Circle of Willis | The Common Vein

Uncategorized

Circle of Willis

Ashley Davidoff MD

Definition

The Circle of Willis

The cerebral circulation has a unique system that allows for compensatory flow when any one of the 4 vessels is narrowed or occluded.

This cerebral circulation is centered on the circle of Willis which has two basic systems that feed it; the carotid system (in this case salmon pink) and the vertebro-basilar system (brighter pink). They both feed into the circle of Willis (bright red) via communicating branches. The middle cerebral artery is the vessel that feeds into the COW by providing the anterior communicating artery and the posterior cerebral artery connects via the posterior communicating artery. Conceptually as depicted in this diagram the circle of Willis is the centre of the cerebral circulation and from it blood flows into the anterior (bright green), middle (darker green) and posterior cerebral (maroon) regions.

Branches To and From the Circle of Willis

Structures of the Circle of Willis

The diagram shows the main branches of the blood supply to the brain which includes the carotid and vertebro-basilar systems. These are the vessels that particpate in the formationofthe circle of Willis The carotid system supplies the brain from the internal carotid (salmon pink) ? a branch of the common carotid which arises from the aorta. Its terminal bifuracation into the middle cerebral (dark green) and anterior green (bright green) are shown. The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and travel as a single artery over the upper medulla and the entire pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the vessels contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally and the carotid system provides the anterior communicating arteries via the anterior cerebral artery. code brain

The Circle of Willis Overlaid on a Coronal View of the Brain

The diagram shows the main branches of the blood supply to the brain including the circle of Willis overlaid on coronal MRI image to portray the approximate position of the vessels in the brain. The carotid system supplies the brain from the internal carotid we demonstrate its terminal bifurcation into middle cerebral (dark green) and anterior cerebral (bright green). The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and it travels as a single artery over the upper medulla and the pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.

MRA – Circle of Willis

Centre of the Brain and the Center of the Circulation of the Brain

The MRA (3D TOF) in axial projection demnonstrates circle of Willis

The COW is central to the brain, and central to the cerebral circulation. This concept is well demonstrated in this image

MRA in Axial Projection Using a 3T Magnet

The axial MRA using 3T magnet shows the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.

MRA of the Circle of Willis

The axial MRA using 3T magnet shows a magnified view of the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.

Applied Biology

Anterior Communicating Artery Aneurysm

Aneurysm of the Anterior Communicating Artery

The CT with contrast in axial projection shows an enhancing aneurysm in the region of the circle of Willis that was shown to arise from the anterior communicating artery. See angiogram below

Courtesy Ashley Davidoff MD 16004c01

Anterior Communicating Artery Aneurysm

The angiogram in the A-P projection shows the aneurysm in the region of the circle of Willis. The aneurysm arose from the anterior communicating artery. The middle cerebral artery appears normal. Both anterior cerebral arteries fill suggesting that the anterior communicating artery is patent.

16006.800 Courtesy Ashley Davidoff MD

Anterior Communicating Artery Aneurysm – CTA

The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green.

3D Volume Rendering of the Aneurysm Enabling Identification of the Anterior Communicating Artery

The CTA through the circle of Willis with 3D volume rendering shows an aneurysm in close association with the anterior cerebral arteries (bright green). These views allow the visualization of the anterior communicating artery (red) confirming that the origin of the aneurysm is in fact from the anterior communicating artery. The 3D views allow more definitive evaluation of the origin of the aneurysm

Aneurysm in Contextual Perspective

The CTA through the circle of Willis shows an aneurysm in close association with the anterior cerebral arteries (bright green). It appears to lie between the anterior cerebral arteries and likely represents an aneurysm of the anterior communicating artery. The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green. Image b shows 3D volume rendered anterior and posterior circulation in the context of the base of the skull giving a contextual perspective of the aneurysm.

Aneurysm of the Basilar Artery

Basilar Tip Aneurysm

The axial (a) and coronal (b) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa with the circle of Willis in view shows a basilar tip aneurysm.

