Intracranial Arteries Overview
Main Text
TERMINOLOGY
Abbreviations
- • Anterior, middle, posterior cerebral arteries (ACA, MCA, PCA)
- • Anterior, posterior communicating arteries (ACoA, PCoA)
- • Basilar artery (BA)
- • Vertebral artery (VA)
- • Anterior, posterior inferior cerebellar arteries (AICA, PICA)
- • Anterior choroidal artery (AChoA)
- • Recurrent artery of Heubner (RAH)
IMAGING ANATOMY
Overview
- • ICA
Proximal to termination gives off ophthalmic artery, AChoA, PCoA
Terminal bifurcation into ACA (smaller, medial), MCA (larger, lateral)
ACA has 4 segments
- – Horizontal or precommunicating (A1) segment courses medially above optic chiasm, joined by ACoA to contralateral A1
- – Vertical or postcommunicating (A2) segment courses superiorly in interhemispheric fissure, around corpus callosum genu
- – Distal (A3) segment courses posteriorly under inferior free margin of falx cerebri, gives off cortical branches
- – Perforating arteries arise from A1, ACoA
- – RAH arises from distal A1 or proximal A2
MCA has 4 segments
- – Horizontal (M1) segment courses laterally to sylvian fissure below anterior perforated substance, bi- or trifurcates
- – “Genu” or “knee” of MCA is gentle posterosuperior turn toward lateral cerebral (sylvian) fissure
- – Insular (M2) segments course within lateral cerebral fissure, over insula
- – Opercular (M3) segments begin at top of insula, turn laterally in sylvian fissure to reach overhanging frontal/parietal/temporal operculae
- – Cortical (M4) branches emerge from lateral cerebral fissure, course over hemispheric surface
- – Perforating arteries arise from M1
- • BA
Courses cephalad in prepontine cistern to terminal bifurcation ventral to midbrain
Bifurcates into PCAs, each of which has 4 segments
- – Mesencephalic or precommunicating (P1) segment lies within interpeduncular cistern, curves posterolaterally from BA to PCoA junction
- – Ambient (P2) segment extends from PCA-PCoA junction, curving around cerebral peduncles just above tentorium, above oculomotor nerve
- – Quadrigeminal (P3) segment extends posteromedially from level of quadrigeminal plate
- – Cortical (P4) branches arise from distal PCA at or just before reaching calcarine fissure
- – Perforating branches arise from P1
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