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Cayron AF, Bejuy O, Vargas MI, Colin DJ, Aoki T, Lövblad KO, Bijlenga P, Kwak BR, Allémann E, Morel S. Time-of-flight and black-blood MRI to study intracranial arteries in rats. Eur Radiol Exp 2024; 8:3. [PMID: 38191711 PMCID: PMC10774247 DOI: 10.1186/s41747-023-00407-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 11/07/2023] [Indexed: 01/10/2024] Open
Abstract
Intracranial aneurysms (IAs) are usually incidentally discovered by magnetic resonance imaging (MRI). Once discovered, the risk associated with their treatment must be balanced with the risk of an unexpected rupture. Although clinical observations suggest that the detection of contrast agent in the aneurysm wall using a double-inversion recovery black-blood (BB) sequence may point to IA wall instability, the exact meaning of this observation is not understood. Validation of reliable diagnostic markers of IA (in)stability is of utmost importance to deciding whether to treat or not an IA. To longitudinally investigate IA progression and enhance our understanding of this devastating disease, animal models are of great help. The aim of our study was to improve a three-dimensional (3D)-time-of-flight (TOF) sequence and to develop a BB sequence on a standard preclinical 3-T MRI unit to investigate intracranial arterial diseases in rats. We showed that our 3D-TOF sequence allows reliable measurements of intracranial artery diameters, inter-artery distances, and angles between arteries and that our BB sequence enables us to visualize intracranial arteries. We report the first BB-MRI sequence to visualize intracranial arteries in rats using a preclinical 3-T MRI unit. This sequence could be useful for a large community of researchers working on intracranial arterial diseases.Relevance statement We developed a black-blood MRI sequence to study vessel wall enhancement in rats with possible application to understanding IAs instability and finding reliable markers for clinical decision-making.Key points• Reliable markers of aneurysm stability are needed for clinical decision.• Detection of contrast enhancement in the aneurysm wall may be associated with instability.• We developed a black-blood MRI sequence in rats to be used to study vessel wall enhancement of IAs.
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Affiliation(s)
- Anne F Cayron
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, CMU, Rue Michel-Servet 1, CH-1211, Geneva, Switzerland
- Geneva Center for Inflammation Research, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, Geneva, Switzerland
| | - Olivia Bejuy
- CIBM Center for BioMedical Imaging, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Small Animal Preclinical Imaging Platform, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Maria Isabel Vargas
- Division of Neuroradiology, Faculty of Medicine, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
| | - Didier J Colin
- Small Animal Preclinical Imaging Platform, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Tomohiro Aoki
- Department of Pharmacology, Jikei University School of Medicine, Tokyo, Japan
| | - Karl-Olof Lövblad
- Division of Neuroradiology, Faculty of Medicine, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
| | - Philippe Bijlenga
- Division of Neurosurgery, Department of Clinical Neurosciences, Faculty of Medicine, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
| | - Brenda R Kwak
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, CMU, Rue Michel-Servet 1, CH-1211, Geneva, Switzerland
- Geneva Center for Inflammation Research, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Eric Allémann
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, Geneva, Switzerland
- Small Animal Preclinical Imaging Platform, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Sandrine Morel
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, CMU, Rue Michel-Servet 1, CH-1211, Geneva, Switzerland.
- Geneva Center for Inflammation Research, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
- Division of Neurosurgery, Department of Clinical Neurosciences, Faculty of Medicine, Geneva University Hospitals and University of Geneva, Geneva, Switzerland.
