C4 segment (after ICA exit cavernous sinus)
P-com, Ant choroid artery
1. Ophthalamic segment (before P-com, blue color)
1-4 perforating artery
infundibulum(stalk, called Superior hypophyseal artery), optic chiasm
less common: optic nerve, premamilary portion of floor of 3rd ventricle
2. Communicating segment (p-com and ant choroid artery)
occasionally 1-3 perforating branch
optic tract, premamilary portion of floor of 3rd ventricle, optic chiasm, infundibulum
3. Choroidal segment (a choroid a to bifurcation)
~4 perforating branch
anterior perforating substance, optic tract and uncus
Superior hypophyseal artery: 1-4 branch to stalk, gland, optic nerve, chiasm, 3rd ventricle floor
Infundibular artery: from p-com to infundibulum
Superior hypophyseal artery and Infundibular artery: circuminfundibulum anastomosis give ascending to (tuber cinereum, median eminence, inferior surface of chiasm) and decending branch to (stalk and anterior lobe)
Inferior hypophyseal artery from meningohypophyseal trunk from intracavernous ICA to posterior lobe
8% originate from within cavernous sinus, rare from middle meningeal artery.
78% from superior medial 1/3 surface of ICA, 22% from middle third and none from larteral 1/3 surfacr
To access ophthalamic a, remove anterior clinoid process and roof of optic canal and incision of falciform process
Posterior communicating artery
Arise from posterior medial or posterior aspect of C4
Dilation of origin from C4 in 6% of hemisphere (infundibular dilation or functional dilation)
4-14 perforating branch into tuber cinereum, premamilary portion of floor of 3rd ventricle, posterior perforating substance, optic tract, chiasm, stalk. Thalamus, hypothalamus and internal capsule.
Anterior group perforating a: hypothalamus, ventral thalamus, ant 1/3 optic tract, posterior limb of internal capsule
Posterior group: posterior perforated substance, subthalamic nucleus (may lead to hemiballism)
Premamilary artery (anterior thalamoperforating artery): enter floor of 3rd ventricle to posterior hypothalamus, anterior thalamus, posterior limb of internal capsule and subthalamus.
Anterior 1/3 of the internal capsule???
Anterior choroidal artery
In AP view, initial medial to ICA (posteriomedial) from choroid fissure into temporal horn.
Cisternal segment: before the fissure. Brance penetrate optic tract, uncus, cerbral peduncle, temporal horn, lateral geniculate body, hippocampus, dentate gyrus and fornix and anterior perforated substance. More common to optic tract, lateral part of lateral geniculate body, posterior 2/3 of posterior limb of internal capsule, most of globus pallidus, the origin of optic radiation and middle 1/3 of cerebral peduncl. Less common to head of caudate nucleus, pyriform cortex, uncus, , posterior amygdaloid n, substatia nigra, red nucleus, subthalamic n, ventrolateral n of thalamus
Plexal segment: may anastomosis with lateral posterior choroidal artery.
S/S of ACA occlusion: contralateral hemiplegia, hemianesthesia (all sensory) and hemianopsia