A Case-control Study of Independent Predictors of Middle Cerebral Artery Aneurysm.
Conditions: Middle Cerebral Artery Aneurysm
Sponsor: Medical University of Silesia

 
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1. STUDY IDENTIFICATION  
Unique Protocol Identification Number: NCT03493035 
Brief Title: Risk Factors of Middle Cerebral Artery Aneurysm (MCAA) 
Official Title: A Case-Control Study of Independent Predictors of Middle Cerebral Artery 
Aneurysm 
Study Type: Observational 
 
2. STUDY STATUS 
Entered Document Date: July 12, 2017 
Record Verification Date: February 14, 2019 
Overall Recruitment Status: Completed 
Study Start Date: June 2015 
Study Completion Date: June 2017 
 
3. SPONSORS/COLLABORATORS 
Responsible Party, by Official Title: Principal Investigator 
Investigator Information: 
Investigator Name: Department of Neurosurgery, Regional Hospital in Sosnowiec, Medical 
University of Silesia in Katowice, Poland 
 
4. OVERSIGHT 
Human Subjects Review: The protocol of the study was approved by the Institutional 
Review Board, and written informed consent will be sought from all the study participants. 
Human Subjects Protection Review Board Status: Submitted, approved 
 
5. STUDY DESCRIPTION 
Brief Summary: 
Current evidence suggests that a principal factor involved in formation, enlargement and 
rupture of cerebral aneurysms are hemodynamic forces acting at arterial bifurcation [1]. Both 
experimental studies in dogs and computational fluid dynamics (CFD) studies demonstrated 
that high levels of wall shear stress (WSS) at arterial bifurcation and high positive WSS 
gradient (WSSG) may lead to remodelling of vascular epithelium and destruction of internal 
elastic membrane, and thus, may play a role in aneurysm formation [2]. While the 
contribution of WSS to aneurysm development raises no controversies, the question whether 

 
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arterial bifurcation morphology might influence the shear stress level is still a matter of 
discussion. The results of glass model studies conducted in the 1970s and more recent CFD 
simulations imply that the magnitude of hemodynamic stress and its distribution at arterial 
bifurcation depend on blood flow characteristics and the bifurcation’s geometry [3-7].  
MCA is one of three sites predisposed to aneurysm formation [8]. Unlike other two 
predilected locations, anterior communicating artery complex (ACoA) and internal carotid 
artery (ICA), MCA is not strictly a part of the arterial circle of Willis. The use of the MCA 
model will enable to minimize the influence of collateral blood flow through communicating 
arteries in asymmetrical forms of the circle of Willis on hemodynamic parameters, and the 
effect of circle geometry on the size of bifurcation angles. 
 
Objectives of Study:   
i) to determine morphometric and hemodynamic parameters of aneurysmal and non-
aneurysmal MCA bifurcations and ii) to analyse their relationship with aneurysm formation. 
 
6. CONDITIONS AND KEYWORDS 
Primary Disease or Condition Being Studied in the Trial, or the Focus of the Study: 
1. Patients (further referred to as cases) diagnosed with unruptured MCA aneurysm.  
2. Patients (further referred to as controls) with no evidence of intracranial pathologies on 3D 
CTA, directed at CT examination due to minor symptoms, such as headache or vertigo.  
 
7. STUDY DESIGN (OBSERVATIONAL) 
Observational Study Model: Case-Control 
Time Perspective: Prospective 
Enrollment Type: Actual 
Number of Groups/Cohorts: 2; Case/Control 
Patient Registry Information: All patients were admitted to the unit based on their signed 
consent form 
Target Follow-Up Duration: NA 
 
Study Design: 
3D CTA Protocol: 
All studies will be performed with a 64-row 128-slice CT system (GE Optima CT 660, GE 
Healthcare, USA) using the following parameters: collimation 39.38 x 0.625 mm, spiral pitch 

 
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0.516:1, anode voltage 120 kV, anode amperage 40-500 mA, rotation time 0.6 seconds, slice 
thickness 0.625 mm. Patients will receive intravenous non-ionic contrast agent (Iomeron 350, 
Bracco Imaging Deutschland GmbH, Konstanz, Germany) at volume adjusted to their body 
weight, up to 50 mL, followed by a 30 mL NaCl flush. Iomeron 350 will be given to the 
basilic vein at a rate of 4-4.5 mL/second with the aid of an automatic syringe (OptiVantage 
DH, Mallincrodt, St Louis, MO, USA). The scanning will begin 15-20 seconds after 
administration of the contrast agent, after reaching attenuation of 100-HU above the baseline 
attenuation, and will last for 6 seconds. The images will be recorded as digital imaging and 
communications in medicine (DICOM) files on a HP Z800 workstation. 
 