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Cayron AF, Morel S, Allémann E, Bijlenga P, Kwak BR. Imaging of intracranial aneurysms in animals: a systematic review of modalities. Neurosurg Rev 2023; 46:56. [PMID: 36786880 PMCID: PMC9928939 DOI: 10.1007/s10143-023-01953-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 11/28/2022] [Accepted: 01/23/2023] [Indexed: 02/15/2023]
Abstract
Intracranial aneurysm (IA) animal models are paramount to study IA pathophysiology and to test new endovascular treatments. A number of in vivo imaging modalities are available to characterize IAs at different stages of development in these animal models. This review describes existing in vivo imaging techniques used so far to visualize IAs in animal models. We systematically searched for studies containing in vivo imaging of induced IAs in animal models in PubMed and SPIE Digital library databases between 1 January 1945 and 13 July 2022. A total of 170 studies were retrieved and reviewed in detail, and information on the IA animal model, the objective of the study, and the imaging modality used was collected. A variety of methods to surgically construct or endogenously induce IAs in animals were identified, and 88% of the reviewed studies used surgical methods. The large majority of IA imaging in animals was performed for 4 reasons: basic research for IA models, testing of new IA treatment modalities, research on IA in vivo imaging of IAs, and research on IA pathophysiology. Six different imaging techniques were identified: conventional catheter angiography, computed tomography angiography, magnetic resonance angiography, hemodynamic imaging, optical coherence tomography, and fluorescence imaging. This review presents and discusses the advantages and disadvantages of all in vivo IA imaging techniques used in animal models to help future IA studies finding the most appropriate IA imaging modality and animal model to answer their research question.
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Affiliation(s)
- Anne F Cayron
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Rue Michel-Servet 1, CH-1211, Geneva, Switzerland
- Geneva Center for Inflammation Research, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, Geneva, Switzerland
| | - Sandrine Morel
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Rue Michel-Servet 1, CH-1211, Geneva, Switzerland
- Geneva Center for Inflammation Research, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Department of Clinical Neurosciences - Division of Neurosurgery, Geneva University Hospitals and Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Eric Allémann
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, Geneva, Switzerland
| | - Philippe Bijlenga
- Department of Clinical Neurosciences - Division of Neurosurgery, Geneva University Hospitals and Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Brenda R Kwak
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Rue Michel-Servet 1, CH-1211, Geneva, Switzerland.
- Geneva Center for Inflammation Research, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
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Hemodynamic Analysis Shows High Wall Shear Stress Is Associated with Intraoperatively Observed Thin Wall Regions of Intracranial Aneurysms. J Cardiovasc Dev Dis 2022; 9:jcdd9120424. [PMID: 36547421 PMCID: PMC9780790 DOI: 10.3390/jcdd9120424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 11/23/2022] [Accepted: 11/26/2022] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND Studying the relationship between hemodynamics and local intracranial aneurysm (IA) pathobiology can help us understand the natural history of IA. We characterized the relationship between the IA wall appearance, using intraoperative imaging, and the hemodynamics from CFD simulations. METHODS Three-dimensional geometries of 15 IAs were constructed and used for CFD. Two-dimensional intraoperative images were subjected to wall classification using a machine learning approach, after which the wall type was mapped onto the 3D surface. IA wall regions included thick (white), normal (purple-crimson), and thin/translucent (red) regions. IA-wide and local statistical analyses were performed to assess the relationship between hemodynamics and wall type. RESULTS Thin regions of the IA sac had significantly higher WSS, Normalized WSS, WSS Divergence and Transverse WSS, compared to both normal and thick regions. Thicker regions tended to co-locate with significantly higher RRT than thin regions. These trends were observed on a local scale as well. Regression analysis showed a significant positive correlation between WSS and thin regions and a significant negative correlation between WSSD and thick regions. CONCLUSION Hemodynamic simulation results were associated with the intraoperatively observed IA wall type. We consistently found that elevated WSS and WSSNorm were associated with thin regions of the IA wall rather than thick and normal regions.
