Cerebrovascular Reserve Capacity Research Articles

Assessment of Intracranial Collateral Circulation Using Novel TCCS Grading System in Patients With Symptomatic Carotid Occlusion.

Objectives: To establish a novel transcranial color-coded sonography (TCCS) grading system for collateral circulation in cases of symptomatic chronic total carotid occlusion (TCO), and to correlate this new grading system with cerebrovascular reserve capacity (CVR) measured by SPECT.Methods: Thirty-four patients with symptomatic chronic TCO recruited from the neurovascular ultrasound laboratory of the department of Neurology at Cairo University Hospital during 3 years' time period and diagnosed by color-coded duplex were subjected to: clinical assessment, grading of cerebral collaterals using a proposed TCCS criteria, Brain SPECT studies at rest and with dipyridamole stress.Results: The new grading system for cerebral collateral circulation showed a significant positive correlation with CVR (P < 0.001 and Spearman correlation coefficient 0.686).Conclusion: The current study showed that this new TCCS grading system for cerebral collaterals is a reliable indicator for cerebral perfusion and reserve capacity in cases of chronic symptomatic TCO.

Arterial transit artifacts observed by arterial spin labeling in Moyamoya disease

Objectives: Arterial spin labeling (ASL) is a magnetic resonance imaging (MRI) technique used to assess cerebral perfusion. When tissue perfusion is impaired, such as in Moyamoya disease, a hyperintense band called the arterial transit artifact (ATA) may occur, which interferes with accurate measurements on ASL-MRI. In this study, we evaluated the correlation of ATAs with magnetic resonance angiography (MRA) and single-photon emission computed tomography (SPECT) imaging results in Moyamoya disease. The aim of our study was to elucidate the pathophysiology of ATAs and risk factors for high ATA scores. Materials and Methods: This retrospective study included 28 patients (56 hemispheres) with Moyamoya disease treated at our institution. MRI, MRA, ASL perfusion, and N-isopropyl-[123I] b-iodoamphetamine (123I-IMP) SPECT were performed. In order to semi-quantitatively evaluate the degree of ATA, the ATA scores were measured according to the number of hyperintense signal bands in the cerebral cortex. The relationship between the ATA scores and clinical and radiological factors were analyzed. Results: Regional cerebral blood flow (rCBF) determined with ASL weakly correlated with that determined by 123I-IMP SPECT (ρ=0.31, p=0.027). There was no significant association between the ATA scores and rCBF values determined with 123I-IMP SPECT (p=0.872, 0.745, 0.743 at PLD1000 (post-labeling delay), 1500, and 2000, respectively). However, there was a significant correlation between ATA scores and MRA scores (ρ=0.427 p=0.001; ρ=0.612 p=0.001; ρ=0.563 p=0.001 at PLD1000, 1500, and 2000, respectively). An analysis of patient background characteristics revealed a significantly higher incidence of high ATA scores in female patients, patients with high MRA scores, and patients with a distinguishable ivy sign. A multivariate analysis confirmed that female sex, high MRA score, and presence of an ivy sign were risk factors for high ATA scores. Conclusion: ATA scores were moderately correlated with MRA scores, and presence of an ivy sign was the most predictive factor for high ATA scores. A high ATA score determined using ASL in a patient with Moyamoya disease might suggest an advanced disease stage and a reduction in cerebrovascular reserve capacity.

Effects of Increased Hemoglobin Oxygen Affinity on Cerebrovascular Reserve Capacity in Sickle Cell Disease

Sickle cell disease (SCD) is associated with a high incidence of ischemic stroke. SCD is characterized by hemolytic anemia, resulting in limited oxygen (O2) delivery to tissues, increased nitric oxide (NO) scavenging, and impaired cerebrovascular hemodynamics. Cerebral blood flow (CBF) is a key metric in determining proper O2 delivery to cerebral tissue. CBF is tightly regulated to maintain constancy of cerebral perfusion by both local mechanisms and autonomic control. Independent from cerebral autoregulation, the influence of the partial arterial carbon dioxide (PaCO2) tension on CBFis known as the cerebrovascular CO2 responsiveness and reflects the vasodilatory capacity of the cerebral vasculature or cerebrovascular reserve capacity. Since cerebrovascular CO2 responsiveness is oxygen dependent and has been related to an increased stroke risk in microvascular diseases such as SCD. This study determines the effects of changes in hemoglobin O2 affinity in cerebrovascular CO2 responsiveness in SCD. CBF was measured using a laser Doppler probe placed over the cortex. The Hb O2 affinity was manipulated via intravenous administration of 5‐hydroxymethyl‐2‐furfural (5HMF), to decrease the Hb‐O2 affinity of homozygous Townes transgenic SCD mice form 32 mmHg to 16 mmHg. To estimate the cerebrovascular reserve capacity animals were challenged with hypercapnia (5% CO2/21% O2 over 20 minutes) for three cycles. Animals with increased Hb O2 affinity showed increased cerebrovascular reserve capacity compared to animals with normal Hb O2 affinity. In conclusion, increasing Hb‐O2 affinity of sickle cell mice protects cerebrovascular CO2 responsiveness, suggesting a increased cerebrovascular reserve capacity which might protect from stroke in SCD.Support or Funding InformationThis work was supported by the NIH Heart Lung and Blood Institute under Grants T32‐HL105373, R01‐HL126945, and the DOD DMRDP under Grant W81XWH‐18‐1‐0059

