Vascular anatomy of the brain

1. ‫الرحيم‬ ‫الرحمن‬ ‫هللا‬ ‫بسم‬,
‫هلل‬ ‫والحمد‬‫العالمين‬ ‫رب‬,
‫أشرف‬ ‫علي‬ ‫والسالم‬ ‫والصالة‬
‫علي‬ ‫و‬ ‫محمد‬ ‫نبينا‬ ‫المرسلين‬
‫أجمعين‬ ‫صحبه‬ ‫و‬ ‫اله‬

2. Brain
anatomy
Protective
coverings
Scal
p Bone Meninges
Brain
parenchyma
Cerebrum
Cerebellu
m Brain stem
Cranial
Nerves.
Limbic
system
Vascular
anatomy
Arterial Venous
CSF
spaces
Ventricular system Cisterns

3. Intended learning objectives (ILOs)
1. To understand vascular anatomy
that is fundamental to
interpretation of neuroimaging.
2. Answering the following questions:
A. Which vascular territory
affected in this case?

4. Intended learning objectives (ILOs)
Answering the following questions
B. Which arrowed vessel in that
angiographic image?

5. Brain
anatomy
Protective
coverings
Scal
p Bone Meninges
Brain
parenchyma
Cerebrum
Cerebellu
m Brain stem
Cranial
Nerves.
Limbic
system
Vascular
anatomy
Arterial Venous
CSF
spaces
Ventricular system Cisterns

6. Arterial supply of the brain
■ Brain derive its blood supply
through two circulations:-
– Anterior from ICA.
– Posterior from vertebrobasilar
artery.

7. Internal Carotid
artery (ICA)
■ Origin: arising as one of two terminal
branches of the CCA between C3-C5 level.
■ Course: There are several classification
systems, the most recent and most widely
used is Bouthillier Classification

8. These image are:-
*DSA
*CTA
*MRA

9. ICA
■ Bouthillier classification:
■ Cervical segment C1…how to
differentiate it from ECA?
■ Petrous segment C2:
– enters carotid canal in petrous
temporal bone.
– 3parts:-
• Short vertical segment –
anterior to IJV
• Genu – petrous ICA turns
anteromedially in front of
cochlea
• Longer horizontal segment
― exit at petrous apex

10. Internal Carotid
artery (ICA)
■ Lacerum segment C3:
 Small segment that
extends above foramen
lacerum curving upwards
to enter the cavernous
segment
 Covered by trigeminal
ganglion

11. Internal Carotid
artery (ICA)
■ Cavernous segment C4
 Terminates adjacent to anterior clinoid
process.
 4parts:-
1. Ascending (posterior vertical )
2. Posterior genu
3. Horizontal
4. Anterior genu
5. Anterior vertical

12. 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
Posterior genu
Carotid sulcus
Anterior genu
Post. Clinoid
process

13. Internal Carotid
artery (ICA)
■ Clinoid segment C5:
■ Starts distal to cavernous sinus
■ Ends at anterior clinoid process
■ Ophthalmic (supraclinoid) segment C6:
■ Extends from superior to ant. clinoid
process to just proximal to (PCOM)
origin
■ communicating (terminal) segment C7:
■ Extends from distal to PCOM to
terminal ICA bifurcation.
■ Passes between optic and oculomotor
nerve.

14. Internal Carotid
artery (ICA)
■ Branches:
■ C1: cervical segment, none
■ C2: petrous (horizontal) segment
– Caroticotympanic artery
– Vidian artery
■ C3: lacerum segment, none
■ C4: cavernous segment
– Meningohypophyseal
– Inferolateral trunk
■ C5: clinoid segment, none
■ C6: ophthalmic (supraclinoid) segment
– Ophthalmic
– Superior hypophyseal
■ C7: communicating segment
– PCOM.
– ACA.
– MCA.
– A.CH.A.