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Chen J, Liu J, Liu X, Zeng C, Chen Z, Li S, Zhang Q. Animal model contributes to the development of intracranial aneurysm: A bibliometric analysis. Front Vet Sci 2022; 9:1027453. [DOI: 10.3389/fvets.2022.1027453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 10/27/2022] [Indexed: 11/21/2022] Open
Abstract
IntroductionStudies on intracranial aneurysms (IAs) using animal models have evolved for decades. This study aimed to analyze major contributors and trends in IA-related animal research using bibliometric analysis.MethodsIA-related animal studies were retrieved from the Web of Science database. Microsoft Excel 2010, GraphPad Prism 6, VOSviewer, and CiteSpace were used to collect and analyze the characteristics of this field.ResultsA total of 273 publications were retrieved. All publications were published between 1976 and 2021, and the peak publication year is 2019. Rat model were used in most of the publications, followed by mice and rabbits. Japan (35.5%), the United States (30.0%), and China (20.1%) were the top three most prolific countries. Although China ranks third in the number of publications, it still lacks high-quality articles and influential institutions. Stroke was the most prolific journal that accepted publications related to IA research using animal models. Circulation has the highest impact factor with IA-related animal studies. Hashimoto N contributed the largest number of articles. Meng hui journal published the first and second highest cited publications. The keywords “subarachnoid hemorrhage,” “macrophage,” “rupture,” “mice,” “elastase,” “gene,” “protein,” “proliferation,” and “risk factors” might be a new trend for studying IA-related animal research.ConclusionsJapan and the Unites States contributed the most to IA–related animal studies, in terms of both researchers and institutions. Although China ranks third in terms of the number of publications, it should strengthen the quality of its publications. Researchers should pay attention to the latest progress of Stroke, Journal of Neurosurgery, Neurosurgery, and Circulation for their high-quality IA-related animal studies. Using animal IA models, especially mice, to investigate the molecular mechanisms of IA may be the frontier topic now and in future.
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García Feijoo P, Carceller F, Isla Guerrero A, Sáez-Alegre M, Gandía González ML. Beyond Classic Anastomoses Training Models: Overview of Aneurysm Creation in Rodent Vessel Model. Front Surg 2022; 9:884675. [PMID: 35521434 PMCID: PMC9062134 DOI: 10.3389/fsurg.2022.884675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 03/14/2022] [Indexed: 11/29/2022] Open
Abstract
Nowadays, due to the decline in the number of microsurgical clippings for cerebral aneurysms and revascularization procedures, young neurosurgeons have fewer opportunities to participate and train on this type of surgery. Vascular neurosurgery is a demanding subspecialty that requires skills that can only be acquired with technical experience. This background pushes the new generations to be ready for such challenging cases by training hard on different available models, such as synthetic tubes, chicken wings, or placenta vessels. Although many training models for vascular neurosurgery have been described worldwide, one of the best is the rodent vessels model. It offers pulsation, coagulation, and real blood flow conditions in a physiologic atmosphere that mimics perfectly the intracranial human vessels environment, especially in terms of size. However, the current differences in governmental different regulations about the use of living animals in medical experimentation and the social awareness, as well as the lack of financial support, cause more difficulties for neurosurgeons to start with that kind of training. In this review, we describe the tools and techniques as basic steps for vascular microsurgery training by using rodent models, that provide an accurate copy of brain vessels environment under stable conditions. The initial three classical known microanastomoses for neurosurgeons are end-to-end, end-to-side, and side-to-side, but in literature, there have been described other more complex exercises for training and investigation, such as aneurysm models. Although there is still little data available, we aim to summarize and discuss aneurysm's training models and reviewed the current literature on the subject and its applications, including a detailed description of the techniques.
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Chen B, Tao W, Li S, Zeng M, Zhang L, Huang Z, Chen F. Medial Gap: A Structural Factor at the Arterial Bifurcation Aggravating Hemodynamic Insult. J Neuropathol Exp Neurol 2022; 81:282-290. [PMID: 35312777 DOI: 10.1093/jnen/nlac017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Previous studies have reported that intracranial aneurysms frequently occur adjacent to the medial gap. However, the role of the medial gap in aneurysm formation is controversial. We designed this study to explore the potential role of the medial gap in aneurysm formation. Widened artery bifurcations with or without medial gaps were microsurgically created and pathologically stained in the carotid arteries of 30 rats. Numerical artery bifurcation models were constructed, and bidirectional fluid-solid interaction analyses were performed. Animal experiments showed that the apexes of widened bifurcations with a medial gap were prone to being insulted by blood flow compared to those without a medial gap. The bidirectional fluid-solid interaction analyses indicated that artery bifurcations with the medial gap exhibited higher wall shear stress (WSS) and von Mises stress (VMS) at the apex of the bifurcation. The disparity of stress between the gap and no-gap model was larger for widened bifurcations, peaking at 180° with a maximum of 1.9 folds. The maximum VMS and relatively high WSS were located at the junction between the medial gap and the adjacent arterial wall. Our results suggest that the medial gap at the widened arterial bifurcation may promote aneurysm formation.
