Adequate Cerebral Blood Flow Research Articles

Three-dimensional pseudocontinuous arterial spin labeling with dual postlabeling delay for reflecting cerebral blood flow regulation in patients with hydrocephalus: a retrospective cross-sectional study.

Three-dimensional pseudo-continuous arterial spin-labeling (3D pCASL) with dual postlabeling delay (PLD) captures both early and delayed cerebral blood flow (CBF), yet its potential in reflecting blood flow regulation in hydrocephalus patients remains uncertain. This study investigated the hemodynamic characteristics in patients with hydrocephalus and whether the difference in cerebral blood flow using short and long PLDs (ΔCBF = CBFPLD =2.5 s - CBFPLD =1.5 s) could reflect cerebral regulation and further aimed to demonstrate the associations between regional ΔCBF and the degree of ventricular dilatation. This retrospective study included consecutive patients with hydrocephalus and control participants attending The Second Affiliated Hospital of Nanchang University from December 2017 to December 2022. The CBF in 18 brain regions was manually delineated by two radiologists. Regional CBF and ΔCBF were compared via covariance analyses. The associations between ΔCBF and the degree of ventricular dilatation were investigated using linear regression analyses and interaction analysis. In total, 58 patients with communicating hydrocephalus, 57 patients with obstructive hydrocephalus, and 52 controls were analyzed. CBF of the hydrocephalus groups was lower than that of the control group at the shorter PLD. CBF was higher at a longer PLD, with no difference between the hydrocephalus groups and the control group in some regions. The hydrocephalus groups showed a higher ΔCBF compared to the control group. Furthermore, in the left medial watershed (10.6±5.66 vs. 7.01±5.88 mL/100 g/min; P=0.038), communicating hydrocephalus exhibited greater ΔCBF than did obstructive hydrocephalus. ΔCBF of the right posterior external watershed [adjusted β: 0.276; 95% confidence interval (CI): 0.047-0.505; P=0.019] and right parietal cortex (adjusted β: 0.277; 95% CI: 0.056-0.498; P=0.015) in the obstructive hydrocephalus group and ΔCBF of the left internal watershed (adjusted β: 0.274; 95% CI: 0.013-0.536; P=0.040) in the communicating hydrocephalus group were associated with the degree of ventricular dilatation, respectively. Patients with hydrocephalus showed cerebral regulation in maintaining adequate CBF, resulting in longer arterial transit times. The ability to regulate CBF in brain regions represented by the watershed was associated with the degree of ventricular dilation.

Age-related decline in cerebral oxygen consumption in multiple sclerosis

Cerebral oxygen metabolism is altered in relapsing-remitting multiple sclerosis (RRMS), possibly a result of disease related cerebral atrophy with subsequent decreased oxygen demand. However, MS inflammation can also inhibit brain metabolism. Therefore, we measured cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) using MRI phase contrast mapping and susceptibility-based oximetry in 44 patients with early RRMS and 36 healthy controls. Cerebral atrophy and white matter lesion load were assessed from high-resolution structural MRI. Expanded Disability Status Scale (EDSS) scores were collected from medical records. The CMRO2 was significantly lower in patients (−15%, p = 0.002) and decreased significantly with age in patients relative to the controls (−1.35 µmol/100 g/min/year, p = 0.036). The lower CMRO2 in RRMS was primarily driven by a higher venous oxygen saturation in the sagittal sinus (p = 0.007) and not a reduction in CBF (p = 0.69). There was no difference in cerebral atrophy between the groups, and no correlation between CMRO2 and MS lesion volume or EDSS score. Therefore, the progressive CMRO2 decline observed before the occurrence of significant cerebral atrophy and despite adequate CBF supports emerging evidence of dysfunctional cellular respiration as a potential pathogenic mechanism and therapeutic target in RRMS.

Distinctions between the Koizumi and Zea Longa methods for middle cerebral artery occlusion (MCAO) model: a systematic review and meta-analysis of rodent data

