Evidence That a Subset of Aneurysms Less Than 7 mm Warrant Treatment

Toward Grading Subarachnoid Hemorrhage Risk Prediction: A Machine Learning-Based Aneurysm Rupture Score

OBJECTIVE

Existing approaches neither provide an accurate prediction of subarachnoid hemorrhage (SAH) nor offer a quantitative comparison among a group of its risk factors. To evaluate the population, hypertension, age, size, earlier subarachnoid hemorrhage, and location (PHASES) and unruptured intracranial aneurysm treatment score (UIATS) scores and develop an Artificial Intelligence-based 5-year and lifetime aneurysmal rupture criticality prediction (ARCP) score for a set of risk factors.

METHODS

We design various location-specific and ensemble learning models to develop lifetime rupture risk, employ the longitudinal data to develop a linear regression-based model to predict an aneurysm's growth score, and use the Apriori algorithm to identify risk factors strongly associated with SAH. We develop ARCP by integrating output of Apriori algorithm and ML models and compare with PHASES and UIATS scores along with the scores of a multidisciplinary team of neurosurgeons.

RESULTS

The PHASES and UIATS scores show sensitivities of 22% and 35% and specificities of 76% and 79%, respectively. Location-specific models show precision and recall of 93% and 90% for the middle cerebral artery, 83% and 80% for the anterior communicating artery, and 80% and 80% for the supraclinoid internal carotid artery, respectively. The ensemble method shows both precision and recall of 80%. The validation of the models shows that ARCP performs better than our control group of neurosurgeons. Data-driven knowledge produces comparisons among 61 risk factor combinations, 11 ranked minor, 8 moderate, and 41 severe, and 1 of which is a critical factor.

CONCLUSIONS

The PHASES and UIATS are weak predictors, and the ARCP score can identify, and grade, risk factors associated with SAH.

Differential Diagnosis of Multiple Systemic Aneurysms

Atherosclerosis and systemic hypertension are the most common pathogeneses of solitary acquired arterial aneurysms. The rare occurrence of multiple synchronous or metachronous arterial aneurysms requires considering alternative underlying causes. We present the unusual case of a male patient who sequentially developed multiple co-existing arterial aneurysms between the ages of 51 and 59. The sites of involvement included high-pressure systemic arteries and low-pressure pulmonary arteries. We discuss the broad differential diagnosis that includes heritable and non-inheritable etiologies. A keen clinical awareness of this broader array of arterial aneurysms is essential for accurate early diagnosis and proper management.

Risk factors for aneurysm rupture among Kazakhs: findings from a national tertiary

BACKGROUND

Rupture of intracranial aneurysms (RIA) leads to subarachnoid hemorrhage (SAH) with severe consequences. Although risks for RIA are established, the results vary between ethnic groups and were never studied in Kazakhstan. This study aimed to establish the risk factors of RIA in the Kazakh population.  METHODS: Retrospective analysis of 762 patients with single IAs, who attended the neurosurgical center from 2008 until 2018, was conducted. Demographic characteristics, such as age, sex, smoking status, and hypertension were considered. Descriptive and bivariate analyses were performed. A multivariable logistic regression model was built to identify factors correlated with RIA.

RESULTS

The mean age of participants was 48.49 ± 0.44 years old. The majority (68.37%) of IAs have ruptured. Of the ruptured aneurysms, 43.76% were < 6 mm, and 38.39% were located on the anterior cerebral and anterior communicating arteries (ACA). Logistic regression model indicates younger age group (16-40 years), smoking, having stage 3 hypertension, smaller IA size and its location on ACA increase the odds of rupture.

CONCLUSIONS

This study has revealed that younger, smoking patients with stage 3 arterial hypertension are at higher risk for RIA. Small aneurysms (< 6 mm) and location on ACA had increased odds of rupture, while larger aneurysms on internal carotid arteries had lower odds.

Demographic and anatomical comparison of ruptured and unruptured intracranial aneurysms: a case control study

BACKGROUND

Our understanding of the pathophysiology and management of intracranial aneurysms (IAs) continuously advances. This case-control study analyzed the demographics of patients with IAs and the morphological Digital Subtraction Angiography (DSA) characteristics of ruptured and unruptured IAs.

METHODS

Two patient groups with saccular ruptured and unruptured IAs eligible for coiling were prospectively analyzed during a 3-year period. Patient groups were compared regarding gender, age, arterial vasculature side, anatomical location, diameter, preoperative DSA appearance, aneurysmal and anatomical Circle of Willis variations (CWV) co-existence.

