Haemodynamics of the circle of Willis and the leptomeningeal anastomoses: an electromagnetic flowmeter study of intracranial arterial occlusion in the monkey

Ishikawa, Susumu; Handa, Jyoji; Meyer, John Stirling; Huber, Peter M.

doi:10.1136/jnnp.28.2.124

Cited by 29 publications

(7 citation statements)

References 23 publications

(24 reference statements)

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“…13 The response to clamp release involves all collateral pathways such as the leptomeningeal arteries. 12,18,26 It is unlikely that differences in MAP influenced our results since there were no differences during baseline in groups 1 to 3 or during occlusion in groups 1 and 2, and MAP was highest in group 3 during occlusion where FVm was lowest (Tables 2 and 3). If pressure autoregulation had been impaired during carotid artery cross-clamping, the effect of higher MAP would have minimized the differences between groups 1 and 2 compared with group 3.…”

Section: Discussionmentioning

confidence: 75%

Predicting the Effect of Carotid Artery Occlusion During Carotid Endarterectomy

Doblar

Plyushcheva

Jordan

et al. 1998

Stroke

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Background and Purpose-We correlated the mean transcranial Doppler blood flow velocity (FVm) during carotid endarterectomy with the functional collateral pathway(s) documented by angiography. Methods-Three patient groups were established: group 1 was dependent on the anterior communicating artery, group 2 on the anterior communicating artery and ipsilateral posterior communicating artery, and group 3 on the ipsilateral posterior communicating artery. Continuous middle cerebral artery FVm and electroencephalographic monitoring were performed in 45 patients during carotid endarterectomy. Results-Clamped FVm was lowest in group 3 at 17Ϯ9 cm/s versus 36Ϯ16 and 33Ϯ11 cm/s for groups 1 and 2 (PϽ0.01).FVm values in groups 1 and 2 were similar. There was significant cerebral arterial vasodilation in group 3 patients on the basis of a pulsatility index of 0.38Ϯ0.15. The maximum FVm after clamp release was similar among the 3 groups. Normalized blood flow velocity 1 minute before release of the clamp was increased from the minimum flow velocity after clamping only in group 1 and 2 patients. Conclusions-The

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Section: Discussionmentioning

confidence: 75%

Predicting the Effect of Carotid Artery Occlusion During Carotid Endarterectomy

Doblar

Plyushcheva

Jordan

et al. 1998

Stroke

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“…The vertebral artery supplies a few small branches to the cervical muscles. Under physiological circumstances, this extracerebral contribution represents a small proportion of the total internal carotid or vertebral flow (9). When acute hypertension is produced, the relation between intra- cranial and extracranial flow may be altered.…”

