parameters in identifying rupture status, suggesting the need for aneurysm type–based analyses in future studies. The current most commonly used clinical risk assessment metric, Dmax, was found to be of no value in differentiating between ruptured and unruptured bifurcation aneurysms.

Incremental Contribution of Size Ratio as a Discriminant for Rupture Status in Cerebral Aneurysms: Comparison With Size, Height, and Vessel Diameter

Neurosurgery 70:944–952, 2012 DOI: 10.1227/NEU.0b013e31823bcda7

Aneurysm size ratio (SR), variably defined as the ratio of dome height (H) or maximal dimension (Dmax) over average parent vessel diameter (PV) diameter, has been proposed as a promising aneurysm rupture status predictor.

OBJECTIVE: To evaluate the incremental contribution of SR to retrospective rupture status determination in a large high-resolution aneurysm database.

METHODS: Measurements were performed on catheter 3D-rotational angiographic volumetric datasets for 267 aneurysms (98 ruptured). SR was computed both as H/PV (SR1) and as Dmax/PV (SR2), and its discriminant performance was evaluated on the whole dataset, on aneurysm-type subsets (bifurcation [BIF] vs sidewall [SW]), and at specific aneurysm locations. Univariate and multivariate statistical analyses were performed by the use of area under the curve (AUC) of the receiver-operating characteristics.

RESULTS: Neither SR1 nor SR2 were statistically correlated to rupture status in the BIF group, where only PV (AUC = 0.61) achieved significance. All parameters were statistically significant in the combined group, but with modest performance (AUC range, 0.62- 0.74). SR1 (AUC = 0.84) and SR2 (AUC = 0.78) were strong predictors in the SW group, similar to H (AUC = 0.83) and Dmax (AUC = 0.77). Multivariate statistics failed to support SR as an incremental independent parameter from PV, Dmax, and H.

CONCLUSION: SR provides an uneven performance that depends strongly on the BIF/ SW distribution of the data and is not useful for bifurcation lesions. In the SW subset, the incremental contribution of the SR over its H or Dmax individual component measurements could not be validated, suggesting prior findings of its utility to be the result of aneurysm-type selection bias.