RESULTS

One hundred and three patients with ruptured and eighty-six patients with unruptured IAs were studied. Anterior communicating and internal carotid artery IAs were the dominant locations: 42.7 % and 23.3 % in ruptured and 29 % and 41.9 % in unruptured IAs, respectively. The female-to-male ratio was 1.78 in ruptured and 2.44 in unruptured IAs (p =0.317), while the rupture was more frequent in younger patients (p =0.034). Angiographically, smaller diameter (p =0.01), abnormal morphology (p =0.0001), and co-existence of CWV (p =0.016) were reported in ruptured IAs. Location at bifurcation/trifurcation (p =0.487) and the co-existence of additional or mirror IA did not differ significantly (p =0.879).

CONCLUSIONS

On DSA, ruptured and unruptured IAs differed in size, morphology, and co-existence of CWV; findings that may favor the treatment of specific unruptured IAs. However, a higher level of evidence is needed to include all these factors in the treatment decision process, provide patient-oriented treatment and reliably identify unruptured IAs at greater risk. HIPPOKRATIA 2021, 25 (3):100-107.

Application of unruptured aneurysm scoring systems to a cohort of ruptured aneurysms: are we underestimating rupture risk?

The predictive values of current risk stratification scales such as the Unruptured Intracranial Aneurysm Treatment Score (UIATS) and the PHASES score are debatable. We evaluated these scores using a cohort of ruptured intracranial aneurysms to simulate their management recommendations had the exact same patients presented prior to rupture. A prospectively maintained database of ruptured saccular aneurysm patients presenting to our institution was used. The PHASES score was calculated for 992 consecutive patients presenting between January 2002 and December 2018, and the UIATS was calculated for 266 consecutive patients presenting between January 2013 and December 2018. A shorter period was selected for the UIATS cohort given the larger number of variables required for calculation. Clinical outcomes were compared between UIATS-recommended "observation" aneurysms and all other aneurysms. Out of 992 ruptured aneurysms, 54% had a low PHASES score (≤5). Out of the 266 ruptured aneurysms, UIATS recommendations were as follows: 68 (26%) "observation," 97 (36%) "treatment," and 101 (38%) "non-definitive." The UIATS conservative group of patients developed more SAH-related complications (78% vs. 65%, p=0.043), had a higher rate of non-home discharge (74% vs. 46%, p<0.001), and had a greater incidence of poor functional status (modified Rankin scale >2) after 12-18 months (68% vs. 51%, p=0.014). Current predictive scoring systems for unruptured aneurysms may underestimate future rupture risk and lead to more conservative management strategies in some patients. Patients that would have been recommended for conservative therapy were more likely to have a worse outcome after rupture.

Small intracranial aneurysms in the Barrow Ruptured Aneurysm Trial (BRAT)

BACKGROUND

Treatment of small ruptured aneurysms (SRAs) remains controversial, with literature reporting difficulty with endovascular versus microsurgical approaches. This paper analyzes outcomes after endovascular coiling and microsurgical clipping among patients with SRAs prospectively enrolled in the Barrow Ruptured Aneurysm Trial (BRAT).

METHOD

All BRAT patients were included in this study. Patient demographics, aneurysm size, aneurysm characteristics, procedure-related complications, and outcomes at discharge and at 1-year and 6-year follow-up were evaluated. A modified Rankin scale (mRS) score > 2 was considered a poor outcome.

RESULTS

Of 73 patients with SRAs, 40 were initially randomly assigned to endovascular coiling and 33 to microsurgical clipping. The rate of treatment crossover was significantly different between coiling and clipping; 25 patients who were assigned to coiling crossed over to clipping, and no clipping patients crossed over to coiling (P < 0.001). Among SRA patients, 15 underwent coiling and 58 underwent clipping; groups did not differ significantly in demographic characteristics or aneurysm type (P ≥ 0.11). Mean aneurysm diameter was significantly greater in the endovascular group (3.0 ± 0.3 vs 2.6 ± 0.6; P = 0.02). The incidence of procedure-related complications was similar for endovascular and microsurgical treatments (odds ratio [95% confidence interval], 1.0 [0.1-10.0], P = 0.98). Both groups had comparable overall outcome (mRS score > 2) at discharge and 1-year and 6-year follow-up (P = 0.48 and 0.73, respectively).

CONCLUSIONS

Most SRA patients in the BRAT underwent surgical clipping, with a high rate of crossover from endovascular approaches. Endovascular treatment was equivalent to surgical clipping with regard to procedure-related complications and neurologic outcomes.

Twisting: Incidence and Risk Factors of an Intraprocedural Challenge Associated With Pipeline Flow Diversion of Cerebral Aneurysms

BACKGROUND

Pipeline Embolization Device (PED; Medtronic) "twisting" manifests with the appearance of a "figure 8" in perpendicular planes on digital subtraction angiography. This phenomenon has received little attention in the literature, requires technical precision to remediate, and has potential to cause ischemic stroke if not properly remediated.

OBJECTIVE

To report incidence, risk factors, and sequelae of PED twisting and to discuss techniques to remediate a PED twist.