Section: Discussionmentioning

confidence: 99%

Autoregulation of Cerebral Blood Flow

Yoshida

Meyer

Sakamoto

et al. 1966

Circulation Research

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Changes in blood flow through the internal carotid, vertebral and external carotid arteries were measured by electromagnetic flowmeters during and after acute hypertension induced by closing a clamp around the thoracic aorta in anesthetized monkeys.The internal carotid and vertebral arterial system showed both rapid and delayed autoregulatory responses to rapid increases in blood pressure; the rapid (primary) responses occurred within seconds, the progressive (delayed) within 3 to 4 minutes. In contrast, the flow response within the external carotid system appeared to be passive. Cervical sympathetic innervation and myogenic reflexes (Bayliss reflex) both appear to play a part in the rapidly occurring (primary) regulation of cerebral blood flow. The mechanism responsible for delayed and progressive (secondary) autoregulation in the cerebral vasculature appeared to be metabolic, since it was predominantly influenced by changes in blood Pco 2 . Changes in intracranial pressure did not seem to be involved in autoregulation. ADDITIONAL KEY WORDS vertebral blood flow carotid blood flow intracranial pressure cerebral vascular resistance baroreceptor denervation• In a previous study, autoregulation of internal carotid artery flow was demonstrated when the blood pressure was reduced by fractional withdrawal of venous blood (1). Cerebral arterial blood flow showed little or no decrease until a critical blood pressure was reached, then a sharp drop in cerebral blood flow accompanied any further fall in blood pressure. Some data from studies in man suggest that there is autoregulation of cerebral blood flow during hypertension. In essential hypertension (2), toxemia of pregnancy with hypertension, and during drug-induced hypertension, cerebral blood flow was within normal limits. These data and the whole question of autoregulation of cerebral blood flow are summarized in Lassen's excellent review and are often quoted to support the concept that autoregulation also exists in man, although effects of age and the level of carbon dioxide tension in arterial blood were not considered (3). We are unaware of quantitative studies of autoregulation of cerebral blood flow during nonpharmacologically induced hypertension, although there are the qualitative observations that pial vessels constrict during elevation of the blood pressure (5-7). The present study was designed to measure blood flow through the major cerebral arteries in the necks of monkeys, by means of electromagnetic flowmeters before and after induction of acute hypertension without the use of drugs. From quantitative data on pressure, flow, and resistance, the existence of autoregulation within the cerebral arterial system was determined and its mechanisms were investigated. 727Methods Twenty-two monkeys (6 Macacus rhesus and 16 Anubis baboons) weighing 3 to 4 kg were used. Results obtained from the two species were not significantly different. Each animal was anesthetized with pentobarbital sodium (initially 35 to 40 mg/kg, intravenously), with supplements g...

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“…This may be due, in part, to the wellrecognized ability of the component parts of the circle of Willis to adjust to asymmetrical inputs in arterial inflow. 29 A fall in resistance on one side of the circle of Willis or its immediate branches is accompanied not only by an increased flow in the ipsilateral carotid artery, but quite possibly also by alterations in arterial inflow pressure that may influence flow in the contralateral carotid artery. In this respect, our results may be analogous to those obtained in other chronically sympathectomized vasculatures.…”

Section: Relationship Between Changes In the Brain Arteriovenous Oxygmentioning

confidence: 99%

The Role of the Peripheral Sympathetic Nervous System in Cerebral Blood Flow Autoregulation

Hernández-Pérez

Raichle

Stone

1975

Stroke

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Abstract:The Role of the Peripheral Sympathetic Nervous System in Cerebral Blood Flow A utoregulation• The effect of chronic, unilateral superior cervical ganglionectomy on cerebral blood flow and blood flow autoregulation to changes in perfusion pressure was examined in seven phencyclidine anesthetized monkeys. Ten to 14 days prior to the experiments Doppler ultrasonic flow transducers were placed on both carotid, arteries after ligation of the external carotid branches and removal of one superior cervical ganglion. Autoregulation was tested by exsanguination and metaraminol infusion with the monkeys inspiring room air, 9% and 12% carbon dioxide in air. Immediately following experimentation the cerebral vessels were examined for the presence of noradrenergic fibers. The results of the study demonstrate that: (1) superior cervical ganglionectomy produces a significant reduction in the noradrenergic innervation of ipsilateral extraparenchymal arteries; (2) the peripheral sympathetic nervous system contributes to overall cerebral vascular resistance primarily by affecting resistance in extraparenchymal arteries; and (3) as a result, it determines the contribution of the extraparenchymal arteries to overall cerebral blood flow autoregulation.

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Haemodynamics of the circle of Willis and the leptomeningeal anastomoses: an electromagnetic flowmeter study of intracranial arterial occlusion in the monkey

Cited by 29 publications

References 23 publications

Predicting the Effect of Carotid Artery Occlusion During Carotid Endarterectomy

Predicting the Effect of Carotid Artery Occlusion During Carotid Endarterectomy

Autoregulation of Cerebral Blood Flow

The Role of the Peripheral Sympathetic Nervous System in Cerebral Blood Flow Autoregulation

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