High Intravascular Signal Arterial Transit Time Artifacts Have Negligible Effects on Cerebral Blood Flow and Cerebrovascular Reserve Capacity Measurement Using Single Postlabel Delay Arterial Spin-Labeling in Patients with Moyamoya Disease.

Arterial spin-labeling-derived CBF values may be affected by arterial transit time artefacts. Thus, our aim was to assess to what extent arterial spin-labeling-derived CBF and cerebrovascular reserve capacity values in major vascular regions are overestimated due to the arterial transit time artifacts in patients with Moyamoya disease. Eight patients with Moyamoya disease were included before or after revascularization surgery. CBF maps were acquired using a 3D pseudocontinuous arterial spin-labeling sequence, before and 5, 15, and 25 minutes after an IV acetazolamide injection and were registered to each patient's 3D-T1-weighted images. Vascular regions were defined by spatial normalization to a Montreal Neurological Institute-based vascular regional template. The arterial transit time artifacts were defined as voxels with high signal intensity corresponding to the right tail of the histogram for a given vascular region, with the cutoff selected by visual inspection. Arterial transit time artifact maps were created and applied as masks to exclude arterial transit time artifacts on CBF maps, to create corrected CBF maps. The cerebrovascular reserve capacity was calculated as CBF after acetazolamide injection relative to CBF at baseline for corrected and uncorrected CBF values, respectively. A total of 16 examinations were analyzed. Arterial transit time artifacts were present mostly in the MCA, whereas the posterior cerebral artery was generally unaffected. The largest differences between corrected and uncorrected CBF and cerebrovascular reserve capacity values, reported as patient group average ratio and percentage point difference, respectively, were 0.978 (95% CI, 0.968-0.988) and 1.8 percentage points (95% CI, 0.3-3.2 percentage points). Both were found in the left MCA, 15 and 5 minutes post-acetazolamide injection, respectively. Arterial transit time artifacts have negligible overestimation effects on calculated vascular region-based CBF and cerebrovascular reserve capacity values derived from single-delay 3D pseudocontinuous arterial spin-labeling.

Abstract WP171: Are We Correctly Measuring Cerebrovascular Reserve Capacity: A Study on Multiple Sequential Post-Acetazolamide Injection Cerebral Blood Flow Measurements Using Arterial Spin Labeling in a Moyamoya Patient Population?

Introduction: Cerebrovascular reserve capacity (CVRC), an important predictor and prognostic factor for patients with moyamoya disease (MMD), can be derived by measuring cerebral blood flow (CBF) before and after administration of acetazolamide (ACZ). Commonly, a single CBF measurement is performed after ACZ injection at a time point varying between 5 to 20 minutes, whereas the dynamic temporal response using sequential CBF measurements has not been studied extensively. Furthermore, current literature reports group averaged CVRCs with high standard deviations indicating a patient-specific CVRC is spread over a wide range of values. The aim of this study was to assess the temporal dynamic response of CBF and derived CVRC during the ACZ challenge using arterial spin labeling in patients with MMD. Methods: Ten patients with MMD were included before and/or after revascularisation surgery and examined on a 3T MR scanner. CBF maps, based on 3D-pseudocontineous arterial spin labeling, were acquired before and 5, 15 and 25 minutes after an i.v. ACZ injection and registered to each patient’s 3D-T1-weighted image. A vascular territory template was spatially normalised to patient-specific space, defined by the 3D-T1-weighted image, including bilateral ACA, MCA and PCA. A post label delay of 2500 ms and large regions-of-interests were used to account for possible arterial transit time artefacts. CVRC was calculated as CBF augmentation post-ACZ injection relative to baseline. Results: A total of sixteen examinations were analysed. Average peak CBF augmentation occurred at 5 min post-ACZ injection, successively decreasing at 15 - and 25 min post-ACZ injection . CVRC followed a similar pattern. Peak CBF augmentation mostly occurred at 5 min for all vascular regions (frequency distribution 5 min: 64 %, 15 min: 23 %, 25 min: 13 %). Average ratio between CVRC calculated using 15 min CBF augmentation and CVRC using true peak CBF augmentation (5, 15 or 25 min) was 0.80 to 0.90 for all vascular regions. Conclusion: CVRC assessed using 15 min as a single post-ACZ injections time point may underestimate CVRC in average by 10 % to 20 % because of individual temporal patient response. The use of multiple post-injection time points is warranted.