Morphometric Analysis of MCA Bifurcations: 
3D CTA scans data in DICOM format will be transferred to Mimics Innovation Suite (MIS) 
platform (Materialise, Leuven, Belgium). Image segmentation and creation of 3D models will 
be carried out with Mimics v.17.0 MIS software (Materialise, Leuven, Belgium). The process 
of segmentation will include main trunks of the MCA and the post-bifurcation branches. 
Trifurcations of the main MCA trunk will be excluded from the morphometric analysis. MCA 
bifurcations from the aneurysm patients will be divided into two groups: the An group with 
aneurysmal MCA bifurcations and the non-An group with contralateral non-aneurysmal MCA 
bifurcations. Also, MCA bifurcations from the controls will be divided into two groups: R-
MCA group with bifurcations of the right MCA and the L-MCA group with bifurcations of 
the left MCA. Before the morphometric calculations, the MCA aneurysms in the An group 
will be digitally erased using the Mimics software. After completing the 3D model, the vessel 
centreline will be fitted automatically with a computer-aided design (CAD) tool. The other 
parameters: tortuosity, the largest curvature of MCA main trunk and the largest curvatures of 
the two post-bifurcations branches will be calculated automatically according to the 
centreline. The points of the largest curvature will be set as close to the bifurcation as 
possible, but in a distance longer than 5 mm. Based on these points, the cross-sectional area 
and the best fit diameter of the MCA trunk (p0 and d0, respectively) and its two post-
bifurcation branches (p1, d1 and p2, d2 for the larger and smaller branch, respectively) will be 
estimated. The best fit diameters will be then used to calculate the radii of the main MCA 
trunk (r0) and its branches (r1 and r2 for the larger and smaller branch, respectively) using the 
following formula: 
r=d/2 
(1) 

 
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where r – radius and d – the best fit diameter. The radii will be used to calculate two ratios 
describing the bifurcation asymmetry:  
asymmetry ratio=r2
2r1
-2 
(2) 
and 
area ratio=(r1
2+r2
2)r0
-2 
(3) 
The centrelines and the largest curvature points will be exported to 3-matic v.9.0 MIS 
software to determine angles between the bifurcation components. The apices of the angles 
will be defined as the largest curvature points for the MCA trunk and its both branches, and 
the intersection of both centrelines. The angle between the post-bifurcation branches (α angle) 
will be calculated, along with the angles between the MCA trunk and the larger and the 
smaller branch (β and γ angle, respectively). Finally, the angles between each post-bifurcation 
branch and the direction of the MCA trunk will be calculated as: 
Φ1=180-β 
(4) 
Φ2=180-γ 
(5) 
 
Transcranial Color-Coded Sonography (TCCS) Protocol: 
All TCCS examinations will be performed by the same researcher using a Vivid 3 Pro (GE 
Healthcare, Chicago, Illinois, USA) equipped with a multi-frequency transcranial probe (1.5-
3.6 MHz), according to the previously described standards [9]. Anterior cerebral circulation 
will be imaged through the temporal acoustic window with the subject in a supine position. 
Angle-corrected mean blood flow velocity (Vm), peak systolic velocity (Vps) and end-diastolic 
velocity (Ved) will be measured for both MCAs. Pulsatility index (PI) and volume flow rate 
(VFR) in each vessel will be calculated as:  
PI=(Vps-Ved)Vm
-1 
(6) 
VFR=Vmp0 
(7) 
where p0 – a cross-sectional area of the main MCA trunk. 
 
