Anatomic variants of the anterior part of the cerebral arterial circle at multidetector computed tomography angiography

Prevalence of ACA variations: A systematic review and meta‑analysis

The anterior cerebral artery (ACA) and its divisions enclose symptomatically critical and supplementary differentiations. Anatomical variations of the distal ACA that are irregularly detected can be separated into three major groups, namely, azygos, bihemispheric and median ACA variations. The present study performed a systematic review and meta-analysis. The PICOS criteria and electronic databases, namely the Cochrane Library, PubMed (until December, 2023), Embase (until December, 2023) and MEDLINE (until December, 2023) were used to identify 48 articles to fulfill the eligible criteria. As a limited number of studies exist on the prevalence of ACA anatomical variations, the present meta-analysis aimed to determine the precise incidence of these variants. In addition, with the comparative description between cadaveric (autopsy) and imaging cases, more accurate results were extract from the prevalence presentation of the distal ACA variants. On the whole, no statistically significant differences were found between autopsy and imaging studies.

Identifying hemodynamic factors associated with the rupture of anterior communicating artery aneurysms based on global modeling of blood flow in the cerebral artery network

Anterior communicating artery (ACoA) aneurysms are more prone to rupture compared to aneurysms present in other cerebral arteries. We hypothesize that systemic blood flow in the cerebral artery network plays an important role in shaping intra-aneurysmal hemodynamic environment thereby affecting the rupture risk of ACoA aneurysms. The majority of existing numerical studies in this field employed local modeling methods where the physical boundaries of a model are confined to the aneurysm region, which, though having the benefit of reducing computational cost, may compromise the physiological fidelity of numerical results due to insufficient account of systemic cerebral arterial hemodynamics. In the present study, we firstly carried out numerical experiments to address the difference between the outcomes of local and global modeling methods, demonstrating that local modeling confined to the aneurysm region results in inaccurate predictions of hemodynamic parameters compared with global modeling of the ACoA aneurysm as part of the cerebral artery network. Motivated by this finding, we built global hemodynamic models for 40 ACoA aneurysms (including 20 ruptured and 20 unruptured ones) based on medical image data. Statistical analysis of the computed hemodynamic data revealed that maximum wall shear stress (WSS), minimum WSS divergence, and maximum WSS gradient differed significantly between the ruptured and unruptured ACoA aneurysms. Optimal threshold values of high/low WSS metrics were determined through a series of statistical tests. In the meantime, some morphological parameters of aneurysms, such as large nonsphericity index, aspect ratio, and bottleneck factor, were found to be associated closely with aneurysm rupture. Furthermore, multivariate logistic regression analyses were performed to derive models combining hemodynamic and morphological parameters for discriminating the rupture status of aneurysms. The capability of the models in rupture status discrimination was high, with the area under the receiver operating characteristic curve reaching up to 0.9. The findings of the study suggest that global modeling of the cerebral artery network is essential for reliable quantification of hemodynamics in ACoA aneurysms, disturbed WSS and irregular aneurysm morphology are associated closely with aneurysm rupture, and multivariate models integrating hemodynamic and morphological parameters have high potential for assessing the rupture risk of ACoA aneurysms.

Anterior Interhemispheric Approach for the Surgical Treatment of Azygos Anterior Cerebral Artery Aneurysms: A Case Series

The azygos artery is an uncommon vascular variant of the anterior cerebral artery (ACA). This anomaly is associated in a high percentage with aneurysms. Management of azygos ACA aneurysms represents a surgical challenge. We present five patients who underwent microsurgical treatment for distal azygos ACA aneurysms with complex morphology. Four patients showed subarachnoid hemorrhage (SAH) and one complained of sentinel headache. Early preoperative digital subtraction angiography (DSA) or computerized tomography angiography (CTA) was performed. All patients were treated by surgical clipping via an anterior interhemispheric approach. During follow-up, all patients had a satisfactory outcome, with postoperative angiograms showing complete resolution of aneurysms.

