Cerebral Artery Flow Research Articles

Middle cerebral artery velocity is associated with the severity of MRI brain injury in neonates received therapeutic hypothermia

BackgroundNo previous study has investigated the relationship between middle cerebral artery (MCA) flow velocity and the severity of hypoxic ischemic encephalopathy (HIE) evaluated by magnetic resonance imaging (MRI). The aim of this study was to assess the correlation between cerebral blood flow as assessed by transcranial Doppler sonography and the severity of MRI brain injury in asphyxiated neonates with clinical HIE who received therapeutic hypothermia. MethodsThis retrospective cohort study was conducted in the neonatal intensive care unit at Chang Gung Memorial Hospital between April 2011 and May 2014. All neonates with HIE who received therapeutic hypothermia, transcranial Doppler examinations, and brain MRI were eligible. Brain MRI was performed at 11 days of age (interquartile range: 8.5–15 days) and the severity of MRI brain injuries was evaluated using the MR scoring system proposed by Barkovich et al. Serial transcranial Doppler examinations were performed in pre-hypothermia, hypothermia, and post-hypothermia phases. ResultsTwenty-six neonates met the eligibility criteria for this study. Neonates with an abnormal MCA mean flow velocity (MFV) during the hypothermia phase had a higher risk of brain MRI abnormalities (77.8% vs. 22.2%, p = 0.017) and neonates with abnormal high MFV of MCA had higher MR scores of basal ganglia (p = 0.022). However, there were no statistical differences between abnormal MFV of MCA and brain MRI abnormalities during pre- and post-hypothermia phases. ConclusionsDuring therapeutic hypothermia, mean cerebral blood flow velocity of the MCA was associated with the severity of MRI brain injury in the neonates with clinical HIE.

Fetal Umbilical Arterial Pulsatility Correlates With 2-Year Growth and Neurodevelopmental Outcomes in Congenital Heart Disease

BackgroundChildren with congenital heart disease (CHD) are at risk of adverse long-term neurodevelopmental outcomes, believed to be, in part, secondary to prenatal insults. Placental pathology and altered fetal middle cerebral arterial (MCA) flow suggestive of brain sparing have been documented in fetal CHD. In the present study we investigated the relationship between MCA and umbilical arterial (UA) flow patterns in fetal transposition of the great arteries (d-TGA) and hypoplastic left heart syndrome (HLHS) and growth and 2-year neurodevelopmental outcomes. MethodsWe included children with d-TGA and HLHS who had third-trimester fetal echocardiograms between 2004 and 2014, at which time umbilical artery (UA) and MCA pulsatility indices (PIs) were measured, and who underwent 2-year growth and neurodevelopmental assessments. ResultsWe identified 24 children with d-TGA and 36 with HLHS. Mean age at fetal echocardiography was 33.8 ± 3.5 weeks. At 2-year follow-up, head circumference z score (standard deviation [SD]) was –0.09 (1.07) and 0.17 (1.7) for the d-TGA and HLHS groups, respectively. Bayley III mean (SD) cognitive, language, and motor scores were 97.7 (10.8), 94.7 (13.4), and 98.6 (8.6) for the d-TGA group and 90.3 (13.9), 87.2 (17.5), and 85.3 (16.2) for the HLHS group. On multivariate linear regression analysis, UA-PI was associated (effect sizes [95% CI]) with length (–1.45 [–2.7, –0.17], P = 0.027), weight (–1.46 [–2.6 to –0.30], P = 0.015) and cognitive scores (–14.86 [–29.95 to 0.23], P = 0.05) at 2 years of age. MCA PI showed no statistically significant correlation. ConclusionsIn fetal d-TGA and HLHS, a higher UA-PI in the third trimester, suggestive of placental insufficiency—but not MCA-PI—is associated with worse 2-year growth and neurodevelopment.

