Anatomy of the posterior cerebral circulation

Interventional Neuroradiology
Anatomy
Posterior Cerebral Circulation
Mohamed M.A. Zaitoun, MD
Interventional Radiology Consultant, Zagazig University Hospitals, Egypt
FINR-Switzerland
zaitoun82@gmail.com
Interventional Radiology Unit,
Zagazig University, Egypt

Knowing as much as possible
about your enemy precedes
successful battle and learning
about the disease process
precedes successful
management.

Vertebrobasilar System
-The vertebrobasilar or posterior cerebral
circulation supplies the posterior part of the brain
, namely the occipital lobes , parts of the
temporal and parietal lobes , thalamus and
cerebral peduncles , the brain stem , cerebellum
and the superior portion of the cervical cord
-It supplies cranial nerves and contributes to the
blood supply of dura and extracerebral
structures of the skull base and upper spine
-It comprises the vertebral , basilar and posterior
cerebral arteries and their branches
-It is normally connected to the carotid territory by
the posterior communicating arteries

Vertebral Artery
1-Origin
2-Course
3-Branches

1-Origin :
-The vertebral arteries are paired and have
variable calibers of about 3-4 mm with the
left usual larger (dominant)
-They are the first branch of the subclavian
arteries , arise from its superior aspect

2-Course :
-Arise from the superior aspect of the
subclavian artery and run vertically and
posteriorly to the level of the sixth cervical
vertebra (C6) (V1) where they enter the
foramen in the transverse process
-The VA then runs superiorly in the vertebral
canal passing through foramina in the
transverse processes of all the upper
cervical vertebrae (V2)

-After leaving the superior border of the foramen of
the atlas (C2) , it runs horizontally and
posteriorly to pass through the more laterally
positioned foramen of the axis (C1) and then
turns medially to the foramen magnum (V3)
-There , it penetrates the atlantooccipital
membrane and dura to enter the cranial cavity
through the foramen magnum and then runs
upwards and medially to terminate as the basilar
artery , formed by joining its contralateral
counterpart anterior to the upper border of the
medulla oblongata (V4)

-Frontal 2D view
following right vertebral
artery injection , there is
a normal appearance of
the cervical vertebral
artery extending
approximately to the
vertebral-basilar
junction
1 vertebral artery
2 muscular branches
3 radiculomedullary
feeder to anterior spinal
artery
4 PICA
C1 first cervical
vertebrae
C2 second cervical
vertebrae

-3D frontal view
following right
vertebral artery
injection , there is a
normal appearance
of the cervical
vertebral artery
extending
skull base
1 vertebral artery
2 muscular branches
C1 first cervical
vertebrae
C2 second cervical
vertebrae

-3D posterior view
following right
vertebral artery
injection , there is a
normal appearance
of the cervical
vertebral artery
extending
skull base
1 vertebral artery
2 muscular
branches
C1 first cervical
vertebrae
C2 second cervical
vertebrae

3-Branches :
a) Extracranial Branches
b) Intracranial Branches

a) Extracranial Branches :
-In its extracranial course , the VA gives branches
which supply the spinal cord and its dura ,
cervical vertebrae and muscles as well as the
dura of the inferior posterior fossa
-These include (from proximal to distal) :
1-Branches to the stellate ganglion
2-Spinal branches from C6 to C1
3-Arteries of the cervical expansion
4-Muscular branches
5-Anterior meningeal artery

1-Branches to the stellate ganglion
2-Spinal branches from C6 to C1 , the VA
contributes to the supply of the roots , nerve root
sheaths and bony structures of the vertebra
together with the deep cervical artery
(costocervical trunk) and ascending cervical
artery , at the C3 to C1 levels , spinal branches
of the VA contribute to the odontoid arterial
arcade together with collaterals from the
ascending pharyngeal artery and occipital artery

3-Arteries of the cervical expansion , spinal
radiculomedullary arteries support the anterior
spinal artery in the lower cervical spine (i.e. the
cervical expansion) and arise between C6 and
C4 , they are usually bilateral , they may arise
from the thyrocervical trunk
4-Muscular branches to the paraspinal muscles ,
these anastomose with branches of the deep
cervical and occipital arteries

5-Anterior meningeal artery , this very
small artery arises from the distal VA and
supplies the dura of the anterior foramen
magnum and the inferior clivus , it also
takes part in the anastomoses forming the
odontoid arterial arcade