Machine Learning for Onset Prediction of Patients with Intracerebral Hemorrhage

Objective: Intracerebral hemorrhage (ICH) has a high mortality and long-term morbidity and thus has a significant overall health–economic impact. Outcomes are especially poor if the exact onset is unknown, but reliable imaging-based methods for onset estimation have not been established. We hypothesized that onset prediction of patients with ICH using artificial intelligence (AI) may be more accurate than human readers. Material and Methods: A total of 7421 computed tomography (CT) datasets between January 2007–July 2021 from the University Hospital Basel with confirmed ICH were extracted and an ICH-segmentation algorithm as well as two classifiers (one with radiomics, one with convolutional neural networks) for onset estimation were trained. The classifiers were trained based on the gold standard of 644 datasets with a known onset of >1 and <48 h. The results of the classifiers were compared to the ratings of two radiologists. Results: Both the AI-based classifiers and the radiologists had poor discrimination of the known onsets, with a mean absolute error (MAE) of 9.77 h (95% CI (confidence interval) = 8.52–11.03) for the convolutional neural network (CNN), 9.96 h (8.68–11.32) for the radiomics model, 13.38 h (11.21–15.74) for rater 1 and 11.21 h (9.61–12.90) for rater 2, respectively. The results of the CNN and radiomics model were both not significantly different to the mean of the known onsets (p = 0.705 and p = 0.423). Conclusions: In our study, the discriminatory power of AI-based classifiers and human readers for onset estimation of patients with ICH was poor. This indicates that accurate AI-based onset estimation of patients with ICH based only on CT-data may be unlikely to change clinical decision making in the near future. Perhaps multimodal AI-based approaches could improve ICH onset prediction and should be considered in future studies.

Bilateral aplasia of the anterior cerebral artery in the presence of its vascular source: a case report

PURPOSE

Our goal was to investigate the cases of bilateral aplasia of the anterior cerebral artery (ACA).

METHODS

The macro- and microdissection of the target human brain arteries of 388 cadaveric cases was applied under the magnifying glass. Each case was photographed and diagrammatically represented in the workbook. The length and the outer diameter of the corresponding arteries on the photos were measured using a computer software program.

RESULTS

There was only one case (1/388 or 0.25%) of bilateral ACA aplasia that belonged to a male adult cadaver. Except for the variations of the posterior communicating artery on one side and the basilar artery, the instance of cerebral pathology was not recorded in this case. We compared the recent case with available literature cases.

CONCLUSION

Summarizing small number of literature cases, the recent case of bilateral ACA aplasia as the fifth case discovered so far, represents a true morphological rarity.

Variable Anatomy of the Middle Cerebral Artery from Its Origin to the Edge of the Sylvian Fissure: A Direct Fresh Brain Study

The middle cerebral artery (MCA) is a major artery supplying blood to the brain and a common site of surgically treatable intracranial aneurysms. The MCA has anatomic variations that may have clinical significance. In order to investigate and document the extent of such variations, the MCA in 100 fresh brain hemispheres from 50 deceased patients, obtained from the Police Surgeon Office, Yangon General Hospital, Myanmar, was dissected and examined. Double MCA was observed in 2% of specimens. The termination patterns were bifurcation (72%), trifurcation (16%), and primary trunk (12%); early bifurcation was also observed (3%). The mean length of the main trunk (MT) was 20.6 ± 6.2 mm. The number of perforators ranged from 4 to 15 (mean = 9); most arose from the MT (96%), and the others originated at the bifurcation point (3%) and in postbifurcation divisions (1%). All of the perforators (100%) had a single branching pattern. The number of cortical branches ranged from 6 to 13 and included the orbitofrontal (98%), prefrontal (99%), precentral (95%), central (98%), temporopolar (87%), anterior temporal (89%), middle temporal (24%), posterior temporal (62%), temporo-occipital (69%), anterior parietal (88%), angular (83%), and posterior parietal (57%) arteries. Early cortical branches emerged from the MT in 52% of specimens. These data can help anatomists, radiologists, and neurosurgeons in preoperative assessment, surgical planning, and selection of surgical approach.

Radiological classification of azygos anterior cerebral artery and evaluation of the accompanying vascular anomalies

PURPOSE

There is not a classification of azygos anterior cerebral artery (ACA) based on anatomical branching levels in the literature. In the present study, a classification of azygos ACA was made based on radiological imaging for a common terminology, and frequency, accompanying vascular anomalies and malformations were investigated.

METHODS

A total of 4913 cases who had brain CTA, MRA, contrast-enhanced MRI and DSA in January 2010-January 2020 period were screened for the study. Based on anatomical branching level, azygos ACAs were classified into four groups. Aneurysms, anomalies and malformations accompanying azygos ACA were identified. The associations of azygos ACA types with the presence of aneurysm or ACA A1 segment anomalies were investigated.