Courtesy Philips Medical Systems 92584c

Fusiform Aneurysm of the Basilar Artery

The MIP (left) and 3D volume rendered (right) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa shows a diffuse fusiform aneurysm of the basilar artery.

Courtesy Philips Medical Systems 92415c.8

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Fusiform Aneurysm of the Basilar Artery



The MIP (left) and 3D volume rendered (right) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa shows a diffuse fusiform aneurysm of the basilar artery.
Courtesy Philips Medical Systems 92415c.8




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Fusiform Aneurysm of the Basilar Artery



The MIP (left) and 3D volume rendered (right) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa shows a diffuse fusiform aneurysm of the basilar artery.
Courtesy Philips Medical Systems 92415c.8




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The MIP (left) and 3D volume rendered (right) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa shows a diffuse fusiform aneurysm of the basilar artery.
Courtesy Philips Medical Systems 92415c.8

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The MIP (left) and 3D volume rendered (right) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa shows a diffuse fusiform aneurysm of the basilar artery.
Courtesy Philips Medical Systems 92415c.8

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Basilar Tip Aneurysm



The axial (a) and coronal (b) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa with the circle of Willis in view shows a basilar tip aneurysm.
Courtesy Philips Medical Systems 92584c




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Basilar Tip Aneurysm



The axial (a) and coronal (b) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa with the circle of Willis in view shows a basilar tip aneurysm.
Courtesy Philips Medical Systems 92584c




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The axial (a) and coronal (b) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa with the circle of Willis in view shows a basilar tip aneurysm.
Courtesy Philips Medical Systems 92584c

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The axial (a) and coronal (b) image of the vertebro- basilar circulation looking into the middle and posterior cranial fossa with the circle of Willis in view shows a basilar tip aneurysm.
Courtesy Philips Medical Systems 92584c

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Aneurysm in Contextual Perspective



The CTA through the circle of Willis shows an aneurysm in close association with the anterior cerebral arteries (bright green). It appears to lie between the anterior cerebral arteries and likely represents an aneurysm of the anterior communicating artery. The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green. Image b shows 3D volume rendered anterior and posterior circulation in the context of the base of the skull giving a contextual perspective of the aneurysm.
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c.81




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Aneurysm in Contextual Perspective



The CTA through the circle of Willis shows an aneurysm in close association with the anterior cerebral arteries (bright green). It appears to lie between the anterior cerebral arteries and likely represents an aneurysm of the anterior communicating artery. The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green. Image b shows 3D volume rendered anterior and posterior circulation in the context of the base of the skull giving a contextual perspective of the aneurysm.
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c.81




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The CTA through the circle of Willis shows an aneurysm in close association with the anterior cerebral arteries (bright green). It appears to lie between the anterior cerebral arteries and likely represents an aneurysm of the anterior communicating artery. The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green. Image b shows 3D volume rendered anterior and posterior circulation in the context of the base of the skull giving a contextual perspective of the aneurysm.
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c.81

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The CTA through the circle of Willis shows an aneurysm in close association with the anterior cerebral arteries (bright green). It appears to lie between the anterior cerebral arteries and likely represents an aneurysm of the anterior communicating artery. The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green. Image b shows 3D volume rendered anterior and posterior circulation in the context of the base of the skull giving a contextual perspective of the aneurysm.
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c.81

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Aneurysm in Contextual Perspective
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Aneurysm in Contextual Perspective
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3D Volume Rendering of the Aneurysm Enabling Identification of the Anterior Communicating Artery



The CTA through the circle of Willis with 3D volume rendering shows an aneurysm in close association with the anterior cerebral arteries (bright green). These views allow the visualization of the anterior communicating artery (red) confirming that the origin of the aneurysm is in fact from the anterior communicating artery. The 3D views allow more definitive evaluation of the origin of the aneurysm
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c04.8s




