Middle Cerebral Artery Vasodilation Research Articles

Impact of bariatric surgery on cerebral vascular reactivity and cognitive function: a non-randomized pilot study

BackgroundBariatric surgery is an effective long-term weight loss strategy yielding improvements in neurocognitive function; however, the mechanism(s) responsible for these improvements remains unclear. Here, we assessed the feasibility of using magnetic resonance imaging (MRI) to evaluate whether cerebral vascular reactivity (CVR) is impaired in severely obese bariatric surgery candidates compared with normal weight healthy controls and whether CVR improves following bariatric surgery. We also investigated whether changes in CVR were associated with changes in cognitive function.MethodsBariatric surgery candidates (n = 6) were compared with normal weight healthy controls of a similar age (n = 10) at baseline, and then reassessed 2 weeks and 14 weeks following sleeve gastrectomy bariatric surgery. Young reference controls (n = 7) were also studied at baseline to establish the range of normal for each outcome measure. Microvascular and macrovascular CVR to hypercapnia (5% CO2) were assessed using blood-oxygen-level-dependent (BOLD) MRI, and changes in the middle cerebral artery (MCA) cross-sectional area, respectively. Cognitive function was assessed using a validated neurocognitive software.ResultsCompliance with the CVR protocol was high. Both macro- and micro-cerebrovascular function were highest in the young reference controls. Cognitive function was lower in obese bariatric surgery candidates compared with normal weight controls, and improved by 17% at 2 weeks and 21% by 14 weeks following bariatric surgery. To our surprise, whole-brain CVR BOLD did not differ between obese bariatric surgery candidates and normal weight controls of similar age (0.184 ± 0.101 vs. 0.192 ± 0.034 %BOLD/mmHgCO2), and did not change after bariatric surgery. In contrast, we observed vasoconstriction of the MCA during hypercapnia in 60% of the obese patients prior to surgery, which appeared to be abolished following bariatric surgery. Improvements in cognitive function were not associated with improvements in either CVR BOLD or MCA vasodilation after bariatric surgery.ConclusionsAssessing CVR responses to a hypercapnic challenge with MRI was feasible in severely obese bariatric patients. However, no changes in whole-brain BOLD CVR were observed following bariatric surgery despite improvements in cognitive function. We recommend that future large trials assess CVR responses to cognitive tasks (rather than hypercapnia) to better define the mechanisms responsible for cognitive function improvements following bariatric surgery.

Involvement of Hydrogen Sulfide in Endothelium-Derived Relaxing Factor-Mediated Responses in Rat Cerebral Arteries

Background/Aim: H₂S is a novel vasoactivator. To verify the hypothesis that H₂S may act as an endothelium-derived hyperpolarizing factor (EDHF) in the rat cerebrovasculature, the role of H₂S in endothelium-derived relaxing factor (EDRF)-mediated responses was investigated. Methods: Cystathionine-γ-lyase (CSE) was knocked down with an siRNA technique. Artery diameter, hyperpolarization and Ca²⁺-activated K⁺ (K_Ca) current were measured. Results: CSE knockdown was indicated by a decrease in protein and mRNA expression in the rat middle cerebral artery (MCA) and cerebral basilar artery (CBA). Acetylcholine (ACh) induced significant hyperpolarization and vasodilation in endothelium-intact MCA and CBA. Removal of the endothelium abolished these responses. The nitric oxide (NO) synthase inhibitor <smlcap>L</smlcap>-NAME, but not the PGI₂ production inhibitor indomethacin, significantly inhibited ACh-induced hyperpolarization and vasodilation in the CBA. In the presence of <smlcap>L</smlcap>-NAME and indomethacin, ACh-induced hyperpolarization and vasodilation in the MCA and CBA were attenuated. The non-NO/PGI₂-mediated responses were abolished by the K_Ca channel blockers charybdotoxin and apamin. In the cerebral arteries from the CSE knockdown rat, non-NO/PGI₂-mediated responses were significantly attenuated, and the remaining responses were abolished by charybdotoxin and apamin or the CSE inhibitor propargylglycine. CSE knockdown did not affect <smlcap>L</smlcap>-NAME-sensitive responses in the CBA. Sodium hydrosulfide (NaHS) augmented the K_Ca current in CBA vascular smooth muscle cells. Conclusion: EDHF-mediated responses in rat cerebral arteries were due to H₂S activating the K_Ca channel.

Risk of ultrasound-detected neonatal brain abnormalities in intrauterine growth-restricted fetuses born between 28 and 34 weeks' gestation: relationship with gestational age at birth and fetal Doppler parameters.