Validation and Application for the Berlin Grading System of Moyamoya Disease in Adult Patients.

Traditional moyamoya disease (MMD) classification relies on morphological digital subtraction angiography (DSA) assessment, which do not reflect hemodynamic status, clinical symptoms, or surgical treatment outcome. To (1) validate the new Berlin MMD preoperative symptomatology grading system and (2) determine the clinical application of the grading system in predicting radiological and clinical outcomes after surgical revascularization. Ninety-six MMD patients (192 hemispheres) with all 3 investigations (DSA, magnetic resonance imaging [MRI], Xenon-CT) performed preoperatively at our institution (2007-2013) were included. Two clinicians independently graded the imaging findings according to the proposed criteria. Patients' modified Rankin Score (mRS) scores (preoperative, postoperative, last follow-up), postoperative infarct (radiological, clinical) were collected and statistical correlations performed. One hundred fifty-seven direct superficial temporal artery-middle cerebral artery bypasses were performed on 96 patients (66 female, mean age 41 yr, mean follow-up 4.3 yr). DSA, MRI, and cerebrovascular reserve capacity were independent factors associated hemispheric symptomatology (when analyzed individually or in the combined grading system). Mild (grade I), moderate (grade II), severe (grade III) were graded in 45, 71, and 76 hemispheres respectively; of which, clinical symptoms were found in 33% of grade I, 92% of grade II, 100% of grade III hemispheres (P<.0001). Two percent of grade I, 11% of grade II, 20% of grade III hemispheres showed postoperative radiological diffusion weighted image-positive ischemic changes or hemorrhage on MRI (P=.018). Clinical postoperative stroke was observed in 1.4% of grade II, 6.6% of grade III hemispheres (P=.077). The grading system also correlated well to dichotomized mRS postoperative outcome. The Berlin MMD grading system is able to stratify preoperative hemispheric symptomatology. Furthermore, it correlated with postoperative new ischemic changes on MRI, and showed a strong trend in predicting clinical postoperative stroke.

Occipital artery-anterior cerebral artery bypass with posterior auricular artery-middle cerebral artery bypass for stenosis of the internal carotid artery bifurcation

Superficial temporal artery (STA)-middle cerebral artery (MCA) bypass, and STA-anterior cerebral artery (ACA) bypass, are options for direct revascularisation of anterior circulation. However, some patients don't have a suitable STA to use as a donor, so an alternative procedure must be performed. A 59-year-old, right-handed man presented with dysphasia and right-sided hemiparesis due to a transient ischaemic attack. Imaging studies revealed severe stenosis of the left internal carotid artery bifurcation. Iodoamphetamine single photon emission computed tomography demonstrated reduced cerebrovascular reserve capacity in the left hemisphere. The patient was started on antiplatelet therapy, but the ischaemic attacks persisted after one month. Thus, revascularisation of the ACA and MCA territories was considered. Digital subtraction angiography revealed prominence in the left occipital artery (OA) and posterior auricular artery (PAA), while the left STA was hypoplastic, terminating at the squamous suture level. Therefore, anastomoses were performed between both the OA and ACA and the PAA and MCA. Revascularisation was successful, and the ischaemic attacks disappeared. OA-ACA bypass, together with PAA-MCA bypass, may be effective for wide cerebral revascularisation when the STA is not available.

Predictors of poor cerebral collaterals and cerebrovascular reserve in patients with chronic total carotid occlusion

Background: This study aims to investigate the relationship between cerebrovascular reserve (CVR) capacity, as measured by single-photon emission computed tomography (SPECT) and collateral blood flow, according to a transcranial colour-coded duplex(TCCD), in patients with symptomatic total carotid occlusion (TCO). Additionally, the study aims to determine whether vascular risk factors have an effect on collateral blood flow, as well as on the CVR.Methods: Thirty-four patients with chronic TCO, diagnosed by carotid duplex scanning and confirmed by other vascular imaging modalities, who had ischaemic symptoms either as stroke or transient ischaemic attack, were subjected to clinical assessment, SPECT under dipyridamole stress, and grading of cerebral collateral blood flow using TCCD. Demographics and vascular risk factors were correlated with SPECT and TCCD findings.Results: CVR showed a significant positive correlation with the intensity of collaterals with P value <0.001 and a Spearman correlation coefficient of 0.686. Hypertension was the only predictor of poor collaterals (p value =0.049; OR =11.5 with 95% CI 1.01–131.16).Smoking was predictive of poor CVR as measured by qualitative SPECT (p value =0.02; OR =13.2 with 95% CI 1.4–120.6).Conclusion: Cerebral collaterals have an important role in the maintenance of CVR in patients with TCO. Preventive measures should be directed towards hypertension and smoking to preserve cerebral collateral patency and consequently improve CVR in patients with TCO.