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3D Volume Rendering of the Aneurysm Enabling Identification of the Anterior Communicating Artery



The CTA through the circle of Willis with 3D volume rendering shows an aneurysm in close association with the anterior cerebral arteries (bright green). These views allow the visualization of the anterior communicating artery (red) confirming that the origin of the aneurysm is in fact from the anterior communicating artery. The 3D views allow more definitive evaluation of the origin of the aneurysm
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c04.8s




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The CTA through the circle of Willis with 3D volume rendering shows an aneurysm in close association with the anterior cerebral arteries (bright green). These views allow the visualization of the anterior communicating artery (red) confirming that the origin of the aneurysm is in fact from the anterior communicating artery. The 3D views allow more definitive evaluation of the origin of the aneurysm
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c04.8s

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The CTA through the circle of Willis with 3D volume rendering shows an aneurysm in close association with the anterior cerebral arteries (bright green). These views allow the visualization of the anterior communicating artery (red) confirming that the origin of the aneurysm is in fact from the anterior communicating artery. The 3D views allow more definitive evaluation of the origin of the aneurysm
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c04.8s

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3D Volume Rendering of the Aneurysm Enabling Identification of the Anterior Communicating Artery
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3D Volume Rendering of the Aneurysm Enabling Identification of the Anterior Communicating Artery
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Anterior Communicating Artery Aneurysm – CTA



The CTA through the circle of Willis shows an aneurysm in close association with the anterior cerebral arteries (bright green).  It appears to lie between the anterior cerebral arteries and likely represents an aneurysm of the anterior communicating artery.
The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green.
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c01b8




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Anterior Communicating Artery Aneurysm – CTA



The CTA through the circle of Willis shows an aneurysm in close association with the anterior cerebral arteries (bright green).  It appears to lie between the anterior cerebral arteries and likely represents an aneurysm of the anterior communicating artery.
The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green.
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c01b8




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The CTA through the circle of Willis shows an aneurysm in close association with the anterior cerebral arteries (bright green).  It appears to lie between the anterior cerebral arteries and likely represents an aneurysm of the anterior communicating artery.
The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green.
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c01b8

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The CTA through the circle of Willis shows an aneurysm in close association with the anterior cerebral arteries (bright green).  It appears to lie between the anterior cerebral arteries and likely represents an aneurysm of the anterior communicating artery.
The distal internal carotid is seen in salmon pink while the middle cerebral artery is overlaid in dark green.
Image courtesy Philips medical Systems Image rendering Ashley Davidoff MD Copyright 2010 92577c01b8

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Anterior Communicating Artery Aneurysm – CTA
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Anterior Communicating Artery Aneurysm – CTA
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Anterior Communicating Artery Aneurysm



The angiogram in the A-P projection shows the aneurysm in the region of the circle of Willis.  The aneurysm arose from the anterior communicating artery.  The middle cerebral artery appears normal.  Both anterior cerebral arteries fill suggesting that the anterior communicating artery is patent.
16006.800 Courtesy Ashley Davidoff MD




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Anterior Communicating Artery Aneurysm



The angiogram in the A-P projection shows the aneurysm in the region of the circle of Willis.  The aneurysm arose from the anterior communicating artery.  The middle cerebral artery appears normal.  Both anterior cerebral arteries fill suggesting that the anterior communicating artery is patent.
16006.800 Courtesy Ashley Davidoff MD




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The angiogram in the A-P projection shows the aneurysm in the region of the circle of Willis.  The aneurysm arose from the anterior communicating artery.  The middle cerebral artery appears normal.  Both anterior cerebral arteries fill suggesting that the anterior communicating artery is patent.
16006.800 Courtesy Ashley Davidoff MD

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The angiogram in the A-P projection shows the aneurysm in the region of the circle of Willis.  The aneurysm arose from the anterior communicating artery.  The middle cerebral artery appears normal.  Both anterior cerebral arteries fill suggesting that the anterior communicating artery is patent.
16006.800 Courtesy Ashley Davidoff MD

