Greenberg's - Vascular Anatomy

Question 1

Origin: Recurrent artery of Heubner = medial striate artery

Answer 1

Junction of the ACA and A-Comm in 62%

Proximal A2 in 23%

A1 14%

Question 2

Angiography: Circle of Willis

Answer 2

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

Question 3

Anterior Cerebral Artery - A1

Answer 3

Precommunicating

ACA from origin to ACoA

Question 4

Anterior Cerebral Artery - A2

Answer 4

Postcommunicating

ACA from ACoA to branch-point of callosmarginal

Question 5

Anterior Cerebral Artery - A3

Answer 5

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

Question 6

Anterior Cerebral Artery - A4

Answer 6

Supracallosal

Question 7

Anterior Cerebral Artery - A5

Answer 7

Postcallosal

Terminal branch

Question 8

Middle Cerebral Artery - M1

Answer 8

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%

Question 9

Segments of the ICA - Cincinnati system

Answer 9

C1 cervical
C2 petrous
C3 lacerum
C4 cavernous
C5 clinoid
C6 ophthalmic
C7 communicating

Question 10

Middle Cerebral Artery - M2

Answer 10

MCA trunks from bifurcation to emergence from Sylvian fissure

Question 11

Middle Cerebral Artery - M3 to 4

Answer 11

Distal branches

Question 12

Middle Cerebral Artery - M5

Answer 12

Terminal branch

Question 13

Posterior Cerebral Artery - P1

Answer 13

PCA from origin to P-Comm artery

- Long and short circumflex and thalamoperforating arteries arise from P1

Question 14

Posterior Cerebral Artery - P2

Answer 14

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

Question 15

Posterior Cerebral Artery - P3

Answer 15

PCA from origin of the inferior temporal branches to the origin of the terminal branches

P3 traverses the quadrigeminal cistern

Question 16

Posterior Cerebral Artery - P4

Answer 16

segment after the origin of the parieto-occipital and calcarine arteries, includes cortical branches of the PCA

Question 17

External Carotid

Answer 17

Superior thyroid artery - 1st anterior branch
Ascending pharyngeal artery
Lingual artery
Facial artery
Occipital artery
Posterior auricular
Superifical temporal
Internal maxillary artery

Question 18

Ascending pharyngeal artery

Answer 18

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

Question 19

Facial artery

Answer 19

Branches anastamose with ophthalmic artery

- important in collateral flow with ICA occlusion

Question 20

Occipital artery

Answer 20

Supplies posterior scalp

Question 21

Branches: Superficial temporal artery

Answer 21

Frontal branch

Parietal branch

Question 22

Branches: Internal Maxillary Artery

Answer 22

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

Question 23

Internal Carotid Artery - C1

Answer 23

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

Question 24

Internal Carotid Artery - C2

Answer 24

Petrous

• Surrounded by PGSNs
• Ends at posterior edge of foramen lacerum, inferomedial to the edge of the Gasserian ganglion in Meckel’s cave

1. Vertical segment - ICA ascends then bends as the…
2. Posterior loop - anterior to cochlea, bends antero-medially becoming the…
3. Horizontal segment - deep and medial to greater and lesser superficial petrosal nerves, anterior to tympanic membrane

Question 25

Internal Carotid Artery - C3

Answer 25

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): 1. Caroticotympanic (inconsistent) - supplies tympanic cavity 2. Pterygoid (vidian) - passes through foramen lacerum, present in only 30% may continue as artery of pterygoid canal

Question 26

Internal Carotid Artery - C4

Answer 26

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: 1. Meningohypophyseal trunk (largest and most proximal) 2. Anterior Meningeal artery 3. Anterior to inferior portion of Cavernous sinus (present in 80%) 4. Capsular arteries of McConnell (in 30%) - supply the capsule of pituitary

Question 27

2 Causes of Prominent MHT

Answer 27

Tumour - usually petroclival meningioma Dural AVM

Question 28

Branches of meningohypophyseal trunk

Answer 28

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

Question 29

Internal Carotid Artery - C5

Answer 29

Clinoid - Begins at proximal dural ring, ends at distal dural ring (which completely encircles ICA) where the ICA becomes intradural

Question 30

Internal Cartoid Artery - C6

Answer 30

Ophthalmic - Begins at distal dural rings, ends just proximal to p-comm Branches: 1. 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 2. Superior hypophyseal artery - supplies anterior lobe of pituitary and stalk - 1st branch of supraclinoid ICA

Question 31

Internal Carotid Artery - C7

Answer 31

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: 1. 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 2. 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

Question 32

Internal Carotid Artery - Carotid Siphon

Answer 32

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

Question 33

Differentiating a P-Comm from ACh on arteriogram

Answer 33

1. P-Comm origin is proximal to that of the anterior choroidal artery (ACh) 2. P-Comm is usually larger than ACh 3. P-Comm usually goes up or down a little, then straight back and usually bifurcates 4. ACh usually has a superior 'hump' (plexal point) where it passes through the choroidal fissure to enter the ventricle.