ICA anatomy

Internal Carotid Artery
Anatomy and segments
Mohamed Elsayed Elsebaey
Neurosurgery Registrar
Egypt, Ismailia
Ministry of Health
Seba3y700025@gmail.com
Mohamed E Elsebaey

Cervical segment C1
• Begins in the neck at the carotid bifurcation
where the CCA divides into internal & external
• Goes within the carotid sheath with IJV & vagus
• Encircled with PGSN
• Ends where the ICA enter carotid canal of petrous
bone
• branches ??? Mention them

Carotid sheath
• Fibrous connective tissue that surrounds the
vascular compartment of the neck.
• Part of the Deep Cervical Fascia of the neck, that
include :
1. The investing layer (encloses the SCM and Trapezius)
2. The carotid sheath (encloses the vascular region of the
neck)
3. The pretracheal fascia (encloses the visceral region of
the neck)
4. The prevertebral fascia (encloses the vertebral region
of the neck

• Located at the lateral border of the retropharyngeal
space , at the level of the oropharynx on each side,
deep to the SCM muscle , extending from the base of
the skull to the sternum and 1st rib.
• Contain :

• Cr. Ns. 9, 11 & 12 pierces the carotid sheath
in the upper part. How ?
• Ansa Cervicalis is embedded in the Anterior
wall of the sheath.

PostGanglionic Sympathetic Nerves
PGSN
• Internal Carotid plexus is mainly located in the
lateral side of the Carotid A.
PGSN
ascend from the superior cervical ganglion
Creep on the ICA wall
Enter the ICA plexus then
Emerge into
Superior Tarsal Ms & Pupillary dilator Ms
 Some fibers converge and form the Deep petrosal N.

How many Nucleui of the 3rd Cr. N. ??? Edenger Westephal N
Motor Nucleus
Nucleus of Perli  Medial rectus M alone

Temporal Bone
• Parts:
1. Squamous part
2. Petrous
3. Mastoid
4. Styloid

Petrous segment C2
• Still surrounded by PGSN
• Ends at the posterior edge of foramen
lacerum.
• Three divisions:
1. Vertical segment
2. Posterior segment
3. Horizontal segment

Petrous Bone
Part of the Temporal Bone
Very complicated bone
Many so important relations
Like the pyramid

• Base  fused with the internal surfaces of the
squamous and mastoid parts of temporal
bone.
• Apex  rough, forms the Postero lateral
boundary of the F. lacerum.
• