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

The Two Systems – Carotid and Vertebrobasilar

There are two systems that supply the brain with blood. The MRA depicted in the axial, sagittal, and coronal views depict the general areas covered by the two systems. The carotid system gives rise to the anterior and middle cerebral arteries which cover the green area. The vertebro-basilar system, mostly through the posterior cerebral artery and cerebellar arteries, supply the maroon portion.

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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

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

Map of the ACA and MCA

The MRA in sagittal (upper images) and coronal projections (lower images) provide a map of the first and second order branches of the anterior and middle cerebral vessels.

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The Intracranial Circulation Derfinition of the Smaller Vessels

Digital Angiogram of the Internal Carotid in the Lateral Projection

The lateral digital angiogram of a selective internal carotid artery injection shows f the anterior and middle circulation supplied by the internal carotid artery. It is difficult to discern the origins of the anterior cerebral artery (ACA) and middle cerebral artery (MCA) in this projection. The study does however demonstrate the more distal portions of the ACA and MCA, and the smaller peripheral vessels. More specifically the loops of the distal middle cerebral arteries in the Sylvian fissure are well recognized. The intracranial portion of the internal carotid is well seen as well.

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Anterior and Middle Cerebral Artery Distributions from a Lateral Perspective

The anterior and middle cerebral circulation is demonstrated on the overlaid lateral angiogram of a selective internal carotid artery injection. The anterior cerebral circulation is overlaid in bright green and the middle cerebral circulation in dark green. The distal internal carotid artery and the ophthalmic artery (red) are shown (red) The ophthalmic artery is the smaller anterior horizontal vessel coursing to the orbit originates at the junction of the cavernous and supraclinoid segment.

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The Intracranial Circulation Derfinition of the Smaller Vessels

Digital Angiogram of the Internal Carotid in the A-P Projection

The intracerebral angiogram shows the normal appearance in the A-P projection of the anterior and middle cerebral territory. The supraclinoid portion of the terminal portion of the internal carotid artery divides into the anterior cerebral artery (AC – bright green) that courses medially and the middle cerebral artery (MCA- dark green) that branches laterally.

The study does also demonstrates the more distal portions of the ACA and MCA, and the smaller peripheral vessels. More specifically the loops of the distal middle cerebral arteries in the Sylvian fissure are well recognized. The supraclinoid portion of the internal carotid is overlaid in salmon pink.

Image Courtesy of Ram Chavalli MD 49422g01

Peripheral Branches of the Middle Cerebral Artery

This series of axial images is from a CTA of the cerebral circulation and shows the middle cerebral artery at its origin (a) and its major branching pattern exemplified by the vessels branching in the Sylvian fissure to the frontal, temporal, and parietal lobes. The basal ganglia are fed by the middle cerebral vessels but they are relatively hypovascular compared to the cortex. The images proceed from inferior(a) to superior(f).

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Middle Cerebral Arteries Highlighted

This series of axial images is from a CTA of the cerebral circulation and shows the middle cerebral artery at its origin (a) and its major branching pattern exemplified by the vessels branching in the Sylvian fissure to the frontal, temporal, and parietal lobes. The branches of the MCA have been overlaid in red. The basal ganglia are fed by the middle cerebral vessels but they are relatively hypovascular compared to the cortex. The images proceed from inferior(a) to superior(f).

Image Courtesy Ashley Davidoff MD Copyright 2010 76500c03.8s

Regions Perfused by the MCA

This series of axial images is from a CTA of the cerebral circulation and shows the middle cerebral artery at its origin (a) and its major branching pattern exemplified by the vessels branching in the Sylvian fissure to the frontal, temporal, and parietal lobes. The branches of the MCA have been overlaid in red, and the approximate territory perfused by these vessels overlaid in green. The basal ganglia are fed by the middle cerebral vessels but they are relatively hypovascular compared to the cortex.

Image Courtesy Ashley Davidoff MD Copyright 2010 76500c04b.8s

Perfusion territory of Anterior Middle and Posterior Cerebral Arteries

This series of axial images is from a CTA of the cerebral circulation and shows the middle cerebral artery at its origin and its major branching pattern exemplified by the vessels branching in the Sylvian fissure to the frontal, temporal, and parietal lobes. The branches of the MCA have been overlaid in red, and the approximate territory perfused by these vessels overlaid in dark green. The anterior cerebrl regions are overlaid in bright green and the regions of the posterior cerebral artery overlaid in salmon pink. The basal ganglia and thalamus are outline in orange and they receive most of their blood supply from the middle cerebral artery, but they are relatively hypovascular compared to the cortex.

Image Courtesy Ashley Davidoff MD Copyright 2010 76500c02b.8s

Right MCA Infarct – DWI

The diffusion weighted MRI in axial projection shows a high intensity region in the right parietal and right temporal region revealing an acute infarction poattern in these regions reflecting right middle cerebral artery territory. Note that the basal ganglia have been spared, but the insula and operculum are involved.

Courtesy Ashley Davidoff MD Copyright 2010 71275c01.800 71275c01c03

Chronic Frontoparietal Infarction

This 60 year old male has the classical appearance of hypertonia of his upper limb and hand muscles as shown in this CT volume rendered image. The hand and elbow are flexed as a result of involvement on the contralateral motor cortex. The CT images show a hypodense region in the right frontoparietal region associated with encphalomalacia and ex vacuo changes in the right frontal horn consistent with a chronic stroke.

Courtesy Ashley Davidoff MD 48641c01.800

Left MCA Aneurysm – MRA

The MRA performed on a 3T magnet shows an aneurysm of the left middle cerebral artery (MCA) demonstrated in the global frontal view (left image) by a large white arrow, and in the magnified view of the MCA (yellow arrow)

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Right MCA Aneurysm and Ectasia of MCA’s Bilaterally

CT – Volume Rendering

The 3 D volume rendered image of the cerebral circulation looking into the middle and posterior cranial fossa with the circle of Willis in view shows a right sided middle cerebral artery aneurysm. Both middle cerebral arteries appear ectatic as well.

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MRA of LMCA stenosis

The MRA performed on a 3T magnet shows a stenosis (arrow) of the left middle cerebral artery (MCA) demonstrated in the global frontal view (left image) , and in the magnified view of the MCA

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MCA AVM

The MRA with 2d TOF in the coronal projection (a) and in the axial projection(b). It shows an arteriovenous malformation (AVM) in the right temperoparietal region fed by an enlarged middle cerebral artery (red arrow) and draining into a large

Courtesy Philips Medical Systems 92465c01L.8