Intracranial Arteriovenous Malformations During Pregnancy and Puerperium-A Retrospective Nationwide Population-Based Cohort Study.

BACKGROUND AND OBJECTIVES: The knowledge about the management of patients with brain arteriovenous malformations (AVM) during pregnancy is limited, owing partly to insufficient evidence about the outcomes of newborns. This study aims to explore symptomatic AVMs and their outcomes during pregnancy, delivery, and the postpartum period. METHODS: We conducted a retrospective analysis by combining patients with symptomatic AVM from a nationwide population-based cohort of all women with a pregnancy resulting in delivery during 1987 to 2016 (n = 1 773 728 deliveries) and our AVM database (n = 805, 1942-2014). Cerebrovascular events during pregnancy were identified through International Classification of Diseases-9, International Classification of Diseases-10, or surgical procedure codes from the Hospital Discharge and Medical Birth Registers. Our analysis focused on treatment characteristics and outcomes of patients with AVM hemorrhage or symptomatic AVM during pregnancy, delivery, or puerperium. RESULTS: A total of 28 women with symptomatic AVMs during pregnancy, delivery, or postpartum period were followed for an average of 12.8 years (SD = 15.5) after admission. Among them, 21 (75%) experienced AVM hemorrhages during pregnancy, puerperium, or delivery. The mean age of patients was 28.9 years (SD = 5.5). Hemorrhages occurred predominantly during the second (n = 9, 43% of all ruptures) or the third trimester (n = 5, 24%). Two AVM ruptures occurred during labor. Treatment for AVM took place during pregnancy (n = 7, 25%) or puerperium (n = 3, 14%) in 10 patients (35.7%). Only 5 mothers (17.8%) had not been previously pregnant. There was no significant difference in mean Apgar scores between those with AVM hemorrhage (8.3) and those without (8.4). CONCLUSION: Most mothers in the study had prior pregnancies, suggesting a potentially weaker association between AVM rupture and pregnancy compared to previous reports. Notably, 2 AVM ruptures occurred during spontaneous vaginal deliveries. Outcomes were generally favorable in both mothers and infants. More research is needed to refine our understanding of the optimal timing for invasive treatment during pregnancy.

Proteomics on human cerebral cavernous malformations reveals novel biomarkers in neurovascular dysfunction for the disease pathology.

BACKGROUND: Cerebral cavernous malformation (CCM) is a disease associated with an elevated risk of focal neurological deficits, seizures, and hemorrhagic stroke. The disease has an inflammatory profile and improved knowledge of CCM pathology mechanisms and exploration of candidate biomarkers will enable new non-invasive treatments. METHODS: We analyzed protein signatures in human CCM tissue samples by using a highly specific and sensitive multiplexing technique, proximity extension assay. FINDINGS: Data analysis revealed CCM specific proteins involved in endothelial dysfunction/inflammation/activation, leukocyte infiltration/chemotaxis, hemostasis, extracellular matrix dysfunction, astrocyte and microglial cell activation. Biomarker expression profiles matched bleeding status, especially with higher levels of inflammatory markers and activated astrocytes in ruptured than non-ruptured samples, some of these biomarkers are secreted into blood or urine. Furthermore, analysis was also done in a spatially resolving manner by separating the lesion area from the surrounding brain tissue. Our spatial studies revealed that although appearing histologically normal, the CCM border areas were pathological when compared to control brain tissues. Moreover, the functional relevance of CD93, ICAM-1 and MMP9, markers related to endothelial cell activation and extracellular matrix was validated by a murine pre-clinical CCM model. INTERPRETATION: Here we present a novel strategy for proteomics analysis on human CCMs, offering a possibility for high-throughput protein screening acquiring data on the local environment in the brain. Our data presented here describe CCM relevant brain proteins and specifically those which are secreted can serve the need of circulating CCM biomarkers to predict cavernoma's risk of bleeding.

Hemangioblastoma and arteriovenous malformation in the same patient: a not random association or two isolated entities? Systematic review starting from a unique case.