Analysis Plan: 
The following variables will be evaluated as potential risk factors for MCA aneurysm 
formation: radii and cross-sectional area of the main MCA trunk (r0, p0) and its branches (r1, 
p1 and r2, p2 for the larger and smaller branch, respectively), tortuosity of MCA trunk, 
asymmetry ratio, r2
2r1
-2, area ratio, (r1
2+r2
2)r0
-2, Φ1 (°), Φ2 (°), α (°), Vm, (cm/s), VFR (cm3/s) 
and PI. Normal distribution of the study variables will be verified with Shapiro-Wilk test. The 
significance of intergroup and intragroup differences will be verified with Mann-Whitney U-

 
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test and Wilcoxon signed-rank test, respectively. All morphological and hemodynamic 
parameters shown to differ significantly between the study groups will be subjected to logistic 
regression analysis with stepwise addition mode. The potential predictors of MCA aneurysm 
will be identified on univariate analysis, and the relationship between pairs of the significant 
predictors will be determined based on Pearson’s linear correlation coefficients. The variables 
with P-values <0.1 on univariate analysis, except those being correlated with one another, will 
be included in multivariate logistic regression model, to identify independent predictors of 
MCA aneurysm. The results will be presented as odds ratios (ORs) and their 95% confidence 
intervals (CIs). The independent predictors of MCA aneurysm will be subjected to receiver 
operating characteristic (ROC) analysis to identify their cut-off values with optimal sensitivity 
and specificity. The results will be considered statistically significant for p-values < 0.05. 
Statistical analyses will be performed with Statistica v.13.3 package (StatSoft, Tulsa, 
Oklahoma, USA). 
 
Limitations: 
First, we will examine patients who had already been diagnosed with the MCA aneurysms. 
Thus, it cannot be excluded that at early stages of the aneurysm formation, morphometric and 
hemodynamic parameters of the MCA bifurcation might have been slightly different than they 
will be at the time of the study. Second, although the MCA aneurysms will be erased from the 
vascular images before the morphometric analysis, their presence might interfere with the 
bifurcation geometry. Third, the study might also suffer from a selection bias. Although the 
participants will be enrolled prospectively, some might be inadvertently excluded due to small 
size of aneurysms missed on CT scans.  
 
8. OUTCOME MEASURES 
Primary Outcome Measure:  
1. Computed tomography angiography (CTA) analysis of the cross-sectional area of the MCA 
bifurcations.  
CTA scans in DICOM format will be used to create three-dimensional (3D) models of MCA 
bifurcation using Mimics Innovation Suite platform (Materialise, Leuven, Belgium). The 
points including the largest curvature of MCA main trunk and two post-bifurcations branches 
will be automatically calculated according to the centreline fitted with a computer-aided 

 
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design (CAD) tool. In these points the cross-sectional area (mm2) of the MCA trunk and its 
two post-bifurcation branches will be calculated automatically. 
2. Computed tomography angiography (CTA) analysis of the best fit diameter of the MCA 
bifurcations.  
CTA scans in DICOM format will be used to create three-dimensional (3D) models of MCA 
bifurcation using Mimics Innovation Suite platform (Materialise, Leuven, Belgium). The 
points including the largest curvature of MCA main trunk and two post-bifurcations branches 
will be automatically calculated according to the centreline fitted with a computer-aided 
design (CAD) tool. In these points the best fit diameter (mm) of the MCA trunk and its two 
post-bifurcation branches will be calculated automatically. 
3. Computed tomography angiography (CTA) analysis of the angles between the MCA 
bifurcations components.  
CTA scans in DICOM format will be used to create three-dimensional (3D) models of MCA 
bifurcation using Mimics Innovation Suite platform (Materialise, Leuven, Belgium). The 
points of the largest curvature of MCA main trunk and two post-bifurcations branches will be 
calculated according to the centreline fitted automatically with a computer-aided design 
(CAD) tool. The centrelines and the largest curvature points will be exported to 3-matic v.9.0 
MIS software. Three points of the largest curvatures (the main MCA trunk and two post-
bifurcations branches) together with the point of the intersection of both centrelines passing 
through the main trunk MCA and both branches will determine the arms and the apex of the 
three angles. The following angle values will be calculated automatically: the angle between 
the post-bifurcation branches (α angle) and the angles between the MCA trunk and the larger 
and the smaller branches (β and γ angle). 
4. Pulsatility Index (PI) as calculated from transcranial color-coded sonography (TCCS) blood 
flow velocities (cm/s)  
The assessment of blood flow velocities in both MCAs will be performed by transcranial 
color-coded sonography (TCCS) using a Vivid 3 Pro (GE Healthcare, Chicago, Illinois, USA) 
equipped with a multi-frequency transcranial probe (1.5-3.6 MHz). For both MCAs the 
following will be automatically measured: 