Higher Aortic Stiffness Is Related to Lower Cerebral Blood Flow and Preserved Cerebrovascular Reactivity in Older Adults

Mechanisms underlying the association between age-related arterial stiffening and poor brain health remain elusive. Cerebral blood flow (CBF) homeostasis may be implicated. This study evaluates how aortic stiffening relates to resting CBF and cerebrovascular reactivity (CVR) in older adults. Vanderbilt Memory & Aging Project participants free of clinical dementia, stroke, and heart failure were studied, including older adults with normal cognition (n=155; age, 72±7 years; 59% male) or mild cognitive impairment (n=115; age, 73±7 years; 57% male). Aortic pulse wave velocity (PWV; meters per second) was quantified from cardiac magnetic resonance. Resting CBF (milliliters per 100 g per minute) and CVR (CBF response to hypercapnic normoxia stimulus) were quantified from pseudocontinuous arterial spin labeling magnetic resonance imaging. Linear regression models related aortic PWV to regional CBF, adjusting for age, race/ethnicity, education, Framingham Stroke Risk Profile (diabetes mellitus, smoking, left ventricular hypertrophy, prevalent cardiovascular disease, atrial fibrillation), hypertension, body mass index, apolipoprotein E4 ( APOE ε4) status, and regional tissue volume. Models were repeated testing PWV× APOE ε4 interactions. Sensitivity analyses excluded participants with prevalent cardiovascular disease and atrial fibrillation. Among participants with normal cognition, higher aortic PWV related to lower frontal lobe CBF (β=-0.43; P=0.04) and higher CVR in the whole brain (β=0.11; P=0.02), frontal lobes (β=0.12; P<0.05), temporal lobes (β=0.11; P=0.02), and occipital lobes (β=0.14; P=0.01). Among APOE ε4 carriers with normal cognition, findings were more pronounced with higher PWV relating to lower whole-brain CBF (β=-1.16; P=0.047), lower temporal lobe CBF (β=-1.81; P=0.004), and higher temporal lobe CVR (β=0.26; P=0.08), although the last result did not meet the a priori significance threshold. Results were similar in sensitivity models. Among participants with mild cognitive impairment, higher aortic PWV related to lower CBF in the occipital lobe (β=-0.70; P=0.02), but this finding was attenuated when participants with prevalent cardiovascular disease and atrial fibrillation were excluded. Among APOE ε4 carriers with mild cognitive impairment, findings were more pronounced with higher PWV relating to lower temporal lobe CBF (β=-1.20; P=0.02). Greater aortic stiffening relates to lower regional CBF and higher CVR in cognitively normal older adults, especially among individuals with increased genetic predisposition for Alzheimer's disease. Central arterial stiffening may contribute to reductions in regional CBF despite preserved cerebrovascular reserve capacity.

Reduced Cerebrovascular Reserve Capacity as a Biomarker of Microangiopathy in Alzheimer’s Disease and Mild Cognitive Impairment

Cerebral microangiopathy in Alzheimer's disease (AD) causes chronic hypoperfusion and probably accelerates neurodegenerative changes. We hypothesize microvascular impairment could be present already in mild cognitive impairment (MCI) and can be revealed using transcranial color-coded sonography (TCCS) and the breath-holding maneuver. Three groups of subjects (AD in the stage of dementia, MCI, and cognitively normal controls) with detailed neuropsychological testing and low cerebrovascular burden (no history of stroke, no intra- or extracranial artery stenoses, and no severe vascular lesions on brain MRI), underwent a TCCS assessment of peak systolic (PSV), mean flow (MFV), and end diastolic velocities (EDV) and resistance and pulsatility indices (RI, PI) in large intracranial vessels bilaterally. Cerebrovascular reserve capacity was assessed using the breath-holding index (BHI) in middle cerebral artery (MCA) bilaterally. The ultrasound parameters were compared between the groups, correlated with neuropsychological tests, and compared between amnestic and non-amnestic MCI subtypes. Fourteen AD (3 males, 67.9±11.1 years, MMSE 18.0±4.6), 24 MCI (13 males, 71.9±7.3 years, MMSE 28.0±1.6), and 24 risk factor-matched controls (14 males, 67.8±6.4 years, MMSE 29.1±1.2) were enrolled. Significant differences were found between AD and controls in MFV, EDV, RI, PI in right MCA after breath holding, in PSV, MFV, EDV in left MCA after breath holding, and in BHI on the left side. The left BHI correlated positively with verbal memory test. Results show decreased cerebrovascular reserve capacity in AD as a sign of impaired cerebral hemodynamic status without severe underlying atherosclerosis. This can be identified using TCCS and BHI.