Vertebral artery DSA (lateral view of the right side) , at C3 , a spinal artery branch is seen
running cranially to the odontoid arcade (white arrow) , the anterior spinal artery is
seen in the midcervical spine with contributing segmental spinal arteries at C4 and C5
(arrowheads) , the posterior-lateral spinal artery fills in the upper spine (short arrow)
via a contribution from the lateral spinal artery (double arrows) , the lateral spinal
artery is a descending branch of the intracranial vertebral artery

**N.B. : Odontoid Arterial Arcade
-The odontoid arcade represents a pathway whereby both
Ascending Pharyngeal and Vertebral arteries can all
connect to each other at the C1-C3 level
-The arcade is formed by branches of the AP and vertebral
arteries
-It outlines the odontoid process and upper cervical region ,
coursing behind the odontoid process and C2 body
-The arcade is formed as follows :
1-The hypoglossal division enters the hypoglossal canal
2-A descending branch from this division exits from the
foramen magnum and heads inferiorly along the back of
the dens and C2 body , eventually anastomosing with
the vertebral artery at the C3 level
3-Transverse branches at C1 and C2 levels project from
this descending branch to its contralateral homolog ,
eventually connecting to the contralateral vertebral and
ascending pharyngeal arteries , thus a system exists
whereby both AP and vertebral arteries are connected to
each other

AP view of right Hypoglossal division microcatheter injection with exquisite
demonstration of the odontoid arcade , a descending branch of the RT
hypoglossal division opacifies the arcade with visualization of the
contralateral AP anastomosis and vertebral arteries , the arcade is seen to
advantage because the remainder of right hypoglossal division has been
embolized , thereby diverting flow into the arcade

Dominant RT VA , an injection into the RT VA refluxes the LT VA , to interpret this
Townes projection , recall that one is looking at the posterior fossa from above ,
therefore , the PCOM (long arrows) course across the SCA bilaterally and
opacify the MCA (arrowheads) bilaterally , the arcade of the odontoid process is
well seen in this image filling from the C3 branches of the vertebral arteries
bilaterally (curved arrows)

b) Intracranial Branches :
-In its intracranial portion , the VA gives branches
that supply dura and the medulla oblongata ,
upper cervical cord and cerebellum , these are :
1-Posterior meningeal artery and artery of the falx
cerebelli
2-Medial Group of Perforator Branches
3-Anterior Spinal Artery
4-Lateral Spinal Artery
5-Posterior Inferior Cerebellar Artery

1-Posterior meningeal artery and artery
of the falx cerebelli :
-The vertebral artery may be the dominant
source of the artery of the falx cerebelli
-This easy-to-recognize vessel may arise
from the extracranial VA or from the
occipital artery or PICA , therefore ,
another potential route of anastomosis
between the occipital artery and the VAs

Anterior spinal artery and artery of the falx cerebelli , a lateral projection of the LT VA
shows a well-visualized anterior spinal artery (a.sp.a.) directed inferiorly along the
anterior surface of the medulla and spine , the LT PICA has a relatively high origin off
the intradural left vertebral artery , the artery of the falx cerebelli (f.cb.) arises from
the extracranial vertebral artery , it courses diagonally toward the torcular deviating
away from the inner table of the skull

Anterior spinal artery collateral flow to the basilar artery , PA views of the LT VA (a) & RT VA
(b) in a patient with bilateral distal vertebral artery occlusions and ischemia of the basilar
artery territory , the left vertebral artery is occluded distal to the origin of the LT PICA ,
however , the artery of cervical enlargement lower in the neck opacifies the anterior spinal artery ,
which has collateralized the vertebrobasilar junction , the midline course of the artery of the falx
cerebelli is well seen , the RT VA (b) is occluded just proximal to the dural margin , the anterior
spinal artery is seen again from this side flowing retrogradely to opacify the intracranial circulation

2-Medial Group of Perforator Branches :
-These supply the medulla oblongata and
pyramids
-An artery to the foramen caecum is described
which is one of this medial group of perforators ,
it ascends to the pontomedullar junction where a
concentration of perforator arteries congregate
in the midline to pass deep into the brain stem
and supply nuclei of the floor of the fourth
ventricle and long tracts

3-Anterior Spinal Artery :
-Usually bilateral , they descend medially to unite
and form a median artery usually at the C2/C3
level
4-Lateral Spinal Artery :
-This small branch supplies cranial nerve IXth and
runs caudally supplying the lateral spinal cord to
join the postero-lateral spinal artery at C4 , it
may arise from PICA

