Decrease In Cerebral Blood Volume Research Articles

The clinical value of deep gray matter 3T MRI perfusion in patients with multiple sclerosis

Background. Multiple sclerosis (MS) is a common neurological disorder between adults. Magnetic resonance imaging (MRI) is the imaging modality of choice, new MRI techniques helped in more accurate assessment of the disease extent, activity and severity. In dynamic susceptibility contrast (DSC), the perfusion of the lesions as well as normally appearing white and gray matter of the brain have been assessed. Objective. To highlight the role of MRI perfusion of the deep gray matter in multiple sclerosis patients and its relation to their clinical disability and cognitive impairment Methods. 40 patients with MS were enrolled in this study, they were divided into two groups (group A with mild clinical disease and preserved cognitive functions, and group B with marked clinical disease and cognitive functions impairment) they were divided according to their clinical disability and cognitive impairment assessed by experienced neurologist, Additional 20 healthy controls were included. Perfusion parameters including cerebral blood volume(CBV), cerebral blood flow (CBF) and mean transit time (MTT) of the deep gray matter were compared for healthy controls and for the study groups. Results. The perfusion values of the thalamus, putamen and caudate were significantly changed in group B that shows marked decrease in CBV and CBF and increased MTT compared with group A and the controls, With respect to group (A), there was no significant difference between the patients and controls Conclusion. The decrease of perfusion of the deep gray matter in patients with MS is associated with the severity of the disease and cognitive impairment.

Effect of quercetin glycosides on cognitive functions and cerebral blood flow: a randomized, double-blind, and placebo-controlled study.

This study aimed to examine the effects of quercetin glycoside-containing beverages on cognitive function and cerebral blood flow (CBF) in adult men and women aged between 60 and 75 years. Eighty healthy men and women with no cognitive impairment and aware of ageing-related forgetfulness underwent a placebo-controlled, randomized, double-blind, and parallel-group trial. They regularly consumed 500 mL of beverage containing 110 mg of quercetin glycoside as isoquercitrin for 40 weeks. Cognitive function assessment by Cognitrax was the endpoint of the study. The participants were assessed for CBF, health-related quality of life, as well as physical, biological, and hematological parameters, and lateral index. Cognitrax demonstrated that the reaction time significantly improved in the quercetin glycoside intake group. The CBF measurement suggested that quercetin glycoside intake could likely suppress the decrease in cerebral blood volume, CBF, and cerebral activity owing to stress alleviation and inhibition of the accumulation of amyloid β (Aβ), a waste product in the brain, although there were no significant differences between the groups. Quercetin glycoside intake as a beverage could improve reaction time and may potentially inhibit the decrease in CBF and suppress Aβ accumulation.

Cerebral blood volume increment after resuscitation measured by near-infrared time-resolved spectroscopy can estimate degree of hypoxic\u2013ischemic insult in newborn piglets

Neonatal hypoxic–ischemic encephalopathy is a notable cause of neonatal death and developmental disabilities. To achieve better outcomes, it is important in treatment strategy selection to categorize the degree of hypoxia ischemia and evaluate dose response. In an asphyxia piglet model with histopathological brain injuries that we previously developed, animals survived 5 days after insult and showed changes in cerebral blood volume (CBV) that reflected the severity of injuries. However, little is known about the relationship between changes in CBV during and after insult. In this study, an HI event was induced by varying the amount and timing of inspired oxygen in 20 anesthetized piglets. CBV was measured using near-infrared time-resolved spectroscopy before, during, and 6 h after insult. Change in CBV was calculated as the difference between the peak CBV value during insult and the value at the end of insult. The decrease in CBV during insult was found to correlate with the increase in CBV within 6 h after insult. Heart rate exhibited a similar tendency to CBV, but blood pressure did not. Because the decrement in CBV was larger in severe HI, the CBV increment immediately after insult is considered useful for assessing degree of HI insult.

Computed tomography perfusion imaging after aneurysmal subarachnoid hemorrhage can detect cerebral vasospasm and predict delayed cerebral ischemia after endovascular treatment.

