Talk:Circle of Willis

Diagram
Why on earth is there a early 20th Century diagram illustrating this article? While I appreciate that the science may be very little out of date, and it may be difficult to obtain something which is similarly not bound by copyright, shouldn't something more up-to-date be gracing this page to ensure its respectibility? --84.68.200.235 20:43, 8 January 2006 (UTC)


 * That "old" diagram is anatomically accurate. The human vascular system has not changed in 100 years. What more up-to-date information would you like reflected in the diagram? Alex.tan 22:43, 8 January 2006 (UTC)


 * Not really the point, but... meh. Fine. --84.68.200.235 00:00, 15 January 2006 (UTC)


 * IMO, it's nice to have a consistent look to the anatomical diagrams that grace Wikipedia's pages. If there's a more recent, freely available set of beautifully drawn images of human anatomy, then I'd support their inclusion in WP. But until then, I see many reasons to use Gray's Anatomy and few reasons not to. --David Iberri (talk) 02:19, 4 June 2006 (UTC)


 * I made this new diagram based on Netter and Grays. Hope you enjoy! 201.37.87.187 20:44, 24 January 2007 (UTC)


 * Very nice! Thank you. --Arcadian 21:04, 24 January 2007 (UTC)


 * I took out the image as it looked a bit redundant.
 * Seraphim Whipp 13:39, 22 June 2007 (UTC)

Physiologic significance
If any one of the arteries in the circle become blocked or narrowed (stenosed) or one of the arteries supplying the circle is blocked or narrowed, blood flow from the other blood vessels is usually insufficient to maintain cerebral perfusion.

although there is are anastamosis, it is insufficient to maintain blood flow to the brain.
 * AFAIK, the above assertion is not true in the clinical context. In carotid stenosis the cerebral arterial circle often perserves flow. See the following -- Hendrikse J, Eikelboom BC, van der Grond J. Magnetic resonance angiography of collateral compensation in asymptomatic and symptomatic internal carotid artery stenosis. J Vasc Surg. 2002 Oct;36(4):799-805.  and de Boorder MJ, van der Grond J, van Dongen AJ, Klijn CJ, Jaap Kappelle L, Van Rijk PP, Hendrikse J. Spect measurements of regional cerebral perfusion and carbondioxide reactivity: Correlation with cerebral collaterals in internal carotid artery occlusive disease. J Neurol. 2006 Oct 24; [Epub ahead of print]  .  Please modify if you believe I'm incorrect but provide us with a reference to bolster your case.  I changed the article to reflect that fact that people have measured differences with magnetic resonance.  That said, many people with a carotid artery occulsion are asymptomatic.  Nephron  T|C 23:18, 26 October 2006 (UTC)

quote from haines 2002 "branches of the three cerebral aterties anasomose with each other on the surface of the brain, however if a cereral artery is obstructed by cerebral embolism, these microscopic anasmoses are not capable of providing enough blood for the area of cerebral cortex concerned. consequently cerebral ischemia and infarction occur and an area of necrosis results"


 * The wording was ambiguous. I've changed the wording to clarify that a blockage or stenosis in the section that forms the circle (itself) are of little consequence (if the circle is complete).  It appears you read the section as pertaining to the section of the cerebral vessels distal to the arterial circle.  I agree these blockages/stenoses are significant.  That said, a blockage of, for example, one A1 segment of the anterior cerebral artery that develops over time (due to atherosclerosis) is unlikely to clinical be significant. Also, a block of an ICA is not significant if it develops over time and does not shed a thrombus and cause an ischemic stroke in the process of occluding. Feel free to tweak some more... if you think it needs further clarification. Nephron  T|C 00:19, 31 October 2006 (UTC)

- If someone can add in what is SUPPLIED by the circle of Willis, that would be useful indeed. Just a thought! (Not one I can do much about myself tbh)

I added the supply of the Circle of Willis for you, the cortical and central branches. i only did central as it pertained to the topic, and i dont know where to put the cortical. basically, all i can say about it concerns the ACA, MCA and PCA. [i know MCA isnt a part of the circle]. the ACA goes on to supply a narrow strip of the cortex above the corpus callosum, up to the central sulcus posteriorly, the MCA supplies below the corpus callosum, and the PCA pretty much supplies the remaining bit - of particular importance is the visual cortex. dont forget that there is an overlap, thus it isnt as clear cut as i have stated. i hope i hepled you!

Preservation of blood flow in the face of stenosis/embolus etc
Although the paragraph on blood flow within the circle states that it is 'often' preserved if there is stenosis, I think it should be clearer on limitations.

I refer to the fact that flow can be quite well preserved within the circle but this protective mechanism is only useful for problems on the same side. Flow however, is not well compensated for across the midline.

Anatomy
= = Anatomy: Components = = The Basilar artery is part of the vertebral-basilar system and is not part of the circle of Willis. The vertebral-basilar system, also know as the posterior circulation to the brain includes the vertebral artery, the posterior inferior artery, the basilar artery, and the spinal arteries. The anterior circulation to the brain is supplied by a ring of blood vessels called the circle of Willis which is located at the base of the brain. The circle of Willis is composed of the posterior cerebral arteries, the posterior communicating arteries, the interior and middle cerebral arteries, anterior communicating branches, and the internal carotid arteries. ^ Silvestri, L. A., MSN, RN. (2008). Comprehensive review NCLEX-RN examination, 4th ed., Canada: Saunders --Aplexy (talk) 01:19, 3 April 2012 (UTC)

Commentary removed from main text
The following text has been moved from the main article as it seems to be more appropriately placed here:

"(The author of the above information was wrong, the MIDDLE CEREBRAL arteries are the continuation of the Internal Carotid arteries. Which means he/she is also wrong that the Middle Cerebral arteries DO indeed contribute to the circle. The Anterior Cerebral and Posterior Communicating arteries branch off the Middle Cerebral).

(I'm also is of opinion that middle cerebral artery should not be considered part of circle of Willis. The simple reason being that middle cerebral artery, with direction of blood flow through it, cannot contribute to the blood supply of the circle in case of occlusion in one of arteries of circle. Moreover ICA trifurcates rather than MCA)."

I believe the original text they are commenting on (The posterior communicating artery is given off ... middle cerebral artery does not contribute to the circle.) is accurate as far as I understand the circle of Willis, but I am no expert on the subject.

GadBeebe (talk) 17:05, 5 May 2012 (UTC)