BACKGROUND: The association between intracranial hemangioblastomas and arteriovenous malformations has been documented in very few cases in literature since 1965 and might present in three modalities: "intermixed, adjacent and separated (spatially and temporally)". Often, the pattern of presentation is "intermixed". According to our systematic review, we propose an adjustment of the previous classification, specifically for these entities. We describe the first case of a truly "spatially separated" association between these two lesions. METHODS: Our study encompassed all adult patients diagnosed with both intracranial hemangioblastoma and AVM who were evaluated in the last 20-year period, from 2003 to 2023 at Helsinki University Hospital. Cases of this coexistence were retrospectively identified and collected from clinical records. For the systematic review, studies reporting the coexistence of hemangioblastoma and AVM in adult patients (>18 years old) were selected. Given the rarity of this pattern, case reports were also included. RESULTS: The combined analysis of our systematic review and institutional retrospective study revealed a total of only seven identified cases. We applied the classification of neoplasms and AVM by Yano, modifying and adapting it into our screened patient series. We systematically reclassified "adjacent" and genuinely "spatially separated" patterns based on the vascular axis supplying both lesions. CONCLUSIONS: Hemangioblastomas and AVMs rarely coexist in the same patient. Our study reports the first instance of a truly "spatially separated" sporadic association between these vascular lesions. The rarity of such coexistence underscores the need for a nuanced and systematic classification to guide the management of these infrequent cases.

Immunoliposomes for detection of rupture-prone intracranial aneurysms.

BACKGROUND: It is estimated that significant (3.2%) of population carries intracranial aneurysm (IA). An increasing number of imaging studies have caused that the chance of finding an incidental aneurysm is becoming more common. Since IA rupture causes subarachnoidal hemorrhage (SAH) and have significant mortality and morbidity prophylactic treatment should be considered when IA is detected. The benefit and risk of treatment of IA is based on epidemiological estimate which takes account patient and aneurysm characteristics. However we know that aneurysm rupture is biological process where inflammation of aneurysm wall is actively leading to degeneration of aneurysm wall and finally weakens it until it bursts. Until now, there have not been imaging method to detect inflammatory process of aneurysm wall METHODS: We created targeting immunoliposome for use in the imaging of aneurysm. Immunoliposome comprises antibodies against at least one vascular inflammatory marker associated with aneurysm inflammation and a label and/or a contrast agent. RESULTS: Histological analysis of IAs where immunoliposome comprises antibodies against vascular inflammation with a label shows promising results for selectively detecting aneurysms inflammation. In magnetic resonance imaging (MRI) we were able to detect immunoliposomes carrying gadolinium. CONCLUSION: Our work opens a new avenue for using contrast labeled immunoliposomes for detecting rupture-prone aneurysms. Immunoliposomes can cary gadolinium and selectively bind to inflammatory section of aneurysm that can be detected with MRI. Further research is needed to develop immunoliposomes to be used with MRI in humans to target treatment to those patients who benefit from it the most.

Recurrence of brain arteriovenous malformations in pediatric patients: a long-term follow-up study.

BACKGROUND: Previously thought to be congenital, AVMs have shown evidence of de-novo formation and continued growth, thus shifting thoughts on their pathophysiology. Pediatric AVM patients have been reported to be more prone to develop AVM recurrence after a seemingly complete cure. Therefore, we assessed the risk of AVM treated in childhood to recur in adulthood after a long-term follow-up in our own cohort. METHODS: Control DS-angiography was arranged during 2021-2022 as part of a new protocol for all AVM patients who were under 21 years of age at the time of their treatment and in whom the treatment had occurred at least five years earlier. Angiography was offered only to patients under 50 years of age at the time of the new protocol. The complete eradication of AVM after the primary treatment had been originally confirmed with DSA in every patient. RESULTS: A total of 42 patients participated in the late DSA control, and 41 of them were included in this analysis after excluding the patient diagnosed with HHT. The median age at the time of admission for AVM treatment was 14.6 (IQR 12-19, range 7-21 years) years. The median age at the time of the late follow-up DSA was 33.8 years (IQR 29.8-38.6, range 19.4-47.9 years). Two recurrent sporadic AVMs and one recurrent AVM in a patient with hereditary hemorrhagic telangiectasia (HHT) were detected. The recurrence rate was 4.9% for sporadic AVMs and 7.1% if HHT-AVM was included. All the recurrent AVMs had originally bled and been treated microsurgically. The patients with sporadic AVM recurrence had been smoking their whole adult lives. CONCLUSIONS: Pediatric and adolescent patients are prone to develop recurrent AVMs, even after complete AVM obliteration verified by angiography. Therefore, imaging follow-up is recommended.

Study Design for Navigated Repetitive Transcranial Magnetic Stimulation for Speech Cortical Mapping.