15. Carotid angiogram DSA
Lateral

16. AP projection

18. Middle cerebral artery (MCA)
■ Origin: The MCA arises from the internal carotid
artery (ICA) as the larger of the two main terminal
branches (the other being the anterior cerebral artery),
■ Course: coursing laterally into the lateral sulcus where it
branches.
– The MCA is divided into four segments:
– M1: also known as the horizontal or sphenoidal
segment
– M2: also known as the insular segment
– M3: also known as the opercular segment
– M4: branches emerging from the Sylvian fissure onto
the convex surface of the hemisphere; also known as
the cortical segment

20. Middle cerebral artery
(MCA)
■ Supply:
– The majority of the lateral surface of the
hemisphere, except the superior portion of
the parietal lobe (via the ACA) and the inferior
portion of the temporal lobe and occipital
lobe (via the PCA).
– Part of the internal capsule and basal ganglia.
In its territory lie the motor and sensory areas
auditory and speech areas, So its occlusion
leads to presentation with contralateral hemi
sensory and motor syndrome.
Its occlusion caused by embolism, angitits or
vasospasm due to SAH or drugs.

21. Anterior cerebral artery (ACA)
■ Origin: The ACA arises from the internal carotid
artery (ICA) as the smaller of the two main terminal
branches.
■ Course: coursing medially into the interhemispheric
fissure .
– The ACA is divided into three segments:
– A1 (horizontal): origin from the ICA to the anterior
communicating artery (ACOM),
– A2 (vertical): from ACOM to the origin of
the callosomarginal artery
– A3 (callosal): distal to the origin of the
callosomarginal artery

24. ACA branches
• A1
• medial lenticulostriate arteries
• recurrent artery of Heubner
• anterior communicating artery
• A2
• orbitofrontal artery
• frontopolar artery
• A3
• Pericallosal artery
• callosomarginal artery (runs in the cingulate sulcus)
In its territory lie medial upper frontal and parietal hemispheres and
paramedian hemispheres.
Its occlusion caused by embolism, angitits or vasospasm due to
SAH or drugs and leads to contralateral hemiparesis.

27. Anterior choroidal artery (AChA)
■ Origin
– The AChA originates from the posterior wall of
the ICA midway between the origin of PCOM proximally
and the internal carotid bifurcation distally.
■ Course
– The AChA is located lateral to the optic tract.
■ Segments
– The AChA can be divided into two segments:
■ cisternal segment: extends from its origin until the
choroidal fissure
■ intraventricular segment: after entering the choroidal
fissure
■ Vascular territory
– cisternal segment
■ optic tract
■ lateral geniculate nucleus and lateral aspect of thalamus
■ posterior limb of the internal capsule
■ lateral aspect of the midbrain
– intraventricular segment
■ choroid plexus of the anterior part of the temporal horns of
the lateral ventricles
■ Plexal point :denotes the location which the AChA enters the
choroidal fissure into the lateral ventricle

31. Vertebrobasilar
system
■ Vertebral artery:
■ origin:
– branches off the 1st part of
the subclavian artery
■ course:
– ascends posterior to the internal carotid
artery in the transverse foramina of
the cervical vertebrae C6 up to C2.
■ branches
– ASA.
– PSAs.
– PICA (the largest branch).
■ termination:
– combines with the contralateral
vertebral artery to form the basilar
artery

32. Vertebrobasilar system
■ Vertebral artery:
■ V1 (preforaminal)
– Also known as the extraosseous segment, to
enter the transverse foramen of C6.
■ V2 (foraminal)
– V2 ascends through the transverse foramina of
the cervical vertebrae, C6-C2.
■ V3 (Atlantic, extradural or extraspinal)
– V3 passes around the posterior border of the
lateral mass of C1.
■ V4 (intradural or intracranial)
– V4 ascends anterior to the roots of
the hypoglossal nerve (CN XII) and joins its
contralateral counterpart at the lower border of
the pons to form the basilar artery.

33. Vertebrobasilar system
■ Basilar artery:
■ origin:
– vertebral artery confluence
■ course:
– ventral to pons in the pontine cistern
■ branches:
– AICA.
– Pontine branches.
– PCA.
– SCA.