Perioperative stroke: pathophysiology and management.

Although perioperative stroke is uncommon during low-risk non-vascular surgery, if it occurs, it can negatively impact recovery from the surgery and functional outcome. Based on the Society for Neuroscience in Anesthesiology and Critical Care Consensus Statement, perioperative stroke includes intraoperative stroke, as well as postoperative stroke developing within 30 days after surgery. Factors related to perioperative stroke include age, sex, a history of stroke or transient ischemic attack, cardiac surgery (aortic surgery, mitral valve surgery, or coronary artery bypass graft surgery), and neurosurgery (external carotid-internal carotid bypass surgery, carotid endarterectomy, or aneurysm clipping). Concomitant carotid and cardiac surgery may further increase the risk of perioperative stroke. Preventive strategies should be individualized based on patient factors, including cerebrovascular reserve capacity and the time interval since the previous stroke.

Reduced Cerebrovascular Reserve Capacity in Adults with Sickle Cell Disease

Introduction: Sickle Cell Disease (SCD) is frequently complicated by stroke. Although transcranial Doppler effectively identifies children at risk for stroke, adult patients do not benefit from this test. In SCD, chronic hemolytic anemia leads to cerebral vasodilation, elevated cerebral blood flow (CBF) and subsequently, impaired cerebrovascular reserve (CVR) capacity. CVR represents the maximum increase in CBF in response to metabolic stressors. CVR mapping is a promising imaging biomarker for stroke risk assessment, potentially identifying patients with preclinical hemodynamic impairment. Our laboratory performs CVR mapping by measuring CBF prior to and following maximum cerebral vasodilation with acetazolamide (ACZ). The primary aim of this study was to quantitatively assess CVR in adult patients with SCD compared to healthy controls.Methods: Adult SCD patients (HbSS/HbSβ0) were recruited for this IRB-approved study with ACZ-induced vasodilation and venous blood sampling. Patients with a history of clinically overt stroke were excluded. Controls were selected from patients' friends and family members without SCD and matched on age, sex, and race. The following MRI images were acquired at 3T (Philips Healthcare, Best, NL): time of flight MRA for visualization of major cerebral vessels, T2 FLAIR for manual segmentation of white matter hyperintensities (WMHs), and pseudo-continuous arterial spin labeling (ASL) for CBF assessment. CBF was measured at baseline and 10min post ACZ (16mg/kg intravenous infusion over 3min). MRI images were processed with the ExploreASL toolbox, to obtain registered maps of quantified CBF and CVR (% change in CBF). We measured T1blood in each subject to improve quantification accuracy as these values can differ in SCD. Group comparisons were performed using non-parametric two-sample tests. Correlations were characterized by Spearman's rho (ρ). P<0.05 was considered significant. Median values with interquartile range (IQR) are reported for non-normally distributed variables, otherwise mean and standard deviation are reported.Results: 30 patients with SCD (mean age 33±12y,19M) and 11 controls (mean age 37±15y, 6M) were included in this cross-sectional controlled cohort study. Mean hemoglobin levels in patients with SCD were 8.8±1.4 g/dL and in healthy controls were 13.7±1.3 g/dL. Patients with SCD had higher baseline CBF compared to healthy controls (median 73(IQR:25) vs 42(IQR:6) mL/100g/min, p<0.001, F1a). CBF was inversely related to hemoglobin (ρ=-0.84, p<0.001, F1b). ACZ elicited an increase in CBF(p<0.001) which was similar in magnitude in both groups (patients 29±16, controls 35±11, mL/100g/min, F1c), resulting in a lower mean CVR in patients compared to controls (41±24% vs 81±27%, p<0.001, F1d). Baseline CBF predicted CVR (ρ=-0.68, p<0.001, F1e). WMHs were present in both groups, and WMH volume correlated with age (ρ = 0.54, p<0.001). There were no statistical associations between WMH volume and CVR (ρ = -0.15, p=0.4) or CBF(ρ = 0.02, p=0.9), however, two patients with the largest WMH volume (>6 mL) had the lowest CVR (<20%).Discussion: This study shows that regional CVR can be measured using ASL-MRI with ACZ challenge. ACZ was well-tolerated and elicited a robust cerebrovasodilatory response in both groups. However, the relative increase in oxygen delivery (CVR) was much lower in SCD patients, which suggests that patients with SCD have nearly maximal cerebrovascular dilation at baseline. Our data suggest that chronic vasodilation due to anaemia has let to outward remodelling of vessels in adult patients, permitting a larger vascular bed to compensate their anemia. Our premise is that resting O2 delivery is normal in SCD patients; we showed that increasing CBF overcomes severe anemia. However, high resting CBF limits the brain's ability to recruit additional O2 under times of stress. SCD patients have many transient interruptions in O2 delivery including aplastic crisis, splenic sequestration and sleep apnea, as well as metabolic stressors such as fever, sickle cell crisis, infection, and seizure. While baseline CBF predicted global CVR, ASL provides information regarding regional O2 delivery that may offer insight into distribution of ischemic white matter damage. Further study is needed to determine the impact of blood transfusions and hydroxyurea on CVR and whether there is a critical CVR threshold that predicts stroke risk. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Cerebrovascular CO2 reactivity during isoflurane-nitrous oxide anesthesia in patients with chronic renal failure.

