1,721,128 research outputs found
Impact of A1 segment asymmetry on hemodynamic conditions around the circle of Willis and anterior communicating artery aneurysm formation
No full textBackground: This study aims to investigate how A1 segment asymmetry—also known as A1 dominancy—influences the development of the anterior communicating artery aneurysm (AcomA) as it affects hemodynamic conditions within the circle of Willis (COW). Using time-of-flight magnetic resonance angiography (TOF-MRA), the research introduces a novel approach to assessing shear stress in A1 segments to uncover the hemodynamic factors contributing to AcomA formation. Method: An observational study was conducted over 6 years at a tertiary university hospital’s outpatient clinic. Recruited patients who underwent TOF-MRA imaging were divided into AcomA and non-AcomA groups. MRA images were analyzed using semi-automatic software (VINT, Mediimg, Inc.) to calculate the signal intensity gradient (SIG), which reflects wall shear stress. The comparison metrics included general demographics, anatomical characteristics, and hemodynamic attributes of the COW, mainly focusing on A1 segment asymmetry. Results: Among the 700 subjects, 106 were categorized into the AcomA group, while 594 were placed in the non-AcomA group. The AcomA group showed a more significant difference in the bilateral A1 diameter (49.0% vs. 20.8%, p < 0.001) and a greater prevalence of unilateral A1 aplasia (32.1% vs. 6.7%, p < 0.001) compared to the non-AcomA group. Increased bilateral A1 asymmetry in the AcomA group corresponded with notable variations in A1 SIG, indicating increased wall shear stress. The occurrence of AcomA is associated with both anatomical factors of the circle of Willis, represented by the bilateral A1 diameter ratio, and hemodynamic factors, represented by the bilateral A1 SIG ratio, suggesting that both factors are almost equally significant. Conclusion: Our findings suggest that A1 segment asymmetry influences hemodynamic changes within the COW, contributing to AcomA formation. Hemodynamic factors provide an intuitive understanding of how anatomical characteristics within the COW can lead to aneurysm development
Convolutional neural network-based method for the real-time detection of reflex syncope during head-up tilt test
No full textBACKGROUND AND OBJECTIVES: Reflex syncope (RS) is the most common type of syncope caused by dysregulation of the autonomic nervous system. Diagnosing RS typically involves the head-up tilt test (HUTT), which tracks physiological signals such as blood pressure and electrocardiograms during postural changes. However, the HUTT is time-consuming and may trigger RS symptoms in patients. Therefore, a real-time monitoring system for RS risk assessment is necessary to enhance medical efficiency and patient convenience. Although several methods have been developed, most depend on manually extracted features from physiological signals, making them susceptible to feature extraction methods and signal noise. METHODS: This study introduces a deep learning-based method for real-time RS detection. This method removes the need for manually extracted features by employing an end-to-end architecture consisting of residual and squeeze-and-excitation blocks. The likelihood of RS occurrence was quantified using the proposed method by analyzing a raw blood pressure signal. RESULTS: Data from 1348 patients (1291 normal and 57 with RS) were used to develop and evaluate the proposed method. The area under the receiver operating characteristic curve was 0.972 for RS detection using ten-fold cross-validation. A threshold between zero and one can adjust the performance characteristics of the proposed method. At a threshold of 0.75, the method achieved sensitivity and specificity values of 94.74 and 94.27 %, respectively. Notably, the technique detected RS 165.35 s before its occurrence, on average. CONCLUSIONS: The proposed method outperformed conventional methods in RS detection. In addition to its excellent detection performance, this method only requires blood pressure monitoring, reducing reliance on the number of input signals and enhancing its applicability compared to procedures that require multiple signals. These advantages contribute to the development of safer, more convenient, and more efficient RS detection systems
Reinforcement of Transdural Angiogenesis: A Novel Approach to Treating Ischemic Stroke With Cerebral Perfusion Impairment
Full text linkCerebral hypoperfusion plays a critical role in early neurological deterioration and long-term outcomes in patients with acute ischemic stroke, which remains a major global health challenge. This review explored transdural angiogenesis as a promising therapeutic strategy to restore cerebral perfusion in patients with ischemic stroke. The multiple burr hole procedure has been preliminarily used as an indirect revascularization method to induce transdural arteriogenesis. Theoretically, its efficacy could be enhanced by combining it with angiogenic boosters, such as erythropoietin. Recent clinical and preclinical studies have revealed that this combination therapy promotes angiogenesis and arteriogenesis, leading to successful revascularization across the dura mater and improved cerebral blood flow. This strategy may be particularly beneficial for high-risk patients with recurrent ischemic events, such as those with moyamoya disease or intracranial arterial occlusion, representing an effective strategy when conventional medical treatments are insufficient. This review highlights the potential of transdural angiogenesis enhancement as a novel intervention for ischemic stroke, offering an alternative to thrombolysis or endovascular treatment, particularly in acute stroke patients with impaired cerebral perfusion. This approach has the potential to bridge the treatment gap for patients outside the therapeutic window for acute stroke interventions. Although further research is required to refine this technique and validate its efficacy in broader clinical settings, early results have revealed promising outcomes at reducing stroke-related complications and improving patient prognosis. This review indicates that this novel strategy may offer hope for managing ischemic stroke and related conditions associated with significant cerebral hypoperfusion