Background: Endovascular treatment (ET) can improve angiographic cerebral vasospasm (CV) after aneurysmal subarachnoid hemorrhage, but was unrelated to clinical outcomes in previous analyses. Appropriate detection of CV and precise indications for ET are required. This study investigated whether changes in computed tomography perfusion (CTP) parameter can determine indications for ET in CV and predict its effectiveness.Methods: Participants comprised 140 patients who underwent neck clipping or coil embolization. CTP was performed a week after aneurysmal treatment or when clinical deterioration had occurred. Patients were divided into ET and non-ET groups by propensity score matching. In addition, the ET group was divided into subgroups with and without new cerebral infarction (CI). All CTP images in the three groups were retrospectively investigated qualitatively and quantitatively. CI was diagnosed from CT at 3 months postoperatively.Results: Of the 121 patients examined, 15 patients (11%) needed ET. In qualitative analysis, all ET group patients displayed extension of time-to-peak (TTP) at the region of vasospastic change, regardless of the presence of CI. Quantitative analysis showed significant decreases in cerebral blood volume (P < 0.01), cerebral blood flow (CBF) (P < 0.001), and extension in TTP (P < 0.01) in the ET group compared with the non-ET group. A significant decrease in CBF (P < 0.001) and extension in mean transit time (P < 0.001) was seen in the ET with CI subgroup compared with the ET without CI subgroup.Conclusion: CTP in the vasospastic period may be an indication for ET and predict the effectiveness of ET for CV to improve clinical outcomes.

Prediction of survival and progression in glioblastoma patients using temporal perfusion changes during radiochemotherapy

BackgroundThe aim of this study was to investigate changes in structural magnetic resonance imaging (MRI) according to the RANO criteria and perfusion- and permeability related metrics derived from dynamic contrast-enhanced MRI (DCE) and dynamic susceptibility contrast MRI (DSC) during radiochemotherapy for prediction of progression and survival in glioblastoma. MethodsTwenty-three glioblastoma patients underwent biweekly structural and perfusion MRI before, during, and two weeks after a six weeks course of radiochemotherapy. Temporal trends of tumor volume and the perfusion-derived parameters cerebral blood volume (CBV) and blood flow (CBF) from DSC and DCE, in addition to contrast agent capillary transfer constant (Ktrans) from DCE, were assessed. The patients were separated in two groups by median survival and differences between the two groups explored. Clinical- and MRI metrics were investigated using univariate and multivariate survival analysis and a predictive survival index was generated. ResultsMedian survival was 19.2 months. A significant decrease in contrast-enhancing tumor size and CBV and CBF in both DCE- and DSC-derived parameters was seen during and two weeks past radiochemotherapy (p < 0.05). A 10%/30% increase in Ktrans/CBF two weeks after finishing radiochemotherapy resulted in significant shorter survival (13.9/16.8 vs. 31.5/33.1 months; p < 0.05). Multivariate analysis revealed an index using change in Ktrans and relative CBV from DSC significantly corresponding with survival time in months (r2 = 0.843; p < 0.001). ConclusionsSignificant temporal changes are evident during radiochemotherapy in tumor size (after two weeks) and perfusion-weighted MRI-derived parameters (after four weeks) in glioblastoma patients. While DCE-based metrics showed most promise for early survival prediction, a multiparametric combination of both DCE- and DSC-derived metrics gave additional information.