Ischemic stroke in rodents is usually induced by intraluminal middle cerebral artery occlusion (MCAO) via the common carotid artery plugging filament invented by Koizumi et al. (MCAO-KM), or the external carotid artery plugging filament created by Zea Longa et al. (MCAO-LG). A systematic review of the distinctions between them is currently lacking. Here, we performed a meta-analysis in terms of model establishment, cerebral blood flow (CBF), and cerebral ischemia–reperfusion injury (CIRI) between them, Weighted Mean Differences and Standardized Mean Difference were used to analyze the combined effects, Cochrane's Q test and the I2 statistic were applied to determine heterogeneity, sensitivity analysis and subgroup analysis were performed to explore the source of heterogeneity. Literature mining suggests that MCAO-KM brings shorter operation time (p = 0.007), higher probability of plugging filament (p < 0.001) and molding establishment (p = 0.006), lower possibility of subarachnoid hemorrhage (p = 0.02), larger infarct volume (p = 0.003), severer brain edema (p = 0.002), and neurological deficits (p = 0.03). Nevertheless, MCAO-LG shows a more adequate CBF after ischemia–reperfusion (p < 0.001), a higher model survival rate (p = 0.02), and a greater infarct rate (p = 0.007). In conclusion, the MCAO-KM method is simple to operate with a high modeling success rate, and is suitable for the study of brain edema under long-term hypoperfusion, while the MCAO-LG method is highly challenging for novices, and is suitable for the study of CIRI caused by complete ischemia–reperfusion. These findings are expected to benefit the selection of intraluminal filament MCAO models before undertaking ischemic stroke preclinical effectiveness trials.

The role of the autonomic nervous system in cerebral blood flow regulation in stroke: A review.

Stroke is a pathophysiological condition which results in alterations in cerebral blood flow (CBF). The mechanism by which the brain maintains adequate CBF in presence of fluctuating cerebral perfusion pressure (CPP) is known as cerebral autoregulation (CA). Disturbances in CA may be influenced by a number of physiological pathways including the autonomic nervous system (ANS). The cerebrovascular system is innervated by adrenergic and cholinergic nerve fibers. The role of the ANS in regulating CBF is widely disputed owing to several factors including the complexity of the ANS and cerebrovascular interactions, limitations to measurements, variation in methods to assess the ANS in relation to CBF as well as experimental approaches that can or cannot provide insight into the sympathetic control of CBF. CA is known to be impaired in stroke however the number of studies investigating the mechanisms by which this occurs are limited. This literature review will focus on highlighting the assessment of the ANS and CBF via indices derived from the analyses of heart rate variability (HRV), and baroreflex sensitivity (BRS), and providing a summary of both clinical and animal model studies investigating the role of the ANS in influencing CA in stroke. Understanding the mechanisms by which the ANS influences CBF in stroke patients may provide the foundation for novel therapeutic approaches to improve functional outcomes in stroke patients.

The effects of ECMO on neurological function recovery of critical patients: A double-edged sword.

Extracorporeal membrane oxygenation (ECMO) played an important role in the treatment of patients with critical care such as cardiac arrest (CA) and acute respiratory distress syndrome. ECMO is gradually showing its advantages in terms of speed and effectiveness of circulatory support, as it provides adequate cerebral blood flow (CBF) to the patient and ensures the perfusion of organs. ECMO enhances patient survival and improves their neurological prognosis. However, ECMO-related brain complications are also important because of the high risk of death and the associated poor outcomes. We summarized the reported complications related to ECMO for patients with CA, such as north-south syndrome, hypoxic-ischemic brain injury, cerebral ischemia-reperfusion injury, impaired intracranial vascular autoregulation, embolic stroke, intracranial hemorrhage, and brain death. The exact mechanism of ECMO on the role of brain function is unclear. Here we review the pathophysiological mechanisms associated with ECMO in the protection of neurologic function in recent years, as well as the ECMO-related complications in brain and the means to improve it, to provide ideas for the treatment of brain function protection in CA patients.

Near-infrared spectroscopy monitoring of neonatal cerebrovascular reactivity: where are we now?

Cerebrovascular reactivity defines the ability of the cerebral vasculature to regulate its resistance in response to both local and systemic factors to ensure an adequate cerebral blood flow to meet the metabolic demands of the brain. The increasing adoption of near-infrared spectroscopy (NIRS) for non-invasive monitoring of cerebral oxygenation and perfusion allowed investigation of the mechanisms underlying cerebrovascular reactivity in the neonatal population, confirming important associations with pathological conditions including the development of brain injury and adverse neurodevelopmental outcomes. However, the current literature on neonatal cerebrovascular reactivity is mainly still based on small, observational studies and is characterised by methodological heterogeneity; this has hindered the routine application of NIRS-based monitoring of cerebrovascular reactivity to identify infants most at risk of brain injury. This review aims (1) to provide an updated review on neonatal cerebrovascular reactivity, assessed using NIRS; (2) to identify critical points that need to be addressed with targeted research; and (3) to propose feasibility trials in order to fill the current knowledge gaps and to possibly develop a preventive or curative approach for preterm brain injury. IMPACT: NIRS monitoring has been largely applied in neonatal research to assess cerebrovascular reactivity in response to blood pressure, PaCO2 and other biochemical or metabolic factors, providing novel insights into the pathophysiological mechanisms underlying cerebral blood flow regulation. Despite these insights, the current literature shows important pitfalls that would benefit to be addressed in a series of targeted trials, proposed in the present review, in order to translate the assessment of cerebrovascular reactivity into routine monitoring in neonatal clinical practice.

