div style=”display:none;”> Circle of Willis Main Text TERMINOLOGY Synonyms • Circulus arteriosus Definitions • Central arterial anastomotic ring of brain GROSS ANATOMY Overview • Circle of Willis (COW) is arterial polygon • 10 components 2 internal carotid arteries (ICAs) 2 proximal or horizontal (A1) anterior cerebral artery (ACA) segments 1 anterior communicating artery (ACoA) 2 posterior communicating arteries (PCoAs) 1 basilar artery (BA) 2 proximal or horizontal (P1) posterior cerebral artery (PCA) segments IMAGING ANATOMY Overview • Entire COW rarely seen on single DSA but completely imaged on CTA/MRA Anatomy Relationships • COW lies above sella, in suprasellar cistern • Surrounds ventral surface of diencephalon, inferolateral to hypothalamus • Horizontal (A1) ACA segments normally course above optic nerves (CNII) • PCoAs course below optic tracts, above oculomotor nerves (CNIII) Branches • Important perforating branches arise from all parts of COW • ACAs Medial lenticulostriate arteries Recurrent artery of Heubner • ACoA Unnamed perforating branches to anterior hypothalamus, optic chiasm, cingulate gyrus, corpus callosum, and fornix Occasionally, large vessel, median artery of corpus callosum, arises from ACoA • PCoA Anterior thalamoperforating arteries • BA, PCAs Posterior thalamoperforating arteries Thalamogeniculate arteries Vascular Territory • Entire central base of brain (including hypothalamus, internal capsule, optic tracts, thalamus, midbrain) Normal Variants, Anomalies • Variation is rule, not exception! Absent/hypoplastic components (60%) Hypoplastic/absent PCoA (25-33%) Hypoplastic/absent A1 (10-20%) “Fetal” origin of PCA from ICA (15-25%) – PCoA is same diameter as ipsilateral PCA – P1 is hypoplastic/absent Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related posts: Frontal Pole (Area 10) Glossopharyngeal Nerve (CNIX) Retrosplenial Cingulate Cortex (Areas 29, 30) Hypoglossal Nerve (CNXII) Medulla Ventricles and Choroid Plexus Stay updated, free articles. Join our Telegram channel Join Tags: Imaging Anatomy Brain and Spine Mar 13, 2021 | Posted by admin in NUCLEAR MEDICINE | Comments Off on Circle of Willis Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access
div style=”display:none;”> Circle of Willis Main Text TERMINOLOGY Synonyms • Circulus arteriosus Definitions • Central arterial anastomotic ring of brain GROSS ANATOMY Overview • Circle of Willis (COW) is arterial polygon • 10 components 2 internal carotid arteries (ICAs) 2 proximal or horizontal (A1) anterior cerebral artery (ACA) segments 1 anterior communicating artery (ACoA) 2 posterior communicating arteries (PCoAs) 1 basilar artery (BA) 2 proximal or horizontal (P1) posterior cerebral artery (PCA) segments IMAGING ANATOMY Overview • Entire COW rarely seen on single DSA but completely imaged on CTA/MRA Anatomy Relationships • COW lies above sella, in suprasellar cistern • Surrounds ventral surface of diencephalon, inferolateral to hypothalamus • Horizontal (A1) ACA segments normally course above optic nerves (CNII) • PCoAs course below optic tracts, above oculomotor nerves (CNIII) Branches • Important perforating branches arise from all parts of COW • ACAs Medial lenticulostriate arteries Recurrent artery of Heubner • ACoA Unnamed perforating branches to anterior hypothalamus, optic chiasm, cingulate gyrus, corpus callosum, and fornix Occasionally, large vessel, median artery of corpus callosum, arises from ACoA • PCoA Anterior thalamoperforating arteries • BA, PCAs Posterior thalamoperforating arteries Thalamogeniculate arteries Vascular Territory • Entire central base of brain (including hypothalamus, internal capsule, optic tracts, thalamus, midbrain) Normal Variants, Anomalies • Variation is rule, not exception! Absent/hypoplastic components (60%) Hypoplastic/absent PCoA (25-33%) Hypoplastic/absent A1 (10-20%) “Fetal” origin of PCA from ICA (15-25%) – PCoA is same diameter as ipsilateral PCA – P1 is hypoplastic/absent Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related posts: Frontal Pole (Area 10) Glossopharyngeal Nerve (CNIX) Retrosplenial Cingulate Cortex (Areas 29, 30) Hypoglossal Nerve (CNXII) Medulla Ventricles and Choroid Plexus Stay updated, free articles. Join our Telegram channel Join Tags: Imaging Anatomy Brain and Spine Mar 13, 2021 | Posted by admin in NUCLEAR MEDICINE | Comments Off on Circle of Willis Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access
