ARTERIAL AND VENOUS SUPPLY OF BRAIN- Neuroimaging

BY : Dr . Sameeha Khan(MDRD)

Part 1

Introduction -

Understanding vascular anatomy is fundamental to neuroimaging.

About 18% of the total blood volume in the body circulates in the brain, which accounts for about 2% of the body weight.

The blood transports oxygen, nutrients, and other substances necessary for proper functioning of the brain tissues and carries away metabolites.

Loss of consciousness occurs in less than 15 seconds after blood flow to the brain has stopped, and irreparable damage to the brain tissue occurs within 5 minutes.

Cerebrovascular disease or stroke, occurs as a result of vascular compromise or haemorrhage and is one of the most frequent sources of neurologic disability.

Overview

Part 1 – Aortic arch and great vessels Carotid arteries Circle of Willis

Part 2 – Cerebral arteries Posterior fossa arteries –

vertebrobasilar system

Modalities for vascular imaging

1. Conventional intra-arterial angiography – DSA system - techniques of image acquisition

Standard radiographic projections carotid angio- ▪ Lateral projection – centered on pituitary fossa ▪ AP view – with petrous ridge projected over the roof

of orbit ▪ I/L anterior oblique – for aneurysms in SAH

Vertebral angio – ▪ lateral , half-axial ( Towne’s) and AP – petrous ridge

superimposed on lower border of orbit

2. Computed tomography angiography 3. Magnetic resonance angiography

I. Time of flight – inflow of unsaturated spin II. Phase contrast – accumulation of phase shifts

proportional to flow velocityIII. Contrast enhanced MRA Intracerebral vessels -3D TOF MRA is technique of choice Circle of willis – single slab 3D TOF Larger part of intracranial circulation – 3-4 multiple

overlapping slabs ( MOTSA ) Phase contrast sensitive for slow flow – used for cerebral

veins

4. Doppler ultrasound

ARTERIAL ANATOMY

Starts from aortic arch :

Aortic arch

Innonimate artery

Left common carotid

Left subclavia

n

Aortic arch:

3 . Innonimate artery 10. Left subclavian artery 15. Left common carotid artery

1.Innonimate artery

A.k.a Brachiocephalic trunk . 1st vessel arising from the aortic arch .

Innonimate artery

Right subclavian

artery

Right common carotid artery

Innonimate artery 4. Right subclavian artery 5. Right common carotid artery

1A.Right subclavian artery

Right subclavian artery

Right vertebral artery

Internal mammary artery

Thyrocervical

trunk

Costocervical

trunk

1A. Right Subclavian Artery :

6. Right vertebral artery 9. Internal mammary artery 16. Thyrocervical trunk

16

Variants-Aberrant Right Subclavian Artery Common arch anomaly 0.5-1% of all cases Here it is the last

brachiocephalic vessel arising from aortic arch -4th branch

Often asymptomatic – 10 % of people can have dysphagia lusoria.

Right common carotid arises directly from arch – first branch

Aberrant Right Subclavian artery

Barium studies – fixed narrowing of esophagus at the level of arch without mucosal deformity – bayonet deformity

Right Vertebral Artery

1st Branch of right subclavian artery Right vertebral artery dominant -

25% Anomalous origin – uncommon

1B. Right Common Carotid

Arises from proximal IA Only cervical part as it arises caudally

Variants:

RCCA – directly from aortic arch ( when right SCA is aberrant )

RCCA RSC

A

2. Left common carotid 2nd major branch from aortic arch Thoracic and cervical part –in thoracic it travels upwards

throu superior mediastinum to the level of left sternoclavicular joint and continues as cervical

15.Left common carotid

CCA bifurcates into ICA and ECA at midcervical level C3-C6 level.