Management of the Vertebral Artery in Craniovertebral Junction Stabilization Surgery.

The vertebral artery (VA) has an intimate relationship with the bones of the craniovertebral junction. An exact understanding of the VA anatomy in general and in the specific surgical case in particular is absolutely necessary in order to avoid intraoperative vascular injury. The course of the VA on the inferior aspect of the superior facet of the C2 vertebra makes it susceptible to damage during transarticular and interarticular fixation with the screw insertion in the adjacent lateral mass. The consequences of the intraoperative VA injury will depend on the patency of other arteries supplying the brain. In case of this complication, quick decision-making is essential to avoid excessive blood loss and to preserve adequate cerebral blood flow.

Abstract 08: Computed Tomography Perfusion Of Cerebral Blood Flow During Open Cardiac Massage For Hypovolemic And Normovolemic Cardiac Arrest In Swine

Introduction: Adequate cerebral blood flow (CBF) during open cardiac massage (OCM) in cardiac arrest is critical for survivors to be neurologically intact. Cerebral perfusion is known to be poor during OCM but has not been quantified using a brain perfusion technique. The aim of this study is to measure CBF in swine undergoing OCM in hypovolemia and normovolemia using computed tomography perfusion (CTP) scanning. Methods: Anesthetized swine underwent instrumentation with right atrial and aortic pressure catheters. A pigtail catheter placed in the ascending aorta was used to administer iodinated contrast and CTP imaging acquired. Brain parenchymal attenuation was measured over time from which CBF (mL/100g of brain) and time to peak (TTP; secs) were derived. Animals were then euthanized exsanguination (hypovolemic group) or potassium chloride injection (normovolemic group). Animals were subject to a clamshell thoracotomy, OCM and repeated CTP. Data pertaining to peak coronary perfusion pressure (pCPP; mmHg) was collected and % CPP &gt;15mmHg (% CPP; secs) calculated post hoc. Results: Normovolemic animals achieved superior pCPP compared to the hypovolemic animals (pCPP: 39.3 vs 12.3, p&lt;0.001; % CPP: 14.5 ± 1.9 vs 30.9 ± 6.5, p&lt;0.001). CTP was successfully performed during OCM generating an attenuation curve (figure). The TTP elongated from spontaneous circulation, normovolemia to hypovolemia (5.7 vs 10.8 vs 14.8, p=0.01). CBF during OCM was similar between hypovolemic and normovolemic groups (7.5 ± 8.1 vs 4.9 ± 6.0, p =0.73) which was lower than baseline values (51.9 ± 12.1, p&lt;0.001). Conclusions: OCM in normovolemia generates superior coronary hemodynamics compared to hypovolemia. Despite this, neither generates adequate CBF as measured by CTP, compared to baseline. To improve the rate of neurologically intact survivors, novel resuscitative techniques need to be investigated that specifically target cerebral perfusion as existing techniques are inadequate.

Identifying the optimal blood pressure for cerebral autoregulation in infants after cardiac surgery by monitoring cerebrovascular reactivity-A pilot study.