The cortical areas involved in human speech should be characterized reliably prior to surgery for brain tumors or drug-resistant epilepsy. The functional mapping of language areas for surgical decision-making is usually done invasively by electrical direct cortical stimulation (DCS), which is used to identify the organization of the crucial cortical and subcortical structures within each patient. Accurate preoperative non-invasive mapping aids surgical planning, reduces time, costs, and risks in the operating room, and provides an alternative for patients not suitable for awake craniotomy. Non-invasive imaging methods like MRI, fMRI, MEG, and PET are currently applied in presurgical design and planning. Although anatomical and functional imaging can identify the brain regions involved in speech, they cannot determine whether these regions are critical for speech. Transcranial magnetic stimulation (TMS) non-invasively excites the cortical neuronal populations by means of electric field induction in the brain. When applied in its repetitive mode (rTMS) to stimulate a speech-related cortical site, it can produce speech-related errors analogous to those induced by intraoperative DCS. rTMS combined with neuronavigation (nrTMS) enables neurosurgeons to preoperatively assess where these errors occur and to plan the DCS and the operation to preserve the language function. A detailed protocol is provided here for non-invasive speech cortical mapping (SCM) using nrTMS. The proposed protocol can be modified to best fit the patient- and site-specific demands. It can also be applied to language cortical network studies in healthy subjects or in patients with diseases that are not amenable to surgery.

Correlation between arteriovenous malformation nidus size and intraparenchymal hematoma volume in the event of rupture.

•Our study did not support the hypothesis that small AVMs lead to larger hematoma volumes in the event of a rupture.•AVM size did not correlate with the clinical severity of the bleeding as measured with HH and WFNS scores.•Larger supratentorial hematomas were associated with a more severe clinical manifestation and a poorer outcome.•In the event of a rupture, the AVM size did not correlate with the 2-4-month GOS.•AVICH score showed a good correlation with the 2-4-month GOS score.

Intracranial Aneurysm Classifier Using Phenotypic Factors: An International Pooled Analysis.

Intracranial aneurysms (IAs) are usually asymptomatic with a low risk of rupture, but consequences of aneurysmal subarachnoid hemorrhage (aSAH) are severe. Identifying IAs at risk of rupture has important clinical and socio-economic consequences. The goal of this study was to assess the effect of patient and IA characteristics on the likelihood of IA being diagnosed incidentally versus ruptured. Patients were recruited at 21 international centers. Seven phenotypic patient characteristics and three IA characteristics were recorded. The analyzed cohort included 7992 patients. Multivariate analysis demonstrated that: (1) IA location is the strongest factor associated with IA rupture status at diagnosis; (2) Risk factor awareness (hypertension, smoking) increases the likelihood of being diagnosed with unruptured IA; (3) Patients with ruptured IAs in high-risk locations tend to be older, and their IAs are smaller; (4) Smokers with ruptured IAs tend to be younger, and their IAs are larger; (5) Female patients with ruptured IAs tend to be older, and their IAs are smaller; (6) IA size and age at rupture correlate. The assessment of associations regarding patient and IA characteristics with IA rupture allows us to refine IA disease models and provide data to develop risk instruments for clinicians to support personalized decision-making.

Immunothrombosis and vascular heterogeneity in cerebral cavernous malformation.

Cerebral cavernous malformation (CCM) is a neurovascular disease that results in various neurological symptoms. Thrombi have been reported in surgically resected CCM patient biopsies, but the molecular signatures of these thrombi remain elusive. Here, we investigated the kinetics of thrombi formation in CCM and how thrombi affect the vasculature and contribute to cerebral hypoxia. We used RNA sequencing to investigate the transcriptome of mouse brain endothelial cells with an inducible endothelial-specific Ccm3 knock-out (Ccm3-iECKO). We found that Ccm3-deficient brain endothelial cells had a higher expression of genes related to the coagulation cascade and hypoxia when compared with wild-type brain endothelial cells. Immunofluorescent assays identified key molecular signatures of thrombi such as fibrin, von Willebrand factor, and activated platelets in Ccm3-iECKO mice and human CCM biopsies. Notably, we identified polyhedrocytes in Ccm3-iECKO mice and human CCM biopsies and report it for the first time. We also found that the parenchyma surrounding CCM lesions is hypoxic and that more thrombi correlate with higher levels of hypoxia. We created an in vitro model to study CCM pathology and found that human brain endothelial cells deficient for CCM3 expressed elevated levels of plasminogen activator inhibitor-1 and had a redistribution of von Willebrand factor. With transcriptomics, comprehensive imaging, and an in vitro CCM preclinical model, this study provides experimental evidence that genes and proteins related to the coagulation cascade affect the brain vasculature and promote neurological side effects such as hypoxia in CCMs. This study supports the concept that antithrombotic therapy may be beneficial for patients with CCM.