Dynamic 23Na MRI - A non-invasive window on neuroglial-vascular mechanisms underlying brain function

A novel magnetic resonance imaging (MRI) acquisition and reconstruction method for obtaining a series of dynamic sodium 23Na-MRI acquisitions was designed to non-invasively assess the signal variations of brain sodium during a hand motor task in 14 healthy human volunteers on an ultra high field (7T) MR scanner. Regions undergoing activation and deactivation were identified with reference to conventional task-related BOLD functional MRI (fMRI). Activation observed in the left central regions, the supplementary motor areas and the left cerebellum induced an increase in the sodium signal observed at ultra short echo time and a decrease in the 23Na signal observed at long echo time. Based on a simple model of two distinct sodium pools (namely, restricted and mobile sodium), the ultra short echo time measures the totality of sodium whereas the long echo time is mainly sensitive to mobile sodium. This activation pattern is consistent with previously described processes related to an influx of Na+ into the intracellular compartments and a moderate increase in the cerebral blood volume (CBV). In contrast, deactivation observed in the right central regions ipsilateral to the movement, the precuneus and the left cerebellum induced a slight decrease in sodium signal at ultra short echo time and an increase of sodium signal at longer echo times. This inhibitory pattern is compatible with a slight decrease in CBV and an efflux of intracellular Na+ to the extracellular compartments that may reflect neural dendritic spine and astrocytic shrinkage, and an increase of sodium in the extracellular fraction. In conclusion, cerebral dynamic 23Na MRI experiments can provide access to the ionic transients following a functional task occurring within the neuro-glial-vascular ensemble. This has the potential to open up a novel non-invasive window on the mechanisms underlying brain function.

Relationship between prolonged neural suppression and cerebral hemodynamic dysfunction during hypothermia in asphyxiated piglets

ObjectivesHypothermia (HT) improves the outcome of neonatal hypoxic-ischemic encephalopathy. Here, we investigated changes during HT in cortical electrical activity using amplitude-integrated electroencephalography (aEEG) and in cerebral blood volume (CBV) and cerebral hemoglobin oxygen saturation using near-infrared time-resolved spectroscopy (TRS) and compared the results with those obtained during normothermia (NT) after a hypoxic-ischemic (HI) insult in a piglet model of asphyxia. We previously reported that a greater increase in CBV can indicate greater pressure-passive cerebral perfusion due to more severe brain injury and correlates with prolonged neural suppression during NT. We hypothesized that when energy metabolism is suppressed during HT, the cerebral hemodynamics of brains with severe injury would be suppressed to a greater extent, resulting in a greater decrease in CBV during HT that would correlate with prolonged neural suppression after insult. MethodsTwenty-six piglets were divided into four groups: control with NT (C-NT, n = 3), control with HT (C-HT, n = 3), HI insult with NT (HI-NT, n = 10), and HI insult with HT (HI-HT, n = 10). TRS and aEEG were performed in all groups until 24 h after the insult. Piglets in the HI-HT group were maintained in a hypothermic state for 24 h after the insult. ResultsThere was a positive linear correlation between changes in CBV at 1, 3, 6, and 12 h after the insult and low-amplitude aEEG (<5 µV) duration after insult in the HI-NT group, but a negative linear correlation between these two parameters at 6 and 12 h after the insult in the HI-HT group. The aEEG background score and low-amplitude EEG duration after the insult did not differ between these two groups. Discussion and conclusionA longer low-amplitude EEG duration after insult was associated with a greater CBV decrease during HT in the HI-HT group, suggesting that brains with more severe neural suppression could be more prone to HT-induced suppression of cerebral metabolism and circulation.

Cerebral Blood Volume During Neonatal Transition in Term and Preterm Infants With and Without Respiratory Support

Background: Recently, we demonstrated that in healthy newborn infants cerebral blood volume (CBV) was decreasing continuously after birth. We hypothesized that this was due to the increase in oxygen delivery to the brain during neonatal transition. Thus delayed cerebral oxygen delivery in infants in need for respiratory support (RS) during postnatal stabilization might influence changes in CBV.Objective: Aim of the study was to evaluate transitional changes in CBV immediately after birth in term and preterm infants with and without need of RS.Methods: We performed a post-hoc analysis of data collected as primary and secondary outcome parameters in prospective observational studies and randomized controlled trials at the Medical University of Graz (Austria). NIRS measurements by using “NIRO 200-NX” (Hamamatsu, Japan) were carried out over the first 15 min after birth in term and preterm infants delivered by cesarean section with and without requirement for RS.Results: In 204 neonates, we observed a significant decrease in CBV within the first 15 min after birth (p < 0.001) with a trend toward smaller ΔCBV in neonates receiving RS (p = 0.097) compared to neonates without RS. Differences of ΔCBV between groups reached statistically significance (p < 0.05) at minutes 2, 6, and 7, and showed a trend (p < 0.1) at minutes 3, 4, and 5. After adjusting for gestational age, these differences became smaller and failed to reach significance.Conclusions: We observed a significant decrease of CBV in term and preterm infants with and without RS. Interestingly, ΔCBV was smaller in the first 7 min in neonates with RS reaching statistically significance (p < 0.05) at minutes 2, 6, and 7. This study cannot differentiate, whether RS itself or the condition leading to requirement for RS is responsible for the observed CBV behavior.