Advances in the treatment of pediatric congenital heart disease have increased survival rates. Despite efforts to prevent neurological injury, many patients suffer from impaired neurodevelopmental outcomes. Compromised cerebral autoregulation can increase the risk of brain injury following pediatric cardiac surgery with cardiopulmonary bypass. Monitoring autoregulation and maintaining adequate cerebral blood flow can help prevent neurological injury. Our objective was to evaluate autoregulation parameters and to define the optimal blood pressure as well as the lower and upper blood pressure limits of autoregulation. Autoregulation was monitored prospectively in 36 infants after cardiopulmonary bypass surgery for congenital heart defects between January and December 2019. Autoregulation indices were calculated by correlating invasive arterial blood pressure, cortical oxygen saturation, and relative tissue hemoglobin levels with near-infrared spectroscopy parameters. The mean patient age was 4.1 ± 2.8months, and the mean patient weight was 5.2 ± 1.8kg. Optimal mean arterial pressure could be identified in 88.9% of patients via the hemoglobin volume index and in 91.7% of patients via the cerebral oxygenation index, and a lower limit of autoregulation could be found in 66.7% and 63.9% of patients, respectively. No significant changes in autoregulation indices at the beginning or end of the monitoring period were observed. In 76.5% ± 11.1% and 83.8% ± 9.9% of the 8 and 16 h monitoring times, respectively, the mean blood pressure was inside the range of intact autoregulation (below in 21.5% ± 25.4% and 11.3% ± 16.5% and above in 8.7% ± 10.4% and 6.0% ± 11.0%, respectively). The mean optimal blood pressure was 57.4 ± 8.7 mmHg and 58.2 ± 7.9 mmHg and the mean lower limit of autoregulation was 48.8 ± 8.3 mmHg and 45.5 ± 6.7 mmHg when generated via the hemoglobin volume index and cerebral oxygenation index, respectively. Postoperative noninvasive autoregulation monitoring after cardiac surgery in children can be reliably and safely performed using the hemoglobin volume index and cerebral oxygenation index and provides robust data. This monitoring can be used to identify individual hemodynamic targets to optimize autoregulation, which differs from those recommended in the literature. Further evaluation of this subject is needed.

Cool Head-out Water Immersion Augments Cerebral Artery Blood Velocity In Healthy Young Adults

Adequate cerebral blood flow (CBF) is critical for brain function. Thermoneutral head-out water immersion (HOWI) may be a useful modality to increase CBF but it is unclear whether a colder water temperature influences the cerebrovascular responses. PURPOSE: We tested the hypothesis that middle cerebral artery blood velocity (MCAv) and cerebrovascular reactivity to hypercapnia (CVRCO2) would be higher during an acute bout of thermoneutral (TN; 35 °C) vs. cool (COOL; 25 °C) HOWI. METHODS: Ten healthy participants (age: 23 ± 3 y; BMI: 23 ± 3 kg/m2; 4 females) completed two randomized 45-minute HOWI visits. Core temperature (Tcore) was recorded every five minutes via an ingested telemetry pill. Right mean MCAv, end-tidal CO2 tension (PETCO2), and mean arterial pressure (MAP) were continuously recorded. CVRCO2 was assessed using a fixed inspired stepped hypercapnia protocol before (PRE), at 30 minutes of HOWI (HOWI), and 45 minutes after cessation of HOWI (POST). CVRCO2 was calculated as the slope of the linear regression line between MCAv and PETCO2. Values are reported as a change from PRE (mean ± SD). RESULTS: There were no differences between conditions at PRE (all P ≥ 0.09). During HOWI, the change in Tcore, MCAv, PETCO2, MAP, CVRCO2 were not different between TN and COOL (all P ≥ 0.22). Tcore did not change during TN (-0.10 ± 0.14 °C; P = 0.55) or COOL (-0.00 ± 0.22 °C; P > 0.99). MCAv did not increase during TN (4 ± 5 cm/s; P = 0.06) but increased during COOL (7 ± 6 cm/s; P < 0.01). PETCO2 did not change during TN (1 ± 2 mmHg; P = 0.20) or COOL (1 ± 2 mmHg; P = 0.16). MAP increased during TN (11 ± 7 mmHg; P < 0.01) and COOL (16 ± 4 mmHg; P < 0.01). At POST, the change in Tcore, MCAv, and PETCO2 was greater in COOL vs. TN (all P < 0.01). Tcore did not change in TN (P > 0.99), but decreased in COOL (P = 0.04) at POST. MCAv did not change in TN (1 ± 7 cm/s; P > 0.99) but increased in COOL (9 ± 5 cm/s; P < 0.01) at POST. PETCO2 did not change in TN (-1 ± 2 mmHg; P = 0.42) or COOL (1 ± 1 mmHg; P = 0.06) at POST. MAP did not increase in TN (5 ± 8 mmHg; P = 0.06) but increased in COOL (11 ± 10 mmHg; P < 0.01) at POST. CVRCO2 did not change over time (P ≥ 0.11) or between conditions (P ≥ 0.32). CONCLUSION: Cool water augmented MCAv during immersion and MCAv was greater following COOL HOWI vs. TN at 45 minutes post. However, neither condition altered CVRCO2 in healthy young adults. Supported by ONR N00014-17-1-2878