We assessed the cerebrovascular CO2 reactivity (CO2R) in chronic renal failure (CRF) patients without diabetes mellitus (DM), uncontrolled hypertension, peripheral vascular disease, or neurological disease under isoflurane-nitrous oxide anesthesia. Forty-nine patients undergoing surgery, including 36 CRF patients (30 receiving dialysis and six pre-dialysis patients) and 13 patients without CRF (controls). Middle cerebral artery flow velocity (VMCA) was measured by transcranial Doppler ultrasonography at an end-tidal CO2 of 35 to 45mmHg. CO2R was calculated as an absolute value (change in VMCA per mmHg PaCO2) and a relative value (absolute CO2R/baseline VMCA×100). Factors associated with CO2R were evaluated simultaneously. Despite no significant differences in the absolute and relative values of CO2R between the CRF (mean 2.5cm/s/mmHg; median 5.0%/mmHg) and control (2.4cm/s/mmHg; 5.0%/mmHg) groups, blood urea nitrogen (BUN) concentrations in the CRF group correlated inversely with both absolute and relative CO2R. BUN concentration was higher (mean 72 versus 53mg/dl, p=0.006) and relative CO2R was lower (mean 2.6 versus 5.7%/mmHg, p=0.011) in patients with pre-dialysis CRF (n=6) versus CRF patients receiving dialysis (n=30). CO2R in CRF patients was not significantly different from that in controls. However, in CRF patients with high BUN concentrations, CO2R might be impaired, leading to reduced cerebrovascular reserve capacity. Because DM is a major cause of CRF and we excluded DM patients, our results might not be applicable to patients with DM-induced CRF.

Effects of sevoflurane versus propofol on cerebrovascular reactivity to carbon dioxide during laparoscopic surgery.

PurposeCerebrovascular reactivity to carbon dioxide (CVR-CO2) reflects cerebrovascular reserve capacity, which is important in many brain disorders, including cerebrovascular and Alzheimer’s diseases. Meanwhile, there is a relationship between CVR-CO2 and cognitive function. Therefore, the study is aimed at investigating the effects of sevoflurane versus propofol on CVR-CO2 during laparoscopic surgery, as well as the role of CVR-CO2 on cognitive function during perioperative period.Patients and methodsEighty-eight patients, aged 18–65 years undergoing elective laparoscopic cholecystectomy, were randomly assigned to group S and group P. The patients in group S were induced with propofol and maintained with sevoflurane. The patients in group P were induced and maintained with propofol (target-controlled infusion). Remifentanil was given to both groups. CVR-CO2 at baseline (before induction), before pneumoperitoneum and during pneumoperitoneum, as well as Mini-Mental State Examination scores at baseline and 24 hours after surgery were recorded.ResultsIn group S, CVR-CO2 before and during pneumoperitoneum increased significantly compared with baseline (P<0.05). In group P, CVR-CO2 before pneumoperitoneum increased significantly (P<0.05), but CVR-CO2 during pneumoperitoneum was not different compared with baseline. In either group, there was no significant correlation between mean blood pressure and CVR-CO2 during surgery, and there was no significant difference between Mini-Mental State Examination scores at baseline and 24 hours after surgery.ConclusionSevoflurane could maintain CVR-CO2 at a higher level during pneumoperitoneum in surgery. Therefore, in patients with impaired cerebrovascular reserve capacity, inhaled anesthetic could be a priority strategy for anesthesia maintenance to improve the compensatory vasodilation ability of cerebral small vessels.

Carotid artery stenosis in hypertensive rats impairs dilatory pathways in parenchymal arterioles.