Interval Change in Diffusion and Perfusion MRI Parameters for the Assessment of Pseudoprogression in Cerebral Metastases Treated With Stereotactic Radiation

Apparent increases in the size of cerebral metastases after stereotactic radiosurgery (SRS) can be caused by pseudoprogression or true disease progression, which poses a diagnostic challenge at conventional MRI. The purpose of this study was to assess whether interval change in DWI and perfusion MRI parameters can differentiate pseudoprogression from progressive disease after treatment with SRS. Patients with apparent growth of cerebral metastases after SRS treatment who underwent pre- and post-SRS DWI, dynamic susceptibility contrast (DSC)-MRI, and perfusion dynamic contrast-enhanced (DCE)-MRI were retrospectively evaluated. Final assignment of pseudoprogression or progressive disease was determined at 6-month follow-up imaging using the Response Assessment in Neuro-Oncology Brain Metastases criteria. Mean values of apparent diffusion coefficient (ADC), DCE-MRI-derived volume transfer constant (Ktrans), and DSC-MRI-derived relative cerebral blood volume (CBV) from pre- and post-SRS MRI scans were compared between groups using univariate and regression analysis. Fisher exact test was used to compare interval change of imaging biomarkers. Of 102 cerebral metastases evaluated, 32 lesions in 29 patients met our inclusion criteria. The mean duration of follow-up was 7.2 months (range, 6-14 months). Twenty-two lesions were determined as pseudoprogression, and 10 lesions were determined as progressive disease using the Response Assessment in Neuro-Oncology Brain Metastases criteria at 6-month follow-up MRI. The interval change pattern of our imaging parameters matched the expected patterns of treatment response for ADC (23/32 lesions; 72%; p = 0.055; odds ratio, 5.1), Ktrans (24/32 lesions; 75%; p = 0.006; odds ratio, 19.2), and relative CBV (27/32 lesions; 84%; p = 0.001; odds ratio, 25.3). Pseudoprogression can be distinguished from disease progression in cerebral metastases treated with SRS via an interval decrease in relative CBV and Ktrans values.

The effect of carotid artery stenting on capillary transit time heterogeneity in patients with carotid artery stenosis.

Carotid revascularisation improves haemodynamic compromise in cerebral circulation as an additional benefit to the primary goal of reducing future thromboembolic risk. We determined the effect of carotid artery stenting on cerebral perfusion and oxygenation using a perfusion-weighted MRI algorithm that is based on assessment of capillary transit-time heterogeneity together with other perfusion and metabolism-related metrics. A consecutive series of 33 patients were evaluated by dynamic susceptibility contrast perfusion-weighted MRI prior to and within 24 h of the endovascular procedure. The level of relative change induced by stenting, and relationship of these changes with respect to baseline stenosis degree were analysed. Stenting led to significant increase in cerebral blood flow (p < 0.001), and decrease in cerebral blood volume (p = 0.001) and mean transit time (p < 0.001); this was accompanied by reduction in oxygen extraction fraction (p < 0.001) and capillary transit-time heterogeneity (p < 0.001), but an overall increase in relative capillary transit-time heterogeneity (RTH: CTH divided by MTT; p = 0.008). No significant change was observed with respect to cerebral metabolic rate of oxygen. The median volume of tissue with MTT > 2s decreased from 24 ml to 12 ml (p = 0.009), with CTH > 2s from 29 ml to 19 ml (p = 0.041), and with RTH < 0.9 from 61 ml to 39 ml (p = 0.037) following stenting. These changes were correlated with the baseline degree of stenosis.Discussion: Stenting improved the moderate stage of haemodynamic compromise at baseline in our cohort. The decreased relative transit-time heterogeneity, which increases following stenting, is probably a reflection of decreased functional capillary density secondary to chronic hypoperfusion induced by the proximal stenosis.Conclusion: Carotid artery stenting, is not only important for prophylaxis of future vascular events, but also is critical for restoration of microvascular function in the cerebral tissue.