Long-term health-related quality of life in patients with ruptured arteriovenous malformations treated in childhood.

OBJECTIVE: The aim of this study was to reveal the long-term health-related quality of life (HRQOL), educational level, and impact on occupation in 55 patients who experienced ruptured brain arteriovenous malformations (AVMs) that were treated during childhood. METHODS: In 2016, questionnaires including the 15D instrument were sent to all living patients older than 18 years (n = 432) in the Helsinki AVM database. The cohort was further specified to include only patients with ruptured AVMs who were younger than 20 years at the time of diagnosis (n = 55). Educational level was compared with the age-matched general population of Finland. The mean 15D scores were calculated for independent variables (Spetzler-Ponce classification, admission age, symptomatic epilepsy, and multiple bleeding episodes) and tested using the independent-samples t-test or ANCOVA. Linear regression was used to create a multivariate model. Bonferroni correction was used with multiple comparisons. RESULTS: The mean follow-up time from diagnosis to survey was 24.2 (SD 14.7) years. The difference in the mean 15D scores between Spetzler-Ponce classes did not reach statistical significance. The youngest age group (< 10 years at the time of diagnosis) performed less well on the dimension of usual activities than the older patients. Symptomatic epilepsy significantly reduced the long-term HRQOL. Multiple hemorrhages significantly reduced the scores on three dimensions: mobility, speech, and sexual activity. In the regression model, symptomatic epilepsy was the only significant predictor for a lower 15D score. The educational level of the cohort was for the most part comparable to that of the general population in the same age group. AVM was the reason for early retirement in 11% of the patients, while lowered performance because of the AVM was reported by 37% of the patients. CONCLUSIONS: Patients with ruptured AVMs treated in childhood can live an independent and meaningful life, even in the case of the highest-grade lesions. Symptomatic epilepsy significantly reduced the long-term HRQOL, highlighting the need for continuing support for these patients.

Method for the Intraoperative Detection of IDH Mutation in Gliomas with Differential Mobility Spectrometry.

Isocitrate dehydrogenase (IDH) mutation status is an important factor for surgical decision-making: patients with IDH-mutated tumors are more likely to have a good long-term prognosis, and thus favor aggressive resection with more survival benefit to gain. Patients with IDH wild-type tumors have generally poorer prognosis and, therefore, conservative resection to avoid neurological deficit is favored. Current histopathological analysis with frozen sections is unable to identify IDH mutation status intraoperatively, and more advanced methods are therefore needed. We examined a novel method suitable for intraoperative IDH mutation identification that is based on the differential mobility spectrometry (DMS) analysis of the tumor. We prospectively obtained tumor samples from 22 patients, including 11 IDH-mutated and 11 IDH wild-type tumors. The tumors were cut in 88 smaller specimens that were analyzed with DMS. With a linear discriminant analysis (LDA) algorithm, the DMS was able to classify tumor samples with 86% classification accuracy, 86% sensitivity, and 85% specificity. Our results show that DMS is able to differentiate IDH-mutated and IDH wild-type tumors with good accuracy in a setting suitable for intraoperative use, which makes it a promising novel solution for neurosurgical practice.

Inflammation and neutrophil extracellular traps in cerebral cavernous malformation.

Cerebral Cavernous Malformation (CCM) is a brain vascular disease with various neurological symptoms. In this study, we describe the inflammatory profile in CCM and show for the first time the formation of neutrophil extracellular traps (NETs) in rodents and humans with CCM. Through RNA-seq analysis of cerebellum endothelial cells from wild-type mice and mice with an endothelial cell-specific ablation of the Ccm3 gene (Ccm3iECKO), we show that endothelial cells from Ccm3iECKO mice have an increased expression of inflammation-related genes. These genes encode proinflammatory cytokines and chemokines, as well as adhesion molecules, which promote recruitment of inflammatory and immune cells. Similarly, immunoassays showed elevated levels of these cytokines and chemokines in the cerebellum of the Ccm3iECKO mice. Consistently, both flow cytometry and immunofluorescence analysis showed infiltration of different subsets of leukocytes into the CCM lesions. Neutrophils, which are known to fight against infection through different strategies, including the formation of NETs, represented the leukocyte subset within the most pronounced increase in CCM. Here, we detected elevated levels of NETs in the blood and the deposition of NETs in the cerebral cavernomas of Ccm3iECKO mice. Degradation of NETs by DNase I treatment improved the vascular barrier. The deposition of NETs in the cavernomas  of patients with CCM confirms the clinical relevance of NETs in CCM.