Hypertension is a leading risk factor for vascular cognitive impairment and is strongly associated with carotid artery stenosis. In normotensive rats, chronic cerebral hypoperfusion induced by bilateral common carotid artery stenosis (BCAS) leads to cognitive impairment that is associated with impaired endothelium-dependent dilation in parenchymal arterioles (PAs). The aim of this study was to assess the effects of BCAS on PA function and structure in stroke-prone spontaneously hypertensive rats, a model of human essential hypertension. Understanding the effects of hypoperfusion on PAs in a hypertensive model could lead to the identification of therapeutic targets for cognitive decline in a model that reflects the at-risk population. We hypothesized that BCAS would impair endothelium-dependent dilation in PAs and induce artery remodeling compared with sham rats. PAs from BCAS rats had endothelial dysfunction, as assessed using pressure myography. Inhibition of nitric oxide and prostaglandin production had no effect on PA dilation in sham or BCAS rats. Surprisingly, inhibition of epoxyeicosatrienoic acid production increased dilation in PAs from BCAS rats but not from sham rats. Similar results were observed in the presence of inhibitors for all three dilatory pathways, suggesting that epoxygenase inhibition may have restored a nitric oxide/prostaglandin-independent dilatory pathway in PAs from BCAS rats. PAs from BCAS rats underwent remodeling with a reduced wall thickness. These data suggest that marked endothelial dysfunction in PAs from stroke-prone spontaneously hypertensive rats with BCAS may be associated with the development of vascular cognitive impairment. NEW & NOTEWORTHY The present study assessed the structure and function of parenchymal arterioles in a model of chronic cerebral hypoperfusion and hypertension, both of which are risk factors for cognitive impairment. We observed that impaired dilation and artery remodeling in parenchymal arterioles and abolished cerebrovascular reserve capacity may mediate cognitive deficits.

Brain Perfusion Imaging Under Acetazolamide Challenge for Detection of Impaired Cerebrovascular Reserve Capacity: Positive Findings with 15O-Water PET in Patients with Negative 99mTc-HMPAO SPECT Findings.

Cerebrovascular reserve capacity (CVRC) is an important parameter for treatment decisions in chronic cerebrovascular diseases. It can be assessed by measuring the acetazolamide-induced change in regional cerebral blood flow using SPECT with 99mTc-labeled hexamethylpropyleneamine oxime (99mTc-HMPAO) or PET with 15O-water. Methods: Our database was searched for patients with moyamoya vasculopathy or atherosclerotic cerebrovascular disease who had undergone 15O-water PET after normal 99mTc-HMPAO SPECT results with respect to CVRC. 15O-water PET was analyzed visually and quantitatively. Quantitative analysis was based on parametric CVRC maps generated by voxelwise image subtraction. Results: The search identified 18 patients (43 ± 15 y, 12 moyamoya vasculopathy). PET revealed impaired CVRC in 8 patients (44%). Quantitative analysis confirmed the positive visual findings in 15O-water PET and the negative findings in 99mTc-HMPAO SPECT. Conclusion:15O-water PET enables detection of impaired CVRC in a considerable fraction of symptomatic patients with stenoocclusion and negative 99mTc-HMPAO SPECT.

Effect of acupuncture on cerebrovascular reserve in patients with acute cerebral infarction: protocol for a randomized controlled pilot study

BackgroundThe incidence of cerebral infarction has been growing year by year in China and around the world. According to clinical observation, acupuncture utilizing the “waking up the spirit” needling method is widely used in patients with cerebral infarction, though the underlying mechanisms remain unclear. Additionally, a number of studies have begun to focus on the relationship between cerebrovascular reserve (CVR) and cerebral infarction. The present study aims to investigate whether CVR is one of potential mechanisms underpinning this effect of acupuncture on patients with cerebral infarction.MethodsThis is a single-centre, prospective, single-blinded, randomized controlled pilot study. Sixty eligible patients will be randomized into an intervention group (waking up the spirit acupuncture) and a control group (hand and foot 12-meridian acupuncture) in a 1:1 ratio. All treatments will be conducted once a day on weekdays followed by a 2-day rest period on the weekend, over a total treatment course of 2 weeks. The primary outcome measures are cerebrovascular reserve (CVR) capacity and Breath-holding Index (BHI) which will be evaluated at baseline and 2 weeks after the first acupuncture treatment, and the secondary outcome measures are National Institutes of Health Stroke Scale (NIHSS) and Barthel Index scores which will be used to further evaluate the efficacy of the intervention.DiscussionCerebrovascular reserve is an independent risk factor for the occurrence, progression, and recurrence of cerebral infarction that requires attention. This trial aims to investigate whether acupuncture utilizing the waking up the spirit needling method can improve CVR capacity in patients with acute cerebral infarction, thus reducing NIHSS scores and preventing further progression of the disease. Furthermore, data and evidence gained from this study will be utilized in the development of future research projects regarding the effects of acupuncture in patients with acute cerebral infarction.Trial registrationISRCTN, ID: ISRCTN99117074. Registered on 20 April 2016.