Assessment of MRI contrast agent concentration by quantitative susceptibility mapping (QSM): application to estimation of cerebral blood volume during steady state

ObjectiveOne major issue in dynamic susceptibility contrast MRI (DSC-MRI) is to accurately determine contrast agent (CA) concentration, since T2* relaxivity in vivo is generally unknown and varies between blood and tissue. In this study, quantitative susceptibility mapping (QSM) was used for quantification of CA concentration.Materials and methodsA DSC-MRI protocol, including phase data acquisition, was applied to 20 healthy volunteers in a test–retest study. By selecting a CSF reference region of interest (ROI), the values of all QSM images were shifted to show no CA-induced change in CSF. CA concentration and cerebral blood volume (CBV) were estimated using shifted QSM data. CSF reference ROI optimization was evaluated by investigation of CBV repeatability. The CBV age dependence was analysed and tissue T2* relaxivity was estimated.ResultsThe best repeatability of CBV, using an optimal CSF reference ROI, showed test-versus-retest correlations of r = 0.81 and r = 0.91 for white and grey matter, respectively. A slight CBV decrease with age was observed, and the estimated in vivo T2* relaxivity was 85 mM−1s−1.ConclusionProvided that a carefully selected CSF reference ROI is used to shift QSM image values, susceptibility information can be used to estimate concentration of contrast agent and to calculate CBV.

Transitional Changes in Cerebral Blood Volume at Birth

Background: Near-infrared spectroscopy (NIRS) enables non-invasive measurements of changes in the concentration of oxygenated (ΔHbO₂) and reduced (ΔHbR) haemoglobin. Changes in total haemoglobin (ΔHbT = ΔHbO₂ + ΔHbR) provide information on changes in cerebral blood volume (CBV). Objective: The aim was to evaluate the behaviour of CBV during immediate postnatal transition in term infants. Design: This observational study was conducted at the Medical University of Graz. NIRS measurements were carried out in term infants without need for respiratory support by using ‘NIRO 200-NX' (Hamamatsu) over the first 15 min after birth. Results: 109 infants with a mean gestational age of 38 + 6 weeks (±7 days) and birth weight of 3,242 g (±481) were included. Related to a reference value at minute 15, a significant decrease of HbT was observed for each minute within the study period. The mean (±SD) decrease of HbT of 17 (±40) µmol/l from minutes 2 to 15 represents a decrease of CBV of 1.0 ml/100 g brain (±2.2). Conclusions: In healthy newborns, CBV decreased over the whole study period. This likely reflects a physiological process. The impact and clinical relevance of different CBV behaviour during immediate transition needs to be investigated in further studies.

The Effect of Decreasing Flow Rate on Cerebral Hemodynamics During Veno-Arterial Extracorporeal Membrane Oxygenation in Piglets.