METHODS

Case images were reviewed for instances of twisting from a prospectively-maintained, Institutional Review Board-approved cohort of patients undergoing flow diversion for cerebral aneurysm.

RESULTS

From August 2011 to December 2017, 999 PED flow diverting stents were attempted in 782 cases for 653 patients. A total of 25 PED twists were observed while treating 20 patients (2.50%, 25/999). Multivariate analysis revealed predictors of twisting to be: Large and giant aneurysms (odds ratio (OR) = 9.66, P = .005; OR = 27.47, P < .001), increased PED length (OR = 1.14, P < .001), and advanced patient age (OR = 1.07, P = .002). Twisted PEDs were able to be remediated 75% of the time, and procedural success was achieved in 90% of cases. PED twisting was not found to be a significant cause of major or minor complications. However, at long-term follow-up, there was a trend towards poor occlusion outcomes for the cases that encountered twisting.

CONCLUSION

Twisting is a rare event during PED deployment that was more likely to occur while treating large aneurysms with long devices in older patients. While twisting did not lead to major complications in this study, remediation can be challenging and may be associated with inferior occlusion outcomes.

Management of Small Unruptured Intracranial Aneurysms: To Treat or Not to Treat?

Unruptured intracranial aneurysms measuring <7 mm in diameter have become increasingly prevalent due to advances in diagnostic imaging. The most feared complication is aneurysm rupture leading to a subarachnoid hemorrhage. Based on the current literature, the 3 main treatments for an unruptured intracranial aneurysm are conservative management with follow-up imaging, endovascular coiling, or surgical clipping. However, there remains no consensus on the best treatment approach. The natural history of the aneurysm and risk factors for aneurysm rupture must be considered to individualize treatment. Models including population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage from a prior aneurysm, site of aneurysm score, Unruptured Intracranial Aneurysm Treatment Score, and advanced neuroimaging can assist physicians in assessing the risk of aneurysm rupture. Macrophages and other inflammatory modulators have been elucidated as playing a role in intracranial aneurysm progression and eventual rupture. Further studies need to be conducted to explore the effects of therapeutic drugs targeting inflammatory modulators.

Aspirin associated with decreased rate of intracranial aneurysm growth

OBJECTIVE

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.

Safety of Aspirin Use in Patients With Stroke and Small Unruptured Aneurysms

OBJECTIVE

We initiated a multicenter, prospective cohort study to test the hypothesis that aspirin is safe for patients with ischemic cerebrovascular disease (ICVD) harboring unruptured intracranial aneurysms (UIAs) <7 mm.

METHODS

This prospective, multicenter cohort study consecutively enrolled 1,866 eligible patients with ICVD harboring UIAs <7 mm in diameter from 4 hospitals between January 2016 and August 2019. Baseline and follow-up patient information, including the use of aspirin, was recorded. The primary endpoint was aneurysm rupture.

RESULTS

After a total of 4,411.4 person-years, 643 (37.2%) patients continuously received aspirin treatment. Of all included patients, rupture occurred in 12 (0.7%). The incidence rate for rupture (IRR) was 0.27 (95% confidence interval [CI] 0.15-0.48) per 100 person-years. The IRRs were 0.39 (95% CI 0.21-0.72) and 0.06 (95% CI 0.010-0.45) per 100 person-years for the nonaspirin and aspirin groups, respectively. In the multivariate analysis, uncontrolled hypertension and UIAs 5 to <7 mm were associated with a high rate of aneurysm rupture, whereas aspirin use was associated with a low rate of aneurysm rupture. Compared with other groups, the high-risk group (UIAs 5 to <7 mm with concurrent uncontrolled hypertension) without aspirin had higher IRRs.

CONCLUSION

Aspirin is a safe treatment for patients with concurrent small UIAs and ICVD. Patients who are not taking aspirin in the high-risk group warrant intensive surveillance.

CLINICALTRIALSGOV IDENTIFIER

NCT02846259.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that for patients harboring UIAs <7 mm with ICVD, aspirin does not increase the risk of aneurysm rupture.

Aspirin and Growth of Small Unruptured Intracranial Aneurysm

Background and Purpose:

The role of aspirin in unruptured intracranial aneurysm (UIA) growth remains largely unknown. We aim to identify whether aspirin is associated with a lower rate of UIA growth in patients with UIA <7 mm.

Methods:

This prospective cohort study consecutively enrolled patients with UIAs <7 mm with ischemic cerebrovascular disease between January 2016 and December 2019. Baseline and follow-up patient information, including the use of aspirin and blood pressure level, were recorded. Patients were considered aspirin users if they took aspirin, including standard- and low-dose aspirin, ≥3× per week. The primary end point was aneurysm growth in any direction or an indisputable change in aneurysm shape.