RESULTS

Azygos ACA was observed in 57 cases (29 male and 28 female) and frequency of azygos ACA was 1.16%. Average age of the cases with ACA was 56.19 ± 19.65 years. Forty-eight of the cases had type C azygos ACA, four cases type B, four cases type D and one case type A azygos ACA. A total of nine intracranial aneurysms were identified in seven of the cases (12.28%). Five of the aneurysms were located in MCA and four in distal ACA. Most common vascular anomalies accompanying azygos ACA were unilateral vertebral artery hypoplasia and ACA A1 segment hypoplasia. Azygos types did not have significant correlations with the presence of aneurysms or ACA A1 segmental anomalies (p = 0.683 and p = 0.949, respectively).

CONCLUSION

Azygos ACA is a rare variation, but it could be accompanied by aneurysms or other vascular anomalies.

A1 asynchrony, a potential risk factor for the rupture of anterior communicating artery aneurysms: A computational fluid dynamics study

INTRODUCTION AND OBJECTIVES

The anterior communicating complex is one the most common locations for aneurysm development. It receives blood from both carotid circulations and the effect of synchrony on the arrival of blood flow has not been previously studied. The objective of this study was to compare the asynchrony conditions of the A1 pulse and its effects on the haemodynamic conditions of anterior communicating artery (ACoA) aneurysms.

MATERIALS AND METHODS

From 2008 to 2017, 54 anterior communicating artery aneurysms treated at our centre were included in the study. Computational fluid dynamics (CFD) techniques were employed and simulations consisted of complete conditions of synchrony and introducing a delay of 0.2s in the non-dominant A1 artery. Time-averaged wall shear stress (TAWSS), low shear area (LSA), A1 diameter and ACoA angles were measured.

RESULTS

The difference in the LSA in conditions of synchrony and asynchrony resulted in a broad range of positive and negative values. The symmetry index (p=0.04) and A1/A2 angle on the dominant artery (p=0.04) were associated with changes in LSA.

CONCLUSIONS

In asynchrony, LSA increased in the absence of A1 asymmetry and low A1/A2 angles, potentially increasing the risk of aneurysm rupture in this location.

Magnetic resonance angiography of hypoplastic A1 segment of anterior cerebral artery at 3.0-Tesla in Andhra Pradesh population of India

Pre-communicating or A1 segment of anterior cerebral artery (A1ACA) hypoplasia can negotiate the anterior cerebral circulation. Not many studies have been examined the association of hypoplastic A1ACA and cerebral ischemic stroke (CIS). In this study the authors' want to accomplish the relationship between hypoplastic A1ACA and outcomes among the patients with CIS in Andhra Pradesh population of India. Retrospective review of prospectively identified 201 adult patients with CIS from 2015 to 2017 was achieved. Patients underwent 3.0T intracranial magnetic resonance angiography were compared with clinical and radiological aspects between male and female cases of A1ACA hypoplasia with associated variations in the circle of Willis. The obtained data was statistically analysed using SPSS software version 16.0 for Windows and P-value <0.05 was considered as significant. Chi-square test was applied to find out the association between the sex and incidence of hypoplastic A1ACA. Sixty-four of 201 patients with A1ACA hypoplasia with no aplastic cases were recorded. It was found to be more in males than females and common on right than left side. Frequent neurological indications such as headache, dizziness, visual instability, nausea, weakness of extremities and seizure were noted and most cases were associated with CIS. Hypoplastic A1ACA often associated with ischemia of terminal branches of ipsilateral ACA which is compromised by the blood flow via contralateral ACA. In this study, though the CIS is not directly related to hypoplastic A1ACA, any alterations in A1 segment is a considerable risk factor of stroke.

A difficult-to-treat Acom aneurysm with the combined vascular anomaly of Acom fenestration and accessory anterior cerebral artery

Background:

Vascular anomaly and aneurysmal formation of an anterior communicating artery (Acom) complex has often been reported. Because of such a complicated relationship between the vascular structure and aneurysms, Acom aneurysm is one of the most difficult aneurysms to treat among other common anterior circulation aneurysms. We experienced an extremely rare and difficult-to-treat case of ruptured Acom aneurysm with the combined vascular anomaly of the Acom fenestration and an accessory anterior cerebral artery (ACA).

Case Description:

A 29-year-old man underwent a clipping surgery for a ruptured Acom aneurysm with an Acom fenestration and an accessory ACA. By reasons of the complicated Acom structure and a posteriorly-projecting aneurysm, the patient was operated via an interhemispheric approach, which is generally reported to provide the best operative view for all types of Acom aneurysms. However, we could not help applying a clip in the narrow working space and the limited operative view, due to the poor mobilization of Acom complex and the interruption by an accessory ACA.