To explore the influence of decreasing flow rate on cerebral hemodynamics during veno-arterial extracorporeal membrane oxygenation (va-ECMO), six normoxemic and six hypoxemic piglets were put on va-ECMO. The ECMO flow rate was decreased from the maximal achievable level to 50 mL min1 with steps of 50 mL min1 every 2 minutes. Changes in mean arterial blood pressure (MABP), left common carotid artery blood flow (Qcar), and other physiologic variables were continuously measured. Changes in concentrations of oxyhemoglobin and deoxyhemoglobin were measured using near infrared spectrophotometry (NIRS). Changes in difference between cerebral oxygen hemoglobin and deoxyhemoglobin concentration (ΔcHbD) and total hemoglobin concentration (ΔctHb) were calculated. ΔcHbD represents changes in cerebral blood flow (CBF), and ΔctHb reflects changes in cerebral blood volume (CBV). Data analysis was performed using mixed models and demonstrated a significant positive correlation between ECMO flow and, respectively, MABP (r = 0.7, p < 0.001), Qcar (r = 0.7, p < 0.001), cHbD (r = 0.8, p < 0.001), and ctHb (r = 0.7, p < 0.001). There was no significant relation between oxygenation state preceding ECMO and Qcar, cHbD, and ctHb during decreasing ECMO flow rate. We conclude that decreasing ECMO flow rate ultimately leads to concurrent decrease in MABP, CBF, and CBV.

Cerebral blood volume and vasodilation are independently diminished by aging and hypertension: a near infrared spectroscopy study.

Senescent changes in brain microvascular circulation may cause or contribute to age-related cognitive decline. Such changes are promoted partly by aging, but also by chronic hypertension, a leading treatable cause of cognitive decline. We aimed to non-invasively detect in vivo the senescent changes in brain microvascular circulation associated with age and hypertension, and inquired whether decrements driven by aging would be exacerbated by chronic hypertension. In this longitudinal study, absolute near infrared spectroscopy (NIRS) was used to quantify in vivo cerebral blood volume (CBV) and assess the hemodynamic response to a hypercapnic respiratory challenge in normotensive Wistar-Kyoto (WKY) and spontaneous-hypertensive (SHR) rats. The impact of age and hypertension were evaluated by repeating these measurements on the same animals at 4- and 16-months of age. CBV decreased markedly with age in both strains, from 4.5 ± 0.2 to 2.6 ± 0.1 ml/100g tissue, on average. Chronic hypertension, however, did not significantly exacerbate this age-related decrease in CBV (-48.1 ± 3.7% in WKYs versus -53.3 ± 5.4% in SHRs). In contrast, vasoreactivity was already impaired in the young hypertensive rats (ΔVMR 0.017 ± 0.014 in young SHRs versus 0.042 ± 0.005 in young WKYs) and further worsened by middle-age (ΔVMR 0.011 ± 0.017 middle-aged SHRs). Whereas a decrease in brain blood volume correlated with age but not hypertension, vasodilatory capacity was diminished due to hypertension but did not appear affected by age alone. The ability of absolute NIRS to distinguish between such senescent changes in brain (micro)vascular circulation in life may allow early detection and intervention to preserve cerebrovascular health with age.

Contralateral dissociation between neural activity and cerebral blood volume during recurrent acute focal neocortical seizures.

ObjectiveWhether epileptic events disrupt normal neurovascular coupling mechanisms locally or remotely is unclear. We sought to investigate neurovascular coupling in an acute model of focal neocortical epilepsy, both within the seizure onset zone and in contralateral homotopic cortex.MethodsNeurovascular coupling in both ipsilateral and contralateral vibrissal cortices of the urethane-anesthetized rat were examined during recurrent 4-aminopyridine (4-AP, 15 mm, 1 μl) induced focal seizures. Local field potential (LFP) and multiunit spiking activity (MUA) were recorded via two bilaterally implanted 16-channel microelectrodes. Concurrent two-dimensional optical imaging spectroscopy was used to produce spatiotemporal maps of cerebral blood volume (CBV).ResultsRecurrent acute seizures in right vibrissal cortex (RVC) produced robust ipsilateral increases in LFP and MUA activity, most prominently in layer 5, that were nonlinearly correlated to local increases in CBV. In contrast, contralateral left vibrissal cortex (LVC) exhibited relatively smaller nonlaminar specific increases in neural activity coupled with a decrease in CBV, suggestive of dissociation between neural and hemodynamic responses.SignificanceThese findings provide insights into the impact of epileptic events on the neurovascular unit, and have important implications both for the interpretation of perfusion-based imaging signals in the disorder and understanding the widespread effects of epilepsy.