5-Posterior Inferior Cerebellar Artery :
a) Origin
b) Sections
c) Branches

(1) PCA , (2) SCA , (3) Pontine branches of the BA , (4) AICA , (5)
Internal auditory artery , (6) VA , (7) PICA , (8) Anterior spinal artery
, (9) BA

a) Origin :
-Posterior inferior cerebellar artery (PICA) typically
arises ca. 15 mm proximal to the confluence of
the VAs
-It is of variable caliber being reciprocal in size to
that of the ipsilateral anterior inferior cerebellar
artery (AICA)
b) Sections :
-Classically , the PICA course is separated into
five sections : anterior medullary , lateral
medullary , tonsillomedullary (posterior
medullary) , telovelotonsillar (supratonsillar) and
cortical

-The anterior medullary section is intimately
related to the hypoglossal nerve (which lies
anterior and between PICA and its parent
vertebral artery)
-The lateral medullary section runs around the
inferior surface of the olive to the XIth cranial
nerve
-The tonsillomedullary (posterior medullary)
section carries the artery between the spinal and
cranial roots of the XIth cranial nerve and then
behind the Xth and IXth cranial nerves to the
telovelotonsilar (supratonsillar) section where it
runs medial to the cerebellar tonsil , it enters the
telovelotonsilar section at the midpoint of the
tonsil , then it runs medial to the tonsil and
lateral to the vermis to reach the cortical surface
of the cerebellar hemisphere and its last
(cortical) section

-2D frontal view following right vertebral
artery injection , an intracranial view is
shown , these images show normal
intracranial vertebral basilar circulation
1 vertebral artery
2 (PICA)
2v vermian branch of PICA
2h hemispheric branch of PICA
3 basilar artery
4 (AICA)
5 (SCA)
5h hemispheric branch of SCA
6 (PCA)
6.2 P2 segment of PCA
7 PCOM
8 posterior temporal branch of PCA
9 parieto-occipital branch of PCA
10 calcarine branch of PCA
11 anterior thalamoperforators
12 posterior thalamoperforators
13m medial posterior choroidal arteries
13L lateral posterior choroidal arteries
14 vertebral-basilar junction
15 splenial branch (posterior
pericallosal artery) of PCA
17 anterior spinal artery
** region of quadrigeminal plate cistern

-2D lateral early arteiral view
following left vertebral artery
injection , the intracranial view of
the vertebral basilar circulation is of
a patient with vasculitis , the
vasculitis is illustrated by the
multifocal areas of stenosis
(narrowing) , the vascular
branching pattern shows a typical
appearance of vertebral basilar
circulation
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
6.2 P2 segment of (PCA)
7 PCOM
11 anterior thalamoperforating
arteries
12 posterior thalamoperforating
arteries
13m medial posterior choroidal
artery
13L lateral posterior choroidal
artery

c) Branches :
1-Perforators to the lateral and posterior aspect of
the medullar oblongata from the proximal three
sections
-These are small branches that supply the lateral
medulla and olive , they are sometimes
described as circumferential arteries depending
on their length
2-Choroidal arteries :
-These arise from the tonsillomedullary and
telovelotonsillar sections
-The apex of the cranial loop (telovelotonsillar
sections) is described as the choroidal point
which marks the roof of the fourth ventricle on
the lateral angiogram
-It is the distal limit for perforator arteries to arise
from the PICA trunk

3-The distal PICA usually bifurcates into two
main trunks :
a) The smaller (vermian) stays close to the
midline and supplies the median structures
along the inferior surface of the vermis
b) The larger (tonsillohemispheric) trunk
serves the posterior aspects of the tonsil
and fans over the lateral inferior cerebellar
surface
4-The lateral spinal artery and the posterior
meningeal arteries may arise from PICA
rather than the vertebral artery

Inferior vermian branches (i.v.a.) of the PICA , the superior vermian
branches of the SCA (s.v.a.) are also enlarged in this arteriovenous
malformation of the vermis

-2D lateral view following vertebral
artery injection , intracranial vertebral
basilar circulation is seen with a
moderate-size aneurysm arising from
the distal vertebral artery near the
origin of the PICA
vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
6 (PCA)
arteries
13m medial posterior choroidal
arteries
13L lateral posterior choroidal
arteries
pericallosal artery) branch of PCA

