Normal cerebral angio-gram

Presenter: Dr. Nikhil panpaliaGuide: Dr.K.R.Naik

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 angiography4. Doppler ultrasound

ARTERIAL ANATOMYStarts from aortic arch :

Aortic arch

Innonimate or brachiocephalic artery Left common carotid Left subclavian

Brachiocephalic or innonimate

Rt common carotid Rt subclavian

Aortic arch:

3 . Innonimate artery 10. Left subclavian artery 15. Left 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 brachicephalic Only cervical part as it arises caudally

Variants: RCCA – directly from aortic arch

( when right SCA is aberrant )

RCCARSCA

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

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) (VNA)

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

AnteriorSuperior

thyroidal (sister)

Lingual (lucy)

Facial (face)

Posterior

Occipital

Posterior auricular (powdered)

Medial Ascending

pharyngeal (attracts)

Terminal Maxillary (many)

Superficial temporal (so)

ECA – branches

ECA – branches

Superior thyroid arteryLingual 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

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 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

ICAECA

Petrous segment C2

Vertical

• 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

Petrous – branchesPetrous

segment of ICA

Intrapetrous

Vidian artery (artery of

Pterygoid canal )

Corticotympanic artery

Axial NECT inferior to superior ( bone window )

MRA

Variant -Aberrant ICA

Aberrant course •Posterolateral course thro temporal bone •Vertical segment of carotid canal absent Normal course of ICA

•Anteromedial course thro temporal bone •3 segments

Persistent stapedial arteryRare- 0.48%Intrapetrous embryonic vascular channel.Origin – petrous ICA Course – passes throu the footplate of stapes. 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 and then 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

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

Menigohypophyseal artery •Posterior trunk•Arises at junction of c4 and c5•Supplies – •pituitary gland•tentorium•cavernous sinus• clival dura• CN 3 , 4 •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 .•Enlarged – vascular neoplasm / malformation / collaterals to ECA

Clinoid segment C5•Starts distal ly to cavernous sinus •Ends as near anterior clinoid process •No important branches

Opthalmic segment C6 Extends from 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

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. 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

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

Even gives the branches

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

Extracranial to intracranial vascular anastamosis

•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)

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

circulation 2 B/L ICAs

2ACAs

Unpaired ACoA anteriorly

Posterior circulation

Basilar bifurcation

from merged VAs

2PCAs from BAs

B/L PCoAs

3DVRT CTA MRA

CT MRA

1. A12. P13. PCo

A4. ACo

A

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

Carotid vertebrobasilar anastomosis

Represent persistent embryonic circulatory patterns

Channels between caudal carotid artery and paired 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

PTAOtic

Hypoglossal

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

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

Part 2

Cerebral arteries Vertebral artery Basilar artery

CEREBRAL ARTERIESDistal ICA

Anterior cerebral artery

Middle cerebral artery

Basilar artery

Posterior cerebral artery

Anterior cerebral artery

A1 horizontal segment

• From ACA origin to ACoA junction.• Inferior br – supply superior surface

of optic nerve and chaisma.• Superior br – anterior hypothalamus

, septum pellucidum , anterior commisure , fornix , anterior inferior portion of corpus straitum.

Arise from A1 segment- perforating branches. • Pass cephalad

thro anterior perforated substance.

• Supply head of caudate nucleus and anterior limb of IC, putamen .

Medial lenticulostriate artery.

Recurrent Artery of Heubner

• Largest of the perforating branches.

• May arise from A1 or A2 segment.

• A1 – 44%• Proximal A2 – 50%• ACoA – less common • Derives its name from

the fact that it doubles back on its parent artery at an acute angle to join lenticulostriate vessel.

• Lies parallel to A1 .

A2 segment- Interhemispheric segment

From ACoA junction

Ascend in front of 3rd ventricle in cistern of lamina terminalis

br –Orbitofrontal, frontopolar

Curves around corpus callosum genu gives terminal branches

A2 termin al br an ches-

Pericollasal

Collasomar g inal

Cortical A3 segment • Supply the anterior

2/3rds of medial hemispheric surface + small superior area over the convexities.