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Anterior Communicating Artery Aneurysm
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Aneurysm of the Anterior Communicating Artery



The CT with contrast in axial projection shows an enhancing aneurysm in the region of the circle of Willis that was shown to arise from the anterior communicating artery.  See angiogram below
Courtesy Ashley Davidoff MD 16004c01




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Aneurysm of the Anterior Communicating Artery



The CT with contrast in axial projection shows an enhancing aneurysm in the region of the circle of Willis that was shown to arise from the anterior communicating artery.  See angiogram below
Courtesy Ashley Davidoff MD 16004c01




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The CT with contrast in axial projection shows an enhancing aneurysm in the region of the circle of Willis that was shown to arise from the anterior communicating artery.  See angiogram below
Courtesy Ashley Davidoff MD 16004c01

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The CT with contrast in axial projection shows an enhancing aneurysm in the region of the circle of Willis that was shown to arise from the anterior communicating artery.  See angiogram below
Courtesy Ashley Davidoff MD 16004c01

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Aneurysm of the Anterior Communicating Artery
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MRA of the Circle of Willis



The axial MRA using 3T magnet shows a magnified view of the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Image Courtesy Philips Medical Systems Image Rendered Ashley Davidoff MD Copyright 2010 All rights reserved 92550c02.8




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MRA of the Circle of Willis



The axial MRA using 3T magnet shows a magnified view of the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Image Courtesy Philips Medical Systems Image Rendered Ashley Davidoff MD Copyright 2010 All rights reserved 92550c02.8




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The axial MRA using 3T magnet shows a magnified view of the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Image Courtesy Philips Medical Systems Image Rendered Ashley Davidoff MD Copyright 2010 All rights reserved 92550c02.8

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The axial MRA using 3T magnet shows a magnified view of the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Image Courtesy Philips Medical Systems Image Rendered Ashley Davidoff MD Copyright 2010 All rights reserved 92550c02.8

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MRA of the Circle of Willis
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MRA in Axial Projection Using a 3T Magnet



The axial MRA using 3T magnet shows the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Image Courtesy Philips Medical Systems Image Rendered Ashley Davidoff MD Copyright 2010 All rights reserved 92550c01.8s




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MRA in Axial Projection Using a 3T Magnet



The axial MRA using 3T magnet shows the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Image Courtesy Philips Medical Systems Image Rendered Ashley Davidoff MD Copyright 2010 All rights reserved 92550c01.8s




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The axial MRA using 3T magnet shows the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Image Courtesy Philips Medical Systems Image Rendered Ashley Davidoff MD Copyright 2010 All rights reserved 92550c01.8s

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The axial MRA using 3T magnet shows the circle of Willis overlaid in color to reflect the component vessels. The supraclinoid portion of the internal carotid (salmon pink) divides into the middle cerebral (MCA dark green) and anterior cerebral (ACA bright green). There is a tiny anterior communicating artery (bright red) that runs between the two anterior cerebrals. The basilar artery (bright pink) gives rise to the posterior cerebral (PCA maroon) and superior cerebellar arteries (white) carotid system. The posterior cerebral artery gives rise to the posterior communicating artery which plugs into the region of the origins of the MCA and ACA. Note the left posterior communicating artery is relatively small which is a normal variant. Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Image Courtesy Philips Medical Systems Image Rendered Ashley Davidoff MD Copyright 2010 All rights reserved 92550c01.8s

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MRA in Axial Projection Using a 3T Magnet
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MRA – Circle of Willis
Centre of the Brain and the Center of the Circulation of the Brain



The MRA (3D TOF)  in axial projection demnonstrates circle of Willis
The COW is central to the brain, and central to the cerebral circulation.  This concept is well demonstrated in this image
46353 Courtesy Ashley Davidoff MD Copyright 2010




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MRA – Circle of Willis
Centre of the Brain and the Center of the Circulation of the Brain