Variants -Bovine arch

LCCA- common origin with IA

LCCA Variants :

LCCA – hypoplastic or absent – here the ECA and ICA arise directly from aortic arch

Non bifurcating carotid artery – origin to all the ECA branches

3. Left subclavian artery

Last branch from aortic arch Major branches -

Left subclavian artery Left

vertebral artery

Internal mammar

y

Thyrocervical

trunk

Costocervicaltrun

k

Left vertebral artery

First branch of left subclavian artery Dominant in 50-60% In 25% right and left VA are equal in

size

11.Left vertebral artery 14.Left internal mammary

Variant Left vertebral artery –directly from

aortic arch -5% ( nondominant )

MRA – aortic arch

RSCA

LSCA

Innominate artery

LCCA

RCCA RVA

LVA

Common carotid artery Course - Runs within a

fascial plane – the carotid sheath –also contains IJV and vagus nerve, vein lateral to artery , nerve between the two

Runs obliquely upwards from the level of sternoclavicular joint to the level of thyroid cartilage

Bifurcates at the level of C3- C5 into external and internal carotid artery

At bifurcation ICA usually lies posterior and lateral to the ECA

External carotid artery

Smaller of the 2 carotids. Origin anterior and medial to ICA. Supplies the extracranial structures. Branches –( Sister Lucy’s Powdered Face

Attracts SO Many Medicos )

Internal carotid artery External carotid artery

Common carotid artery

ECA-branches

External carotid artery

Anterior

Superior thyroidal

Lingual

Facial

Posterior

Occipital

Posterior auricular

Medial

Ascending pharyngeal

Terminal

Maxillary

Superficial temporal

ECA – branches

ECA – branches

Superior thyroid artery

Lingual artery

Facial artery

Occipital arteryPosterior auricular artery

Ascending pharyngeal artery

Early arterial phase of CCA angiogram

ECA – branches

Late arterial phase of CCA angiogram

Posterior auricular artery Occipital artery

Facial artery

Lingual

artery

Superficial temporal artery

Maxillary artery

Transverse facial

ECA – terminal branches

Internal maxillary artery- Runs forward deep to the

mandible. Branches – inferior alveolar,

middle meningeal, deep temporal , accessory meningeal , sphenopalatine , infraorbital , descending palatine, muscular branches.

Middle meningeal artery – runs superiorly crosses STA on lateral projection thro foramen spinosum.

Supplies – dura and inner table of skull.

Superficial temporal artery

On angiogram should be

differentiated from middle meningeal artery – characteristic hairpin turn of STA over zygomatic process

Supplies –part of scalp and ear.

Branch – transverse facial artery

Variant – TFA may arise from ECA directly

STA

Middle meningeal artery

hairpin turn of STA

ECA – MRA

Oblique view – MRA

Vertebral artery

Thyrocervical trunk

Facial artery Lingual artery

Superficialtemporal artery

Occipital artery

Maxillary artery

ECA – MRA

Straight AP view – MRA

Superficial temporal artery Hairpin turn of STA

Maxillary artery

Facial artery Lingual artery

Vertebral artery

Middle meningeal

artery

Vascular blushes -

Late arterial phase – prominent vascular blushes in the mucosa of sinuses , nose ,orbit , oropharynnx -

not to be confused with vascular malformations

Oropharynx mucosal blush

High nasopharynx mucosal blush

Orbital mucosal blush

Nasal conchae septal blush

Palatal mucosal blush

Extracranial to intracranial vascular anastamosis

Maxillary artery

•Middle meningeal artery•Foramen rotundum artery•Accessory meningeal•Vidian artery •Ant / mid deep temporal

ICA •Ethmoidal br of opthalmic artery•Inferlolateral trunk of ICA •Inferolateral trunk •Intratemporal ICA•Opthalmic artery

•Occipital•Ascending pharyngeal artery •Ascending pharyngeal artery •Facial artery•Posterior auricular artery

•Vertebral•Vertebral C3 level •ICA (petrous and cavernous )•ICA (opthalmic artery)•ICA (stylomastoid artery)

Extracranial to intracranial vascular anastamosis

Carotid ultrasound

Intima – white endoluminal line Media – darker line underneath

Adventitia –thick peripheral white line

• Laminar flow in lumen of proximal ICA

• Velocity of flow increases towards the aorta ( 9 cm / sec for each cm of distance from the carotid bifurcation)

Internal carotid artery

Left CCA Right CCA

Internal carotid- carotid bulb

ECA

3-D CTA

• Origin -Lateral to ECA.

• Can be divided into number of segments between the bulb and its bifurcation into MCA and ACA.

