Cerebrovascular Reserve Capacity In Patients Research Articles

Leptomeningeal collateral activation indicates severely impaired cerebrovascular reserve capacity in patients with symptomatic unilateral carotid artery occlusion

For patients with symptomatic unilateral internal carotid artery (ICA) occlusion, impaired cerebrovascular reactivity (CVR) indicates increased stroke risk. Here, the role of collateral activation remains a matter of debate, whereas angio-anatomical collateral abundancy does not necessarily imply sufficient compensatory flow provided. We aimed to further elucidate the role of collateral activation in the presence of impaired CVR. From a prospective database, 62 patients with symptomatic unilateral ICA occlusion underwent blood oxygenation-level dependent (BOLD) fMRI CVR imaging and a transcranial Doppler (TCD) investigation for primary and secondary collateral activation. Descriptive statistic and multivariate analysis were used to evaluate the relationship between BOLD-CVR values and collateral activation. Patients with activated secondary collaterals exhibited more impaired BOLD-CVR values of the ipsilateral hemisphere (p = 0.02). Specifically, activation of leptomeningeal collaterals showed severely impaired ipsilateral hemisphere BOLD-CVR values when compared to activation of ophthalmic collaterals (0.05 ± 0.09 vs. 0.12 ± 0.04, p = 0.005). Moreover, the prediction analysis showed leptomeningeal collateral activation as a strong independent predictor for ipsilateral hemispheric BOLD-CVR. In our study, ipsilateral leptomeningeal collateral activation is the sole collateral pathway associated with severely impaired BOLD-CVR in patients with symptomatic unilateral ICA occlusion.

Leptomeningeal collateral activation indicates severely impaired cerebrovascular reserve capacity in patients with symptomatic unilateral carotid artery occlusion

Leptomeningeal collateral activation indicates severely impaired cerebrovascular reserve capacity in patients with symptomatic unilateral carotid artery occlusion

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.

Prediction of Cerebrovascular Reserve Capacity by Computed Tomography Perfusion Using 320-Row Computed Tomography

Acetazolamide loading has been the "gold standard" for evaluating cerebrovascular reserve capacity (CVRC). However, life-threatening side effects of acetazolamide have recently been reported. The aim of the study was to identify alternative methods for evaluating CVRC. We reviewed 6 patients who underwent both computed tomography perfusion (CTP) imaging and xenon CT (XeCT) imaging with and without acetazolamide loading during the same periods. The data were obtained as volume data using 320-row CT and applied to the automated region of interest-determining software and converted to standardized images. Correlations between CVRC and CTP parameters were analyzed by Pearson correlation coefficient analysis, and simple regression was used to assess the relationship between the data. When statistically significant, correlation between CVRC and any CTP data is identified, and cutoff points for CVRC 30% and 10% were calculated with receiver operating characteristic curves. Of 4 CTP parameters evaluated, statistically significant correlations were observed between time to peak (TTP) by CTP and CVRC (P < .0001, r = -.7228) calculated from XeCT. The regression line using CVRC as outcome variable (y) and using TTP as predictor variable (x) was y = -9.062x + 140.1. The cutoff value for the TTP for CVRC less than 10% was 12.56 seconds (sensitivity of 86% and specificity of 85%) and that for CVRC less than 30% was 9.34 seconds (sensitivity of 77% and specificity of 96%). TTP calculated from CTP data correlated well with the CVRC calculated from XeCT data. These results suggest that TTP calculated from CTP could be used to estimate CVRC in patients with occlusive cardiovascular disease.