Results:

Among the 315 enrolled patients, 272 patients (86.3%) underwent imaging examinations during follow-up (mean follow-up time, 19.6±12.7 months). A total of 113 patients were continuously treated with aspirin. UIA growth occurred in 31 (11.4%) patients. In the multivariate Cox analysis, specific aneurysm locations (anterior communicating artery, posterior communicating artery, or middle cerebral artery; hazard ratio, 2.89 [95% CI, 1.22–6.88]; P =0.016) and a UIA size of 5 to <7 mm (hazard ratio, 7.61 [95% CI, 3.02–19.22]; P <0.001) were associated with a high risk of UIA growth, whereas aspirin and well-controlled blood pressure were associated with a low risk of UIA growth (hazard ratio, 0.29 [95% CI, 0.11–0.77]; P =0.013 and hazard ratio, 0.25 [95% CI, 0.10–0.66]; P =0.005, respectively). The cumulative annual growth rates were as high as 40.0 and 53.3 per 100 person-years in the high-risk patients (>1 risk factor) with and without aspirin, respectively.

Conclusions:

Aspirin therapy and well-controlled blood pressure are associated with a low risk of UIA growth; the incidence of UIA growth in high-risk patients in the first year is high, warranting intensive surveillance in this patient group.

Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT02846259.

Characteristics of Unruptured Compared to Ruptured Intracranial Aneurysms: A Multicenter Case-Control Study

BACKGROUND

Only a minority of intracranial aneurysms rupture to cause subarachnoid hemorrhage.

OBJECTIVE

To test the hypothesis that unruptured aneurysms have different characteristics and risk factor profiles compared to ruptured aneurysms.

METHODS

We recruited patients with unruptured aneurysms or aneurysmal subarachnoid hemorrhages at 22 UK hospitals between 2011 and 2014. Demographic, clinical, and imaging data were collected using standardized case report forms. We compared risk factors using multivariable logistic regression.

RESULTS

A total of 2334 patients (1729 with aneurysmal subarachnoid hemorrhage, 605 with unruptured aneurysms) were included (mean age 54.22 yr). In multivariable analyses, the following variables were independently associated with rupture status: black ethnicity (odds ratio [OR] 2.42; 95% confidence interval [CI] 1.29-4.56, compared to white) and aneurysm location (anterior cerebral artery/anterior communicating artery [OR 3.21; 95% CI 2.34-4.40], posterior communicating artery [OR 3.92; 95% CI 2.67-5.74], or posterior circulation [OR 3.12; 95% CI 2.08-4.70], compared to middle cerebral artery). The following variables were inversely associated with rupture status: antihypertensive medication (OR 0.65; 95% CI 0.49-0.84), hypercholesterolemia (0.64 OR; 95% CI 0.48-0.85), aspirin use (OR 0.28; 95% CI 0.20-0.40), internal carotid artery location (OR 0.53; 95% CI 0.38-0.75), and aneurysm size (per mm increase; OR 0.76; 95% CI 0.69-0.84).

CONCLUSION

We show substantial differences in patient and aneurysm characteristics between ruptured and unruptured aneurysms. These findings support the hypothesis that different pathological mechanisms are involved in the formation of ruptured aneurysms and incidentally detected unruptured aneurysms. The potential protective effect of aspirin might justify randomized prevention trials in patients with unruptured aneurysms.

Hemodynamics in a giant intracranial aneurysm characterized by in vitro 4D flow MRI

Experimental and computational data suggest that hemodynamics play a critical role in the development, growth, and rupture of cerebral aneurysms. The flow structure, especially in aneurysms with a large sac, is highly complex and three-dimensional. Therefore, volumetric and time-resolved measurements of the flow properties are crucial to fully characterize the hemodynamics. In this study, phase-contrast Magnetic Resonance Imaging is used to assess the fluid dynamics inside a 3D-printed replica of a giant intracranial aneurysm, whose hemodynamics was previously simulated by multiple research groups. The physiological inflow waveform is imposed in a flow circuit with realistic cardiovascular impedance. Measurements are acquired with sub-millimeter spatial resolution for 16 time steps over a cardiac cycle, allowing for the detailed reconstruction of the flow evolution. Moreover, the three-dimensional and time-resolved pressure distribution is calculated from the velocity field by integrating the fluid dynamics equations, and is validated against differential pressure measurements using precision transducers. The flow structure is characterized by vortical motions that persist within the aneurysm sac for most of the cardiac cycle. All the main flow statistics including velocity, vorticity, pressure, and wall shear stress suggest that the flow pattern is dictated by the aneurysm morphology and is largely independent of the pulsatility of the inflow, at least for the flow regimes investigated here. Comparisons are carried out with previous computational simulations that used the same geometry and inflow conditions, both in terms of cycle-averaged and systolic quantities.