The MRA (3D TOF)  in axial projection demnonstrates circle of Willis
The COW is central to the brain, and central to the cerebral circulation.  This concept is well demonstrated in this image
46353 Courtesy Ashley Davidoff MD Copyright 2010




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The MRA (3D TOF)  in axial projection demnonstrates circle of Willis
The COW is central to the brain, and central to the cerebral circulation.  This concept is well demonstrated in this image
46353 Courtesy Ashley Davidoff MD Copyright 2010

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The MRA (3D TOF)  in axial projection demnonstrates circle of Willis
The COW is central to the brain, and central to the cerebral circulation.  This concept is well demonstrated in this image
46353 Courtesy Ashley Davidoff MD Copyright 2010

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Centre of the Brain and the Center of the Circulation of the Brain
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Centre of the Brain and the Center of the Circulation of the Brain
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The Circle of Willis Overlaid on a Coronal View of the Brain



The diagram shows the main branches of the blood supply to the brain including the circle of Willis overlaid on coronal MRI image to portray the approximate position of the vessels in the brain. The carotid system supplies the brain from the internal carotid we demonstrate its terminal bifurcation into middle cerebral (dark green) and anterior cerebral (bright green). The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and it travels as a single artery over the upper medulla and the pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Courtesy Ashley Davidoff MD Copyright 2010 All rights reserved 89721c06b.8sg04.8s




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The Circle of Willis Overlaid on a Coronal View of the Brain



The diagram shows the main branches of the blood supply to the brain including the circle of Willis overlaid on coronal MRI image to portray the approximate position of the vessels in the brain. The carotid system supplies the brain from the internal carotid we demonstrate its terminal bifurcation into middle cerebral (dark green) and anterior cerebral (bright green). The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and it travels as a single artery over the upper medulla and the pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Courtesy Ashley Davidoff MD Copyright 2010 All rights reserved 89721c06b.8sg04.8s




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The diagram shows the main branches of the blood supply to the brain including the circle of Willis overlaid on coronal MRI image to portray the approximate position of the vessels in the brain. The carotid system supplies the brain from the internal carotid we demonstrate its terminal bifurcation into middle cerebral (dark green) and anterior cerebral (bright green). The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and it travels as a single artery over the upper medulla and the pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Courtesy Ashley Davidoff MD Copyright 2010 All rights reserved 89721c06b.8sg04.8s

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The diagram shows the main branches of the blood supply to the brain including the circle of Willis overlaid on coronal MRI image to portray the approximate position of the vessels in the brain. The carotid system supplies the brain from the internal carotid we demonstrate its terminal bifurcation into middle cerebral (dark green) and anterior cerebral (bright green). The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and it travels as a single artery over the upper medulla and the pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the carotid and vertebro-basilar systems contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally from the posterior cerebral and the carotid system provides the anterior communicating arteries via the anterior cerebral arteries.
Courtesy Ashley Davidoff MD Copyright 2010 All rights reserved 89721c06b.8sg04.8s

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The Circle of Willis Overlaid on a Coronal View of the Brain
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Structures of the Circle of Willis



The diagram shows the main branches of the blood supply to the brain which includes the carotid and vertebro-basilar systems. These are the vessels that particpate in the formationofthe circle of Willis The carotid system supplies the brain from the internal carotid (salmon pink) ? a branch of the common carotid which arises from the aorta. Its terminal bifuracation into the middle cerebral (dark green) and anterior green (bright green) are shown. The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and travel as a single artery over the upper medulla and the entire pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the vessels contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally and the carotid system provides the anterior communicating arteries via the anterior cerebral artery. code brain
Courtesy Ashley Davidoff MD Copyright 2010 All rights reserved 97194b13g04L01.91s




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Structures of the Circle of Willis