Spontaneous angiogram-negative subarachnoid hemorrhage: a retrospective single center cohort study.

BACKGROUND: Spontaneous angiogram-negative subarachnoid hemorrhage (SAH) is considered a benign illness with little of the aneurysmal SAH-related complications. We describe the clinical course, SAH-related complications, and outcome of patients with angiogram-negative SAH. METHODS: We retrospectively reviewed all adult patients admitted to a neurosurgical intensive care unit during 2004-2018 due to spontaneous angiogram-negative SAH. Our primary outcome was a dichotomized Glasgow Outcome Scale (GOS) at 3 months. We assessed factors that associated with outcome using multivariable logistic regression analysis. RESULTS: Of the 108 patients included, 84% had a favorable outcome (GOS 4-5), and mortality was 5% within 1 year. The median age was 58 years, 51% were female, and 93% had a low-grade SAH (World Federation of Neurosurgical Societies grading I-III). The median number of angiograms performed per patient was two. Thirty percent of patients showed radiological signs of acute hydrocephalus, 28% were acutely treated with an external ventricular drain, 13% received active vasospasm treatment and 17% received a permanent shunt. In the multivariable logistic regression model, only acute hydrocephalus associated with unfavorable outcome (odds ratio = 4.05, 95% confidence interval = 1.05-15.73). Two patients had a new bleeding episode. CONCLUSION: SAH-related complications such as hydrocephalus and vasospasm are common after angiogram-negative SAH. Still, most patients had a favorable outcome. Only acute hydrocephalus was associated with unfavorable outcome. The high rate of SAH-related complications highlights the need for neurosurgical care in these patients.

Comparing health-related quality of life in modified Rankin Scale grades: 15D results from 323 patients with brain arteriovenous malformation and population controls.

BACKGROUND: We wanted to understand how patients with different modified Rankin Scale (mRS) grades differ regarding their health-related quality of life (HRQoL) and how this affects the interpretation and dichotomization of the grade. METHODS: In 2016, all adult patients in our brain arteriovenous malformation (AVM) database (n = 432) were asked to fill in mailed letters including a questionnaire about self-sufficiency and lifestyle and the 15D HRQoL questionnaire. The follow-up mRS was defined in 2016 using the electronic patient registry and the questionnaire data. The 15D profiles of each mRS grade were compared to those of the general population and to each other, using ANCOVA with age and sex standardization. RESULTS: Patients in mRS 0 (mean 15D score = 0.954 ± 0.060) had significantly better HRQoL than the general population (mean = 0.927 ± 0.028), p < 0.0001, whereas patients in mRS 1-4 had worse HRQoL than the general population, p < 0.0001. Patients in mRS 1 (mean = 0.844 ± 0.100) and mRS 2 (mean = 0.838 ± 0.107) had a similar HRQoL. In the recently published AVM research, the most commonly used cut points for mRS dichotomization were between mRS 1 and 2 and between mRS 2 and 3. CONCLUSIONS: Using 15D, we were able to find significant differences in the HRQoL between mRS 0 and mRS 1 AVM patients, against the recent findings on stroke patients using EQ-5D in their analyses. Although the dichotomization cut point is commonly set between mRS 1 and 2, patients in these grades had a similar HRQoL and a decreased ability to continue their premorbid lifestyle, in contrast to patients in mRS 0.

Utility of indocyanine green in the detection of radiologically silent hemangioblastomas: case report.

Hemangioblastomas (HBs) are rare, benign, hypervascularized tumors. Fluorescent imaging with indocyanine green (ICG) can visualize tumor angioarchitecture. The authors report a case of multiple HBs involving two radiologically silent lesions only detected intraoperatively by ICG fluorescence. A 26-year-old woman presented with a cystic cerebellar mass on the tentorial surface of the left cerebellar hemisphere on MRI. A left paramedian suboccipital approach was performed to remove the mural nodule with the aid of ICG injection. The first injection, applied just prior to removing the nodule, highlighted the tumor and vessels. After resection, two new lesions, invisible on the preoperative MRI, surprisingly enhanced on fluorescent imaging 35 minutes after the ICG bolus. Both silent lesions were removed. Histological analysis of all three lesions revealed they were positive for HB. The main goal of this report is to hypothesize possible explanations about the mechanism that led to the behavior of the two silent lesions. Intraoperative ICG videoangiography was useful to understand the 3D angioarchitecture and HB flow patterns to perform a safe and complete resection in this case. Understanding the HB ultrastructure and pathophysiological mechanisms, in conjunction with the properties of ICG, may expand potential applications for their diagnosis and future treatments.