34. Posterior cerebral artery (PCA)
• origin: terminal branches of the basilar artery
• course: from basilar towards occiput
• main branches
• Posterior choroidal arteries (medial and lateral)
• calcarine artery
• supply: occipital lobes and posteromedial temporal lobes

35. Posterior cerebral artery (PCA)
• P1: from it origin to PCOM, within
interpeduncular cistern
• P2: from the PCOM around the mid-
brain, divided into P2A (anterior) and
P2P (posterior) sub-segments; P2A is
within crural cistern which then
bridges to the P2P segement 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)

37. PCA
In its territory lie medio basal
temporal and occipital lobes, in
addition to thalami, central part of
midbrain, medial geniculate
bodies.
Its occlusion caused by trans
tentorial herniation, vertebral artery
dissection, embolism, angitits or
vasospasm due to SAH or drugs
and leads to contralateral
homonymous hemianopia and
hemianaesthesia.

38. Circle of Willis
 Site:
o surrounds ventral surface of diencephalon,
o adjacent to optic nerve and tracts, inferolateral
to hypothalamus
 Formation:
– From anterior circulation
■ left and right internal carotid arteries (ICA)
■ horizontal (A1) segments of the left and
right anterior cerebral arteries (ACA)
■ single anterior communicating artery (ACOM)
■ left and right posterior communicating arteries
(PCOM) (although some consider the PCOM to
be anterior circulation)
– From posterior circulation
■ horizontal (P1) segments of left and
right posterior cerebral arteries (PCA)
■ single basilar artery (tip)

40. Circle of Willis
§ A complete circle of Willis is only seen in
20-25% of individuals.
§ Posterior circulation anomalies are more
common than anterior circulation variants
§ Variant:
1. hypoplasia of one or both PCOM ~30%

41. Circle of Willis
§ Variant:
– hypoplastic/absent A1 segment of ACA ~15%

42. Circle of Willis
§ Variant:
3. absent or fenestrated ACOM ~12.5%

43. Circle of Willis
§ Variant:
4. (fetal PCOM) ~20%

44. Circle of Willis
§ Variant:
5. infundibular dilatation of the PCOM origin ~10%

45. Circle of Willis
§ Variant:
6. Artery of Percheron

46. Vascular territory
Cerebral
hemispheres
Cerebellum&Bra
in stem
Basal
Ganglia&Internal
capsule

47. Vascular territory
Cerebral
hemispheres
Cerebellum&Bra
in stem
Basal
Ganglia&Internal
capsule

52. Cerebral vascular territory
■ MCA: Supply the lateral surfaces of parietal, frontal and
superior part of temporal lobes except Upper 1 cm of lateral
surface of parietal and frontal lobes.
■ ACA: Supply the medial surface of parietal and
frontal and Upper 1 cm of their lateral surfaces and
Corpus callosum (except splenium).
■ PCA: Supply the medial and lateral surfaces of
occipital lobe and lateral surface of the inferior part
of temporal lobe in addition to splenium of CC and
whole midbrain.
■ AChA: Supply the medial surface of temporal lobe
(uncus).

53. Vascular territory
Cerebral
hemispheres
Cerebellum&Bra
in stem
Basal
Ganglia&Internal
capsule

57. Basal ganglia and internal capsule
Internal capsule
Anterior
limb
Genu
Posterior
limb
Basal Ganglia
Caudate
nucleus
Lentiform
nucleus
Thalamus

58. Basal ganglia (BG) and internal
capsule (IC)
BG
■ Caudate nucleus: head by ACA
through recurrent artery of
Heubner (the largest branch of
medial lenticulostriate arteries),
body and tail by MCA.
■ Lentiform nucleus: lateral
lenticulostriate arteries of the
MCA.
■ Thalamus: PCA
IC
Anterior
limb
MCA
ACA
Genu
MCA
MCA
Posterior
limb
MCA
PCA&AChA

