2. Objective
1) Understand course and branches of blood vessels supplying brain
2) Identifying vessels on angiograms
3) Knowing common variants of vessels
3. Overview
1)Aortic arch and its branches
2)Internal carotid
3)Anterior cerebral artery
4)Middle cerebral artery
5)Vertebral arteries
6)Basilar artery
7)Posterior cerebral arteries
8)Circle of Willis
9)External carotid artery
11. Aortic arch and its branches
1-aortic arch
2-brachiocephalic artery
3-left common carotid
4-left subclavian artery
5-right common carotid
6-right vertebral artery
7-left vertebral artery
8-left thyrocervical trunk
9-internal mammary arteries
10-right thyrocervical trunk
11-right subclavian
12-right costocervical artery
12. Common variants of aortic arch and its major branches
1)Brachiocephalic trunk and Left CCA
share common origin
2)Left CCA arises from brachiocephalic
trunk
3)Left CCA and Left Subclavian arteries
form left sided brachiocephalic trunk
Seen about 1-2% cases
4)Left vertebral artery arises directly from
arch
13. Common variants of aortic arch and its
major branches
Brachiocephalic trunk and Left CCA share
common origin
• Most frequently encountered normal
variant
• Seen in 27% cases
• Sometimes called bovine arch
14. Common variants of aortic arch and its
major branches
Left CCA arises from brachiocephalic
trunk:
• Seen about 7% of cases
15. Common variants of aortic arch and its major
branches
Left vertebral artery arises
directly from arch
• Seen in about 0.5% cases
• Results in four vessels arising
from arch
• Arises between left CCA and left
Subclavian artery
16. Miscellaneous variants
Aortic spindle:
• Circumferential bulge just beyond
ductus
• Junction between isthmus and spindle
is marked by inferior indentation
• should not be mistaken for dissection
17. Miscellaneous variants
Ductus diverticulum:
• Focal bulge along anteriomedial aspect of
aortic isthmus
• Seen in 9% adults
• In contrast to an aortic pseudoaneurysm,
which usually forms sharp margins with the
aorta, ductus diverticulum usually appears as
a smooth focal bulge with gentle obtuse
angles with the aortic wall
19. Aortic arch anomalies
Left aortic arch with aberrant right subclavian
artery:
• Most common congenital arch anomaly
• Prevalence-0.4-2%
• Right subclavian is last branch to arise from
aorta
• may arise from a dilated diveriticulum like
structure-Kommerell diverticulum
• Not associated with congenital heart disease
Cause dysphagia lusoria by esophageal
compression(arteria lusoria)
21. Internal carotid artery
Origin:
• From common carotid by
bifurcation at level of C3-C4
vertebra
• Initially lies laterally and then
courses medially crossing
external Carotid artery
28. Internal carotid artery
Cervical segment(C1)
Parts:
Carotid bulb
Ascending cervical ICA
Course:
• Common carotid bifurcates at C3-
C4
• ICA is initially posterolateral then
becomes medial to ECA
Branches: NIL
Lateral
Antero-
posterior angio
29. Internal carotid artery
Cervical segment(C1)
Normal variants:
1)High bifurcation(up to C1)
or
low bifurcation(up to T2)
2)Medial origin-
• 10% pts
• can present as retropharyngeal
pulsatile mass
3)Tortuous course
Low bifurcation at C7 level-oblique anteroposterior angio
ICA
31. Internal carotid artery
Cervical segment(C1)
Anomalies:
1)Anomalous origin:
both internal and external carotids arise directly from aortic arch
2) Agenesis:
• 0.01%
• unilateral
• differentiated from acquired ICA occlusion–absent carotid canal on side of
agenesis
• increased chances of aneurysms
3.Hypoplasia
4.Duplication/fenestration
5.Anamolous branches
6.Carotid-basilar anastomosis:
• Persistent hypoglossal artery
• Persistent Proatlantal arteriy
32. Hypoplastic ICA
Lateral view of common carotid-
hypolplastic ICA
Axial fat
saturated MR
Scan –Absent
flow void in right
ICA
CT Scan through skull Base-absent
right carotid canal
33. Cervical segment(C1)
• Anamolous branches:
Includes the vessels that normally
originate from
-ECA :ascending pharyngeal and
occipital arteries
-other segments of ICA like vidian
artery
-vertebrobasilar circulation like
cerebellar arteries
Lateral view- Occipital artery arising from ICA
38. Persistent Pro-Atlantal intersegmental arteries
Association:
one or both VA are typically hypoplastic.
Two types
Type 1:
arises from the ICA and joins the V4
segment
Type 2 :
arises from the ECA and joins the V3
segment
Both entering the skull via the foramen
magnum.
