Circle of Willis and other branches
Internal Carotid artery
- Cervical segment - within the neck. Associated with sympathetic supply.
- Petrous segment - enters skull via foramen lacerum and runs forwards
- Cavernous segment - enters the cavernous sinus and runs with th VIth
nerve and gives off branch superior hypophysial to the posterior
pituitary
- Supraclinoid segment - pierces dura and then splits into
anterior cerebral artery and middle cerebral
artery
Ophthalmic artery
- Central artery to retina runs forward to supply the eye and scalp
around the eye as well as frontal and ethmoidal sinuses.
- Maxillary artery anastomoses provide some collateral flow if
proximal occlusion
Posterior communicating artery
- Joins anterior and posterior circulations
- Closely associated with IIIrd nerve and provides some vascular
support
- Also supplies thalamus, hypothalamus and tail of
caudate
Anterior choroidal artery
Passes posteriorly with branches to supply
- Posterior limb of the internal capsule
- choroid plexus of the lateral ventricle
- optic tract and lateral geniculate body (hemianopia)
- area of midbrain and globus pallidus and substantia
nigra
Anterior cerebral artery
- (Medial surface of
cerebrum. Arches around corpus callosum)
A1 Segment
- From the bifurcation of the internal
carotid to the anterior communicating artery. Branches include
- Medial lenticulostriate artery (contributes to
anterior limb of the internal capsule and basal ganglia)
- Anterior communicating artery connects both ACA
and is a common site of aneurysms
- recurrent artery of heubner supplies head of caudate
and anteroinferior internal capsule
- Pericallosal branch - is the continuation of A1
supplying medial surface of cerebral cortex and corpus callosum. Branches are orbitofrontal, polar frontal and callosomarginal
Middle cerebral artery
- M1 segment from the bifurcation of the internal carotid
passes laterally to the surface of the insula where it bifurcates.
- Occlusion here results in massive infarction depending on collateral
supply.
- A clot may be seen in the artery "the hyperdense MCA sign" on Non
contrast CT.
Lateral lenticulostriate arteries (penetrating
vessels)
- Branch of at right angles from the main MCA to supply the Globus pallidus and putamen,
posterior limb of the internal capsule, head and tail of caudate, thalamus
and Meyer's loop which includes some of the optic radiations can be
caught
- Arterial occlusion typically may cause lacunar type strokes and
vulnerable to lipohyalinosis and occlusion
M2 segment within the sylvian fissure and branch.
- A clot here may result in a "dot" sign on CT. The artery branches into
M3 segments Upper division
- prefrontal (frontal cortex)
- precentral (primary motor and associated areas)
- central (pre/post central gyri)
- post central (primary sensory area)
- parietal (posterior parietal)
M3 segments Lower division
- middle temporal (mid temporal cortex)
- temporal/occipital (temporal and occipital cortex)
- angular (angular and associated gyri)
- R/L Subclavian
artery
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