Basilar Artery
1-Origin
2-Course
3-Branches

1-Origin :
-BA is formed by joining of both VAs anterior
to the upper border of the medulla
oblongata

-3D frontal view following left
vertebral artery injection ,
shows the intracranial vertebral
basilar circulation in a patient
with severe atherosclerotic
vascular disease , note the
moderately severe stenosis of
the midbasilar artery in addition
to a generalized vessel
irregularity
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
5v vermian branch of SCA
8 posterior temporal branch of
PCA
9 parieto-occipital branch of
PCA

-3D frontal view shows
lobulated aneurysm
arising from the tip of the
basilar artery projecting
posteriorly into the
interpeduncular cistern
1 vertebral artery
2 PICA
3 basilar artery
4 AICA
5 SCA
7 PCOM
9 parieto-occipital branch
of PCA
10 calcarine branch of
PCA
14 vertebral basilar
junction

-2D frontal view following vertebral
artery injection , shows normal
intracranial vertebral basilar
circulation , note the blush (*) of the
choroid plexus
1 vertebral artery
2 posterior inferior cerebellar artery
(PICA)
3 basilar artery
4 anterior inferior cerebellar artery
(AICA)
5 superior cerebellar artery (SCA)
6 posterior cerebral artery (PCA)
arteries
13L lateral posterior choroidal artery
16 pontine perforating artery
* blush of choroids plexus

-3D frontal view following vertebral
artery injection , shows normal
circulation
1 vertebral artery
2 posterior inferior cerebellar artery
(PICA)
3 basilar artery
4 anterior inferior cerebellar artery
(AICA)
5 superior cerebellar artery (SCA)
arteries
16 pontine perforating artery

2-Course :
-The basilar artery arises just below the
pontomedullary junction between the VIth cranial
nerves and runs superiorly on the anterior
surface of the pons to terminate at the
pontomesencephalic junction
-The level of the basilar bifurcation is variable :
*In 50 % of individuals , it is usually within 1 cm of
the superior surface of the dorsum sella
*In 30% of individuals , it is above
*In 20% of individuals , below this range
-Relative to the brain stem , the termination can be
as far caudally as 1 cm below the
pontomesencephalic junction and as far rostral
as the mammillary bodies

3-Branches :
-Its branches can be divided into two groups
, the perforating arteries and the long
circumferential arteries

a) The Perforating Arteries :
-Are paramedian and circumferential in
distribution
-They supply the corticospinal tracts , other
connecting white matter tracts and the vital
deep nuclei of the pons and midbrain
-In the physiological state , they are rarely
visible on angiography and do not cross
the midline

-2D frontal view following left vertebral
artery injection , the intracranial view of
the vertebral basilar circulation is of a
patient with vasculitis , the vasculitis is
illustrated by the multifocal areas of
stenosis (narrowing) , the vascular
appearance of vertebral basilar
circulation
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
7 PCOM
11 anterior thalamoperforating arteries
12 posterior thalamoperforating arteries
13m medial posterior choroidal artery
14 vertebral basilar junction

-2D lateral early arteiral view following left
vertebral artery injection , the intracranial
view of the vertebral basilar circulation is
of a patient with vasculitis , the vasculitis
is illustrated by the multifocal areas of
stenosis (narrowing) , the vascular
appearance of vertebral basilar circulation
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
7 PCOM
15 splenial branch (posterior pericallosal
artery) of PCA

-2D lateral late arterial phase view following
left vertebral artery injection , the
intracranial view of the vertebral basilar
circulation is of a patient with vasculitis ,
the vasculitis is illustrated by the multifocal
areas of stenosis (narrowing) , the vascular
appearance of vertebral basilar circulation
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
7 PCOM
artery) of PCA

b) The Long Circumferential Arteries :
1-Internal Auditory Artery (Labyrinthine
Artery)
2-The Anterior Inferior Cerebellar Artery
(AICA)
3-The Superior Cerebellar Artery (SCA)
4-Posterior Cerebral Artery (PCA)

1-Internal Auditory Artery (Labyrinthine
Artery) :
-Arises from the basilar artery or AICA and
runs laterally to the internal auditory canal
where it gives cochlear and vestibular
branches
-A small branch , the subarcuate artery
supplies meninges of the subarcuate fossa
and the bone of the semicircular canals