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Affiliation(s)
- Bo Chen
- From the Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Wengui Tao
- From the Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Shifu Li
- From the Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Ming Zeng
- From the Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Liyang Zhang
- From the Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Zheng Huang
- From the Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Fenghua Chen
- From the Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
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Maupu C, Lebas H, Boulaftali Y. Imaging Modalities for Intracranial Aneurysm: More Than Meets the Eye. Front Cardiovasc Med 2022; 9:793072. [PMID: 35242823 PMCID: PMC8885801 DOI: 10.3389/fcvm.2022.793072] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 01/17/2022] [Indexed: 11/21/2022] Open
Abstract
Intracranial aneurysms (IA) are often asymptomatic and have a prevalence of 3 to 5% in the adult population. The risk of IA rupture is low, however when it occurs half of the patients dies from subarachnoid hemorrhage (SAH). To avoid this fatal evolution, the main treatment is an invasive surgical procedure, which is considered to be at high risk of rupture. This risk score of IA rupture is evaluated mainly according to its size and location. Therefore, angiography and anatomic imaging of the intracranial aneurysm are crucial for its diagnosis. Moreover, it has become obvious in recent years that several other factors are implied in this complication, such as the blood flow complexity or inflammation. These recent findings lead to the development of new IA imaging tools such as vessel wall imaging, 4D-MRI, or molecular MRI to visualize inflammation at the site of IA in human and animal models. In this review, we will summarize IA imaging techniques used for the patients and those currently in development.
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Tutino VM, Zebraski HR, Rajabzadeh-Oghaz H, Waqas M, Jarvis JN, Bach K, Mokin M, Snyder KV, Siddiqui AH, Poppenberg KE. Identification of Circulating Gene Expression Signatures of Intracranial Aneurysm in Peripheral Blood Mononuclear Cells. Diagnostics (Basel) 2021; 11:diagnostics11061092. [PMID: 34203780 PMCID: PMC8232768 DOI: 10.3390/diagnostics11061092] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 06/04/2021] [Accepted: 06/09/2021] [Indexed: 12/18/2022] Open
Abstract
Peripheral blood mononuclear cells (PBMCs) play an important role in the inflammation that accompanies intracranial aneurysm (IA) pathophysiology. We hypothesized that PBMCs have different transcriptional profiles in patients harboring IAs as compared to IA-free controls, which could be the basis for potential blood-based biomarkers for the disease. To test this, we isolated PBMC RNA from whole blood of 52 subjects (24 with IA, 28 without) and performed next-generation RNA sequencing to obtain their transcriptomes. In a randomly assigned discovery cohort of n = 39 patients, we performed differential expression analysis to define an IA-associated signature of 54 genes (q < 0.05 and an absolute fold-change ≥ 1.3). In the withheld validation dataset, these genes could delineate patients with IAs from controls, as the majority of them still had the same direction of expression difference. Bioinformatics analyses by gene ontology enrichment analysis and Ingenuity Pathway Analysis (IPA) demonstrated enrichment of structural regulation processes, intracellular signaling function, regulation of ion transport, and cell adhesion. IPA analysis showed that these processes were likely coordinated through NF-kB, cytokine signaling, growth factors, and TNF activity. Correlation analysis with aneurysm size and risk assessment metrics showed that 4/54 genes were associated with rupture risk. These findings highlight the potential to develop predictive biomarkers from PBMCs to identify patients harboring IAs.
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Affiliation(s)
- Vincent M. Tutino
- Canon Stroke and Vascular Research Center, University at Buffalo, Buffalo, NY 14203, USA; (H.R.-O.); (M.W.); (K.V.S.); (A.H.S.); (K.E.P.)