Dietary nitrate facilitates an acetazolamide-induced increase in cerebral blood flow during visual stimulation

The carbonic anhydrase (CA) inhibitor acetazolamide (AZ) is used routinely to estimate cerebrovascular reserve capacity in patients, as it reliably increases cerebral blood flow (CBF). However, the mechanism by which AZ accomplishes this CBF increase is not entirely understood. We recently discovered that CA can produce nitric oxide (NO) from nitrite, and that AZ enhances this NO production in vitro. In fact, this interaction between AZ and CA accounted for a large part of AZ's vasodilatory action, which fits well with the known vasodilatory potency of NO. The present study aimed to assess whether AZ acts similarly in vivo in the human cerebrovascular system. Hence, we increased or minimized the dietary intake of nitrate in 20 healthy male participants, showed them a full-field flickering dartboard, and measured their CBF response to this visual stimulus with arterial spin labeling. Doing so, we found a significant positive interaction between the dietary intake of nitrate and the CBF modulation afforded by AZ during visual stimulation. In addition, but contrary to studies conducted in elderly participants, we report no effect of nitrate intake on resting CBF in healthy human participants. The present study provides in vivo support for an enhancing effect of AZ on the NO production from nitrite catalyzed by CA in the cerebrovascular system. Furthermore, our results, in combination with the results of other groups, indicate that nitrate may have significant importance to vascular function when the cerebrovascular system is challenged by age or disease.

Abstract TMP39: Identifying Cerebrovascular Reserve Capacity by Arterial Spin Labeling MR in Patients with Moyamoya Disease

Background— The diagnostic accuracy to identify the cerebrocascular reserve capacity (CVRC) by arterial spin labeling (ASL) MR in patients with moyamoya disease is unclear. Methods— We conducted a prospective study to examine the accuracy of ASL as compared with single-photon emission CT (SPECT) in patients with moyamoya disease. Preoperative ASL and SPECT images from 61 adult patients with moyamoya disease were analyzed. For 122 hemispheres from the patients, voxels of interest consisting of bilateral ICA and MCA territories were applied to the spatially normalized cerebral blood flow maps from basal and acetazolamide challenge ASL and SPECT. The correlation between cerebrovascular reserve capacity (CVRC) from ASL and SPECT was analyzed by a using Pearson correlation analysis and the area under the receiver-operating-characteristic curve (AUC) was used to evaluate diagnostic accuracy relative to that of SPECT for various cutoff points by CVRC. Results— Significant relationships were observed between CVRC from ASL and SPECT for the internal carotid artery (ICA) and middle cerebral artery (MCA) (correlation coefficient r = .7093, P &lt; .0001 and r = .7319, P &lt; .0001, respectively) (Table). The diagnostic accuracies of ASL for detecting ICA and MCA areas, in which CVRC are &lt; -5.0%, revealed an AUC of 0.96 (95% confidence interval [CI], 0.91 to 0.99) and 0.96 (95% CI, 0.91 to 0.99, respectively). Conclusions— ASL can identify the reduced CVRC with good performance and has the potential as a noninvasive imaging tool for determining CVRC in patients with moyamoya disease. Table. Correlations between CBF and CVRI values from ASL and SPECT

Acetazolamide-challenged perfusion magnetic resonance imaging for assessment of cerebrovascular reserve capacity in patients with symptomatic middle cerebral artery stenosis: comparison with technetium-99m-hexamethylpropyleneamine oxime single-photon emission computed tomography

Objectives Acetazolamide-challenged perfusion magnetic resonance imaging (MRI) has been shown as a method for assessment of cerebrovascular reserve (CVR) capacity in patients with atherosclerotic steno-occlusive disease of internal carotid artery. We have assessed the feasibility of the acetazolamide-challenged perfusion MRI for evaluating CVR in symptomatic patients with severe middle cerebral artery (MCA) stenosis (≥70%) by comparison with the acetazolamide-challenged technetium-99m-hexamethylpropyleneamine oxime (HMPAO) single-photon emission computed tomography (SPECT). Methods Seventeen prospectively enrolled patients with symptomatic unilateral MCA stenosis underwent technetium-99m-hexamethylpropyleneamine oxime SPECT and perfusion MRI without and with acetazolamide challenge, respectively. Acetazolamide-challenged SPECT and perfusion MRI were compared quantitatively by Region of interest (ROI) analysis. Results At all ROIs, there were no significant differences in percent change between SPECT and perfusion MRI. Patients with impaired CVR showed significant decreases in the percent changes of respective cerebral blood flow ( P=.016) and respective cerebral blood volume ( P=.029). Conclusion Acetazolamide-challenged perfusion MRI is feasible for evaluating CVR in symptomatic patients with severe MCA stenosis quantitatively.