Type 1 PIA-arising from ICA
39. Internal carotid artery
Petrous ICA(C2):
Parts:
Vertical segment
Horizontal segment
Genu(knee)
Branches:
1)Caroticotympanic artery:
• supply middle ear, anastomoses with inferior
tympanic artery (branch of ascending
pharyngeal)-ECA
• Arises from genu
2)Vidian artery(artery of pterygoid canal)
arises from horizontal segment
anastomoses with ECA branches
40. Petrous ICA
Lateral view AP View
Inverted L Shape of petrous segment
White arrow-->lacerum segment
41. Petrous ICA
Lateral view- Vidian artery
Caraticotympanic
artery
Inferior
tympanic
artery
Asc
pharyngeal
art
In abberant ICA with agenesis of vertical segment
of petrous ICA Inferior tympanic artery
hypertrophies and brings blood to ICA
42. Internal carotid artery
Petrous ICA(C2):
Anomalies:
1)Aberrant ICA
2)Persistent stapedial artery
3)Persistent Otic artery:
• one of the rarest variants of the carotid-vertebrobasilar anastomoses
• arise from petrous ICA
• passes through the internal auditory canal to join the BA
43. Petrous ICA(C2):Anomalies
Aberrant ICA :
• It is a congenital vascular anomaly that enters the posterior middle ear
cavity(usually ICA courses anterior to middle ear cavity) from below and
hugs the cochlear promontory as it crosses the middle ear cavity
• The ICA finally resumes its normal, expected course as it joins the
posterior lateral margin of the horizontal petrous ICA.
• Present with pulsatile tinnitus
• otoscopic examination : vascular- appearing retrotympanic mass
• Biopsy may result in fatal haemorrhage
44. Aberrant petrous ICA
• Narrowing at entry into inferior
tympanic canaliculus
• Posterior and lateral course
45. Petrous ICA(C2):Anomalies
Persistent Stapedial Artery.
• embryonic stapedial artery persists postnatally.
• discovered incidentally at imaging or at surgery.
• arises from the C2 (petrous) ICA at the genu
• The PSA passes through the stapes footplate and doubles the size of the
anterior (tympanic) facial nerve segment
• . Intracranially, the PSA becomes the middle meningeal artery (MMA).
Pathognomonic imaging findings
• (1) the absence of the foramen spinosum (because the MMA arises from
the PSA, not the ECA)
(2) an enlarged tympanic segment of the facial nerve
• A PSA is often—but not invariably—associated with an Aberrant ICA
47. LACERUM ICA(C3)
• Small segment that extends from
petrous apex above foramen lacerum
curving upwards and then becomes the
cavernous segment
• Covered by trigeminal ganglion
• No branches
48. CAVERNOUS ICA
• Starts from petrous apex
• Terminates at its entrance into intracranial
subarachnoid space adjacent to anterior
clinoid process.
• Covered by trigeminal ganglion posteriorly.
Segments
• Ascending (posterior vertical )
• Posterior genu
• Horizontal
• Anterior genu
• Anterior vertical
49. CAVERNOUS ICA
Branches:
1)Meningohypophyseal artery:
• arises from the posterior genu
• Supplies- pituitary gland, tentorium, and clival dura
2)Inferolateral trunk:
• arises from the lateral aspect of the intracavernous ICA
• Supplies- cranial nerves and Cavernous Sinus dura.
• anastomoses freely with branches from the ECA that arise in
the pterygopalatine fossa.
• This important connection between the external and internal
carotid circulations may provide a source of collateral blood
flow in the case of ICA occlusion.
52. Anomalies of C4 ICA
Persistent trigeminal artery:
• Most common of the persistent
embryonic carotid-basilar anastomose
• Identified in 0.1-0.2%
• PTA arises from posterior genu of
cavernous segment of ICA
53. Persistent trigeminal artery
Saltzmann type I:
• PTA joins the basilar artery between the superior cerebellar arteries and
anterior inferior cerebellar arteries.
• The basilar artery proximal to the junction is usually hypoplastic
• PCoAs are absent
• PTA supplies the entire vertebrobasilar system distal to the anastomosis.
Saltzmann type II:
similar to type 1 but PCoAs are present and supply the posterior cerebral
arteries
Saltzmann type III :
which directly joins to the cerebellar artery.
54. Anomalies of C4 ICA
Persistent trigeminal artery
Importance of PTA:
• Prior to transsphenoidal surgery for pituitary
adenoma as PTA passes laterally to dorsum
sella /has intrasellar course
• Nearly one-quarter of all PTAs have associated
vascular abnormalities, such as saccular
aneurysm, moya moya, aortic coarctation, and
arterial fenestrations.
• Sagittal CTA and MRA show a "Neptune's
trident" configuration
Neptune's trident sign-
PTA with vetical and horizontal
segments of cavernous ICA
59. Superior hypophyseal artery
• Arises from posteromedial aspect of
supraclinoid ICA
Course – across the ventral surface of
optic chiasma
• 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
60. Communicating segment(C7)
• Begins just proximal to origin of posterior communicating artery
and ends by dividing into anterior and middle cerebral arteries
• Passes between optic nerve and oculomotor nerves
Branches:
1)Posterior communicating artery
2)Anterior choroidal artery
61. Communicating segment(C7)
Posterior communicating artery:
Origin
posterior aspect of l ICA just below anterior
choroidal artery
Course
Posterlaterally above the oculomotor nerve
to join posterior cerebral artery
Branches
Anterior thalamo-perforating arteries
Supplies -optic chiasma, pituitary stalk ,
thalamus , hypothalamus.