Detection of impaired cerebrovascular reactivity in patients with chronic cerebral ischemia using whole-brain 7T MRA

BackgroundCerebrovascular reactivity (CVR) to acetazolamide (ACZ) on single-photon emission computed tomography (SPECT) can be used to assess the severity of chronic cerebral ischemia; however, this is an invasive method. We examined whether whole-brain magnetic resonance angiography (MRA) at 7T could non-invasively detect impaired CVR in patients with chronic cerebral ischemia by demonstrating the leptomeningeal collaterals (LMCs). MethodsFifty-seven patients with symptomatic unilateral cervical stenosis underwent whole-brain time-of-flight MRA at 7T and cerebral perfusion SPECT before/after the ACZ challenge. MRA images were visually assessed based on 6-point grading systems to evaluate the development of LMCs toward the middle cerebral artery (MCA) and antegrade flow of MCA. CVR of the affected side was calculated from the SPECT data. Subsequently, we compared the LMC grades on MRA with CVR on SPECT. ResultsCVR was significantly lower in grades ≥ 2 of LMCs than in grades 0–1 (P < 0.05) when applying LMCs from the anterior cerebral artery (ACA) and/or posterior cerebral artery (PCA). These differences were more evident than those in the grading of the antegrade MCA flow. The LMC grades from ACA/PCA readily detected reduced CVR (< 18.4%) with a sensitivity/specificity of 0.79/0.82. ConclusionThe development of LMCs on whole-brain MRA at 7T can non-invasively detect reduced CVR with a high sensitivity/specificity in patients with unilateral cervical stenosis.

Neuromonitoring Using Neurosonography and Pupillometry in A Weaning and Early Neurorehabilitation Unit.

Long-term surveillance of intracranial pressure (ICP) in neurological/neurosurgical patients during ventilator weaning and early neurorehabilitation currently relies on clinical observation because neuroimaging is rarely readily available. In this prospective study, multimodal neurosonography and pupillometry are evaluated for follow-up monitoring. Sonographic neuromonitoring was used to noninvasively examine patients' ICP during weaning and early neurorehabilitation. It allowed assessments of third ventricle width, possible midline shift, middle cerebral artery flow velocities, and bilateral optic nerve sheath diameters. Quantitative pupillometry was used to determine pupil size and reactivity. Other neuroimaging findings, spinal tap ICP measurements, and clinical follow-up data served as controls. Seventeen patients-11 suffering from intracranial hemorrhage, four from encephalopathies, and two from ischemic stroke-were examined for ICP changes by using neurosonography and pupillometry during a mean observation period of 21 days. In total, 354 of 980 analyses (36.1%) yielded pathological results. In 15 of 17 patients (88.2%), pathological values were found during follow-up without a clear clinical correlate. In two patients (11.8%), clinically relevant changes in ICP occurred and were identified using neurosonography. Abnormal pupillometry findings displayed a high predictive value for absent clinical improvement. Multimodal neurosonography may be a noninvasive means for long-term ICP assessment, whereas pupillometry may only detect rapid ICP changes during acute neurointensive care. The study also illustrates common pitfalls in neuromonitoring in general, with large numbers of pathological albeit nonsignificant findings. Additional controlled studies should validate the influence of detected subtle changes in ICP on neurological outcome.

The effect of age on cerebral blood flow responses during repeated and sustained stand to sit transitions.

IntroductionAging is associated with impaired cerebrovascular blood flow and function, attributed to reduced vasodilatory capacity of the cerebrovascular network. Older adults may also have an impaired relationship between changes in blood pressure and cerebral blood flow; however, previous reports conflict. This study aimed to compare the blood pressure and cerebral blood flow responses to both repeated and sustained stand‐to‐sit transitions in young and older adults, and to assess the relationship with cerebrovascular reactivity.MethodsIn 20 young (age: 24 ± 4 years) and 20 older (age: 71 ± 7 years) adults we compared middle cerebral artery flow velocity (MCAv), end‐tidal partial pressure of carbon dioxide (PETCO2), and blood pressure (mean arterial blood pressure [MAP]) during repeated stand‐to‐sit (10 s standing and 10 s sitting) and sustained stand‐to‐sit (3 min standing followed by 2 min sitting) transitions. Cerebrovascular reactivity to changes in carbon dioxide levels was assessed using a repeated breath‐hold test.ResultsThe % change in MCAv per % change in MAP (%∆MCAv/%∆MAP) was higher in the older adults than in the young adults during repeated stand‐to‐sit transitions. During the sustained protocol the %∆MCAv/%∆MAP response was similar in both age groups. A high %∆MCAv/%∆MAP response during the repeated stand‐to‐sit protocol was associated with low cerebrovascular reactivity to CO2 (r = −.39; p < .01), which was significantly lower in the older adults.ConclusionThese findings suggest that the higher %∆MCAv/%∆MAP during repeated stand–sit transitions was associated with impaired cerebrovascular reactivity. Impairments in endothelial function and vascular stiffness with age may contribute to the altered transient cerebral pressure–flow responses in older adults.