A comparative study of perfusion CT and 99mTc-Hmpao spect measurement to assess cerebrovascular reserve capacity in patients with internal carotid artery occlusion

Background and purposePatients with internal carotid artery (ICA) occlusion can demonstrate impaired cerebral vascular reserve (CVR). The detection of CVR using single photon emission CT (SPECT) is nowadays widely accepted as a predictor in the diagnostic pathway in patients considered for cerebral revascularization. Recently perfusion CT (PCT) gained widely acceptance in stroke imaging The present study was aimed at comparing the results of perfusion CT (PCT) and 99mTc-HMPAO SPECT with acetazolamide challenge in patients with ICA occlusion.Methods13 patients were included in the prospective evaluation. Both PCT and 99mTc-HMPAO SPECT were performed before and after the administration of acetazolamide. In detail, regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), adapted time to peak (Tmax) and mean transit times (MTT) were compared with SPECT data.Results99mTc-HMPAO SPECT demonstrated an impairment of CVR in six patients. A preserved CVR was present in seven patients. All patients with impaired CVR proven by SPECT had a delayed MTT (mean +2.98 s) and a delayed Tmax (mean + 5.9 s), (both p < 0.005 compared with the non occluded side). 66% of patients with impaired CVR in SPECT showed a complete correlation of Tmax measurements in PCT with a high positive predictive value (PPV: 88.8%).ConclusionThe prospective study demonstrated a highly significant correlation of perfusion parameters as' detected by 99mTc-HMPAO SPECT and the Tmax as detected by PCT in patients with ICA occlusion. Therefore this easy-to-perform technique seems to be an adequate method for the evaluation of cerebral perfusion in patients with ICA occlusion.

Perfusion MRI before and after acetazolamide administration for assessment of cerebrovascular reserve capacity in patients with symptomatic internal carotid artery (ICA) occlusion: comparison with 99mTc-ECD SPECT

Impaired cerebral vascular reserve (CVR) in patients with symptomatic internal carotid artery (ICA) occlusion is regarded as a possible indication for performing extra-/intracranial (EC/IC) bypass surgery. As perfusion MR imaging (MRI) can demonstrate cerebral haemodynamics at capillary level, our hypothesis was that perfusion MRI could be used in these patients for the evaluation of CVR following acetazolamide challenge in a similar way to single photon emission CT (SPECT) and might provide additional information. Enrolled in the study were 12 patients (mean age 61.3 years; 11 male, 1 female) with symptomatic unilateral ICA occlusion proven by angiography. Both perfusion MRI and 99m-technetium-ethyl-cysteinate dimer ((99m)Tc-ECD) SPECT were performed before and after injection of acetazolamide (Diamox ,1000 mg i.v.). CVR parameters including regional cerebral blood flow (rCBF) and volume (rCBV), and mean transit times (MTT) were measured by perfusion MRI. The patients with impaired CVR proven by SPECT (n = 9) had a negative mean rCBF increment (-46.52%), negative rCBV increment (-13.5%) and delayed MTT (mean +2.98 s), respectively, on the occluded side (Student's t-test all P < 0.05). The patients with sufficient CVR (n = 3) had a mean rCBF increment of 1.2%, a decrement of rCBV of 10.46%, and a mean MTT shortening of 0.27 s following the acetazolamide injection. Perfusion MRI before and after acetazolamide administration compares favourably with (99m)Tc-ECD SPECT for the detection of impaired CVR. The impact that perfusion MRI studies (before and after acetazolamide administration) might have on the treatment decision in patients with ICA occlusion has yet to be determined by a prospective study.

