PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “CEREBROVASCULAR CIRCULATION”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources
PubMed2004

Assessment of cerebral hemodynamics and oxygen extraction using dynamic susceptibility contrast and spin echo blood oxygenation level-dependent magnetic resonance imaging: applications to carotid stenosis patients.

Blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) has been recently used to quantify cerebral blood volume (CBV) and oxygen extraction ratio (OER). In the present study, we have exploited the intravascular BOLD model to assess gray matter (GM) OER at hemispheric level using parenchymal T(2) and CBV data at 1.5 T, obtained by single spin echo and dynamic susceptibility contrast (DSC) perfusion MRI, respectively. An OER of 0.40 +/- 0.07 was determined in gray matter for control subjects. A group of carotid stenosis (CS) patients (n = 22) was examined by multiparametric MRI. The degree of CS was determined by contrast agent-enhanced magnetic resonance angiography. Within the group, eight cases with <70% narrowing of a carotid lumen, nine cases with 70-99%, and five cases with complete occlusion of either carotid arteries were found. DSC MRI revealed abnormalities in 14 patients in dynamic parameters of perfusion images. These included four cases with elevated hemispheric gray matter CBV ipsilateral to the stenosis, above 2 SD of the level determined in control subjects. These four patients showed large variation in the degree of stenosis. We also found three cases with ipsilateral gray matter CBV below 2 SD of the control value, two of these with >70% stenosis. Gray matter OER ipsilateral to the stenosis was above 2 SD of the control range in eight CS patients, three of these showing also high CBV. Use of the present approach to determine OER for the assessment of hemodynamic adaptations in CS patients is discussed in the light of documented hemodynamic adaptations to carotid stenosis.

Aged↗
PubMed1976

[Moyamoya syndrome of tuberculous cerebral arteritis].

A 55-year old woman, suffering from bacteriologically proven tuberculous meningitis showed the angiographic signs typical of tuberculous arteritis: stenosis of the supraclinoid portion of the carotid syphon on the right stenosis of the basilar artery, multiple peripheral occulsions of mediumsize vessels and mild, internal hydrocephalus. As a rarity there was an unusual collateral supply through the basal Moyamoya net which supplied the occluded right middle branch; there was a transtentorial anastomosis of the left meningeal branch of the vertebral artery which supplied the territory of the right posterior cerebral artery in an orthograde manner. The developmental mechanism and radiological findings of this rare collateral system due to tuberculous meningoarteritis is discussed.

Carotid Arteries↗
PubMed1990

[Quantitative determination of cerebral perfusion using digital subtraction angiography (DSA)].

In a search for a reliable and relatively non-invasive method for quantifying cerebral perfusion, we examined the possible role of DSA. By using special software, it is possible to demonstrate vascular morphology and obtain functional data concerning blood flow. Regions of interest are used for obtaining time-density curves and these are evaluated by a formula designed by Meier and Zierler. Perfusion through the arterial territory in both cerebral hemispheres was correlated with the clinical symptoms of the patients and with the morphological findings. Difficulties and problems are described and discussed.

Angiography, Digital Subtraction↗
PubMed1998

Effect of N-methyl-D-aspartate and inhibition of neuronal nitric oxide on collateral cerebral blood flow after middle cerebral artery occlusion.

OBJECTIVE: To study the role of N-methyl-D-aspartate (NMDA) receptor activation and selective inhibition of neuronal nitric oxide synthase with 7-nitroindazole (7-NI) on blood flow to collateral-dependent tissue (CDT) after middle cerebral artery (MCA) occlusion. METHODS: A left craniotomy was performed in each of 11 dogs with the animals under halothane anesthesia. A branch of the MCA was occluded and cannulated distally for determination of CDT, using a "shadow flow" technique. Cerebral blood flow (CBF) and vascular pressures were measured and used to calculate vascular resistance. TECHNIQUE: Our shadow flow model has the ability to identify an area of CDT, with minimal contamination from overlap flow within a morphologically identified "risk area" for MCA branch occlusion. RESULTS: NMDA increased blood flow to CDT by 56.2%, while normal ipsilateral and contralateral cerebrum increased by at least 35% from baseline. 7-NI caused a significant drop in regional CBF, with the greatest drop of 41.7% occurring in the CDT. Normal ipsilateral and contralateral CBF was reduced by 31.7 and 23.9%, respectively. The dilator response to NMDA was significantly attenuated after 7-NI administration, except in CDT where flow increased ("inverse steal"). Cerebral vascular resistance decreased in response to NMDA and increased with 7-NI. CONCLUSION: Neuronal nitric oxide production seems to play an important role in regulating vascular tone and CBF to CDT after MCA occlusion. Selective preservation of blood flow to CDT seems to be mediated by NMDA receptor activation but independent of neuronal nitric oxide production.

Animals↗
PubMed1998

Qualitative versus quantitative assessment of cerebrovascular reserves.