Age-Related Differences in Cardiovascular and Cerebrovascular Responses During the Head-Up Tilt Test: An Exploratory Study Using Continuous Biosignal Data
No full textThe head-up tilt (HUT) test assesses both cardiovascular autonomic regulation and cerebral autoregulation. This exploratory study examined age-related changes in cardiovascular and cerebrovascular responses during the HUT test in three healthy cohorts (young, middle-aged, and elderly). We recruited 2342 neurologist-diagnosed ‘normal’ individuals from 18 June 2014 to 25 February 2022. Cerebrovascular and cardiovascular responses were assessed during the HUT test, including cerebral blood flow velocity (CBFv) of the middle cerebral artery, systolic arterial pressure (SYS), diastolic arterial pressure (DIA), mean arterial pressure (MAP), pulse pressure (PP), heart rate (HR), stroke volume (SV), cardiac output (CO), and cerebrovascular conductance (CVCi). These variables were analyzed across three groups (young, middle-aged, and elderly) and three periods (resting, post-HUT, and recovery). Participants were stratified into three age groups: young (18–45 years; n = 384), middle-aged (46–59 years; n = 434), and elderly (≥60 years; n = 590). PP increased significantly with age, while CBFv and CVCi decreased significantly across the three periods. As measurements progressed, DIA and HR increased, and SV, CBFv, and CVCi decreased. This study enhances our understanding of age-related differences in cardiovascular and cerebrovascular responses to the HUT test. These insights may improve the clinical utility of the HUT test and guide outcome analysis across age groups
Hemorrhagic Transformation After Ischemic Stroke: Mechanisms and Management
Full text linkSymptomatic hemorrhagic transformation (HT) is one of the complications most likely to lead to death in patients with acute ischemic stroke. HT after acute ischemic stroke is diagnosed when certain areas of cerebral infarction appear as cerebral hemorrhage on radiological images. Its mechanisms are usually explained by disruption of the blood-brain barrier and reperfusion injury that causes leakage of peripheral blood cells. In ischemic infarction, HT may be a natural progression of acute ischemic stroke and can be facilitated or enhanced by reperfusion therapy. Therefore, to balance risks and benefits, HT occurrence in acute stroke settings is an important factor to be considered by physicians to determine whether recanalization therapy should be performed. This review aims to illustrate the pathophysiological mechanisms of HT, outline most HT-related factors after reperfusion therapy, and describe prevention strategies for the occurrence and enlargement of HT, such as blood pressure control. Finally, we propose a promising therapeutic approach based on biological research studies that would help clinicians treat such catastrophic complications
Simultaneous monitoring of the middle cerebral and basilar arteries to detect right-to-left shunts using transcranial Doppler by agitated saline administration
Full text linkTranscranial Doppler (TCD) is an easy, non-invasive, and real-time monitoring device for detecting right-to-left shunts (RLS). Nonetheless, it has limited benefits in patients with poor temporal windows. Therefore, we aimed to investigate whether the basilar artery (BA) window was as effective as the middle cerebral artery (MCA) in detecting RLS during TCD monitoring. Overall, we enrolled 344 patients with stroke, transient ischemic attack, headache, or dizziness. MCA and BA were monitored using a modified headset. To investigate the feasibility of the suboccipital window in detecting RLS, we instituted an evaluation tool with three tiers to evaluate microembolic signals (MESs) during TCD monitoring. Tier 1: TCD monitoring of the MCA (bilaterally) in the resting state, tier 2: TCD monitoring of the MCA (bilaterally) while performing the Valsalva maneuver, and tier 3: TCD monitoring of the index MCA and BA while performing the Valsalva maneuver. In tiers 2 and 3, a high agreement rate of 0.808 and 0.809 (p < 0.001), respectively, on the weighted kappa index, and a high intra-class correlation coefficient of 0.982 and 0.986 (p < 0.001), respectively, were observed on detecting MESs. Our data suggests that the BA window is as effective as the MCA window for detecting RLS on TCD
Somatosound: A review with report of 9 cases with long-term follow-up
No full textSomatosound (somatic tinnitus) is associated with vascular, musculoskeletal, respiratory, or temporomandibular joint disorders. Several studies of its management have been widely reported, but only few presented long-term follow-up results. The purposes of this paper are to review the causes and management, present cases with long-term follow-up, together with previously reported cases in literatures. We treated nine patients with somatosound of vascular, hematologic, endocrinologic, muscular, and cervical origin. Follow-up were conducted routinely, and the final results were collated in 3 to 11 years. Patients with non-life-threatening causes were given counseling and palliative management. Their tinnitus becomes tolerable, gradually decreased, and even disappeared. Patients with life-threatening causes were treated immediately. Among all, there were three cases which to the best of our knowledge, are the first reported of its causes. One case was caused by a compensatory of increasing blood flow in internal carotid artery (ICA) secondary to contralateral ICA stenosis. Another had a combination of anemia and an ipsilateral jugular bulb diverticulum. The tinnitus disappeared after the anemia treated. The last was patient with hyperthyroidism. The tinnitus disappeared by controlling the condition. Even when the causes are benign and the available treatments may carry risks, the patients should not be left unmanaged. Symptomatic treatment should be given, such as counseling, sound therapy, and palliative management. Our long-term observation indicated that overall outcomes are positive when the etiologies are identified early and managed properly
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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