Makindo Medical Notes.com

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