Greenberg's - Vascular Anatomy Flashcards
Origin: Recurrent artery of Heubner = medial striate artery
Junction of the ACA and A-Comm in 62%
Proximal A2 in 23%
A1 14%
Angiography: Circle of Willis
A balanced configuration of the CoW is present in only 18% of population
Hypoplasia of 1 or both p-comms occurs in 22-32%
- Absent or hypoplastic A1 segments occurs in 25%
The ACA pass over the superior surface of the optic chiasm
Anterior Cerebral Artery - A1
Precommunicating
ACA from origin to ACoA
Anterior Cerebral Artery - A2
Postcommunicating
ACA from ACoA to branch-point of callosmarginal
Anterior Cerebral Artery - A3
Precallosal
From branch-point of callosomarginal curving around the genu of the corpus callosum to superior surface of corpus callosum 3cm posterior to the genu
Anterior Cerebral Artery - A4
Supracallosal
Anterior Cerebral Artery - A5
Postcallosal
Terminal branch
Middle Cerebral Artery - M1
MCA from origin to bifurcation
- Classical bifurcation into relatively symmetrical superior and inferior trunks is seen in 50%
- No bifurcation occurs in 2%
25% have a proximal branch (middle trunk) arising from the superior (15%) or inferior (10%) trunk creating a pseudotrifurcation
Pseudotetrafurcation occurs in 5%
Segments of the ICA - Cincinnati system
C1 cervical C2 petrous C3 lacerum C4 cavernous C5 clinoid C6 ophthalmic C7 communicating
Middle Cerebral Artery - M2
MCA trunks from bifurcation to emergence from Sylvian fissure
Middle Cerebral Artery - M3 to 4
Distal branches
Middle Cerebral Artery - M5
Terminal branch
Posterior Cerebral Artery - P1
PCA from origin to P-Comm artery
- Long and short circumflex and thalamoperforating arteries arise from P1
Posterior Cerebral Artery - P2
PCA from origin of P-Comm to the origin of inferior temporal arteries
P2 traverses the ambient cistern
Hippocampal, anterior temporal, peduncular perforating and medial posterior choroidal arteries arise from P2
Posterior Cerebral Artery - P3
PCA from origin of the inferior temporal branches to the origin of the terminal branches
P3 traverses the quadrigeminal cistern
Posterior Cerebral Artery - P4
segment after the origin of the parieto-occipital and calcarine arteries, includes cortical branches of the PCA
External Carotid
Superior thyroid artery - 1st anterior branch Ascending pharyngeal artery Lingual artery Facial artery Occipital artery Posterior auricular Superifical temporal Internal maxillary artery
Ascending pharyngeal artery
Neuromeningeal trunk of the ascending pharyngeal artery - supplies IX, X and XI
- important when embolising glomus tumours, 20% = lower cranial nerve palsy if this branchi soccluded
Pharyngeal branch usually the primary feeder for jugular foramen tumours - essentially the only cause of hypertrophy of the ascending pharyngeal artery
Facial artery
Branches anastamose with ophthalmic artery
- important in collateral flow with ICA occlusion
Occipital artery
Supplies posterior scalp
Branches: Superficial temporal artery
Frontal branch
Parietal branch
Branches: Internal Maxillary Artery
Initially within parotid gland
Middle meningeal artery
- Anterior branch
- Posterior branch
Accessory meningeal
Inferior alveolar
Infra-orbital
Distal branches of which may anastomose with branches of ophthalmic artery in the orbit
Internal Carotid Artery - C1
Cervical
- Begins in the neck at carotid bifurcation where the common carotid artery divides into ICA and ECA
- Travels in carotid sheath with IJV and X, encircled with PGSN
C1 ends where teh ICA enters carotid canal of petrous bone
No branches
Internal Carotid Artery - C2
Petrous
- Surrounded by PGSNs
- Ends at posterior edge of foramen lacerum, inferomedial to the edge of the Gasserian ganglion in Meckel’s cave
- Vertical segment - ICA ascends then bends as the…