- Department of Pathology and Anatomical Sciences, University at Buffalo, Buffalo, NY 14203, USA
- Department of Neurosurgery, University at Buffalo, Buffalo, NY 14203, USA
- Department of Mechanical and Aerospace Engineering, University at Buffalo, Buffalo, NY 14228, USA
- Correspondence: ; Tel.: +1-(716)-829-5400; Fax: +1-(716)-854-1850
| | - Haley R. Zebraski
- Department of Biomedical Engineering, University at Buffalo, Buffalo, NY 14228, USA;
| | - Hamidreza Rajabzadeh-Oghaz
- Canon Stroke and Vascular Research Center, University at Buffalo, Buffalo, NY 14203, USA; (H.R.-O.); (M.W.); (K.V.S.); (A.H.S.); (K.E.P.)
- Department of Neurosurgery, University at Buffalo, Buffalo, NY 14203, USA
| | - Muhammad Waqas
- Canon Stroke and Vascular Research Center, University at Buffalo, Buffalo, NY 14203, USA; (H.R.-O.); (M.W.); (K.V.S.); (A.H.S.); (K.E.P.)
- Department of Neurosurgery, University at Buffalo, Buffalo, NY 14203, USA
| | - James N. Jarvis
- Department of Pediatrics, University at Buffalo, Buffalo, NY 14203, USA;
| | - Konrad Bach
- Department of Neurosurgery and Brain Repair, University of South Florida, Tampa, FL 33620, USA; (K.B.); (M.M.)
| | - Maxim Mokin
- Department of Neurosurgery and Brain Repair, University of South Florida, Tampa, FL 33620, USA; (K.B.); (M.M.)
| | - Kenneth V. Snyder
- Canon Stroke and Vascular Research Center, University at Buffalo, Buffalo, NY 14203, USA; (H.R.-O.); (M.W.); (K.V.S.); (A.H.S.); (K.E.P.)
- Department of Neurosurgery, University at Buffalo, Buffalo, NY 14203, USA
| | - Adnan H. Siddiqui
- Canon Stroke and Vascular Research Center, University at Buffalo, Buffalo, NY 14203, USA; (H.R.-O.); (M.W.); (K.V.S.); (A.H.S.); (K.E.P.)
- Department of Neurosurgery, University at Buffalo, Buffalo, NY 14203, USA
| | - Kerry E. Poppenberg
- Canon Stroke and Vascular Research Center, University at Buffalo, Buffalo, NY 14203, USA; (H.R.-O.); (M.W.); (K.V.S.); (A.H.S.); (K.E.P.)
- Department of Neurosurgery, University at Buffalo, Buffalo, NY 14203, USA
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The association between hemodynamics and wall characteristics in human intracranial aneurysms: a review. Neurosurg Rev 2021; 45:49-61. [PMID: 33913050 DOI: 10.1007/s10143-021-01554-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 04/02/2021] [Accepted: 04/20/2021] [Indexed: 12/28/2022]
Abstract
Hemodynamics plays a key role in the natural history of intracranial aneurysms (IAs). However, studies exploring the association between aneurysmal hemodynamics and the biological and mechanical characteristics of the IA wall in humans are sparse. In this review, we survey the current body of literature, summarize the studies' methodologies and findings, and assess the degree of consensus among them. We used PubMed to perform a systematic review of studies that explored the association between hemodynamics and human IA wall features using different sources. We identified 28 publications characterizing aneurysmal flow and the IA wall: 4 using resected tissues, 17 using intraoperative images, and 7 using vessel wall magnetic resonance imaging (MRI). Based on correlation to IA tissue, higher flow conditions, such as high wall shear stress (WSS) with complex pattern and elevated pressure, were associated with degenerated walls and collagens with unphysiological orientation and faster synthesis. MRI studies strongly supported that low flow, characterized by low WSS and high blood residence time, was associated with thicker walls and post-contrast enhancement. While significant discrepancies were found among those utilized intraoperative images, they generally supported that thicker walls coexist at regions with prolonged residence time and that thinner regions are mainly exposed to higher pressure with complex WSS patterns. The current body of literature supports a theory of two general hemodynamic-biologic mechanisms for IA development. One, where low flow conditions are associated with thickening and atherosclerotic-like remodeling, and the other where high and impinging flow conditions are related to wall degeneration, thinning, and collagen remodeling.
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