Prognostic Significance of Sentinel Headache Preceding Aneurysmal Subarachnoid Hemorrhage

Sentinel headache (SH) is often assumed to portend an increased risk of delayed cerebral ischemia (DCI) and aneurysm rebleeding. This study aimed to re-evaluate the associations between SH and aneurysm rebleeding, DCI, and outcome after SAH. We retrospectively analyzed 1102 patients with spontaneous SAH and available data regarding history of SH who were enrolled in the Columbia University SAH Outcomes Project between 1996 and 2009. Patients were asked whether they had experienced any episodes of acute, sudden-onset severe headache in the 2 weeks preceding the most recent bleeding event. DCI was defined as neurologic deterioration, infarction, or both due to vasospasm. Rebleeding was defined as the appearance of new hemorrhage on computed tomography. Outcome was assessed at 3 months by telephone interview using the modified Rankin Scale. SH was reported in 152 (14%) of 1102 patients. There were no significant differences between patients with and without SH with regard to admission Hunt-Hess grade or modified Fisher Scale. There was also no difference with regard to the frequency of aneurysm rebleeding (10% vs. 8%, P= 0.42), DCI (18% vs, 20%, P= 0.64), moderate-or-severe angiographic vasospasm on follow-up angiography (51% vs. 56%, P= 0.43), highest recorded mean middle cerebral artery flow velocity on transcranial Doppler (134 versus 128 cm/s, P= 0.30), or the distribution of modified Rankin Scale scores at 3 months. A history of sentinel headache before the clinical diagnosis of SAH does not imply an increased risk of DCI or further rebleeding, and carries no prognostic significance.

LEFT ‐RIGHT PUPIL DIAMETER DIFFERENCE‐DURING RADIOGRAPHIC READING OF BRONCOPULMONARY CARCINOMA: AN EXPLORATION WITH COGNITIVE LOAD AMONG NOVICES AND EXPERTS

INTRODUCTIONThe visual reading of an x‐ray image is a necessary process in order to find specific pathological patterns. With Functional Near Infrared Spectroscopy study have shown that increased levels of oxy and deoxy hemoglobin in the left hemisphere are associated with greater cognitive load in visual challenges and Transcranial Doppler has shown an increase on left middle cerebral artery flow associated with cognitive tasks in the face of visual challenges. Nowdays, pupil diameter begins to be recognized as a non‐intrusive method for measuring cognitive load during radiographic, dental radiographic, and histopathological diagnosis processes. The present work’s objective, is to show the difference in left and right pupillary diameters during the radiographic reading of bronchopulmonary carcinoma, to explore the cognitive burdens of novice, intermediate and expert groups.MATERIAL AND METHODSWith a 60 Hz Gazepoint GP3 Eyetracker, the pupil diameter of 8 doctors was quantified during the chest radiographic reading postero‐anterior projection of a bronchopulmonary carcinoma, taken from RadioGrapichs Magazine; first‐to‐fourth year resident physicians with age = 30.6 were classified as novice with 8.5‐month training, intermediate years with 41‐month training and expert doctors with age = 67 years and with 462 months of experience. All the diagnostic challenge was exposed on a monitor with 300 DPI connected to an Intel Core i5 PC with 8GB RAM.RESULTSThe average found of pupil diameter was 4.05 mm to all groups, over the course of 2 minutes, and the difference in pupil diameter went from 3.66 mm to 4.08 mm. However, the expert group demonstrated a pattern of smaller right pupil diameter with 3.98 mm, while the left pupillary diameter reached 4.22 mm. In contrast, during the same diagnostic task, the intermediate and novice groups showed a more homogeneous pupillary opening between left and right eye, being 4.05 mm and 4.01 mm respectively.Differences obtained between the left and right pupillary diameters during the chest x ray reading tasked were observed in all groups. However, it was observed that this difference occurred at different times. The expert group increased left pupillary diameter immediately while novice and intermediate achieved the same pupillary effect 50 seconds after the task was initiated. Fig 1.CONCLUSIONIn the two minutes radiological diagnosis process for bronchopulmonary carcinoma, radiologist doctors express greater left pupil diameter with respect to the right. However, experts make such a statement almost from the beginning of the task; while the intermediate and novice groups reach this same pattern approximately half way through the task’s total time. This finding, suggests that differences in pupil diameter may be associated with visual cognitive processing during diagnostic processes. This possible relationship may be related to cognitive load lateralization to the left hemisphere. Therefore, studies of cognitive load laterality vs. ipsilateral pupil diameter during imaging are necessary, since their possible effects on academic and labor scenarios are yet to be established.Support or Funding InformationPROSEIMLEFT ‐RIGHT PUPIL DIAMETER DIFFERENCE‐ DURING 2 MINUTES OF RADIOGRAPHIC READING OF BRONCHOPULMONARY CARCINOMA AMONG NOVICES AND EXPERTSFigure 1