Modeling the effect of cerebral capillary blood flow on neuronal firing

Adequate cerebral blood flow has long been recognized as essential for the maintenance of the neuronal function while interruption of cerebral blood flow for durations as short as minutes can result in permanent brain damage. A primary goal of this work is to determine how a neuron’s ability to respond to synaptic input depends on parameters that control cerebral blood flow. A complex mathematical model is constructed that integrates detailed biophysical models of neuronal action potentials, mitochondrial ATP production and cerebral capillary blood flow. The model also provides insights of the role of astrocytes in maintaining neuronal responses, as well as the impact of elevated cytosolic calcium, due to increased synaptic activity, on mitochondrial ATP production. Both dynamical systems analysis and numerical simulations are used to determine how the maximum frequency at which the neurons can respond to synaptic input depends on capillary blow flow, as well as the ability of astrocytes to buffer extracellular potassium and cytosolic calcium handling. Results are presented for both the cases of homogenous and heterogeneous capillary networks. These results demonstrate, through this interconnected model, that heterogeneity of the capillary flow results in a decrease in the ability of neurons to respond to synaptic stimulation and that intact glial function provides a further protective role for the neurons.

Improving Collateral Circulation: A Potential Adjunctive Strategy to Prevent or Slow the Progression of Vascular Dementia.

Vascular dementia (VaD), a cognitive disorder caused by cerebrovascular pathologies, is the most common cause of dementia in the elderly, being second only to Alzheimer’s disease. Researches have shown that adequate cerebral blood flow (CBF) is the first condition for maintaining the structural integrity and normal function of the brain, and VaD is generally considered to be resulted from neuronal loss due to reduced CBF. Collateral circulation, a compensation mechanism for CBF, provides an alternative vascular pathway for blood to reach ischemic tissues, which has been confirmed to be associated with better clinical outcomes of ischemic diseases. At present, considerable effort has been devoted to enhancing the functional prognosis of acute ischemic stroke by improving collateral circulation. Since ischemic stroke is the primary contributor to VaD, it is necessary to explore whether improving collateral circulation is beneficial to prevent or slow the progression of VaD. This article reviews the compensatory characteristics of different levels of cerebral collateral circulation, addresses the relationship between collateral circulation and VaD, and highlights that improving collateral circulation may be a potential adjunctive strategy in preventing and slowing the progression of VaD.

Imaging Pattern and the Mechanisms of Postoperative Infarction After Indirect Revascularization in Patients with Moyamoya Disease

To develop preventive strategies against postoperative infarction after indirect revascularization surgery in patients with moyamoya disease (MMD), we evaluated clinical information, with a specific focus on the imaging pattern of postoperative infarction. We retrospectively evaluated 421 surgical procedures performed in 354 (262 pediatric and 159 adult) patients with MMD from April 1991 to March 2021 at our institute. In addition to clinical information, raw images of postoperative infarction were collected and categorized into subtypes by the location of the infarction. Symptomatic and asymptomatic postoperative infarction occurred in 47 and 12 patients (11.1% and 2.6%), respectively, and more than half (51.7%) of these cases of postoperative infarction occurred immediately or the day after the surgery. Cortical infarction around the craniotomy site was the most frequent pattern observed (50/59, 84.8%), and some of these cases seemed to occur under local compression from epidural or subdural hematomas (15/50, 30.0%). Ipsilateral white matter infarctions located in the watershed area (9/59, 15.3%) and contralateral infarctions (3/59, 5.1%) were also observed. Four patients (1.0%) showed sudden occlusions of ipsilateral or contralateral large intracranial arteries immediately after surgery. Postoperative infarction caused permanent neurologic deficits in 7 patients (1.7%), and all included the cortex outside the craniotomy site. Local cortical irritation, hemodynamic fluctuation, and thromboembolic events were suggested as possible mechanisms of postoperative infarction after indirect revascularization in patients with MMD. Minimizing cortical irritation, maintaining adequate cerebral blood flow, and perioperative antiplatelet agents might decrease the incidence of postoperative infarction.