2-The Anterior Inferior Cerebellar Artery
(AICA) :
a) Origin
b) Course
c) Branches

a) Origin :
-Arises at the junction of lower one-third and upper two-
thirds of the basilar artery
b) Course :
-It courses laterally and inferiorly to embrace the belly of
the pons
-It continues to traverse the cerebellopontine angle cistern
to lie anterior and medial to the facial and acoustic
nerves and divides into a rostral (lateral) branch and a
caudal (medial) branch
-The AICA often loops into and out of the internal auditory
canal (referred to as the “meatal loop” ) which is often
seen at angiography

-The meatal loop gives rise to a small
branch supplying the eighth cranial nerve
(vestibular cochlear nerve) called the
acoustic branch (internal auditory artery)
-The AICA then courses laterally to the
terminal branches
-It then supplies the anterior and inferior
cerebellum

c) Branches :
1-The artery of the internal auditory meatus :
-Usually arises from the proximal trunk or loop
of the anterior inferior cerebellar artery and
supplies the nerve roots of the internal
auditory canal and the sensory structures of
the inner ear
-Less frequently , this artery may arise directly
from the basilar artery distal to the origin of
the anterior inferior cerebellar artery

2-It supplies the inferior cerebellar peduncle , the
middle cerebellar peduncle and the inferior
portion of the flocculus and the adjacent
cerebellar hemisphere
3-The choroid plexus of the lateral recess of the
fourth ventricle is also supplied by this artery , it
anastomoses on the surface of the cerebellar
hemispheres with branches of PICA and the
superior cerebellar arteries

-3D frontal ) view following left
vertebral artery injection , this view
show intracranial vertebral basilar
circulation in a patient with severe
atherosclerotic vascular disease ,
note the multifocal areas of vessel
irregularity and narrowing (stenoses)
and the severe narrowing of the
distal right vertebral artery (*) , this is
a good demonstration of a right
AICA-PICA where a medial branch of
AICA supplies all or a portion of the
PICA territory
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
4 – PICA AICA-PICA
5 (SCA)
* severe stenosis (narrowing) distal
right
vertebral artery

3-The Superior Cerebellar Artery (SCA) :
a) Origin
b) Course
c) Branches

a) Origin :
-Arises 1-3 mm below the termination of BA and
parallels the course of the posterior cerebral
arteries (PCA) around the cerebral peduncle in
the ambient cistern
-It has a duplicated origin in 14% to 28% of cases
-With a similar frequency , it may share a common
ostium with the ipsilateral posterior cerebral
artery , less commonly , it arises from the P1
segment

-3D frontal view following right
vertebral artery injection , this
view shows normal
circulation , note the
duplication of the right SCA ,
this is a normal variant
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
5h hemispheric branch of
SCA
6 (PCA)
PCA
9 parieto-occipital branch of
PCA

-3D RAO view following right
vertebral artery injection , this
view shows normal intracranial
vertebral basilar circulation , note
the duplication of the right SCA ,
this is a normal variant
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
6 (PCA)
PCA

-3D complex angle from below
and from the left view following
right vertebral artery injection ,
this view shows normal
circulation , note the duplication
of the right SCA , this is a normal
variant
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
6 (PCA)
PCA

RT PCA and SCA arise as a common trunk (arrowhead)

b) Course :
-It is separated from the PCA by the
oculomotor nerve medially and the
trochlear nerve laterally
-Lying below the free edge of the tentorium it
divides posterolateral to the midbrain into
the superior vermian artery and branches
to the superior cerebellar hemisphere

c) Branches :
-Supplies the lower midbrain , upper pons , upper
vermis and superior aspects of the cerebellar
hemispheres
-The two main terminal branches are the vermian
and hemispheric branches that supply the
superior surface of the cerebellum and
cerebellar vermis as well as supply the
superolateral aspect of the cerebellar
hemispheres, superior cerebellar peduncle , a
portion of the middle cerebellar peduncle and
the dentate nucleus