Effect of dexmedetomidine on dynamic cerebral autoregulation and carbon dioxide reactivity during sevoflurane anesthesia in healthy patients.

BackgroundThere are conflicting opinions on the effect of dexmedetomidine on cerebral autoregulation. This study assessed its effect on dynamic cerebral autoregulation (dCA) using a transcranial Doppler (TCD).MethodsThirty American Society of Anesthesiologists physical status I and II patients between 18 and 60 years, who underwent lumbar spine surgery, received infusions of dexmedetomidine (Group D) or normal saline (Group C), followed by anesthesia with propofol and fentanyl, and maintenance with oxygen, nitrous oxide and sevoflurane. After five minutes of normocapnic ventilation and stable bispectral index value (BIS) of 40–50, the right middle cerebral artery flow velocity (MCAFV) was recorded with TCD. The transient hyperemic response (THR) test was performed by compressing the right common carotid artery for 5–7 seconds. The lungs were hyperventilated to test carbon dioxide (CO2) reactivity. Hemodynamic parameters, arterial CO2 tension, pulse oximetry (SpO2), MCAFV and BIS were measured before and after hyperventilation. Dexmedetomidine infusion was discontinued ten minutes before skin-closure. Time to recovery and extubation, modified Aldrete score, and emergence agitation were recorded.ResultsDemographic parameters, durations of surgery and anesthesia, THR ratio (Group D: 1.26 ± 0.11 vs. Group C: 1.23 ± 0.04; P = 0.357), relative CO2 reactivity (Group D: 1.19 ± 0.34 %/mmHg vs. Group C: 1.23 ± 0.25 %/mmHg; P = 0.547), blood pressure, SpO2, BIS, MCAFV, time to recovery, time to extubation and modified Aldrete scores were comparable.ConclusionsDexmedetomidine administration does not impair dCA and CO2 reactivity in patients undergoing spine surgery under sevoflurane anesthesia.

Study protocol for SFX-01 after subarachnoid haemorrhage (SAS): a multicentre randomised double-blinded, placebo controlled trial

IntroductionSubarachnoid haemorrhage (SAH) from a ruptured cerebral aneurysm carries high morbidity and mortality. Despite huge advances in techniques to secure the aneurysm, there has been little progress in the treatment...

Carotid Revascularization and Its Effect on Cognitive Function: A Prospective Nonrandomized Multicenter Clinical Study

Background: There is conflicting data on the effect of carotid revascularization on cognitive function. Objective: To examine cerebral blood flow and cognitive function after carotid revascularization. Methods: Patients with unilateral, asymptomatic hemodynamically significant carotid artery stenosis (80% by computed tomography angiography or magnetic resonance angiography) were eligible. Cerebral blood flow was measured preoperatively and 1 month postoperatively using quantitative phase contrast magnetic resonance angiography. Preoperative flow impairment was defined as ipsilateral flow at least 20% less than contralateral flow (ie, an ipsilateral and/or contralateral flow ratio ≤0.8). Significant improvement in blood flow was defined as at least a 0.15 increase in flow ratio from pre- to postoperative. A control group was managed medically. Four cognitive domains were assessed at baseline, 1 month, and 6-12 months postoperatively. Results: Seventy-five patients were enrolled at 6 sites; 53 carotid endarterectomy, 11 carotid artery stenting, and 11 medical management only controls. Preoperative Trails B scores were similar between groups. Revascularization was associated with significant improvement in executive function (Trials B) while no improvement was observed in controls (P = .007). Of patients with improvement in middle cerebral artery (MCA) flow, 90% had improved Trails B scores compared to 46.5% of patients without MCA flow improvement (P = .01). Greater absolute improvement in mean Trails B scores was observed in patients with MCA flow improvement compared to those without (48 seconds versus 24.7 seconds, P = .001). Conclusions: In a cohort of patient with asymptomatic carotid stenosis, improvement in MCA flow following carotid revascularization is associated with improvement in executive functioning.