Safety and effectiveness of high flow extracranial to intracranial saphenous vein bypass grafting in the treatment of complex intracranial aneurysms: a single-centre long-term retrospective study

BackgroundTo summarize the safety and effectiveness of high flow extracranial to intracranial saphenous vein bypass grafting in the treatment of complex intracranial aneurysms.MethodsThe data of complex intracranial aneurysms patients for high flow extracranial to intracranial saphenous vein bypass grafting from January 2008 to January 2020 were retrospectively collected and analyzed. Eighty-two patients (31 men and 51 women) with 89 aneurysms underwent 82 saphenous vein bypass grafts followed by immediate parent vessel occlusion. The aneurysm was located at the internal carotid artery, middle cerebral artery, and basilar artery in 75, 11, and 3 cases, respectively.ResultsThe patency rate of bypass grafting was 100, 100, 96.3 and 92.4% on intraoperation, on the first postoperative day, at discharge and 6 months follow-up, respectively. At discharge and 6 months follow-up, 3 and 6 patients had graft occlusions. The main postoperative complications were transient hemiparesis and hemianopsia. 3 patients died due to bypass complications and poor physical condition.ConclusionsHigh flow extracranial to intracranial saphenous vein bypass grafting is safe and effective in the treatment of complex intracranial aneurysms and the saphenous vein can meet the requirements of brain blood supply. A high rate of graft patency and adequate cerebral blood flow can be achieved.HighlightsA single-centre long-term retrospective study was conducted to assess the safety and effectiveness of high flow EC-IC saphenous vein bypass grafting in the treatment of complex intracranial aneurysms. The data of 82 patients from January 2008 to January 2020 were retrospectively collected and analysed.We found the patency rate of bypass grafting was 100, 100, 96.3 and 92.4% on intraoperation, on the first postoperative day, at discharge and 6 months follow-up, respectively. At discharge and 6 months follow-up, 3 and 6 patients had graft occlusions.Finally, we conclude that high flow extracranial to intracranial saphenous vein bypass grafting is safe and effective in the treatment of complex intracranial aneurysms and the selected blood supply vessels can meet the requirements of blood supply.As far as we know, this study is one of the maximum number of cases in the treatment of complex intracranial aneurysms with saphenous vein bypass.

Influence of Intragastric Administration of Traditional Japanese Medicine, Ninjin'Yoeito, on Cerebral Blood Flow via Muscarinic Acetylcholine Receptors.

Ninjin'yoeito (NYT) is a traditional medicine that has been used for mitigating physical frailty, such as fatigue and anorexia, as well as for cognitive dysfunction. Maintenance of adequate cerebral blood flow (CBF) is important for preventing cognitive dysfunction. The present study aimed to examine the effect of NYT on CBF. Male C57BL/6 J mice were anesthetized with urethane and were artificially ventilated. We measured CBF in the neocortex with laser-speckle contrast imaging for 10 min before administration and 60 min after administration. We administered NYT solution (0.25, 0.5, 1, and 2 g/kg) or vehicle (distilled water; DW) over 5 min via an intragastric catheter. We surgically transected the vagus nerve to investigate its contribution as a neural pathway and intraperitoneally injected atropine to block muscarinic acetylcholine receptors. Finally, we tested the CBF response to cutaneous brushing stimulation applied to the left hind paw (30 sec). CBF decreased after DW administration, starting from 30 min onward, whereas CBF did not change after NYT. The averaged CBF change following DW administration differed from that following NYT (1 g/kg) but not from those following the other doses of NYT. Arterial pressure was not affected by either solution. CBF after NYT (1 g/kg) was not affected by vagotomy but was lower following additional atropine. In response to brushing stimulation, CBF in the right (contralateral) parietal cortex increased. The magnitude of CBF increase following NYT was greater than that following DW. These results suggest that NYT prevents CBF decrease via cholinergic activation independent of vagal activity and enhances the CBF response to somatosensory stimulation.

Asymptomatic Complete Occlusion of Extracranial Internal Carotid Artery: A Case Report

This article reports on head-and-neck computed tomography angiography imaging findings and data of ultrasound examination of the extracranial carotid and vertebral arteries of 69-year-old patient with unilateral asymptomatic complete occlusion of extracranial internal carotid artery (ICA) in combination with unusually elongated styloid processes of temporal bone. The aim of the study was to specify the collateral pathways blood supply to the brain and to assess the possible clinical significance of an abnormally elongated styloid pro cess. Adequate cerebral blood flow was provided by anastomoses between the arteries at the base of the brain. This can explain the asymptomatic unilateral complete occlusion of the extracranial ICA. Occlusion of the artery was not associated with the presence of a 5.5 cm styloid process. Computed tomography angiography is a highly informative method for visualizing the individual morphological variants to clarify their clinical significance.