Usefulness of Computed Tomography Perfusion in Treatment of an Acute Stroke Patient with Unknown Time of Symptom Onset

A 43-year-old Caucasian male with history of mechanical mitral valve was found down outside a recreational park shortly after daybreak. Examination on arrival to the emergency department revealed altered mental status, right hemiplegia, forced leftward gaze, and complete aphasia. Patient was ineligible for tissue plasminogen (TPA) therapy due to unknown time of symptom onset. Computed tomography angiogram (CTA) revealed occlusion of the left middle cerebral artery (MCA) with acute thrombus (Figure 1). Computed tomography perfusion scan (CTP) revealed a large ischemic penumbra with no evidence of infarcted brain tissue (Figure 2). The patient was taken for emergent endovascular therapy with successful retrieval of left MCA thrombus. The patient had almost complete resolution of symptoms with a pre-discharge National Institute of Health Stroke Scale of 1. History prior to discharge revealed that the patient was non-compliant and had been off of his warfarin therapy for months prior to the stroke. The patient was discharged home on warfarin and statin therapy. Figure 1 Transverse (left) and coronal (right) computed tomography angiogram demonstrating abrupt cutoff of the left middle cerebral artery at the site of the thrombus (marked by arrows). Figure 2 Computer-generated perfusion map demonstrating the region of the left cerebral hemisphere (CBF) with decreased cerebral blood flow and prolonged mean transit time (MTT) (marked by arrows). Note that this region of the brain has normal cerebral blood volume ... Acute stroke patients with unknown time of symptom onset are traditionally excluded from acute interventional therapy due to increased rates of fatal intracranial hemorrhage when patients with infarcted brain are treated with TPA or endovascular therapy beyond the recommended time windows.1,2 CTP of the brain is a rapid means of distinguishing between viable and non-viable brain tissue.3 Early in the course of stroke, there is prolonged mean transit time (MTT), decreased cerebral blood flow (CBF), and equal or greater cerebral blood volume (CBV) in ischemic areas of the brain. As brain tissue infarcts, both the CBF and CBV decrease. Assessment of differences between CBF and CBV in areas of brain with prolonged MTT allows one to determine both the size of the stroke as well as the amount of salvageable brain tissue. CTP has the potential to guide acute stroke interventional therapy in patients with unknown time of symptom onset.

Pre- and Post-Angioplasty Perfusion CT with Acetazolamide Challenge in Patients with Unilateral Cerebrovascular Stenotic Disease

ObjectivePerfusion computed tomography (PCT) has the ability to measure quantitative value and produce maps of mean transit time (MTT), cerebral blood flow (CBF), and cerebral blood volume (CBV). We assessed cerebral hemodynamics by using these parameters and acetazolamide (ACZ) challenge for pre- and post-procedural evaluation in patients with unilateral cerebrovascular stenotic disease.MethodsThirty patients underwent pre-procedural PCT with ACZ challenge, and 24 patients (80%) was conducted follow up PCT after angioplasty with same protocol. The mean MTT, CBF, and CBV were measured and compared in both middle cerebral arterial (MCA) territories before and after ACZ challenge. Hemispheric ratio and percent change after ACZ challenge were calculated before and after angioplasty.ResultsThe mean stenosis rate was 76.6%. Significant increases in MTT (32.6%, p=0.000) and significant decreases in CBF (-14.2%, p=0.000) were found in stenotic side MCA territories. After ACZ challenge, there were significant changes in MTT (37.4%, p=0.000), CBF (-13.1%, p=0.000), and CBV (-10.5%, p=0.001) in pre-procedural perfusion study. However, no significant increases were found in MTT, or decreases in CBF and CBV in post-procedural study. There were no significant changes after ACZ challenge also. In addition, the degrees of these changes (before and after ACZ challenge) were highly correlated with the stenotic degrees in pre-procedural perfusion study.ConclusionPCT with ACZ challenge appears to be a useful tool to assess the cerebral perfusion status especially in patients with unilateral symptomatic stenotic disease.