Conclusion:

The interhemispheric approach may exceptionally have a blind area behind the Acom complex in the case of Acom aneurysms with an accessory ACA. Additionally, the aneurysms arising from the Acom fenestration strongly require neurosurgeons to take a more accurate surgical approach to obtain a direct visualization for an aneurysmal neck.

Analysis of Accessory Pudendal Artery Transection on Erections During Robot-Assisted Radical Prostatectomy

PURPOSE

To compare the recovery of erections and potency following the transection of accessory pudendal arteries (APAs) in men undergoing robot-assisted radical prostatectomy (RARP) compared with men with normal vascular anatomy.

MATERIALS AND METHODS

A total of 880 consecutive patients who underwent RARP from January 1, 2007 to December 31, 2014 were included with prospectively collected data in cross-sectional analysis. Erectile function (EF) was assessed preoperatively and postoperatively at 3, 6, 12, and 24 months using the International Index of Erectile Function (IIEF)-5, a percent erection fullness compared to preoperative status, and two Expanded Prostate Cancer Index (EPIC) questions: (1) are erections firm enough for penetration and (2) are they satisfactory?

RESULTS

Two hundred thirty-one (33.1%) men had APAs transected. There were no significant differences in baseline demographics or clinical characteristics in men with or without APAs transected. Multivariate analyses demonstrated that age (confidence interval [95% CI]: 0.94, 0.99) and baseline IIEF-5 (95% CI: 1.15, 1.26) strongly correlated with recovery of erections and potency. Transection of APAs was not a significant predictor of erectile dysfunction (ED).

CONCLUSION

Good surgical technique dictates the preservation of APAs. However, when preservation is questioned, we found that APA transection had no measurable effect on recovery of erections or potency regardless of age, preoperative ED, or number of APAs transected.

Detailed description of the anterior cerebral artery anomalies observed in a cadaver population

Anomalies of the anterior cerebral artery (ACA) include the median ACA (MedACA), bihemispheric ACA (BihemACA) and the azygos ACA. Knowledge of these anomalies can be crucial to clinicians and neurosurgeons, especially during surgeries involving the interhemispheric region and in the interpretation of the clinical signs of a stroke. Since few reports exist on the origin, area supplied, diameter and length of the ACA anomalies, the aim of this study is to give a detailed description on the anatomy of the ACA anomalies. The ACAs of 60 brains were injected with a colored silicone. When an anomaly was observed, a detailed illustration of the course and pattern of the ACA and cortical branches were made. The origins and the areas supplied by the anomalous arteries were noted. The external diameter was measured using a digital micrometer and the length was measured using string and a ruler. There were seven cases (11.7%) of a MedACA and 12 cases (20.0%) of a BihemACA. The MedACA originated mostly from the anterior communicating artery, and from the A2 segment in one case. The MedACA was bilateral in four cases and unilateral in three cases. Excluding Cases 5 and 9, the BihemACA cases can be divided into two groups; one branch to the left hemisphere (n=3), and one branch to the right hemisphere (n=7). The average diameter of both the BihemACA and MedACA was 1.8mm. Studies rarely provide additional information on these anomalies. Therefore, the present study elaborated on the origin, diameter, length and the area supplied by these anomalies. The definitions are described in the literature, although additional criteria were still lacking and this was provided in the present study. Since information on these aspects of the ACA anomalies is scarce, future research should give detailed descriptions on the ACA anomalies.

[Microsurgical anatomy of perforating branches of anterior communicating artery]

INTRODUCTION

The anterior communicating artery (ACoA) gives perforating branches to the optic chiasma, the hypothalamus and the corpus callosum. Perforating branches are variable (number, direction). Nevertheless, their knowledge is crucial during surgery of this area to spare injuries leading to ischemic post-operative complications.

OBJECTIVE

The objective was to update the anatomical knowledge about perforating branches of the ACoA.

METHODS

The study was led on a series of seven brains taken from human cadavers. An injection of latex neoprene was performed for every case. The region of interest was observed under operating microscope. Were examined: the length of the ACoA, its diameter, its orientation, its configuration and perforating branches (number and areas).