59. Vascular territory
Cerebral
hemispheres
Cerebellum&Bra
in stem
Basal
Ganglia&Internal
capsule

64. Cerebellar and Brain stem vascular
territory
■ SCS: Supply the whole superior surface of cerebellum in addition to
cerebellar WM and superior vermis.
■ PICA: Supply the posteroinferior part of cerebellum, inferior vermis and
lateral part of medulla oblongata.
■ AICA: Supply the anteroinferior part of cerebellum in addition to folliculus
and middle cerebellar peduncle.
■ PCA: Supply Midbrain
■ Basillar: Supply Pons
■ ASA: Supply the medial aspect of medulla oblongata.
■ vertebral artery: Supply the part of medulla between that supplied by PICA
and ASA

65. Watershed (Border zone) area
■ occur at the border between cerebral vascular
territories where the tissue is furthest from arterial
supply and thus most vulnerable to reductions in
perfusion.
■ Episodes of systemic hypotension particularly with
severe stenosis or occlusion of the feeding arteries
■ Watershed infarction has been classified to:
– cortical (external) border zones infarct
■ between ACA, MCA, and PCA territories
– deep (internal) border zones infarct:
■ between ACA, MCA, and PCA territories, and
perforating medullary, lenticulostriate, recurrent
artery of Heubner and anterior choroidal
arteries

66. Watershed (Border
zone) area
CT and MRI
– Cortical (external) border zones infarct
■ wedge-shaped or gyriform:
■ ACA/MCA: in frontal cortex extending from anterior horn to
the cortex
■ MCA/PCA: in parieto-occipital region extending from
posterior horn to the cortex
– Deep (internal) border zones infarct
■ ≥3 lesions, each ≥3 mm in diameter in a linear fashion
parallel to the lateral ventricles in the centrum semiovale
and corona radiata, which sometimes become more
confluent and band-like

67. Brain
anatomy
Protective
coverings
Scal
p Bone Meninges
Brain
parenchyma
Cerebrum
Cerebellu
m Brain stem
Cranial
Nerves.
Limbic
system
Vascular
anatomy
Arterial Venous
CSF
spaces
Ventricular system Cisterns

68. Venous drainage of the brain
■ Venous drainage of the brain occurs throughout:
1. Dural venous sinuses
2. Cerebral veins which are divided into:
I. Superficial (Cortical) veins
II. Deep veins:
a. Medullary veins
b. Subependymal veins.

69. Venous drainage of the brain
■ General speaking:
Medullary
veins
Subependymal
veins
Dural venous
sinuses
Cortical
veins
Dural venous
sinuses

70. Dural venous sinuses
Paired
■ Transverse
sinus
■ Sigmoid sinus
■ Superior
petrosal sinus.
■ Inferior
petrosal sinus.
■ Cavernous
sinus.
Unpaired
■ SSS
■ ISS
■ SS
■ Intercavernous
sinus.

71. Dural venous sinuses
Unpaired
■ SSS
■ ISS
■ SS
■ Occipital sinus.
■ Intercavernous
sinus.

72. Dural venous sinuses
Paired
■ Transverse
sinus
■ Sigmoid sinus
■ Superior
petrosal sinus.
■ Inferior
petrosal sinus.
■ Cavernous
sinus.

74. Unpaired venous sinuses
1-SSS
■ The largest, begins at foramen
cecum, passing posteriorly within
fixed part of falx cerebri till internal
occipital crest to continue as right
transverse sinus.
2-ISS
■ Passing from front backwards
within free margin of falx to drain
into straight sinus

75. Unpaired venous sinuses
3-SS
■ Receives ISS and VOG, runs
posteroinferiorly to drain into
torcula herophili (60%), left
transverse sinus (20%), or right
transverse sinus (10%).
4-Intercavernous sinuses
■ Anterior and posterior, connecting
both cavernous sinuses.

76. Paired venous sinuses
1-Transverse Sinus
■ Starting at torcula herophili that
drain SSS, ISS and SS, then
continuer as sigmoid sinus that in
terns drain into IJV
■ Usually asymmetric with high
variable anatomy

77. Paired venous sinuses
2-Sigmoid sinus
■ It’s continuation of transverse
sinus as the tentorium ends.
■ It receives superior petrosal
sinuses.
3-Superior petrosal sinus
■ Runs along the posterior border of
the petrous temporal bone to drain
cavernous sinus posterolaterally
into the transverse sinus.