Effects of the α2‐adrenergic receptor agonist dexmedetomidine on neural, vascular and BOLD fMRI responses in the somatosensory cortex

This article describes the effects of dexmedetomidine (DEX) - the active ingredient of medetomidine, which is the latest popular sedative for functional magnetic resonance imaging (fMRI) in rodents - on multiple unit activity, local field potential (LFP), cerebral blood flow (CBF), pial vessel diameter [indicative of cerebral blood volume (CBV)], and blood oxygenation level-dependent (BOLD) fMRI. These measurements were obtained from the rat somatosensory cortex during 10 s of forepaw stimulation. We found that the continuous intravascular systemic infusion of DEX (50 μg/kg/h, doses typically used in fMRI studies) caused epileptic activities, and that supplemental isoflurane (ISO) administration of ~0.3% helped to suppress the development of epileptic activities and maintained robust neuronal and hemodynamic responses for up to 3 h. Supplemental administration of N(2)O in addition to DEX nearly abolished hemodynamic responses even if neuronal activity remained. Under DEX + ISO anesthesia, spike firing rate and the delta power of LFP increased, whereas beta and gamma power decreased, as compared with ISO-only anesthesia. DEX administration caused pial arteries and veins to constrict nearly equally, resulting in decreases in baseline CBF and CBV. Evoked LFP and CBF responses to forepaw stimulation were largest at a frequency of 8-10 Hz, and a non-linear relationship was observed. Similarly, BOLD fMRI responses measured at 9.4 T were largest at a frequency of 10 Hz. Both pial arteries and veins dilated rapidly (artery, 32.2%; vein, 5.8%), and venous diameter returned to baseline slower than arterial diameter. These results will be useful for designing, conducting and interpreting fMRI experiments under DEX sedation.

1615 Effects of Glucose and Non-Nutritive Sucking on Pain Perception

Background and AimSweet tasting solutions and non-nutritive sucking are strong pain reducers for newborns. This study aimed to investigate effects of 30% glucose solution and non-nutritive sucking on amplitude of...

Brain Hemodynamic Changes Associated with Chronic Cerebrospinal Venous Insufficiency Are Not Specific to Multiple Sclerosis and Do Not Increase Its Severity

To investigate the relationship between chronic cerebrospinal venous insufficiency (CCSVI) and cerebral hemodynamic parameters and to disclose any possible involvement in the pathophysiology of multiple sclerosis (MS). The study was approved by the institutional review board, and written informed consent was obtained from all participants. The diagnosis of CCSVI was assigned by using specific color Doppler ultrasonographic criteria. Cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time were assessed with dynamic susceptibility contrast material-enhanced magnetic resonance imaging in normal-appearing white matter (NAWM) in 39 patients with MS. Of these, 25 had CCSVI and 14 did not. Twenty-six healthy control subjects were also evaluated, and of these, 14 had CCSVI and 12 did not. Two-way analysis of variance testing was used for statistical analysis, with Bonferroni correction for multiple comparisons. Correlation analysis was performed by calculating Spearman coefficients. Individuals with CCSVI showed cerebral hemodynamic anomalies, such as decreased CBF and CBV, as compared with individuals without CCSVI, without any delay in mean transit time. No significant interaction between MS and CCSVI was found for any hemodynamic parameters. Furthermore, no correlations were found between CBV and CBF values in NAWM or for severity of disability in patients with MS. The MS group showed prolonged mean transit time in the periventricular NAWM, as compared with the control group, and positive correlation was found between mean transit time values and disability scales in patients with MS. The data support a role of CCSVI in cerebral hemodynamic changes, such as a decrease of CBV and CBF, regardless of the presence of MS. CCSVI had no effect on neurologic function and disability progression in patients with MS.