The diagram shows the main branches of the blood supply to the brain which includes the carotid and vertebro-basilar systems. These are the vessels that particpate in the formationofthe circle of Willis The carotid system supplies the brain from the internal carotid (salmon pink) ? a branch of the common carotid which arises from the aorta. Its terminal bifuracation into the middle cerebral (dark green) and anterior green (bright green) are shown. The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and travel as a single artery over the upper medulla and the entire pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the vessels contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally and the carotid system provides the anterior communicating arteries via the anterior cerebral artery. code brain
Courtesy Ashley Davidoff MD Copyright 2010 All rights reserved 97194b13g04L01.91s




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The diagram shows the main branches of the blood supply to the brain which includes the carotid and vertebro-basilar systems. These are the vessels that particpate in the formationofthe circle of Willis The carotid system supplies the brain from the internal carotid (salmon pink) ? a branch of the common carotid which arises from the aorta. Its terminal bifuracation into the middle cerebral (dark green) and anterior green (bright green) are shown. The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and travel as a single artery over the upper medulla and the entire pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the vessels contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally and the carotid system provides the anterior communicating arteries via the anterior cerebral artery. code brain
Courtesy Ashley Davidoff MD Copyright 2010 All rights reserved 97194b13g04L01.91s

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The diagram shows the main branches of the blood supply to the brain which includes the carotid and vertebro-basilar systems. These are the vessels that particpate in the formationofthe circle of Willis The carotid system supplies the brain from the internal carotid (salmon pink) ? a branch of the common carotid which arises from the aorta. Its terminal bifuracation into the middle cerebral (dark green) and anterior green (bright green) are shown. The anterior communicating artery runs between the two anterior cerebrals (bright red) The basilar artery (pink) is formed by the two vertebral arteries and travel as a single artery over the upper medulla and the entire pons. Its terminal branch is the posterior cerebral artery (maroon). Each of the vessels contributes to the circle of Willis through communicating arteries. The vertebro-basilar system provides the posterior communicating arteries bilaterally and the carotid system provides the anterior communicating arteries via the anterior cerebral artery. code brain
Courtesy Ashley Davidoff MD Copyright 2010 All rights reserved 97194b13g04L01.91s

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Structures of the Circle of Willis
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Branches To and From the Circle of Willis



This cerebral circulation is centered on the circle of Willis which has two basic systems that feed it; the carotid system (in this case salmon pink) and the vertebro-basilar system (brighter pink). They both feed into the circle of Willis (bright red) via communicating branches. The middle cerebral artery is the vessel that feeds into the COW by providing the anterior communicating artery and the posterior cerebral artery  connects via the posterior communicating artery. Conceptually as depicted in this diagram the circle of Willis is the centre of the cerebral circulation and from it blood flows into the anterior (bright green), middle (darker green) and posterior cerebral (maroon) regions.
Image Courtesy Ashley Davidoff MD Copyright 2010 97194b16b.8s




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Branches To and From the Circle of Willis



This cerebral circulation is centered on the circle of Willis which has two basic systems that feed it; the carotid system (in this case salmon pink) and the vertebro-basilar system (brighter pink). They both feed into the circle of Willis (bright red) via communicating branches. The middle cerebral artery is the vessel that feeds into the COW by providing the anterior communicating artery and the posterior cerebral artery  connects via the posterior communicating artery. Conceptually as depicted in this diagram the circle of Willis is the centre of the cerebral circulation and from it blood flows into the anterior (bright green), middle (darker green) and posterior cerebral (maroon) regions.
Image Courtesy Ashley Davidoff MD Copyright 2010 97194b16b.8s




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This cerebral circulation is centered on the circle of Willis which has two basic systems that feed it; the carotid system (in this case salmon pink) and the vertebro-basilar system (brighter pink). They both feed into the circle of Willis (bright red) via communicating branches. The middle cerebral artery is the vessel that feeds into the COW by providing the anterior communicating artery and the posterior cerebral artery  connects via the posterior communicating artery. Conceptually as depicted in this diagram the circle of Willis is the centre of the cerebral circulation and from it blood flows into the anterior (bright green), middle (darker green) and posterior cerebral (maroon) regions.
Image Courtesy Ashley Davidoff MD Copyright 2010 97194b16b.8s