4-Posterior Cerebral Artery (PCA) :
a) Origin
b) Segments
c) Course
d) Branches

a) Origin :
-The paired posterior cerebral arteries are
the terminal branches of the basilar artery
and complete the posterior circle of Willis

b) Segments :
-P1 : From it origin at the termination of the basilar
artery to PCOM within interpeduncular cistern
(thus interpeduncular segment)
-P2 : From the PCOM around the back of the mid-
brain , divided into >>
*P2A (anterior) sub-segment
*P2P (posterior) sub-segment
P2A is within crural cistern which then bridges to
the P2P segment in ambient cistern
(thus ambient segment)
-P3 : Quadrigeminal segment (segment with the
quadrigeminal cistern)
-P4 : Cortical segment (e.g. , calcarine artery ,
within the calcarine fissure)

c) Branches :
-The PCA supplies the posterior cerebral
hemisphere , thalamus , midbrain and structures
in the walls of the third ventricle and choroidal
fissure
-Three broad categories of branches from the PCA
are identified :
a) Direct & Circumflex perforating branches to the
brainstem and thalamus
b) Ventricular branches winding around the
brainstem to the choroidal fissure
c) Cortical branches

a) Direct & Circumflex perforating
branches to the brainstem and
thalamus :
-These centrally directed branches fall into
two patterns :
*Direct branches arise from the PCA and
enter the brainstem immediately , this
pattern includes :
1-The posterior thalamoperforator arteries
from the P1 segment directed superiorly

2-The thalamogeniculate arteries from the
P2 segment directed superiorly and
laterally
3-The peduncular perforating branches from
the P1 and P2 segments directed centrally
into the peduncle and brainstem
*Circumflex branches encircle the
brainstem in a course parallel to that of the
PCA for variable distances before entering
the thalamus or mesencephalon

*Direct Branches >>
1- Posterior Thalamoperforator Arteries
2-Thalamogeniculate Branches
3-Peduncular Perforating Branches

1- Posterior Thalamoperforator Arteries :
-The thalamoperforating arteries enter the
posterior perforating substance and supply the
posterior part of a territory shared with the
anterior thalamoperforating arteries (which arise
from PComA)
-These vessels between them (i.e. anterior and
posterior thalamoperforating arteries) supply the
anterior and posterior parts of the thalamus ,
posterior optic chiasm and tracts , the posterior
limb of the internal capsule , hypothalamus , sub
thalamus , substantia nigra , red nucleus and the
oculomotor and trochlear nuclei , as well as
parts of the rostral mesencephalon including
part of the cerebral peduncles

-They may arise from the terminal basilar
artery or from the SCA
-An azygos posterior thalamoperforator
trunk artery that supplies both thalami is
well described and is generally known as
the artery of Percheron

A single midline vessel (Percheron) (longer arrow) arises from the right P1 segment
and supplies bilateral thalamoperforator vessels , proximal branches of the P1
segments bilaterally (shorter arrows) , probably representing medial posterior
choroidal arteries or circumflex branches , parallel the course of the PCA

2-Thalamogeniculate Branches :
-This group of perforator arteries (usually 8-
10) arise from the P2 segment of the PCA
or , less commonly from the P3 segment
and supply the medial and lateral
geniculate bodies , the lateral and inferior
part of the thalamus and the posterior
internal capsule

3-Peduncular Perforating Branches :
-Up to six branches from the P1 and P2
segments enter the cerebral peduncle
directly to supply the corticospinal and
corticobulbar tracts , substantia nigra and
red nucleus , they also supply the
tegmental and cisternal portions of the
oculomotor nerve

*Circumflex arteries (short and long) :
-The circumflex arteries (two or more arteries)
arise from the distal P1 or proximal P2 and
parallel the course of P2 in the ambient cistern
-They follow the main trunk around the midbrain
and give small branches to the cerebral
peduncles and tectum
-The long circumflex artery extends to the colliculi
and supplies the tectum , tegmentum , cerebral
peduncle and geniculate body

-The short circumflex artery supplies just the
geniculate body , the peduncle and part of
the tegmental area
-The tectum and quadrigeminal plate is also
supplied by branches of the superior
cerebellar artery

b) Ventricular Branches of the PCA :
-Two groups of branches directed toward
the choroid plexus and its adjacent
structures arise from the PCA
1-Medial Posterior Choroidal Arteries
2-Lateral Posterior Choroidal Arteries

1-Medial Posterior Choroidal Arteries :
-The medial posterior choroidal artery arises from
the medial side of the PCA as 1-3 vessels and
run medially to enter the roof of the third
ventricle in the velum interpositum
-It gives branches in its proximal ‘cisternal’ course
(in the ambient , quadrigeminal and pineal
cisterns) to adjacent structures , i.e. the tectum ,
pineal gland , habenula and medial geniculate
body and posterior thalamus