Comparison of Operating Microscope and Exoscope in a Highly Challenging Experimental Setting.

BACKGROUND: The use of a digital three-dimensional (3D) exoscope system in neurosurgery is increasing as an alternative to the operative microscope. The objective of this study was to compare a digital 3D exoscope system with a standard operating microscope as a neurosurgical visualization tool in a highly challenging experimental setting. METHODS: End-to-side bypass procedures, each at a depth of 9 cm, were performed in a simulation setting. The quality of the task and the depth effect, visualization, magnification, illumination, and ergonomics were evaluated. RESULTS: No major differences were noted between the microscope and the 3D exoscope in terms of the quality of the work. Working with the 3D exoscope was more time-consuming than working with the microscope. Changing the depth and focus was faster using the operative microscope. The 3D exoscope enabled higher magnification and offered better ergonomic features. CONCLUSIONS: In a highly challenging experimental setting, comparable procedural quality was found for the microscope and the 3D exoscope. Each visualization tool had advantages and disadvantages. Over time and with technologic advances, the digital 3D exoscope may become the main operative visualization system in microneurosurgery.

Cigarette Smoking Is More Prevalent in Patients With Brain Arteriovenous Malformations Compared to General Population: A Cross-Sectional Population-Based Study.

BACKGROUND: Research on the prevalence of smokers in patients with brain arteriovenous malformation (AVM) remains nonexistent, even though smoking is a well-known risk factor for intracranial aneurysms. OBJECTIVE: To examine the prevalence and smoking habits of AVM patients. METHODS: Data on smoking habits were collected with a quality-of-life questionnaire mailed in 2016 to all patients in our large AVM database. These smoking data were supplemented with registry data derived from medical records. The prevalence of smokers was compared to that of the general population, derived from statistics of National Institute for Health and Welfare. Logit transformation of proportions and Students t distribution were used to calculate the 95% CIs for prevalence estimates. RESULTS: Of the 384 patients aged over 18 yr on admission, 277 (72.1%) returned the questionnaires in 2016. When compared to age, sex, and admission year matched general population, the proportion of smokers in AVM patients was 48% (CI = 41%-55%) and 19% (CI = 16%-21%) in the general population. The difference increased in older age groups; in those aged 65 to 77 yr, the percentage of smokers reached 73% (CI = 46%-90%), while the corresponding percentage in the general population was 7% (CI = 5%-9%). CONCLUSION: We observed considerably higher rates of smoking among AVM patients when compared to age, sex, and admission year matched general population. Our results suggest that in the development of AVMs, the role played by nicotine and other substances in tobacco smoke should be examined. Cigarette smoking could potentially be a common cerebrovascular risk factor.

Comparison of Conventional Microscopic and Exoscopic Experimental Bypass Anastomosis: A Technical Analysis.

BACKGROUND: Recently, the use of digital exoscopes has been increasingly promoted as an alternative to microscopes. The aim of this study is to compare experimental bypass quality in both visualization methods. METHODS: This study used two hundred 1-mm chicken wing vessels, which were used for either exoscopic or microscopic (100 samples each) bypass procedures. All procedures were recorded between July 2018 and September 2018. The bypass quality was evaluated according to our published practical scale (time, stitch distribution, intima-intima attachment, and orifice size). RESULTS: Both methods are effective in doing bypass suturing (practical scale score was good, 86% vs. 85%; P = 0.84). There were no significant differences regarding intima-intima attachment (P = 0.26) and orifice size (P = 0.25). However, suturing time (P < 0.001) was less using the microscope, whereas stitch distribution (P = 0.001) was better using the exoscope. Different suturing techniques (interrupted vs. continuous) had overall comparable results (P = 0.55). CONCLUSIONS: Both methods produced equally satisfactory results in experimental bypass procedures. The exoscope has the potential for better 3-dimensional visualization and sharing the surgeon's view with others for teaching purposes.