Effectiveness of Bypass Surgery in Treatment and Prevention for Cerebrovascular Occlusive Disease

To study the effect of extracranial-intracranial(EC/IC) bypass on symptomatic patients with hemodynamic cerebral ischemia, we prospectively reviewed 76 patients who underwent EC/IC bypass surgery in patients with occlusive cerebrovascular disease. A series of 76 patients treated in a 7 years period met following criteria. ① symptomatic internal carotid artery(ICA) or middle cerebral artery(MCA) obstruction or stenosis over 80%. ② decrease in basal cerebral blood flow(CBF) over 10%. ③ decreased reactivity of CBF in response to acetazolamide. Among these, the types of ischemic episodes were transient ischemic attack(TIA) or reversible ischemic neurological deficit(RIND) in 39, minor stroke in 22, and major stroke in 15. Based on our criteria, superficial temporal artery(STA)-MCA anastomosis was performed in 67 cases and EC-IC bypass grafting using saphenous vein or radial artery in 9. Average follow up period was 26 months(3 months~7 year). Patency of bypass was confirmed by postoperative angiography or magnetic resonence angiography(MRA) in all case except four cases. Of the 72 patients with patiency of bypass, 68 patients(94%) have had an excellent to good outcome with improvement of preoperative neurologic or cognitive dysfunction, 3 patients showed no improvement of preoperative neurologic symptoms and remaining one patient had new developed deficit. All 72 patients with patency of bypass had experienced no further cerebral ischemic events during following period. Postoperative significant improvement of CBF to acetazolamide was showed in 68 cases(94%) of the 72 cases with patency of bypass, while the basal CBF showed significant improved in 31cases. Postoperative permanent neurologic deficit occurred only in one. In view of these finding, the author suggest that EC-IC bypass surgery is a reliable and resonably safe method for establishing new pathways of collateral circulation to the brain and to be considered as an appropriate therapy for improvement of the cerebrovascular reserve capacity in patients with hemodynamic cerebral ischemia, defined using the strict selection criteria employed in this study.

Influence of nitrovasodilators and cyclooxygenase inhibitors on cerebral vasoreactivity in conscious rabbits

Since the nitric oxide (NO) and cyclooxygenase pathways have been suggested to have important roles in most vasodilations, our aim was to study the influence of cyclooxygenase inhibitors and nitrovasodilators on cerebrovascular reserve capacity. Corticocerebral blood flow was measured by hydrogen polarography during hypercapnia and acetazolamide stimuli in conscious rabbits. The measurements were repeated in the presence of N ω-nitro- l-arginine methyl ester ( l-NAME) and indomethacin as nitric oxide synthase (NOS) and cyclooxygenase inhibitors. The effects of nitroglycerin and isosorbide-5-nitrate were also tested. l-NAME completely, while indomethacin markedly inhibited the hypercapnic corticocerebral blood flow response. Nitroglycerin and isosorbide-5-nitrate significantly attenuated hypercapnia elicited corticocerebral blood flow increase. The different treatments reduced only moderately the acetazolamide-induced corticocerebral blood flow response. These results lend support to the hypothesis that antithrombotic and antiinflammatory medication (cyclooxygenase inhibitors) and nitrovasodilator treatments could interfere with the measurement of cerebrovascular reactivity resulting in underestimation of the cerebrovascular reserve capacity in patients taking these drugs.

817 Improvement of Cerebrovascular Reserve Capacity in Patients with Symptomatic Internal Carotid Occlusion after EC-IC Bypass Surgery

Charbel, Fady T. MD; Du, Xinjian MD; Guppy, Kern MD, PhD; Zhao, Meide PhD; Maksoud, Yaser Abdel MD; Ausman, James MD, PhD

Cerebrovascular reserve capacity in patients with hyperlipidemia

Cerebrovascular reserve capacity in patients with hyperlipidemia

Decreased cerebrovascular reserve capacity in patients with various types of mitochondrial disorders

Decreased cerebrovascular reserve capacity in patients with various types of mitochondrial disorders