• Callosomarginal a.– lies in cingulate gyrus supplies medial frontal lobe

• Pericallosal a.– course along the posterior aspect of corpus callosum and supplies it and medial parietal lobe

Lateral DSA mid arterial phase

A1

A2

A3

orbitofrontal

Callosomarginal Pericollasal

Medial lenticulostriate Recurrent

artery heubner

Pericollasal

A2

Orbitofrontal

Frontopolar

A3

Callosomarginal

AP DSA mid arterial

3D MRA

A2Pericollasal

Callosomarginal

Variants -ACoA

ACA – ACoA complex – normal 1/3rd anatomy dissection

Absent , duplicate or multichannel ACoA – 10-15%

• Hypoplasia or absent A1 ACA segment-distal segments fill preferentially from other side via ACoA.

Variants – A1

Duplication ACA

Fenestration / duplication of ACA

Middle cerebral artery

M1 horizontal

Origin -Laterally from ICA

bifurcation Till its

bi/trifurcation at sylvian fissure. Br – Lateral Lenticulostriate branch course

superiorlyAnterior temporal

artery Supplies-Lentiform nucleus

Part of IC , caudate nucleus

M2 insular

At its genu divides into branches

Loop over insula pass laterally to exit from sylvian

fissure

M3 opercular

Emerge from sylvian fissure

Ramify over hemispheric

surfaceSupplies –cerebral cortex and white

matter

Cortical branches 1. Orbitofrontal artery

(lateral frontobasal )2. Prefrontal arteries 3. Precentral

(prerolandic )4. Central sulcus

(rolandic) 5. Postcentral sulcus

(anterior parietal) artery

6. Posterior parietal artery

7. Angular artery 8. Posterior temporal 9. Temporooccipital

artery 10. Medial temporal

AP DSA mid arterial phase

AP DSA early arterial phase

Early arterial phase

Lateral DSA Mid arterial phase

Lateral

•M1 horizontal •MCA bifurcation •M2 insular •M3 opercular

CT

MRA

Lateral Lenticulostriate Artery

• Origin - M1 • Supplies – • Part of head

and body of caudate

• Globus pallidus

• Putamen • Posterior

limb of internal capsule

Sylvian segment territory • Supplies • Inferolateral

frontal lobe • Insular cortex • Parietal lobe • Temporal lobe

Cortical segment territory

• Supplies – • Lateral

cerebrum • Insula • Ant-

lateral temporal lobe

Variants- MCA

Less frequent Fenestration and duplication Single trunk Accessory arteries

All uncommon ≤5 %

MCA fenestration

Accessory MCA • It is either hypertrophied RA heubner or medial ACA

perforator.• To be called accessory MCA it should have cortical

branches.

PCA origin from bifurcation of basilar artery in interpeduncular cistern.Lies above occulomotar nerve. Circles midbrain above tentorium cerebelli.

Posterior cerebral artery

Posterior cerebral artery

P1 precommunicating / peduncular

•Basilar bifurcation extends laterally •Junction with PCoA•Br – •Post thalamoperforating-thalamus , midbrain •Medial posterior choroidal artery – anteromedially along roof of 3rd ventricle –tectal plate , midbrain , thalamus posterior , pineal gland , tele choroidae of 3rd ventricle.

