Disease relevance of Circle of Willis

• Presence of neuropeptide Y in human circle of Willis and its possible role in cerebral vasospasm [1].
• The CO2 response was normal in patients with angiographic signs of circle of Willis collateral flow and without significant contralateral carotid stenosis, whereas it was impaired in patients with a retrograde ophthalmic flow or collateral flow via the circle of Willis and contralateral carotid stenosis greater than or equal to 50% [2].
• Two weeks after bilateral removal of the sphenopalatine ganglion or sectioning of the structures in the ethmoidal foramen, VIP fibers in the anterior part of the circle of Willis completely disappeared [3].
• CONCLUSION: Large asymmetries in volume flow between the right and left ICAs or decreased volume flow in the BA is not necessarily caused by vascular disease but may be caused by variations in the anatomy of the circle of Willis [4].
• Multiple areas of stenosis and occlusion in all branches of the circle of Willis, and hypertrophy of collateral perforating vessels at the base of the brain in a "puff of smoke" appearance typical of moyamoya disease were seen on cerebral angiogram 5 months before the patient died [5].

High impact information on Circle of Willis

• High resolution computed tomography or magnetic resonance imaging of the head with 3-mm sections through the circle of Willis was obtained in 96 patients with autosomal dominant polycystic kidney disease [6].
• In addition, there was decreased eNOS and increased iNOS protein and mRNA in common carotid artery, circle of Willis, and brain microvessels of SHR when compared with WKY rats [7].
• Linkage of familial moyamoya disease (spontaneous occlusion of the circle of Willis) to chromosome 17q25 [8].
• This may result in subtle differences in MMP-9 activity within the circle of Willis, leading to increased susceptibility to ICA formation [9].
• METHODS: In 75 healthy volunteers (mean age, 45.3+/-17.0 years; age range, 17 to 77 years), the circle of Willis and the venous midline vasculature were insonated through a lateral and paramedian frontal bone window [10].

Biological context of Circle of Willis

• Characterization of melatonin receptors and signal transduction system in rat arteries forming the circle of Willis [11].
• The carbon monoxide images, in addition to visualizing the large vessels, clearly show the blood volumes of the cortex, the Sylvian fissure, and the circle of Willis [12].
• Krypton-81m single photon emission tomography and the collateral circulation in carotid occlusion: the role of the circle of Willis and leptomeningeal anastomosis [13].
• The Research Committee on Spontaneous Occlusion of the Circle of Willis (Moyamoya disease) of the Ministry of Health and Welfare, Japan, has studied the pathogenesis, epidemiology, clinical investigations, and treatment of the disease since 1977 [14].

Anatomical context of Circle of Willis

• SP fibres were more numerous in pial vessels belonging to the rostral parts of the circle of Willis as compared to more caudally located blood vessels [15].
• The levels of noradrenaline, neuropeptide Y, 5-hydroxytryptamine, and substance P were measured and compared between the large arteries of the circle of Willis and the small cerebral vessels of the pia mater in the rat, rabbit, cat, and monkey [16].
• Substance P immunoreactivity was most abundant in cerebral arteries from the rostral portion of the circle of Willis [17].
• CONCLUSIONS: A comparison with previously published data obtained in isolated middle cerebral and basilar arteries showed that potassium channel openers of the benzopyrane and cyanoguanidine type are much more potent in pial arteries than in peripheral arteries in situ or in isolated arteries of the circle of Willis and of peripheral vascular beds [18].
• RESULTS: This system allowed depiction of small vessels (diameter < 50-100 microns) of the heart (penetrating transmural artery), brain (perforating arteries that arise directly in the circle of Willis), and intestinal organs (vasa recta and their submucosal communications) and of small branches (down to the fifth order) of the pancreatic duct [19].

Associations of Circle of Willis with chemical compounds

• 5-Hydroxytryptamine concentrations in rats, cats, and rabbits were significantly greater in the small pial vessels, although measurable concentrations existed in the circle of Willis [16].
• CONCLUSIONS: These results suggest that the arteries composing the circle of Willis at the base of the brain are more sensitive to nitric oxide release induced by vasopressin compared with other intracranial and extracranial arteries [20].
• CONCLUSIONS: C57Black/6 mice exhibit enhanced susceptibility to global cerebral ischemic injury, an incompletely formed circle of Willis, and augmented pial vessel dilation to ACh compared with SV-129 mice [21].
• The aims of this study were to characterize the melatonin receptors in rat brain arteries forming the circle of Willis [11].
• Two days after bilateral removal of the superior and middle cervical ganglia of 7-week-old rats, noradrenaline-containing nerves could not be detected along any of the arteries of the rat circle of Willis or of the iris, but 18-32% of neuropeptide Y-like immunoreactive nerves remained [22].

Gene context of Circle of Willis

• Immunocytochemistry and radioimmunoassay of blood vessels from the circle of Willis did not show significant differences in NPY- and VIP-like immunoreactivity 2 days post SAH as compared to control vessels [23].
• The susceptibility to aneurysm formation in the cerebral arteries of the circle of Willis was compared in female heterozygous 'Blotchy' and control mice subjected to unilateral carotid artery ligation either alone or associated with hypertension [24].
• There were no gross differences in the circle of Willis between GFAP-null and wild type mice [25].
• BACKGROUND AND PURPOSE: We examined the presence of systemic etiologic factors causing vascular changes in so-called "spontaneous occlusion of the circle of Willis" (cerebrovascular moyamoya disease) to determine whether extracranial, as well as intracranial, vessels are involved in this disease [26].
• Evaluation of cross-circulation through circle of Willis using an ultrasonic Doppler technique. Part I. Comparison between blood flow velocity by ultrasonic Doppler flowmetry and angiogram [27].

Analytical, diagnostic and therapeutic context of Circle of Willis

• In addition, an HPLC study was performed to quantify the actual amounts of 5-HT and noradrenaline present in circle of Willis vessels at 3 h post-SAH [28].
• The effects of unilateral superior cervical ganglionectomy on 5-HT-containing and noradrenergic nerves to the arteries of the circle of Willis were different [29].
• We present the results of eight patients who underwent MR angiography of the cervical carotids and circle of Willis, MR imaging of the brain and dynamic gadolinium MR perfusion studies before and after the injection of the carbonic anhydrase inhibitor acetazolamide [30].
• One of them represents a fetal circle of Willis (crown-rump length, or CRL, 17 cm), the other one is adult circle from a male cadaver 65 years of age [31].
• 1. Localization and pharmacological properties of the vasoactive intestinal polypeptide (VIP) receptors in rat circle of Willis arteries and in the arteries of pial-arachnoid membrane were studied using light microscope autoradiography combined with radioreceptor binding techniques [32].

References