Comparison of vasodilatory effect of carbon dioxide inhalation and intravenous acetazolamide on brain vasculature using positron emission tomography

Carbon dioxide (C02) and acetazolamide are increasingly being used as vasodilators to detect cerebrovascular reserve capacity in patients of chronic cerebrovascular disease. The functional cerebrovascular reserve or ability of cerebral vessels to lower their resistance in response to decrease in cerebral perfusion pressure is expressed as change in cerebral blood flow from baseline under a vasodilatory stimuli. Theoretically a vasodilator causing maximum vasodilation, and thereby expressing complete reserve capacity would be more suitable for such a purpose. We quantitatively compared the vasodilating effect of 5% CO2 inhalation and 1 g of intravenous acetazolamide by positron emission tomography. Cerebrovascular reserve was quantified in six patients with chronic cerebrovascular disease in the same sitting, using oxygen-15 labeled water (H2 150) positron emission tomography at rest, during 5% CO2 inhalation and after 7 g intravenous acetazolamide. A significant linear correlation in both nonlesion hemisphere (r = 0.7071 p< 0.007) and in lesion hemisphere (r = 0.6261 p< 0.005) was found between CO2 and acetazolamide for cerebrovascular reserve capacity. This correlation improved by considering cerebrovascular reserve per unit change in arterial carbon dioxide (r = 0.7441 P<·0.007 in nonlesion hemisphere and r = 0.7271 P< 0.001 in lesion hemisphere). The quantitative value of global reserve capacity was different by CO2 stimuli (5.2%) and acetazolamide (49.7%). Though a similar vasodilatory response is elicited by both vasodilators, acetazolamide seems to be more potent and therefore should be preferred to detect patients with exhausted cerebrovascular reserve capacity. [Neural Res 1997; 19: 139–144]

Cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease: assessment with dynamic susceptibility contrast-enhanced MR imaging and the acetazolamide stimulation test.

To quantitatively assess cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease. In 21 symptomatic patients with occlusive cerebrovascular disease, magnetic resonance (MR) imaging was performed with a 1.5-T system. Before, during, and after a brief bolus injection of gadopentetate dimeglumine into the antecubital vain, a series of 32 rapid T2*-weighted gradient-echo images of two different sections were acquired simultaneously to measure the concentration-time-curves in the brain tissue and in the brain-feeding arteries. Principles of indicator dilution analysis were applied to compute regional cerebral blood flow (rCBF) and volume. Each patient underwent two examinations, the first before and the second after acetazolamide stimulation. In the asymptomatic hemisphere, a mean increase in rCBF value of 47.1% was observed after acetazolamide stimulation. In the affected areas of the symptomatic hemisphere, a statistically significantly reduced response to acetazolamide stimulation was found, indicating a severely compromised cerebrovascular reserve capacity. MR imaging with the described techniques provides quantitative information about the cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease.

The Effect of Acetazolamide on Regional Cerebral Blood Oxygenation at Rest and under Stimulation as Assessed by MRI

The sensitivity of gradient echo magnetic resonance imaging (MRI) to changes in cerebral blood oxygenation (CBO) has been introduced for mapping functional brain activation. Here, we report that this approach allows monitoring autoregulation in the human brain under vasodilatory stress. Following the administration of acetazolamide, signal intensities of deoxyhemoglobin-sensitive images increased in cortical and subcortical gray matter and to a lesser extent in white matter. This result reflects a venous hyperoxygenation stemming from an increase in cerebral perfusion with oxygen consumption remaining constant. In addition, pharmacologic induction of vasodilation attenuated activity-related MRI signal changes in the visual cortex under photic stimulation. Although intersubject variability was high, this finding indicates individually persisting autoregulatory responsiveness to functional challenge despite an "exhausted" reserve capacity. It is suggested that recording CBO by MRI will foster our understanding of modulation of vasomotor tone and cerebral perfusion. Furthermore, this technique may prove valuable for assessing the cerebrovascular reserve capacity in patients with carotid artery occlusive disease.