Abstract WMP64: From Static Imaging to Hemodynamic Modelling: Validation of Intracranial Blood Flow Simulations Against Population-Based PC-MRI Studies

Purpose: Modelling blood flow in cerebral arteries presents an opportunity to go beyond current luminal stenosis. These models could improve stroke prognostication by adding hemodynamic biomarkers such as translesional shear stress and pressure gradient. Such models, however, are rarely validated against real clinical data. We evaluated the accuracy of a computational fluid dynamics (CFD) model which uses allometric scaling laws against population-based Phase Contrast MRI (PC-MRI) measurements of blood flow in the brain. Methods: 3D models of the anterior circulation of 23 healthy subjects were reconstructed based on their MRA Time of Flight (TOF) images and CFD was used for modelling the blood flow. Lumped parameter Windkessel models were used as boundary conditions and allometric scaling laws were used to divide the flow and tune these boundary conditions, i.e. the resistance at each boundary was automatically adjusted based on the dimensions and branching of upstream vasculature. The results were compared against 4 PC-MRI studies from literature, covering a combined number of 417 healthy subjects. Results: The flow rate across 3 major intracranial arteries (ICA, MCA, and ACA) was obtained from the CFD simulations and was in good agreement with population-based PC-MRI studies. The agreement was 82.6% for the ICA, 85.9% for the MCA, and 80.4% for the ACA when comparing the average flow rate. The inter-patient variability of the flow rate (i.e. standard deviation) obtained from CFD simulations matched closely with the variation range measured in the literature. Allometric scaling enabled the model to accurately divide the flow at bifurcations (MCA/ICA flow ratio was 58.6% for the model vs 56.3% in the literature). We observed an average of 8 mmHg in pressure drop along the anterior circulation of healthy subjects (from ICA to MCA-M1 and ACA-A1), which agrees with the physiological range reported in the literature. Conclusion: This study shows the potential of accurately modelling blood flow based only on static images and demonstrates the validity of using allometric scaling in intracranial CFD simulations. The current modelling approach can potentially assist in stroke prognostication by obtaining hemodynamic risk factors from standard MRA TOF or CTA.

Numerical Analysis of Gravitational Effects on the Blood Flow in Cerebral Arteries Using Computed Tomography Angiography Images: A Case Study of a Healthy Male

Numerical Analysis of Gravitational Effects on the Blood Flow in Cerebral Arteries Using Computed Tomography Angiography Images: A Case Study of a Healthy Male

Effects of sildenafil citrate on impedance to flow in the umbilical and fetal middle cerebral arteries in pregnancies at high risk for fetal growth restriction

Objective: To assess whether sildenafil citrate improves blood flow in fetal um- bilical arteries and middle cerebral arteries in pregnancies at high risk for fetal growth restriction. Methods: A quasi-experimental study was carried out at the Department of Ob- stetrics and Gynecology, Suez Canal University Hospital in Ismail- ia over the period from June 2017 to April 2018. Trans-abdominal obstetric ultrasonography (U/S) was done for 30 pregnant women aged24 to 35 years, gestational age ranged between 33- 36 weeks, at high risk for fetal growth restriction (mild pre-eclampsia, diabetes mellitus, history of previous pregnancy with a small for gestational age, stillbirth, severe pre-eclampsia or pregnancies with abnormal umbilical artery indices-above 90th centile). Fetal umbilical and middle cerebral artery blood flow Doppler indices were determined before and 2 and 6 hours after ingestion of sildenafil citrate 20 mg tablet. Results: There was a statistically significant decrease in umbilical artery Dop- pler indices before, two hours and six hours following sildenafil ci- trate therapy in the studied patients (P<0.05) and a statistically signif- icant increase in middle cerebral artery Doppler indices before, two hours and six hours following sildenafil citrate therapy in the studied patients (P<0.05). Conclusions: Sildenafil citrate significantly increases blood flow in the umbilical arteries and normalizes blood flow in fetal middle cerebral arteries in pregnancies at high risk for fetal growth restriction thereby restoring a normal fetal circulation and corrects the “brain sparing” adaptive mechanism.