-Within the velum interpositum , it runs
forwards to the foramen of Monro ,
supplying choroid plexus and
anastomoses with terminal branches of
the lateral posterior choroidal arteries
,which have come ‘the other way’ through
the lateral ventricle

2-Lateral Posterior Choroidal Arteries :
-The lateral posterior choroidal arteries are a group
of arteries that arise from the lateral surface of
the PCA , usually distal to the medial posterior
choroidal arteries and run superior and anteriorly
to enter the choroidal fissure and the lateral
ventricle
-In their ‘cisternal’ course (in the ambient cistern) ,
they give branches to supply the cerebral
peduncle , the pineal gland , the splenium of the
corpus callosum , posterior commissure , tail of
the caudate nucleus , lateral geniculate body
and thalamus (dorsomedial nucleus and
pulvinar)

-In the ventricle , the arteries pass around
the pulvinar and forwards to the foramen
of Monro
-They supply the choroid plexus and give
additional branches to the thalamus

1-Ant. Thalamoperforating , 2-Post. Thalamoperforating , 3-
Thalamogeniculate , 4-Med. post. Choroidal , 5-Lat. post. Choroidal ,
6-Post pericallosal , 7-Parieto-occipital , 8-Calcarine

c) Cortical branches :
1-Temporal branches
2-Parietal-occipital artery
3-Calcarine artery
4-Splenial (posterior pericallosal) arteries
5-Meningeal branch or artery of Davidoff &
Schechter

1-Temporal branches :
-The temporal lobe supply from the PCA is normally
arranged as :
(a) Hippocampal artery
(b) Anterior temporal artery
(c) Middle temporal artery
(d) Posterior temporal artery
-These supply the brain in partnership with the middle
cerebral artery cortical branches
-The hippocampal artery is found in only two thirds of
dissections , it arises most proximally and supplies the
uncus and hippocampus and dentate gyri
-The middle temporal branch is usually smaller than the
anterior and posterior arteries

-2D frontal early arterial phase shows
(AVM) of the brain , these lesions generally
consist of three main elements , the first
element is the arterial feeder(s) to the
malformation which in this case are
posterior temporal artery branches of the
PCA , the second element of an AVM is the
nidus , the third element consists of
draining vein(s)
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
6.2 P2 segment PCA
7 PCOM
8 posterior temporal branches of PCA
artery) branch of PCA
DV main draining vein of AVM
dv-s AVM draining vein – dural sinus
junction
TV transverse sinus
SS sigmoid sinus

-2D frontal late arterial phase shows (AVM)
of the brain , these lesions generally
draining vein(s)
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
6.2 P2 segment PCA
7 PCOM
junction
TV transverse sinus
SS sigmoid sinus

-2D lateral early arterial phase shows
(AVM) of the brain , these lesions generally
draining vein(s)
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
6.2 P2 segment PCA
7 PCOM
junction
TV transverse sinus
SS sigmoid sinus

-2D lateral late arterial phase shows (AVM)
of the brain , these lesions generally consist
of three main elements , the first element is
the arterial feeder(s) to the malformation
which in this case are posterior temporal
artery branches of the PCA , the second
element of an AVM is the nidus , the third
element consists of draining vein(s)
1 vertebral artery
2 (PICA)
3 basilar artery
4 (AICA)
5 (SCA)
6.2 P2 segment PCA
7 PCOM
junction
TV transverse sinus
SS sigmoid sinus

2-Parietal-occipital artery :
-This is the largest and most superior of the
terminal branches of the PCA
-It runs in the parieto-occipital fissure and is
a cortical branch supplying the cuneas ,
precuneas and superior occipital gyrus
-It may also supply the precentral region
(medial surface of the hemisphere) and
superior parietal lobule
-It often gives an accessory calcarine branch
to the visual cortex

3-Calcarine artery :
-This is the artery of supply to the visual cortex
-It usually arises from the PCA trunk but may arise
from the parieto-occipital artery or posterior
temporal artery
-Typically its origin appears inferior to the parieto-
occipital artery on a lateral angiogram and
because it runs deep in the calcarine fissure , it
appears lateral to the larger parieto-occipital
artery on the frontal view
-It also supplies part of the cuneas and lingual
gyrus as well as the calcarine cortex