- Posterior loop - anterior to cochlea, bends antero-medially becoming the…
- Horizontal segment - deep and medial to greater and lesser superficial petrosal nerves, anterior to tympanic membrane
Internal Carotid Artery - C3
Lacerum
- ICA passes over the foramen lacerum forming the lateral loop
- Ascends in the canalicular portion of the foramen lacerum to juxtasellar position
- Pierces the dura as it passes the ptrolingual ligament to become the cavernous segment
Branches (usually not visible angiographically):
- Caroticotympanic (inconsistent) - supplies tympanic cavity
- Pterygoid (vidian) - passes through foramen lacerum, present in only 30% may continue as artery of pterygoid canal
Internal Carotid Artery - C4
Cavernous
- covered by vascular membrane lining sinus
- surrounded by PGSNs
- Passes anterior then superio-medially, bends posteriorly (medial loop of ICA)
- Travels horizonally and bends anteriorly (part of anterior loop of ICA) to anterior clinoid process
- Ends at proximal dural ring (incompletely encircles ICA)
Multiple branches:
- Meningohypophyseal trunk (largest and most proximal)
- Anterior Meningeal artery
- Anterior to inferior portion of Cavernous sinus (present in 80%)
- Capsular arteries of McConnell (in 30%) - supply the capsule of pituitary
2 Causes of Prominent MHT
Tumour - usually petroclival meningioma
Dural AVM
Branches of meningohypophyseal trunk
Artery of tentorium = artery of Bernasconic and Cassinari - blood supply of petroclival meningioma
Dorsal meningeal artery = dorsal clival artery
Inferior hypophyseal artery - supplies posterior lobe of pituitary
- Post partum occlusion causes pituitary infarcts (sheehan’s necrosis), DI is rare because the stalk is spared
Internal Carotid Artery - C5
Clinoid
- Begins at proximal dural ring, ends at distal dural ring (which completely encircles ICA) where the ICA becomes intradural
Internal Cartoid Artery - C6
Ophthalmic
- Begins at distal dural rings, ends just proximal to p-comm
Branches:
- Ophthalmic artery
- Origin from the ICA is distal to the cavernous sinus in 89% (intracavernous in 8%, ophthalmic artery is absent in 3%)
- Can vary from 5mm anterior to 7mm posterior to the anterior clinoid
- Passes through optic canal into the orbit
- Characteristic bayonet-like ‘kink’ on lateral angiogram - Superior hypophyseal artery
- supplies anterior lobe of pituitary and stalk
- 1st branch of supraclinoid ICA
Internal Carotid Artery - C7
Communicating
- Begins just proximal to P-comm origin, travels between CN II and III
- Terminates just below anterior perforated substance where it bifurcates to the ACA and MCA
Branches:
- Posterior communicating artery
- Few anterior thalamoperforators, supply optic tract, chiasm and posterior hypothalamus
- Plexal segment: enters supracornual recess of temporal horn, supplies only this portion of choroid plexus
- Cisternal segment: passes through crural cistern - Anterior choroidal artery
- Take off 2-4mm distal to P-com, supplies variable portion of optic tract, medial globus pallidus, genu of internal capsule (in 50%), inferior half of posterior limb of IC, uncus, retrolenticular fibres (optic radiation), lateral geniculate body; for occlusion syndromes
Internal Carotid Artery - Carotid Siphon
Not a segment
Region incorporating the cavernous, ophthalmic and communicating segments.
Begins at the posterior bend of the cavernous ICA and ends at the ICA bifurcation
Differentiating a P-Comm from ACh on arteriogram
- P-Comm origin is proximal to that of the anterior choroidal artery (ACh)
- P-Comm is usually larger than ACh
- P-Comm usually goes up or down a little, then straight back and usually bifurcates
- ACh usually has a superior ‘hump’ (plexal point) where it passes through the choroidal fissure to enter the ventricle.