Internal carotid artery

Cervical

Intraosseous / petrous

Lacerum

Cavernous

Intracranial / supraclinoid

Opthalmic

Communicating

ICA SEGMENTS

ICA

Carotid bulb

Petrous

Cavernous Supraclinoid

Cervical

Oblique DSALateral DSA

Carotid bulb Distal 2-4 cm of CCA Bulbous dilatation of

ICA origin Complex flow –

flow distal to bulb is laminar

Flow reversal within posterior bulb

Thinner media and thicker adventitia containing many receptor endings of glossopharyngeal nerve

Cervical segment

No narrowing No dilatation No branches No tapering Course –

crosses behind and medial to ECA

ICA

ICA

ECA

Variants – cervical segment

10%- ICA originates medial to ECA

Anomalous ECA branches arises from cervical ICA

Persistent embryonic vesels may anastomose with vertebrobasilar system

ICAEC

A

Petrous segment C2

Vertical

•2 subsegments joined at genu • Short vertical segment – anterior to IJV • Genu – petrous ICA turns anteromedially in front of

cochlea • Longer horizontal segment

ICA –intraosseous 1. enters carotid

canal in petrous temporal bone.

2. Surrounded by sympathetic plexus

3. exit at petrous apex

Horizontal

Genu

Axial NECT inferior to superior ( bone window )

MRA

Petrous – branches

Petrous segment of ICA

Intrapetrous

Vidian artery (artery of

Pterygoid canal )

Corticotympanic artery

Vidian canal

Foramen lacerum Vidian canal

Variant -Aberrant ICA

Aberrant course •Posterolateral course thro temporal bone •ICA parallel jugular bulb •Inferior aspect of cochlear promontory •Reduced diameter •Visible pulsatile mass in hypotympanum •Bony plate separating ICA from tympanic cavity absent •Vertical segment of carotid canal absent

Normal course of ICA•Anteromedial course thro temporal bone •ICA anterior to IJV•In front of cochlea• 2 segments

ICA courses adjacent to jugular bulb

ICA traverses the hypotympanum

Bony plate along tympanic portion of ICA absent

Axial multidetector CT images

Aberrant ICA

d/d glomus tympanicum paraganglionoma biopsy – disastrous

Persistent stapedial arteryRare- 0.48%Intrapetrous embryonic vascular channel stapedio-hyoid artery Origin – petrous ICA/abICA Course – passes throu the footplate of stapes. Enclosed within a bony canal near cochlear promontary Termination – as middle meningeal arteryCT- absentI/Lforamenspinosumd/d – glomus tumor Recognised before surgery

Lacerum

Small segment that extends from petrous apex above foramen lacerum curving upwards towards and lies extradurally until it reaches petrolingual ligament after this it becomes the cavernous segment Covered by trigeminal ganglion No branches

Lacerum

Carotid angiogram

Cavernous ICA

C4 segments 1. Ascending (posterior vertical )2. Posterior genu 3. Horizontal 4. Anterior genu 5. Anterior vertical

Branches Meningohypophyseal artery Inferolateral trunk Small capsular branches

1

Starts from petrous apex Terminates at its entrance into intracranial subarchnoid space adjacent to anterior clinoid process. Covered by trigeminal ganglion posteriorly.

Carotid angiogram

Axial CT

Posterior genu as it courses anteromedially into the cavernous sinus

ICA courses along the bony grooves of carotid sulcus along the basisphenoid bone

• Throu cavernous sinus proper turns superiorly • Form grooves under anterior clinoid process • Anterior genu of ICA .• Curve upwards towards dural ring• Enter subarchnoid space

Posterior genu

Carotid sulcus

Anterior genu

MRA

CECT

C4 within cavernous sinus

Menigohypophyseal artery

•Posterior trunk•Arises at junction of c4 and c5•Supplies – •pituitary gland•tentorium (artery of Bernasconi and Cassinari )•cavernous sinus• clival dura• cn3 n 4 •High quality D/FSA•Enlarges to supply dural vascular malformation / neoplasm

Inferolateral trunk

•Lateral mainstream artery •Arises – inferolaterally from c4 segment •Supplies – •CN 3,4,6 •gasserian ganglion CN5 •cavernous sinus dura •Anastomose with br of internal maxillary artery . Collaterals b/w ECA N ICA •DSA – lateral view •Enlarged – vascular neoplasm / malformation / collaterals to ECA

Clinoid segment C5

•Between proximal , distal dural rings of cavernous sinus •Ends as ICA enters subarachnoid space near anterior clinoid process •No important branches •Unless OA arises within CS