Quantitative analysis of arterial supply to the developing brain in tetrapod vertebrates.

Understanding the metabolic cost of building developing tetrapod brains is critically important to explaining the more than 10-fold differences in encephalization of adult tetrapods that have emerged during evolution. The exact metabolic costs of developing the variety of tetrapod brains are impossible to determine, but one can compare cerebral artery caliber (internal radius raised to the fourth power-r4 ) across developing tetrapod vertebrate groups as a proxy of cerebral arterial flow, the delivery of nutrients during embryogenesis and early postnatal development, and hence the metabolic costs of brain development. In this study, r4 of aortic outflow and cerebral inflow arteries, as well as aortic wall thickness as a proxy of arterial pressure, were measured and compared between developing representatives of all four tetrapod classes (mammals, birds, reptiles, and amphibians). We found a clear endotherm/ectotherm dichotomy in aortic outflow and cerebral inflow between developing mammals and birds on the one hand, and developing reptiles and amphibians on the other. We did not find strong evidence for functionally significant differences in cerebral arterial caliber between groups at the order level (i.e., within birds, reptiles or amphibians). In particular, we did not find evidence in favor of increased blood supply to the brain for more behaviorally complex and encephalized avian species.

Acute symptomatic extracranial internal carotid occlusion - natural course and clinical impact.

Background: To assess the vascular and clinical course of acute symptomatic extracranial internal carotid artery (ICA) occlusion. Patients and methods: Patients with an acute ischemic event in the anterior circulation and corresponding extracranial ICA occlusion at CT angiography and/or color-coded duplex sonography underwent recurrent duplex follow-up for detection of spontaneous recanalization. Stroke recurrence and functional outcome 4.5 months after the ischemic index event assessed by modified Rankin scale served as secondary outcome parameters. Results: 133 patients (91 men, mean age 62.3years, SD 10.8) demonstrated symptomatic occlusion of the extracranial ICA with open intracranial ICA and open middle cerebral artery and were followed-up for spontaneous recanalization. Twenty-eight recanalized spontaneously, 25 to high-grade focal stenosis within 12 days, revealing an early cumulative recanalization rate of 23%. Detection of recanalization was independently associated with de novo dual anti-platelet therapy (adjusted odds ratio [OR], 3.24; 95% confidence interval [CI], 1.34 to 7.80). Ischemic recurrence occurred in 16 patients, of which 10 deemed to be embolic and 5 hemodynamic. Spontaneous ICA recanalization and an exhausted cerebrovascular reserve in the hemisphere distal to the occluded ICA were both independently associated with the occurrence of a recurrent ischemic event at Cox regression. An increasing NIHSS score at admission, a decreasing middle cerebral artery flow velocity and an ischemic recurrence independently predicted poor outcome (modified Rankin scale 3 to 6) in multivariate analysis. Conclusions: Acute symptomatic extracranial ICA occlusion is an unstable condition with frequent spontaneous recanalization to severe stenosis and early embolic stroke recurrence, demanding appropriate prevention especially in those patients with only mild deficit.