Effects of circulatory arrest and cardiopulmonary bypass on cerebral autoregulation in neonatal swine

BackgroundCerebral autoregulation mechanisms help maintain adequate cerebral blood flow (CBF) despite changes in cerebral perfusion pressure. Impairment of cerebral autoregulation, during and after cardiopulmonary bypass (CPB), may increase risk of neurologic injury in neonates undergoing surgery. In this study, alterations of cerebral autoregulation were assessed in a neonatal swine model probing four perfusion strategies.MethodsNeonatal swine (n = 25) were randomized to continuous deep hypothermic cardiopulmonary bypass (DH-CPB, n = 7), deep hypothermic circulatory arrest (DHCA, n = 7), selective cerebral perfusion (SCP, n = 7) at deep hypothermia, or normothermic cardiopulmonary bypass (control, n = 4). The correlation coefficient (LDx) between laser Doppler measurements of CBF and mean arterial blood pressure was computed at initiation and conclusion of CPB. Alterations in cerebral autoregulation were assessed by the change between initial and final LDx measurements.ResultsCerebral autoregulation became more impaired (LDx increased) in piglets that underwent DH-CPB (initial LDx: median 0.15, IQR [0.03, 0.26]; final: 0.45, [0.27, 0.74]; p = 0.02). LDx was not altered in those undergoing DHCA (p > 0.99) or SCP (p = 0.13). These differences were not explained by other risk factors.ConclusionsIn a validated swine model of cardiac surgery, DH-CPB had a significant effect on cerebral autoregulation, whereas DHCA and SCP did not.ImpactApproximately half of the patients who survive neonatal heart surgery with cardiopulmonary bypass (CPB) experience neurodevelopmental delays. This preclinical investigation takes steps to elucidate and isolate potential perioperative risk factors of neurologic injury, such as impairment of cerebral autoregulation, associated with cardiac surgical procedures involving CPB.We demonstrate a method to characterize cerebral autoregulation during CPB pump flow changes in a neonatal swine model of cardiac surgery.Cerebral autoregulation was not altered in piglets that underwent deep hypothermic circulatory arrest (DHCA) or selective cerebral perfusion (SCP), but it was altered in piglets that underwent deep hypothermic CBP.

Effects of Transient Cerebral Hypoperfusion on Human Auditory Brainstem Responses

Adequate cerebral blood flow perfusion is crucial to maintaining brain function. The auditory brainstem response (ABR) has been demonstrated to be the most powerful diagnostic tool for assessing auditory function. This study aimed to determine the ABR under transient cerebral hypoperfusion caused by using oscillatory lower body negative pressure (OLBNP). As chronic cerebral hypoperfusion has been associated with the prolongation of the latency of ABR waves, we hypothesized that the fluctuation of cerebral blood flow perfusion also affects this latency. As prior data showing that cerebral autoregulation is not effectively engaged when pressure fluctuations are shorter than 30 sec periods (i.e., higher than 0.03 Hz), we used the sinusoidal pattern of an 18 sec period (0.056 Hz) of 0 ~ - 40 mmHg OLBNP to induce transient cerebral hypoperfusion. Here, we measured ABR and cerebral blood flow velocity (MCAv) during 12 min of control and 12 min of OLBNP (40 cycle of 18-sec periods) in 15 subjects (3 of whom were excluded from the analysis due to an insufficient number of data for ABR). Periodical changes in cerebrovascular variables were aligned relative to each 18 sec of OLBNP cycle onset and were subdivided into three phases (phase-1: 0 ~ 6 sec, phase-2: 6 ~ 12 sec, and phase-3: 12 ~ 18 sec of OLBNP onset). For the ABR analysis, a total of 6800 individual sweeps were recorded for 12 min in the control and OLBNP conditions, and the recorded sweeps in the OLBNP condition were subdivided into three phases. We observed that OLBNP caused cyclic fluctuations of MCAv. One-way repeated-measures analysis of variance (ANOVA) and the post-hoc comparison revealed that MCAv decreased significantly in phases-1 and -2 compared to the control and phase-3 (F(3, 33) = 16.54, p < 0.001). As for the ABR data, ANOVA and the post-hoc comparison revealed that the latency of wave V of ABR at phase-2 was delayed compared to phase-1 (F(3, 33) = 3.70, p < 0.05). Moreover, the results showed that the inter-individual difference in the variance over the phase conditions of the latency of wave V was significantly related to that of cerebral blood flow (r = 0.641, p < 0.05). Our data demonstrate that the fluctuation of cerebral blood flow perfusion could lead to the prolongation of the latency of ABR waves. This suggests that the transient cerebral hypoperfusion induced by an acute orthostatic blood shift to the lower body could impair auditory function.