OBJECTIVE: Quantitative studies of cerebral blood flow (CBF) combined with a vasodilatory challenge have defined a subgroup of patients with symptomatic carotid occlusion who have an increased risk for stroke. These are patients whose CBF paradoxically decreases in response to a vasodilatory challenge. Recent reports suggest that qualitative CBF techniques, such as single photon emission tomography with 99m-hexamethylpropyleneamine oxime, can also define the same high-risk subgroup. To determine whether qualitative measures of CBF are sufficient for predicting the risk of stroke, we converted our quantitative CBF data, obtained with xenon-enhanced computed tomography (Xe/CT), to qualitative ratios in a manner similar to that used with single photon emission tomography data. METHODS: We analyzed CBF values within the territory of the middle cerebral artery for 94 patients with symptomatic carotid occlusion. Values obtained using Xe/CT before and after the intravenous administration of 1 g of acetazolamide were used to derive an asymmetry index: (Coccl - Cnon)/Cavg x 100. The difference between the postacetazolamide asymmetry index and the baseline asymmetry index was used to classify the patients into groups according to CBF values. The threshold for abnormal qualitative CBF reactivity was defined as a percent change in the asymmetry index of less than -10%. Quantitative (Xe/CT) CBF was considered abnormal ("steal" response) when the response to acetazolamide (percent change) on the occluded side was a decrease of 5% or greater. RESULTS: Of 34 patients whose cerebrovascular reserves were considered compromised based on qualitative criteria, 17 (50%) did not have a steal response as defined by quantitative Xe/CT CBF (i.e., false positive). Eleven of 62 (18%) who were not considered compromised by qualitative criteria had a steal response (i.e., false negative). Our data indicate that a qualitative approach has a 61% sensitivity and a 75% specificity for detecting patients with compromised reserves. Further, the positive predictive value of this method is only 50%. Therefore, the two methodologies do not predict the same patients as having compromised reserves. CONCLUSION: Previous studies have shown that patients at high risk for stroke can be identified with quantitative CBF methods. This study shows that the important subgroup cannot be accurately defined with qualitative methodology. The implications of using the more reliable methodology are important for individual patient management and for designing clinical trials.

Acetazolamide↗
PubMed1996

Phase-contrast magnetic resonance angiography for the determination of cerebrovascular reserve.

Cerebrovascular reserve (CVR) is the potential for cerebral arteriolar dilatation to occur, in response to decreased cerebral perfusion pressure, in order to maintain constant cerebral blood flow. Diminution or absence of CVR is considered a risk factor for stroke. Current methods for determining CVR include single-photon emission computed tomography, positron emission tomography and transcranial Doppler (TCD) ultrasonography. However, significant advantages could derive from the utilization of magnetic resonance angiography (MRA) based on the concurrent acquisition of hemodynamic information (CVR and collateral flow) with phase-contrast (PC) techniques and vascular morphology with three-dimensional, time-of-flight methods. With a 1.5-T scanner and acetazolamide (AZM), an arteriolar dilator, CVR was determined in 7 normal subjects. Mean flow velocity in the middle cerebral arteries was determined by PC MRA before and after AZM administration. For comparative purposes, mean flow velocities in the same middle cerebral arteries were determined by TCD before and after AZM administration. The mean flow velocities were as follows (mean +/- standard deviation, n = 7): 40 +/- 8 (PC MRA) versus 61 +/- 10 cm/sec (TCD) before AZM treatment and 58 +/- 11 (PC MRA) versus 85 +/- 15 cm/sec (TCD) after AZM administration. The increase in mean flow velocity (before vs after AZM), that is, the CVR, was 45 +/- 11% as shown by PC MRA and 39 +/- 14% as shown by TCD. Although significant differences were present between the mean flow velocities measured before and those after AZM administration, as determined by PC MRA and TCD, the CVR was not significantly different (45 vs 39%, respectively). These preliminary results suggest that PC MRA may be a method for determining CVR.

Acetazolamide↗
PubMedDate not supplied

Clinical predictors of early embolic recurrence in presumed cardioembolic stroke.

BACKGROUND: We determined clinical predictive factors of in-hospital embolic recurrence in presumed cardioembolic stroke patients by means of multivariate analysis based on clinical and neuroimaging prognostic variables assessed within 48 h of stroke onset. METHODS: Data of 347 consecutive patients with presumed cardioembolic stroke included in a prospective stroke registry were collected. Demographic characteristics, clinical events, and outcome in the recurrent and nonrecurrent embolization group were compared. The independent predictive value of each variable on the development of early embolic recurrence was analyzed in two multiple liner regression models - one based on eight demographic, anamnestic, and clinical variables and another based on 10 clinical, neuroimaging, and outcome variables. RESULTS: In-hospital recurrent embolization was diagnosed in 25 (6.9%) patients. The latency period was 12.1 days. The overall in-hospital mortality was 70.8% in the recurrent embolization group and 24.4% in the nonrecurrent embolization group (p < 0.001). Alcohol abuse, the combination of hypertension, valvular heart disease, and atrial fibrillation, nausea and vomiting, and previous cerebral infarction were predictors of recurrent embolization in the model based on clinical variables. In addition to these four variables, cardiac events were selected in the model based on clinical, neuroimaging, and outcome variables. CONCLUSIONS: A small number of clinical features that can be easily obtained on the patient's initial assessment may help clinicians to identify a subgroup of patients with cardioembolic stroke at the highest risk of developing early recurrent brain or systemic embolization.

Acute Disease↗