To estimate the value of gestational age at birth and fetal Doppler parameters in predicting the risk of neonatal cranial abnormalities in intrauterine growth-restricted (IUGR) fetuses born between 28 and 34 weeks' gestation. Fetal Doppler parameters including umbilical artery (UA), middle cerebral artery (MCA), aortic isthmus, ductus venosus and myocardial performance index were evaluated in a cohort of 90 IUGR fetuses with abnormal UA Doppler delivered between 28 and 34 weeks' gestation and in 90 control fetuses matched for gestational age. The value of gestational age at birth and fetal Doppler parameters in predicting the risk of ultrasound-detected cranial abnormalities (CUA), including intraventricular hemorrhage, periventricular leukomalacia and basal ganglia lesions, was analyzed. Overall, IUGR fetuses showed a significantly higher incidence of CUA than did control fetuses (40.0% vs 12.2%, respectively; P < 0.001). Within the IUGR group, all predictive variables were associated individually with the risk of CUA, but fetal Doppler parameters rather than gestational age at birth were identified as the best predictor. MCA Doppler distinguished two groups with different degrees of risk of CUA (48.5% vs 13.6%, respectively; P < 0.01). In the subgroup with MCA vasodilation, presence of aortic isthmus retrograde net blood flow, compared to antegrade flow, allowed identification of a subgroup of cases with the highest risk of CUA (66.7% vs 38.6%, respectively; P < 0.05). Evaluation of fetal Doppler parameters, rather than gestational age at birth, allows identification of IUGR preterm fetuses at risk of neonatal brain abnormalities.

Effects of the acupoints PC 6 Neiguan and LR 3 Taichong on cerebral blood flow in normal subjects and in migraine patients.

Acupuncture has been proven to be effective in the treatment of various cardiovascular disorders; it acts both on the peripheral flow and on the cerebral flow. Our study aimed to evaluate the effects of the insertion of PC 6 Neiguan and LR 3 Taichong acupoints on the cerebral blood flow (CBF) in the middle cerebral artery (MCA). These effects were measured in a group of patients suffering from migraine without aura (Group M) and in a healthy control group (Group C). In the study, we included 16 patients suffering from migraine without aura, classified according to the criteria of the International Headache Society, and 14 healthy subjects as a control group. The subjects took part in the study on two different days, and on each day, the effect of a single acupoint was evaluated. Transcranial Doppler was used to measure the blood flow velocity (BFV) in the MCA. Our study showed that the stimulation of PC 6 Neiguan in both groups results in a significant and longlasting reduction in the average BFV in the MCA. After pricking LR 3 Taichong, instead, the average BFV undergoes a very sudden and marked increase; subsequently, it decreases and tends to stabilize at a slightly higher level compared with the baseline, recorded before needle insertion. Our data seem to suggest that these two acupoints have very different effects on CBF. The insertion of PC 6 Neiguan probably triggers a vasodilation in MCA, while the pricking of LR 3 Taichong determines a rapid and marked vasoconstriction.

Transient Focal Cerebral Ischemia Induces Long-term Cerebral Vasculature Dysfunction in a Rodent Experimental Stroke Model

Constriction and dilation of large arteries of brain regulates cerebral vascular resistance and cerebral microvascular pressure, which play key roles in regulation of cerebral circulation. We investigated the effect of ischemic stroke on vascular reactivity of middle cerebral artery (MCA) using a rat transient focal cerebral ischemia model. Focal cerebral ischemia was induced by 1 hour MCA occlusion followed by reperfusion. MCAs were dissected from ischemic or contralateral hemisphere at 2 days or 2 weeks post reperfusion and mounted on 2 glass micropipettes for assessment of vascular reactivity. MCAs from brains of sham surgeries were used as control. At 2 days post reperfusion, a significant alteration of myogenic reactivity was found in MCAs dissected from both ischemic and non-ischemic hemispheres, which could still be identified at 2 weeks after reperfusion. Phenylephrine (PE) induced remarkable vasoconstriction in MCAs from animals that underwent sham surgery. No significant alteration of vasoconstrictive response to PE was found in MCAs isolated from either ischemic or contralateral hemisphere at 2 days or 2 weeks after ischemic stroke, as compared with MCAs from sham animals. Acetylcholine (ACh) induced mild dilation in normal MCAs, which was reversed in MCAs from both ischemic and non-ischemic hemispheres at 2 weeks after ischemic stroke. Sodium nitroprusside (SNP) induced vasodilation in MCAs from animals with sham operation, which was diminished in MCAs from both ischemic and non-ischemic hemisphere at 2 days and 2 weeks after ischemic stroke. These results demonstrated that focal cerebral ischemia could induce long-term global cerebral vasculature dysfunction.

Neurovascular changes in prolonged migraine aura in FHM with a novel ATP1A2 gene mutation

ObjectivesTo report cerebral blood flow changes during attacks of hemiplegic migraine with prolonged aura (HMPA) longer than 24 h in patients with familial hemiplegic migraine (FHM) with a novel gene...