Reduced cerebrovascular and cardioventilatory responses to intermittent hypoxia in elderly

BackgroundThe impact of aging on cerebrovascular function and tissue oxygenation during graded hypoxemia is incompletely known. This study compared the age effect on these variables during cyclic hypoxemia-reoxygenation. MethodsHypoxia-induced changes in arterial (SaO2) and cerebral tissue (ScO2) O2 saturation, middle cerebral arterial flow velocity (VMCA), estimated cerebral vascular conductance (CVC), heart rate (HR) and ventilation were compared between 12 elderly (71 ± 2 yr, 7 women) and 13 young (24 ± 3 yr, 5 women) adults during the first and fifth 5-min exposures to 10% O2. ResultsAlthough pre-hypoxia SaO2 did not differ between the groups, ScO2 was lower (P < 0.05) in the elderly (68.4 ± 1.2%) than young (73.8 ± 0.9%) adults, commensurate with a lower resting VMCA (P < 0.05). SaO2 fell less sharply (P < 0.05) in the elderly subjects during the first and fifth hypoxia exposures. Moreover, the responses of ScO2, VMCA, CVC, HR and breathing frequency to hypoxia were attenuated in the elderly subjects. Systolic and diastolic arterial pressures fell by 2–6 mmHg during hypoxia in both young and elderly. Thus, hypoxemia developed more gradually in elderly than young adults during normobaric hypoxia, concordant with a reduced metabolic demand in the elderly. ConclusionsThe elderly adults safely tolerated cyclic, moderate hypoxemia which lowered SaO2 by 20–25%, despite dampening of cerebrovascular and cardiac responses to hypoxemia.

Associations between blood and cerebrospinal fluid flow impairments assessed with phase-contrast MRI and brain damage in patients with age-related cerebral small vessel disease

Hemodynamic parameters of blood and cerebrospinal fluid (CSF) flow can be measured in vivo using phase-contrast MRI (PC-MRI). This opens new horizons for studying the mechanisms implicated in the development and progression of age-related cerebral small vessel disease (SVD). In this paper, we analyze associations between cerebral arterial, venous and CSF flow impairments and SVD features visible on MRI. The study was carried out in 96 patients with SVD (aged 60.91 ± 6.57 years) and 23 healthy volunteers (59.13 ± 6.56 years). The protocol of the MRI examination included routine MRI sequences (T2, FLAIR, T1, SWI, and DWI) applied to assess the severity of brain damage according to STRIVE advisory standards and PC-MRI used to quantify blood flow in the major arteries and veins of the neck, the straight and upper sagittal sinuses, and CSF flow at the aqueduct level. We analyzed the associations between linear and volumetric parameters of blood/CSF flow and the degree of brain matter damage using the Fazekas scale. We observed a reduction in tABF, stVBF, sssVBF, aqLF, Saq, and ICC values and a rise in Pi associated with WMH progression, as well as a gradual decline in tABF and an increase in Pi, Saq and ICC associated with a growing number of lacunes (р &lt; 0.05). Patients with early (&lt; 5) MB had lower sssVBF and stVBF rates in comparison with patients without MB; aqLF, Saq, and ICC values were elevated in patients with 5 to 10 MB, as compared to patients without MB or early (&lt; 5) MB. The established associations between MRI findings in patients with SVD and blood/CSF flow impairments suggest the important role of mechanisms implicated in the disruption of Monro–Kellie intracranial homeostasis in promoting SVD.

Collateral Circulation in Moyamoya Disease: A New Grading System.

Background and Purpose- Predicting the risk of stroke and determining intervention indications are highly important for patients with Moyamoya disease (MMD). Here, we evaluated a novel MMD grading system based on collateral circulation and Suzuki stage to evaluate symptoms and predict prognosis. Methods- In total, 301 idiopathic MMD patients were retrospectively analyzed between 2014 and 2016. A collateral circulation grading system with scores ranging from 1 to 12 was established: the anatomic extent of pial collateral blood flow from posterior cerebral artery to middle cerebral artery and anterior cerebral artery was scored from 1 to 6; perforator collateral and internal cerebral artery flow were scored as 6 to 1, which corresponded to Suzuki stages 1 to 6. Dynamic susceptibility contrast-magnetic resonance imaging was used to evaluate hemodynamic status. We assessed the association between the grading system and clinical characteristics. Results- We analyzed 364 symptomatic hemispheres of 301 patients (146 males, 28±16 years). Ischemic patients who presented with infarction were more likely to score <8 points (P<0.001), whereas those with ischemia symptoms (transient ischemic attack and headache) were more likely to score >8 points. Hemorrhagic patients who presented with intraparenchymal hemorrhage were more likely to score <8 points, whereas those who presented with intraventricular hemorrhage were more likely to score >8 points (P<0.001). According to dynamic susceptibility contrast-magnetic resonance imaging, lower scores were correlated with more severe time to peak delay (P<0.001) and worse relative cerebral blood volume ratio (P=0.016) and cerebral flow ratio (P=0.002). Encephaloduroarteriosynangiosis was performed in 348 symptomatic hemispheres. Patients who had collateral scores <4 points were more likely to have a postoperative stroke and a worse prognosis during the follow-up. Conclusions- This new MMD collateral grading system correlated well with clinical symptoms, hemodynamic status, and therapeutic prognosis and may facilitate risk stratification and prognosis predictions in patients with MMD.