RESULTS

Three cases on five presented with an anatomical variation at the level of the ACoA. The average length of AcoA was 2.1 millimeters (min: 2, max: 2.2). The average diameter of the ACoA was 1.67 mm (min: 1.1, max: 2.1). The average number of perforating branches was 4.2 (min: 2, max: 6). The presence of a median artery of the corpus callosum seemed to correlated with a low number of perforating branches. Branches supplying the optic chiasma seemed to be more numerous.

The impact of absent A1 segment on ischemic stroke characteristics and outcomes

BACKGROUND

A1 segment is the proximal portion of anterior cerebral artery. Absence of the A1 segment can compromise anterior cerebral collateral blood flow. Few studies have examined the association of an absent A1 segment and ischemic stroke outcome. We sought to determine the association between A1 absence and affected vessel territory, stroke volume, and outcomes among patients with acute ischemic stroke (AIS).

METHODS

A retrospective review of prospectively identified patients with AIS from July 2008 to March 2013 was performed. Patients without intracranial vascular imaging were excluded. We compared patients with absent A1 to patients with bilateral A1 segments in terms of demographics, stroke severity (as measured by National Institute of Health Stroke Scale [NIHSS]), vascular distribution, and in-hospital mortality using the chi-square test and logistic regression.

RESULTS

Of the 1146 patients with AIS and intracranial vascular imaging, 5.9% patients (n = 68) had absent A1. Compared with other AIS patients, those with absent A1 were older (65 vs. 63 years old, respectively, P = .016). There was no difference between groups in terms of the vascular distribution or the side of the stroke. The median volume of the infracted tissue was similar across the groups even when it was stratified according to the Treatment of Acute Stroke Trial classification. Patients with an absent A1 had twice higher odds of in-hospital mortality (odds ratio, 2.4; 95% confidence interval, 1.1-5.2; P = .028); however, significance was lost after adjusting to age, NIHSS at baseline, and glucose on admission. Other outcome measures were similar across the groups.

CONCLUSIONS

In our sample, patients with an absent A1 segment did not have a specific vascular distribution, larger infarct volume, or worse outcomes.

Mirror image distal anterior cerebral artery aneurysms treated with coil embolization. a report of two cases and literature review

Mirror image aneurysms of the distal anterior cerebral arteries (DACA) are rare. To the best of our knowledge this is the first case report of two patients with mirror image DACA aneurysms treated successfully with coil embolization. The association of aneurysms with anatomic variants has been extensively reported. We may speculate that the remnants of the failed regression of the supreme anterior communicating artery could lead to an increase in stress across their territorial bifurcation, leading to the development of mirror image DACA aneurysms. We found the endovascular treatment of mirror image DACA aneurysms to be feasible and effective. If possible, we suggest the treatment of both aneurysms in one procedure.

Contribution of the hemodynamics of A1 dysplasia or hypoplasia to anterior communicating artery aneurysms: a 3-dimensional numerical simulation study

OBJECTIVE

To explore the association between the hemodynamics and formation, growth, and rupture of aneurysms in anterior communicating arteries (ACoA) with A1 dysplasia or hypoplasia.

METHODS

A series of 3-dimensional numerical simulation models of the anterior communicating artery complex (ACoAC) were designed geometrically. The diameter of A1 was fixed on one side and decreased gradually on the other side. Three groups of ACoA aneurysm model growth were constructed with different positions to the dominant bifurcation. Blood flow was modeled as an incompressible Newtonian fluid described by the unsteady Navier-Stokes equations. Vessel walls were assumed to be rigid; no slip boundary conditions were applied at the walls.

RESULTS

Wall shear stress (WSS), flow velocity, and pressure were influenced by the dynamic variations of A1 diameter. When the diameter of the nondominant A1 gradually decreased, WSS and flow velocity dynamically increased in the dominant bifurcation and pressure decreased. Wall shear stress differences were significant between the dominant and nondominant bifurcations (t = 6.543; P < 0.05). With aneurysm growth, WSS and flow velocity gradually decreased, and turbulence appeared. Wall shear stress was lower at the bifurcation than that 0.02 mm and 0.1 mm to the bifurcation, whereas flow velocity and turbulent flow were more obvious.

CONCLUSIONS

A1 dysplasia/hypoplasia is a potential risk factor in the formation of ACoA aneurysms. Wall shear stress increase may contribute to aneurysm formation. Wall shear stress decrease and turbulent flow may be responsible for the growth and rupture of ACoA aneurysms. The hemodynamic mechanism in the growth and rupture of aneurysms in different locations might be different.