 
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1. mean blood flow velocity (V) [cm/s] 
2. peak systolic velocity (Vps) [cm/s] 
3. end-diastolic velocity (Ved) [cm/s] The velocity measurements will be used 
to calculate in each vessel the pulsatility index (PI), calculated using the 
following formula: PI=(Vps-Ved)/V 
 
5. Volume Flow Rate (VFR) as calculated from transcranial color-coded sonography (TCCS) 
blood flow velocities (cm/s)  
The assessment of blood flow velocities in both MCAs will be performed by transcranial 
color-coded sonography (TCCS) using a Vivid 3 Pro (GE Healthcare, Chicago, Illinois, USA) 
equipped with a multi-frequency transcranial probe (1.5-3.6 MHz). For both MCAs the 
following will be automatically measured: 
1. mean blood flow velocity (V) [cm/s] 
2. peak systolic velocity (Vps) [cm/s] 
3. end-diastolic velocity (Ved) [cm/s] The velocity measurements will be used 
to calculate in each vessel the volume flow rate (VFR) using the following 
formula: VFR=V*p, where p - a cross-sectional area of the main MCA 
trunk, calculated from the morphometric analysis 
 
9. ELIGIBILITY 
Sex/Gender: male and female, a minimum of 75 cases and 75 age- and sex-matched controls  
Age Limits: <75 years 
Eligibility Criteria: The study will include patients (further referred to as cases) with 
unruptured MCA aneurysm diagnosed on three-dimensional computed tomography 
angiography (3D CTA).  
Case inclusion criteria 
- 
all patients with unruptured MCA aged between 18-75 years 
Case exclusion criteria 
- 
refusal to participate in the study 
- 
inability to give informed consent 
- 
presence of multiple cerebral aneurysms 

 
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- 
presence of pathologies, other than MCA aneurysm, in the central nervous system that 
could have a potential effect on cerebral blood flow (e.g. ischemic stroke, intracerebral 
or subarachnoid haemorrhage) 
- 
severe systemic disorders (e.g. neoplastic disease) 
- 
severe heart failure or multi-organ failure 
- 
hemodynamically significant internal carotid artery stenosis 
- 
pregnancy 
- 
family history of cerebral aneurysms. 
 
Definition and Recruitment of Controls: 
The control group will include patients with no evidence of intracranial pathologies on 3D 
CTA, referred to establish the ethology of minor symptoms, such as headache or vertigo. 
Inclusion criteria for the control group 
- 
all patients aged between 18-75 years with no evidence of intracranial pathologies on 
3D CTA 
Exclusion criteria for the control group 
- 
refusal to participate in the study 
- 
inability to give informed consent 
- 
presence of pathologies in the central nervous system that could have a potential effect 
on cerebral blood flow (e.g. ischemic stroke, intracerebral or subarachnoid 
haemorrhage) 
- 
severe systemic disorders (e.g. neoplastic disease) 
- 
severe heart failure or multi-organ failure 
- 
hemodynamically significant internal carotid artery stenosis 
- 
pregnancy 
- 
family history of cerebral aneurysms. 
 
10. CONTACTS, LOCATIONS, AND INVESTIGATOR INFORMATION 
Central Contact Person: Wojciech Kaspera 
Official Title: MD PhD 
Affiliation: Department of Neurosurgery, Regional Hospital in Sosnowiec, Medical 
University of Silesia in Katowice, Poland 
Phone: +48323682551 
Email: wkaspera@sum.edu.pl 

 
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Abbreviations: 3D, three-dimensional; ACoA, anterior communicating artery complex; AUC, 
area under curve; BA, basilar artery; CAD, computer-aided design; CFD, computational fluid 
dynamics; CI, confidence interval; CT, computed tomography; CTA, computed tomography 
angiography; DICOM, digital imaging and communications in medicine; ICA, internal carotid 
artery; MCA, middle cerebral artery; MIS, Mimics Innovation Suite; OR, odds ratio; PI, 

 
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pulsatility index; ROC, receiver operating characteristic; SD, standard deviation; TCCS, 
transcranial color-coded sonography; VFR, volume flow rate; WSS, wall shear stress.