78. Dural venous sinuses
4-Inferior petrosal sinus
■ It is often a plexus of venous
channels rather than a true sinus.
■ Runs along the posterior border of
the petrous temporal bone to drain
blood cavernous sinus to IJV.

79. Dural venous sinuses
5-Cavernous sinus
■ The cavernous sinus is located on
either side of the sella turcica. The
normal lateral wall should be
either straight or concave.
■ Receives blood from ophthalmic
veins and drained by superior and
inferior petrosal sinuses.

80. Dural venous sinuses
10-Cavernous sinus
■ Contents
– In the lateral wall from
superior to inferior
■ oculomotor nerve (CN III)
■ trochlear nerve (CN IV)
■ trigeminal nerve (CN
V): ophthalmic and maxillary
divisions
– Traversing the sinus
■ C4 segment of ICA
■ abducens nerve (CN
VI): inferolateral to the ICA

81. Cortical veins (1); SSS (2); TS (3); sigmoid sinus (4); jugular vein (5); inferior
sagittal sinus (6); septal veins (7); thalamostriate veins (8); internal cerebral
veins (9); basal vein of Rosenthal (10); vein of Galen (11); straight sinus (12);
cavernous sinus (13); inferior petrosal sinus (14); superior petrosal sinus (15);
Sphenoparietal sinus (16).

82. Venous drainage of the brain
■ Venous drainage of the brain occurs throughout:
1. Dural venous sinuses
2. Cerebral veins which are divided into:
I. Superficial (Cortical) veins
II. Deep veins

83. Cerebral veins
■ Superficial (Cortical) veins
1. Superficial middle
cerberal vein (vein of
sylvius): runs in sylvian
fissure to drain into CS.
2. Superior anastimotic vein
(vein of Trolard): connect
Superficial middle
cerberal vein to SSS
3. Inferior anastimotic vein
(vein of Labbé): connect
Superficial middle
cerberal vein to
transverse sinus.

85. Cerebral veins
■ Deep veins divided into:
1. medullary veins: they pass through
white matter and drain into
subependymal veins. The medullary
veins are arranged in a wedge-shaped
manner.

86. Cerebral veins
■ Deep veins divided into:
2. subependymal veins: they receive
medullary veins and aggregate to
form septal veins that unite with
thalamostriate veins to form
internal cerebral veins (red arrow)
which unite with basal vein of
Rosenthal to form VOG which in
turn unite with ISS to form straight
sinus

87. Cortical veins (1); SSS (2); TS (3); sigmoid sinus (4); jugular vein (5);
inferior sagittal sinus; internal cerebral veins (9); vein of Galen (11);
straight sinus (12). The ISS is not visualized. The prominent cortical vein
is the vein of Labbé (*)

106. Pituitary Gland
■ Lies within the sella turcica (pituitary fossa)
■ Consists of two parts:-
1. Anterior pituitary/Adenohypophysis that
is larger of two parts and secretes
prolactin, GH, TSH, ACTH, FSH, LH.
2. Posterior pituitary/Neurohypophysis
that doesn't’ form hormones by secrete
ADH made by hypothalamus and sent
to it through hypothalamohypophyseal
portal circulation

107. Pituitary Gland
■ MRI is the imaging modality of choice for
suspected pituitary lesion
■ Imaging protocol thon sections of T1
sagittal & coronal pre and postcontrast; T2
mostly is not required.
■ T1 Signal intensity of posterior pituitary
bright due to storage of phospholipids
hormones synthesized by hypothalamus
and transported to posterior pituitary by
hypothalamohypophyseal circulation.

108. ‫إله‬ ‫ال‬ ‫أن‬ ‫أشهد‬ ‫بحمدك‬ ‫و‬ ‫اللهم‬ ‫سيحانك‬
‫أليك‬ ‫أتوب‬ ‫و‬ ‫أستغفرك‬ ‫أنت‬ ‫إال‬