Opthalmic segment C6

Extends from distal dural ring at superior clinoid to just below posterior communicating artery (PCoA) origin Branches – •Opthalmic artery •Superior hypophyseal artery

CECT

Anterior clinoid process

C6

Opthalmic artery Origin –• Intradural •Antero-superior ICA • Medial to anterior clinoid process

Course –Anterior throu optic canal

Below optic nerve

Crosses superomedially over the nerve Supply -globe Gives off ocular , lacrimal , muscular branches •Anastomose with ECA

Mid arterial phase DSA

Lateral view MRA

Lateral DSA

Superior hypophyseal trunk

Arises from posteromedial aspect of supraclinoid ICA Course – across the ventral surface of optic chaisma Terminates- pituitary stalk and gland Supplies – anterior pituitary , Infundibulum , optic nerve and chaisma Anastomose - with hypophyseal branch from the contralateral ICA forms plexus – superior hypophyseal plexus DSA – usually not visualized if not enlarged

Unruptured superior hypophyseal aneurysm Normally SHA not easily seen

Communicating C7

•Extends from below PCoA to terminal ICA bifurcation. •Passes between optic and

occulumotor nerve.

C7 segment branches

Posterior communicating artery Anterior choroidal artery

Lateral DSA

AChA

PCoA3D CTA

Posterior communicating artery •Arises – posterior aspect of intradural ICA just below anterior choroidal artery •Course – posterolaterally above the occulumotor nerve to join posterior cerebral artery •Branches – anterior thalamoperforating arteries •Supplies – optic chiasma, pituitary stalk , thalamus , hypothalamus.

Lateral late arterial DSA

MRA

Variants – PCoA

1. Hypoplasia – 1/3 rd cases 2. Persistence of embryonic

configuaration ( fetal origin of posterior cerebral artery ) 20 – 25%

3. Junctional dilatation at PCoA origin ( infundibuli ) 6 %

4. PCoA duplication/ fenestraion – rare PCoA fenestration

PCoA hypoplasia

Fetal origin of PCA • PCoM is larger than P1 segment of

PCA and supplies the bulk of PCA . PCA therefore is a part of anterior circulation

• Non fetal PCA , PCoM lies superomedial to CN3

• Fetal PCA, PCoM lies superior lateral to CN 3

• Hypoplastic / absent P1 segment

• PCoA is same diameter as I/L PCA

Infundibular -PCoA

•Infundibular dilatation of PCoA at origin from ICA- 5-15%• Should be 2 mm or less • Funnel shaped , conical • PCoA arises from apex

Within suprasellar cistern under optic tract

Posteromedially around temporal lobe uncus

Cisternal Course :

Intraventricular course:

AChA angles sharply laterally

Enters choroidal fissure of temporal bone

Abrupt kink – plexal point

AChA-origin few mms above PCoA

Cisternal segment

Intraventricular segment

Anterior choroidal artery

Supplies Choroidal plexus of lateral ventricle ( temporal horn and atrium )Optic tract and cerebral peduncle Uncal and parahippocampal gyri of temporal lobe .Thalamus and posterior limb of internal capsule. Anastamoses – with AChA segments and LPChA and MPChA Variants – uncommon Aplasia rare Hypoplasia – 3 % Hyperplasia – 2.3 %

AP mid arterial DSA

AP Late arterial DSA

MRA lateral view

Choriodal blush

Terminal ICA

Anterior cerebral artery Middle cerebral artery

3D CTA MCA

ACA

ICA

3D CTA Mid arterial phase DSA

Circle of willis- circulus arteriosus

2ICAs

Horizontal segment A1

of both ACAs2 Posterior

communicating

arteries Anterior communicating artery Horizontal segment P1

of both PCA sBasilar artery

Interconnected arterial polygon Location – surrounds ventral surface of diencephalon,adjacent to optic nerve and tracts, inferolateral to hypothalamusAnterior circulatio

n 2 B/L ICAs

2ACAs

Unpaired ACoA

anteriorly

Posterior circulatio

n Basilar bifurcation

from merged VAs

2PCAs from BAs

B/L PCoAs

3DVRT CTA MRA

CT MRA

1. A12. P13. PCo

A4. ACo

A

Modes to visualise COW Cerebral angiography- single injection

Contrast enhanced CT – maximum intensity projection

Invasive

MRA- time of flight sequence with multiple overlapping thin slab technique

Transcranial Doppler ultrasound

Non invasive

COW – branches

• Medial lenticulostriate arteries• Recurrent artery of HeubnerACAs• Perforating branches – hypothalamus ,

optic chiasma , cingulate gyrus , corpus callosum , fornix

• Large vessel – median artery of corpus callosum arises from ACoA

ACoA

• Anterior thalamoperforating arteries PCoA• Posterior thalamoperforating arteries • Thalamogeniculate arteries