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This cerebral circulation is centered on the circle of Willis which has two basic systems that feed it; the carotid system (in this case salmon pink) and the vertebro-basilar system (brighter pink). They both feed into the circle of Willis (bright red) via communicating branches. The middle cerebral artery is the vessel that feeds into the COW by providing the anterior communicating artery and the posterior cerebral artery  connects via the posterior communicating artery. Conceptually as depicted in this diagram the circle of Willis is the centre of the cerebral circulation and from it blood flows into the anterior (bright green), middle (darker green) and posterior cerebral (maroon) regions.
Image Courtesy Ashley Davidoff MD Copyright 2010 97194b16b.8s

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The Circle of Willis



The cerebral circulation has a unique system that allows for compensatory flow when any one of the 4 vessels is narrowed or occluded.
This cerebral circulation is centered on the circle of Willis which has two basic systems that feed it; the carotid system (in this case salmon pink) and the vertebro-basilar system (brighter pink). They both feed into the circle of Willis (bright red) via communicating branches. The middle cerebral artery is the vessel that feeds into the COW by providing the anterior communicating artery and the posterior cerebral artery  connects via the posterior communicating artery. Conceptually as depicted in this diagram the circle of Willis is the centre of the cerebral circulation and from it blood flows into the anterior (bright green), middle (darker green) and posterior cerebral (maroon) regions.
Image Courtesy Ashley Davidoff MD Copyright 2010 97194b09.8s




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The Circle of Willis



The cerebral circulation has a unique system that allows for compensatory flow when any one of the 4 vessels is narrowed or occluded.
This cerebral circulation is centered on the circle of Willis which has two basic systems that feed it; the carotid system (in this case salmon pink) and the vertebro-basilar system (brighter pink). They both feed into the circle of Willis (bright red) via communicating branches. The middle cerebral artery is the vessel that feeds into the COW by providing the anterior communicating artery and the posterior cerebral artery  connects via the posterior communicating artery. Conceptually as depicted in this diagram the circle of Willis is the centre of the cerebral circulation and from it blood flows into the anterior (bright green), middle (darker green) and posterior cerebral (maroon) regions.
Image Courtesy Ashley Davidoff MD Copyright 2010 97194b09.8s




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The cerebral circulation has a unique system that allows for compensatory flow when any one of the 4 vessels is narrowed or occluded.
This cerebral circulation is centered on the circle of Willis which has two basic systems that feed it; the carotid system (in this case salmon pink) and the vertebro-basilar system (brighter pink). They both feed into the circle of Willis (bright red) via communicating branches. The middle cerebral artery is the vessel that feeds into the COW by providing the anterior communicating artery and the posterior cerebral artery  connects via the posterior communicating artery. Conceptually as depicted in this diagram the circle of Willis is the centre of the cerebral circulation and from it blood flows into the anterior (bright green), middle (darker green) and posterior cerebral (maroon) regions.
Image Courtesy Ashley Davidoff MD Copyright 2010 97194b09.8s

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The cerebral circulation has a unique system that allows for compensatory flow when any one of the 4 vessels is narrowed or occluded.
This cerebral circulation is centered on the circle of Willis which has two basic systems that feed it; the carotid system (in this case salmon pink) and the vertebro-basilar system (brighter pink). They both feed into the circle of Willis (bright red) via communicating branches. The middle cerebral artery is the vessel that feeds into the COW by providing the anterior communicating artery and the posterior cerebral artery  connects via the posterior communicating artery. Conceptually as depicted in this diagram the circle of Willis is the centre of the cerebral circulation and from it blood flows into the anterior (bright green), middle (darker green) and posterior cerebral (maroon) regions.
Image Courtesy Ashley Davidoff MD Copyright 2010 97194b09.8s

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TCV