The severity of acute ischemic stroke is associated with the decrease in peak systolic velocity in the common carotid arteries

Abstract Funding Acknowledgements Type of funding sources: None. Introduction A negative effect on the prognosis of ischemic stroke of the aggressive decrease in blood pressure, leading to a decrease in cerebral blood flow, is known. On the other side, increased blood pressure can be a compensatory mechanism. Currently, however, it is difficult to assess the adequacy of cerebral blood flow, one of the indicators of which is the blood flow velocity in the common carotid artery. Purpose The aim of this study was to estimate the peak systolic velocity in the common carotid arteries (CCA PSV) depending on the severity of acute ischemic stroke (IS). Methods 180 patients with acute ischemic stroke (70 females and 110 males, mean age was 66.3 ± 12.3 years) were studied. Including 46 (25.6%) patients with cardioembolic stroke, 25 (13.9%) - with a thrombotic stroke, 27 (15.0%) – with a lacunar stroke and 82 (45.5%) – with undifferentiated stroke. Most of them 173 (96.1%) had grade 3 of arterial hypertension according to ESH/ESC Guidelines for the management of arterial hypertension, 2018. 59 (32.8%) patients had coronary artery disease, 52 (28.9%) - had atrial fibrillation. Patients were categorized according to National Institutes of Health Stroke Scale (NIHSS) severity in mild NIHSS (&amp;lt;9) - 122 (67.8%) patients, moderate NIHSS (9–15) - 35 (19.4%) patients, and severe stroke NIHSS (&amp;gt;16) - 23 (12.8%) patients. Median NIHSS score was 9.2 ± 0.9. All patients underwent a transthoracic echocardiography and a carotid ultrasound examination. A comparative assessment of echographic parameters was performed in patients of lower (NIHSS score ≤ 4.0) and upper (NIHSS score≥11.0) quartile according to the NIHSS score. Results It is shown a decrease of peak systolic velocity in the common carotid arteries with an increase in the severity of IS on the NIHSS scale: in mild stroke, it was 73.9 ± 18.7 cm/s, in moderate stroke - 66.3 ± 19.2 cm/s (p = 0.04), in severe stroke - 62.1 ± 17,4 cm/sec (p = 0.006 and p = 0.4, respectively). Peak systolic velocity in patients with the lower quartile of stroke severity was 73.8 ± 19.1 cm/sec, in the group of patients with the upper quartile – 64.3 ± 19.2 cm/sec (р=0.02). There were no differences in the resistance index of common carotid arteries: 0.75 ± 0.05, 0.76 ± 0.06 and 0.75 ± 0.07 for mild, moderate and severe severity, respectively, p &amp;gt; 0.5). A multiple linear regression analysis in which the severity of ischemic stroke on the NIHSS scale was a dependent variable and age, CCA PSV, common carotid artery intima–media thickness and systolic, diastolic and pulse blood pressure were independent variables, showed that the severity of ischemic stroke was independently correlated with the CCA PSV (β =-0.13, p = 0.009). Conclusions.1. It is shown the decrease of peak systolic velocity in the common carotid arteries with an increase in the severity of ischemic stroke on the NIHSS scale. 2. The reduction of CCA PSV exacerbates brain ischemia and reflecting disorders of autoregulation of cerebral blood flow.

Neurovascular-glymphatic dysfunction and white matter lesions.

Cerebral white matter lesions (WML) represent a spectrum of age-related structural changes that are identified as areas of white matter high signal intensity on brain magnetic resonance imaging (MRI). Preservation of white matter requires proper functioning of both the cerebrovascular and glymphatic systems. The cerebrovascular safeguards adequate cerebral blood flow to supply oxygen, energy, and nutrients through a dynamic process of cerebral autoregulation and neurovascular coupling to keep up with global and regional demands of the brain. The glymphatic system maintains white matter integrity by preserving flow of interstitial fluid, exchanging metabolic waste and eventually its clearance into the venous circulation. Here, we argue that these two systems should not be considered separate entities but as one single physiologically integrated unit to preserve brain health. Due to the process of aging, damage to the neurovascular-glymphatic system accumulates over the life course. It is an insidious process that ultimately leads to the disruption of cerebral autoregulation, to the neurovascular uncoupling, and to the accumulation of metabolic waste products. As cerebral white matter is particularly vulnerable to hypoxic, inflammatory, and metabolic insults, WML are the first recognized pathologies of neurovascular-glymphatic dysfunction. A better understanding of the underlying pathophysiology will provide starting points for developing effective strategies to prevent a wide range of clinical disorders among which there are gait disturbances, functional dependence, cognitive impairment, and dementia.