-2D frontal view following right vertebral
artery injection show the intracranial
vertebral basilar circulation in a patient
with an (AVM) in the right occipital lobe
, this AVM is supplied by enlarged right
calcarine (10) and parieto-occipital (9)
branches of the right PCA , this
demonstrates the enlargement of these
two branches of the PCA due to the
AVM and allows for easy identification ,
a perinidal aneurysm is indicated by (**)
1 vertebral artery
2 (PICA)
3 basilar artery
4 AICA (4)
5 (SCA)
7 PCOM
pericallosal artery)
of PCA
** perinidal aneurysm

-2D lateral view following right vertebral
artery injection show the intracranial
vertebral basilar circulation in a patient
with an (AVM) in the right occipital lobe ,
this AVM is supplied by enlarged right
calcarine (10) and parieto-occipital (9)
branches of the right PCA , this
demonstrates the enlargement of these
two branches of the PCA due to the AVM
and allows for easy identification , a
perinidal aneurysm is indicated by (**)
1 vertebral artery
2 (PICA)
3 basilar artery
4 AICA (4)
5 (SCA)
7 PCOM
artery)
of PCA
** perinidal aneurysm

4-Splenial (posterior pericallosal) arteries:
-These are usually a group of small arteries rather
than solitary bilateral arteries , whose origin
varies between the parieto-occipital artery , the
calcarine and the posterior temporal branches of
the PCA
-They initially run posteriorly and then anteriorly
and superior to the splenium of the corpus
callosum
-They anastomose with the terminal branches of
the pericallosal artery and can form an effective
collateral supply to the anterior cerebral artery
territory

5-Meningeal branch or artery of Davidoff
& Schechter :
-A small dural branch that arises from the
choroidal or distal cortical branches of the
PCA that is seen only seen on
angiography when pathologically enlarged
-It supplies the tentorium and posterior falx

(a) Frontal view of the right vertebral angiogram demonstrating the artery of
Davidoff and Schechter (ADS) supplying the dural AVF (arrows) , (b) Lateral
view of the right vertebral angiogram demonstrating the artery of Davidoff
and Schechter (ADS) supplying the dural AVF (arrows)

**N.B. : Fetal PCOM or Fetal origin of the PCA
-A very common variant in the posterior cerebral circulation
-It is estimated to occur in up to 30% individuals
-The PCOM is larger than the P1 segment of the PCA and
supplies the bulk of the blood to the PCA , and the
dominant blood supply to the occipital lobes comes from
the ICA
-If bilateral , the basilar artery is significantly smaller than
normal
-The term is typically used to refer to the situation where
the PCOM is larger than the P1

(a) Hypoplastic RT A1 segment of the ACA (thin arrow) and bilateral
fetal-type origin of the PCA with bilaterally hypoplastic P1 segments
(thick arrows) and enlarged PcomAs (block arrows) , (b) Unilateral
(left) fetal-type origin of the PCA with the PcomA diameter (thin
arrow) larger than the P1 diameter

-The P1 can be small (hypoplastic) or absent
(uncommon)
-The significance is in the stroke pattern , as the
PCA is therefore part of the anterior circulation ,
additionally a larger PCOM (with P1 present)
allows for collateral circulation
-In case of non fetal PCA , the PCOM lies
superomedial to the occulomotor nerve ,
whereas in case of fetal PCA , it lies superior or
superolateral to the occulomotor nerve

Bilateral large posterior communicating arteries (arrows) which provide
most of the blood supply to the posterior cerebral artery territory ,
both P1 segments are present but hypoplastic

CT angiogram shows bilateral fetal posterior cerebral arteries (arrows) ,
both P1 segments are absent , the arrowheads indicate the superior
cerebellar arteries

-Normally the PCOM
arises from the ICA just
proximal to the ICA
bifurcation joins PCA at
the junction of P1 and P2
segments
-Fetal PCA or Persistent
fetal origin of PCA defined
as a prominent PCOM that
gives rise to or continues
as PCA p2 segment and
onwards with same
diameter
-Ipsilateral PCA p1
segment is usually
hypoplastic or may be
absent

-Lateral view , left carotid injection demonstrates the origin
of the left PCA directly from the supraclinoid region of
ICA

-AP left carotid injection demonstrates the origin of the left
PCA directly from ICA

-2D Phase Contrast MRA demonstrates origin of the left
PCA from the left ICA (arrow)

-Lateral 3D TOF MRA from the same patient showing the
PCA origin from the ICA (arrow)

Anatomy of the posterior cerebral circulation

Anatomy of the posterior cerebral circulation

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Anatomy of the posterior cerebral circulation