Severe carotid stenosis: cerebral autoregulation in the ipsilateral region

To study cerebral autoregulation (CA) in region of the stenotic carotid artery. The study involved 35 patients with critical stenosis of the carotid arteries, including 24 patients were asymptomatic and 11 patients with symptomatic course. Blood flow velocity in middle cerebral arteries was monitored using Multi Dop X (DWL, Germany) with simultaneous noninvasive systemic blood pressure registration (CNAP, Austria). CA was assessed by calculating the phase shift (PS) between spontaneous oscillations of blood flow velocity and blood pressure within the range of systemic Mayer waves (80-120 mHz). In 18 patients, the CA indicators were in the normal range (PS 1.2±0.3 rad). Seventeen patients, including asymptomatic as well as symptomatic types, had impaired CA (PS 0.2±0.2 rad and 0.3±0.2 rad, respectively). Reconstructive surgery, irrespective of clinical manifestations, led to the significant increase in PS (p<0.001) in the early postoperative period (0.9±0.5 and 0.9±0.3 rad, respectively). A significant variability in the cerebrovascular reserve capacity in symptomatic and asymptomatic types of carotid artery stenosis was found. CA can be used in determining the indications for surgical treatment and evaluation of its effectiveness in patients with stenosis of carotid arteries.

Evaluation of cerebrovascular reserve capacity in symptomatic and asymptomatic internal carotid stenosis with transcranial Doppler.

Cerebrovascular reserve capacity (CVRC) is a hemodynamic parameter indicating the brain's capacity to overcome ischemia. Transcranial Doppler (TCD) is a useful device to measure CVRC, with high availability and low cost. The aim of the study is to investigate asymptomatic patients with affected CVRC, who could benefit from CEA. One hundred and forty five consecutive patients (60 symptomatic and 65 asymptomatic), with internal carotid artery (ICA) stenosis >70 % and 20 healthy individuals without internal carotid stenosis underwent TCD-inhalation CO(2) tests in order to measure the CVRC in both hemispheres of each patient. CVRC between asymptomatic and symptomatic patients were significantly different in the 95 % confidence interval (CI) as well as the mean CVRC value in contralateral carotid artery. The correlation between CVRC in the carotid artery with stenosis and the existence of symptoms is significant at the 0.01 level. Additionally, symptoms and CVRC of the contralateral carotid artery are also significant at the 0.05 level and CVRC values in asymptomatic patients and the control group at the 0.01 level. None of the covariant factors, except the age, are significantly correlated with CRVC. CVRC could be an early mark-index to evaluate the risk of stroke in this group of patients and to design their therapeutic approach.

Assessment of Hemodynamic Compromise Using Computed Tomography Perfusion in Combination with 123I-IMP Single-Photon Emission Computed Tomography without Acetazolamide Challenge Test

The acetazolamide challenge test in conjunction with 123I-IMP single-photon emission computed tomography (SPECT) is a known method of assessing cerebrovascular reserve capacity. In this study, we investigated whether CT perfusion in combination with resting state 123I-IMP SPECT could be used instead of the acetazolamide challenge test to evaluate hemodynamic compromise in patients with atherosclerotic occlusive disease. Twenty consecutive patients with unilateral internal carotid artery or middle cerebral artery steno-occlusive disease were enrolled. 123I-IMP SPECT was performed with and without the acetazolamide challenge test, and with CT perfusion. Cerebral blood flow (CBF), cerebral blood volume, and mean transit time (MTT) obtained by CT perfusion were compared with CBF and cerebrovascular reactivity (CVR) obtained by 123I-IMP SPECT. The asymmetry ratio of MTT as measured by CT perfusion showed a strong correlation with the CVR to acetazolamide as measured by 123I-IMP SPECT (ρ = -.780, P <.001). Based on the CBF obtained through 123I-IMP SPECT and the MTT obtained through CT perfusion, hemodynamic compromise was detected with high sensitivity (1.000) and specificity (.929), and a cutoff value of 30% was found to be suitable for the asymmetry ratio of MTT. MTT prolongation was significantly improved after revascularization surgery in hemodynamic compromise (P = .028). MTT as measured by CT perfusion in combination with CBF as measured by resting state 123I-IMP SPECT may be useful for evaluating hemodynamic compromise as an alternative to the acetazolamide challenge test.