Basilar artery, PCAs

Supplies- 1.Optic chiasma and tracts

Variants -COW

Complete COW –only 20 – 25%

Posterior circle anomalies – 50% anatomy specimens

Common variants •Hypoplasia of 1 or both PCoA – 34%•Fetal origin of PCA from ICA

•Hypoplasia or absent A1 ACA segment. •Absent , duplicate or multichannel ACoA – 10-15%

Variants - COW

Anomalies

•Rare – congenital absence of 1 or both ICAs•Common – if 1 ICA absent intrasellar intercommunicating arteries •ICA agenesis – intracranial aneurysm common •ACA- ACoA complex • Infraoptic origin of ACA • Single (azygous) ACA

(holoprosencephalies )•PCoA- PCA- BA complex • Persistent carotid basilar

anastomosis

Absent ICA

Embryology- COW

ICAs develop from 3rd aortic arches , dorsal aortae Embryonic ICAs divide into cranial,caudal

Cranial divisions – ▪ primitive olfactory , anterior / middle cerebral , anterior choroidal

arteries ▪ Anterior communicating artery – forms from coalescence of a

midline plexiform network ,it connects developing ACAs Caudal divisions –▪ becomes posterior communicating arteries ▪ Supply stems of posterior cerebral arteries.

Paired dorsal longitudinal neural arteries fuse – basilar artery

Developing vertebrobasilar circulation usually incorporates PCAs

Caudal ICA divisions regress forming PCoAs.

Carotid vertebrobasilar anastomosis

Represent persistent embryonic circulatory patterns

Channels between embryonic aorta (caudal carotid artery) and paired longitudinal neural arteries (form basilar and vertebral arteries ) fail to regress.

1. Primitive persistent trigeminal artery 2. Primitive hypoglossal artery 3. Persistent otic artery 4. Proatlantal intersegmental artery

PCoA

PTA

Otic Hypogloss

al Proatlantal intersegmental

Variants – Persistent Trigeminal Artery

•Most common carotid vertebro basilar anastomoses - 0.1- 0.6%•In utero – embryonic trigeminal artery supplies basilar artery before the PCoA and vertebral artery develops •As these vessels enlarge – PTA normally disappears

course – arise when ICA exists carotid canal and enters cavernous sinus

Runs posterolaterally along trigeminal nerve 41%

Crosses over / throu dorsum sella before joining basilar artery

Connects ICA to vertebrobasilar system

trident shape on lateral DSA

•PCoA is absent•Supply entire vertebrobasilar circulation distal to anastomosis

Saltzmann type Ι

• Fetal PCA and I/L P1 segment absent • Fill superior cerebral arteries (SCA) with

posterior cerebral arteries (PCA ) fills via patent PCoA

Saltzmann type ΙΙ

•Increased incidence of intracranial aneurysms / malformations•Increased importance in transpenoidal surgery

Hypoplastic basilar

Primitive hypoglossal artery

2nd most common- 0.027- 0.26%

.

Intracranial aneurysms If present – single artery

that supplies brain stem and cerebellum

Courses thro hypoglossal canal

Parallel to CN 12

Connects cervical ICA with basilar artery

Red – PHA

Blue – sigmoid sinus Pink – coil mass with basilar tip aneurysm

Persistent otic artery

Origin – petrous ICA Course – medially thro internal

auditory meatus and joins caudal basilar artery

VA – hypoplastic / absent – POA is the sole arterial supply to basilar artery

Basilar artery POA

Proatlantal Intersegmental Artery

• Proatlantal infact is occipital artery • C1 segment connection is

proatlantal type 1

• C2 connection is proatlantal type 2

• vertebral artery proximal to proatlantal is hypoplastic

Proatlantal intersegmental artery

ICA

Proatlantal intersergmental

PIA – suboccipital anastamosis between ECA / cervical ICA and vertebral artery – typically courses between the arch of C1 and occiput