P2 ambient / crural

•PCA- PCoA junction posterior •Above trochlear nerve and tentorial incisura •Br – •Thalamogeniculate arteries- MGB , pulvinar , brachium superior colliculus , crus cerebri , LGB •Lateral post choroidal artery – over pulvinar of thalamus – posterior thalamus , lateral ventricular choroid plexus

Inferior temporal artery • Undersurf

ace of temporal bone

• Anastamose -MCA

Parietooccipital artery• Posterior

1/3rd interhemispheric surface

• ACA

Calcarine artery( P4 )• Visual

cortex• Occipital

pole

Posterior pericollasal artery (splenial)• Splenium

of corpus callosum

• ACA

AP DSA

AP DSA mid arterial phase

Early arterial phase

Lateral DSA Mid arterial phase

MRA

CTA

Cortical territory

• Supply – • Medial

+posterior temporal lobe

• Medial parietal lobe

• Occipital lobe

Variant – PCA Fetal origin of PCA from ICA instead of basilar – 15-

20 % Carotid basilar anastomosis – supply PCA via

trigeminal artery or other persistent channels

Vertebral artery V1 Courses –Cephalad to enter transverse foramina

at C6

Ascend directly to C2 (V2)

Turns laterally and superiorly thro C1 vertebral

foramina

Looping posteriorly along atlas V3 extraspinal

Each VA passes superomedially thro foramen magnum In Posterior fossa

anterior to medulla (intradural )

VAs unite to form basilar artery

From subclavian arteriesLeft VA dominant 50%

Intracranial VA branches

Vertebral artery Anterior spinal

artery

Medial medullary syndrome

Posterior inferior cerebellar artery

Arises from distal VA

Lateral medullary syndrome

Lateral DSA

AP DSA

V1- extraosseousV2 –foraminal V3 – extraspinal V4 – intradural

Posterior inferior cerebellar artery

• Front of medulla Anterior medullary segment

• Along side of medulla caudally to level of CN 9-11

Lateral medullary segment

• Around inferior half of cerebellar tonsilTonsilomedullary segment

• Cleft btw tela choridae and inferior medullary velum rostrally and superior pole of tonsil caudally

Telovelotonsillar segment

Cortical / hemispheric segment

Lateral DSA early arterial

Lateral DSA late arterial

Anterior medullary segment Posterior medullary segment Lateral medullary segment

• Choroid plexus of 4th ventricle.

• Posterolateral medulla.

• Cerebellar tonsil. • Inferior vermis. • Posteroinferior cerebellar hemisphere.

Supplies

PICA territory

Variants – Persistent

vertebrobasilar anastamosis

Left VA – aortic arch origin – 5%

Hypolastic VA – 40 %

Hypoplastic VA

Hypoplastic VA terminating as PICA

VA terminates in PICA – 1%

Duplicated VA

Orange arrow – duplicated VA Red – original VA from subclavian

VA duplication- ocassionally

Fenestrated VA

VA fenestration – occasionally

Extracranial PICA Extradural origin of PICAPICA from VA below foramen magnum

Basilar artery

Right and left VA s unite – BA

Course cephalad in front of pons

Pontine cistern in the space delineated by lateral margin of clivus and dorsum sellae

Terminates in interpeduncular cistern

Divides into PCAs

•Average length – 3 cm •Width 1.5- 4 mm •Diameter <4.5 mm

BA - Branches 1. AICA – Anterior Inferior

Cerebellar Artery 1st major branch. Posterior laterally in

cerebellopontine angle cistern toward the internal auditory canal. Here typically anteroinferior to facial and vestibulocochlear nerve.

Few mms from origin AICA crossed by abducens nerve.

Supplies- ▪ Nerves ▪ Inferolateral pons ▪ Middle cerebellar peduncle ▪ Flocculus ▪ Anterolateral cerebelllar hemisphere

BA –branches 2. SCA- Superior Cerebellar Artery –

Arises from BA apex. Posterolaterally around Pons

and mesencephalon below tentorial incisura and CNS 3 n 4.

Supplies – ▪ Superior surface of vermis n

cerebellar hemisphere. ▪ Deep cerebellar white matter. ▪ Dentate nucleus.

Perforating branches – short n long segment

BA – terminates into PCA s

AP DSA

MRA

Variants - Nonfused basilar

Variants -Basilar fenestration

Variants -AICA duplication

Variants -SCA origin from PCA / ICA directly

SCAs- can arise from P1 segment

References

Osborne radiology Gionni Boris bradac –Cerebral

angiography