Ultrasound measurements versus invasive intracranial pressure measurement method in patients with brain injury: a retrospective study

BackgroundThe invasive method for intracranial pressure measurement is ‘gold standard’ but not always feasible because the intraventricular catheter/ intraparenchymal micro transducer used in the measurement of intracranial pressure measurement may cause complications. Imaging modalities with clinical examination protocol have a lack of specificity and accuracy. The objective of the study was to compare the accuracy of diagnostic parameters of ultrasound measurements in patients with brain injury underwent invasive intracranial pressure measurement method.MethodsData of invasive intracranial pressure measurement method and ultrasound measurements of 185 patients with brain injury who required admission diagnosis were included in the analysis. Pearson correlation was tested for diagnostic parameters. Logistical regression analysis was performed for diagnostic parameters of death patients to evaluate independent parameter of mortality.ResultsStraight sinus flow velocities, middle cerebral artery flow velocities, and optic nerve sheath diameter were correlated with intracranial pressure (p < 0.0001 for all). Arterial blood pressure (p = 0.127) and middle cerebral artery pulsatility index (p = 0.06) were not correlated with intracranial pressure. A total of 47 patients died during the study period. Intracranial pressure (p = 0.015) and optic nerve sheath diameter (p = 0.035) were found to be independent predictor of mortality.ConclusionsUltrasound measurement especially optic nerve sheath diameter can be successfully used instead of invasive intracranial pressure measurement method in patients with brain injury.Level of evidenceIII.

Prediction of syncope with nonlinear dynamic analysis during head-up tilt in vasovagal syncope patients

To quantify the relationship between cerebral blood flow velocity and peripheral blood pressure during hypotension period, aiming to predict the brain hypotension before symptomatic occurrence. Twenty vasovagal syncope (VVS) patients who had a previous clinical history were selected in groups and 20 pair-matched control subjects underwent 70° tilt-up test. The subjects remained supine for 30 minutes before recordings when Doppler probes, electrodes and Finapres device were prepared. After continuous baseline recordings for 10 min, the subjects underwent head up tilt (HUT) test (70°), and were standing upright for 30 minutes or until syncope was imminent. For ethical reasons, the subjects were turned back to supine position immediately after SBP dropped to ≥20 mmHg, when their consciousness persisted. The point of syncope was synchronized for all the subjects by the point SBP reached the minima. Their beat-to-beat blood pressures (BP) were recorded continuously and bilateral middle cerebral artery (MCA) flow velocities were obtained with two 2 MHz Doppler probes from a transcranial Doppler ultrasonography (TCD) system. A nonlinear dynamic method--multimodal pressure flow (MMPF) analysis was introduced to access cerebral autoregulation during different time intervals. We introduced a new indicator--syncope index (SI), which was extracted from blood flow velocity (BFV) signal to evaluate the variation of cerebral vascular tension, and could reflect the deepness of dicrotic notch in BFV signal. Compared with the syncope index of the baseline value at the beginning of the tilt test, SI in VVS group showed significantly lower when the VVS occurred (0.16±0.10 vs.0.27±0.10,P<0.01),while there was no significant difference in syncope index between the control group at the end of the tilt test and the baseline value at the beginning of the tilt test. For those VVS patients, pulse index and resistance index had no significant change. Syncope index decreased significantly 3 minutes before the point of syncope (0.23±0.07 vs.0.29±0.07,P<0.01). Dynamic regulation is exhausted when vasovagal syncope occurred. Tension decrease of small vessels could have some relationship with loss of the cerebral autoregulation capability. The proposed syncope index could be a useful parameter in predicting syncope of VVS patients since it decreased significantly up to 3 minutes earlier from the point of syncope.