PCoM
Opthalmic
artery
Ant chor Art
Lateral view
62. Communicating segment(C7)
Anterior Choroidal artery:
Arises few mms above PCoA ,from postero-medial aspect of
supraclinoid ICA
Has 2 segments
1)Cisternal segment
courses posteromedially in suprasellar cistern below
optic tract and superomedial temporal lobe uncus
2)Intraventricular segment
enters temporal horn by turning sharply laterally-Plexal
point
66. Communicating segment(C7)
Variants:
PCoA:
1)Hypoplasia-seen in upto 1/3rd of
cases
2)duplication/fenestration-rare
3)Fetal origin of PCA
4)Infundibular PCoA:
• Seen in 5-15% cases
• Should be 2 mm or less
• Funnel shaped , conical
• PCoA arises from apex of
infundibulum
67. • Parts:
• A1(precommunicating segment): from its
origin to the anterior communicating artery
(AcomA)
• A2 (infracallosal segment) - runs into the
interhemispheric fissure upward in front of
the lamina terminalis to the genu of the
corpus callosum
• A3 (precallosal segment) - curves around the
genu of the corpus callosum,
• A4 (supracallosal segment) - It runs
posteriorly in the pericallosal cistern, above
the surface of the corpus callosum, toward
the splenium.
Anterior cerebral artery
76. Persistent primitive olfactory artery
• Hypoplastic proximal ACA takes
a very long anterior and
inferomedial course along the
ipsilateral olfactory tract just
above the cribriform plate. It
then makes a tight
posterosuperior "hairpin" turn
to continue as the normal distal
ACA.
• Long ACoA and absent
Recurrent art of Heubner
• associated with saccular
aneurysm, usually at the
"hairpin" turn
81. Sylvian point and sylvian triangle
-superior insular line should lie half way
between petrous ICA and inner table of
skull-displacement or deformation usually
indicates intracranial mass
89. Vertebral artery
Normal Variants :
• Variation in size:
75%cases- left vertebral dominant(large) and 25% cases right
vertebral is large i.e., dominant
• Vertebral artery terminates as PICA
Anamolies:
Direct origin from aortic arch-5% cases
PICA origin below foramen magnum
Fenestration and duplication
104. Posterior cerebral artery
Variants:
Embryonic/fetal origin of PCA:
• Usually P1 segment is larger than ipsilateral PCoA
• In 20%cases P1 segment is smaller than PCoA and blood supply to
occipital lobe is received from ICA via PCoA instead of vertebro basilar
system
• Should be distinguished from PCA occlusion which is uncommon
though.
• Injecting ipsilateral ICA confirms Fetal PCA
105.
106. Posterior cerebral artery
NORMAL PCA Partial fetal PCA
Complete Fetal
ACA
CAROTID Angio lateral
view with PCA origin
from ICA
Partial fetal PCA Complete fetal PCANORMAL PCA
107. Posterior cerebral artery
Other anomalies associated with PCA
• Persistent carotid basilar anastomosis-persistent trigeminal artery
,pro atlantal intersegmental artery
• Anamolous origin of PCA branches from ICA
108. Circle of Willis
• Anastomotic ring that surrounds the
basal brain structures and connects
the anterior and posterior
circulations with each other
• Source of potential collateral blood
flow to the occluded territory.
• COW has 10 components
Anterior Posterior
circulation
2 B/L ICAs
2ACAs
Unpaired ACoA
anteriorly
Posterior
circulation
Basilar
bifurcation
2 PCAs from Bas
B/L PCoAs
110. Circle of willis-Branches
ACAs
ACoAs
PCoA
Basilar artery
PCA’s
• Medial lenticulostriate arteries
• Recurrent artery of Heubner
• Perforating branches
• median artery of corpus callosum
• Anterior thalamo perforating
arteries
• Posterior thalamoperforating arteries
• Thalamogeniculatearteries
111. Circle of willis-variants
• Complete COW –only 20 – 25%
• Posterior circle anomalies – 50% anatomy
specimens and PCoA most commonly
effected
1) Hypoplasia of 1 or both PCoA – 34%
2) Fetal origin of PCA from ICA
• Anterior circle anomalies-
1)Hypoplasia or absent A1 ACA segment.
2)Absent , duplicate or multichannel
ACoA – 10-15%
Absent ACoA
Hypoplastic A1
112. External Carotid artery
• Smaller of the 2 carotids.
• Origin anterior and medial to
ICA.
• Supplies the extracranial
structures