OC12.04: Increased umbilical artery pulsation in fetal growth restriction increases the risk of ST‐depression of the fetal electrocardiogram during labor

CD and CD for NRFS alone or in combination with MCA Doppler was assessed by decision tree analysis. Results: Retrograde net blood flow in aortic isthmus was observed in 8.3% (14/169) of the cases and only within the group of fetuses with MCA vasodilation (PI < 5th centile). Among the overall study population, cases with reversed aortic isthmus blood flow were associated with a significantly higher risk of CD (85.7% vs. 36.8%, P < 0.001) and CD for NRFS (85.7% vs. 24.5%, P < 0.001) than those with antegrade blood flow. Decision tree analysis indicated that incorporation of aortic isthmus showed an additional predictive value to brain Doppler abnormalities. Among the group with MCA vasodilation, reversed aortic isthmus blood flow allowed discrimination of cases with high or moderate risk of CD (85.7% vs. 54.5%, P < 0.01) and CD for NRFS (85.7% vs. 40.9%, P < 0.05). Conclusions: Identification of aortic isthmus reversed blood flow identifies a subgroup of term SGA fetuses with middle cerebral artery vasodilation with the highest risk of emergency cesarean delivery for non-reassuring fetal status.

Fetal Brain Doppler to Predict Cesarean Delivery for Nonreassuring Fetal Status in Term Small-for-Gestational-Age Fetuses

To estimate the value of fetal brain Doppler in predicting the risk of cesarean delivery for nonreassuring fetal status and neonatal acidosis after labor induction in small-for-gestational-age fetuses with normal umbilical artery Doppler. Fetal brain Doppler parameters, including cerebral tissue perfusion measured by fractional moving blood volume, cerebroplacental ratio, and middle cerebral artery pulsatility index, were evaluated before labor induction in a cohort of 210 term small-for-gestational-age fetuses with normal umbilical artery Doppler and 210 control participants matched by gestational age. The value of the cerebral Doppler indices to predict the risk of cesarean delivery, cesarean delivery for nonreassuring fetal status, and neonatal acidosis was analyzed. Overall, small-for-gestational-age fetuses showed a significant higher incidence of cesarean delivery (37.6% compared with 19.5%, P<.001), cesarean delivery for nonreassuring fetal status (29% compared with 4.8%, P<.001), and neonatal acidosis (7.6% compared with 2.4%, P=.03) than control participants. Within the small-for-gestational-age group, middle cerebral artery vasodilation was associated with the highest risk of cesarean delivery (67.7% compared with 32.4%, P<.001) and cesarean delivery for nonreassuring fetal status (58.1% compared with 24%, P<.001). In the subgroup of normal middle cerebral artery, incorporation of cerebroplacental ratio further distinguished two groups with different risks of cesarean delivery (51.4% compared with 27.5%, P<.01) and cesarean delivery for nonreassuring fetal status (37.8% compared with 20.4%, P=.01). Middle cerebral artery vasodilation was associated with increased risk of neonatal acidosis (odds ratio, 9.0). Fractional moving blood volume was not associated with the risk of cesarean delivery for nonreassuring fetal status or neonatal acidosis. Evaluation of brain Doppler indices before labor induction discriminates small-for-gestational-age fetuses at high risk of cesarean delivery for nonreassuring fetal status and neonatal acidosis.

Relationship of 133Xe cerebral blood flow to middle cerebral arterial flow velocity in men at rest.

Cerebral blood flow (CBF) was measured by 133Xe clearance simultaneously with the velocity of blood flow through the left middle cerebral artery (MCA) over a wide range of arterial PCO2 in eight normal men. Average arterial PCO2, which was varied by giving 4% and 6% CO2 in O2 and by controlled hyperventilation on O2, ranged from 25.3 to 49.9 mm Hg. Corresponding average values of global CBF15 were 27.2 and 65.0 ml 100 g min-1, respectively, whereas MCA blood-flow velocity ranged from 42.8 to 94.2 cm/s. The relationship of CBF to MCA blood-flow velocity over the imposed range of arterial PCO2 was described analytically by a parabola with the equation: CBF = 22.8 - 0.17 x velocity + 0.006 x velocity2 The observed data indicate that MCA blood-flow velocity is a useful index of CBF response to change in arterial PCO2 during O2 breathing at rest. With respect to baseline values measured while breathing 100% O2 spontaneously, percent changes in velocity were significantly smaller than corresponding percent changes in CBF at increased levels of arterial PCO2 and larger than CBF changes at the lower arterial PCO2. These observed relative changes are consistent with MCA vasodilation at the site of measurement during exposure to progressive hypercapnia and also during extreme hyperventilation hypocapnia.