radiology arterial and venous supply of brain neuroimaging part 1
DESCRIPTION
disclaimer - meant for educational purpose only .TRANSCRIPT
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ARTERIAL AND VENOUS SUPPLY OF BRAIN- Neuroimaging
BY : Dr . Sameeha Khan(MDRD)
Part 1
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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.
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Overview
Part 1 – Aortic arch and great vessels Carotid arteries Circle of Willis
Part 2 – Cerebral arteries Posterior fossa arteries –
vertebrobasilar system
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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
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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
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ARTERIAL ANATOMY
Starts from aortic arch :
Aortic arch
Innonimate artery
Left common carotid
Left subclavia
n
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Aortic arch:
3 . Innonimate artery 10. Left subclavian artery 15. Left common carotid artery
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1.Innonimate artery
A.k.a Brachiocephalic trunk . 1st vessel arising from the aortic arch .
Innonimate artery
Right subclavian
artery
Right common carotid artery
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Innonimate artery 4. Right subclavian artery 5. Right common carotid artery
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1A.Right subclavian artery
Right subclavian artery
Right vertebral artery
Internal mammary artery
Thyrocervical
trunk
Costocervical
trunk
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1A. Right Subclavian Artery :
6. Right vertebral artery 9. Internal mammary artery 16. Thyrocervical trunk
16
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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
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Aberrant Right Subclavian artery
Barium studies – fixed narrowing of esophagus at the level of arch without mucosal deformity – bayonet deformity
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Right Vertebral Artery
1st Branch of right subclavian artery Right vertebral artery dominant -
25% Anomalous origin – uncommon
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1B. Right Common Carotid
Arises from proximal IA Only cervical part as it arises caudally
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Variants:
RCCA – directly from aortic arch ( when right SCA is aberrant )
RCCA RSC
A
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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.
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Variants -Bovine arch
LCCA- common origin with IA
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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
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3. Left subclavian artery
Last branch from aortic arch Major branches -
Left subclavian artery Left
vertebral artery
Internal mammar
y
Thyrocervical
trunk
Costocervicaltrun
k
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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
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Variant Left vertebral artery –directly from
aortic arch -5% ( nondominant )
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MRA – aortic arch
RSCA
LSCA
Innominate artery
LCCA
RCCA RVA
LVA
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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
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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
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ECA-branches
External carotid artery
Anterior
Superior thyroidal
Lingual
Facial
Posterior
Occipital
Posterior auricular
Medial
Ascending pharyngeal
Terminal
Maxillary
Superficial temporal
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ECA – branches
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ECA – branches
Superior thyroid artery
Lingual artery
Facial artery
Occipital arteryPosterior auricular artery
Ascending pharyngeal artery
Early arterial phase of CCA angiogram
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ECA – branches
Late arterial phase of CCA angiogram
Posterior auricular artery Occipital artery
Facial artery
Lingual
artery
Superficial temporal artery
Maxillary artery
Transverse facial
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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.
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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
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ECA – MRA
Oblique view – MRA
Vertebral artery
Thyrocervical trunk
Facial artery Lingual artery
Superficialtemporal artery
Occipital artery
Maxillary artery
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ECA – MRA
Straight AP view – MRA
Superficial temporal artery Hairpin turn of STA
Maxillary artery
Facial artery Lingual artery
Vertebral artery
Middle meningeal
artery
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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
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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
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•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
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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)
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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.
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Internal carotid artery
Cervical
Intraosseous / petrous
Lacerum
Cavernous
Intracranial / supraclinoid
Opthalmic
Communicating
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ICA SEGMENTS
ICA
Carotid bulb
Petrous
Cavernous Supraclinoid
Cervical
Oblique DSALateral DSA
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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
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Cervical segment
No narrowing No dilatation No branches No tapering Course –
crosses behind and medial to ECA
ICA
ICA
ECA
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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
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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
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Axial NECT inferior to superior ( bone window )
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MRA
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Petrous – branches
Petrous segment of ICA
Intrapetrous
Vidian artery (artery of
Pterygoid canal )
Corticotympanic artery
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Vidian canal
Foramen lacerum Vidian canal
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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
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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
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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
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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
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Lacerum
Carotid angiogram
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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.
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Carotid angiogram
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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
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MRA
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CECT
C4 within cavernous sinus
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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
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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
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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
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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
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Mid arterial phase DSA
Lateral view MRA
Lateral DSA
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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
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Unruptured superior hypophyseal aneurysm Normally SHA not easily seen
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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
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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
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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
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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
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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
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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
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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
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Terminal ICA
Anterior cerebral artery Middle cerebral artery
3D CTA MCA
ACA
ICA
3D CTA Mid arterial phase DSA
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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
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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
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3DVRT CTA MRA
CT MRA
1. A12. P13. PCo
A4. ACo
A
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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
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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
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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
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•Hypoplasia or absent A1 ACA segment. •Absent , duplicate or multichannel ACoA – 10-15%
Variants - COW
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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
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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.
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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
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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
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•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
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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
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Red – PHA
Blue – sigmoid sinus Pink – coil mass with basilar tip aneurysm
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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
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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
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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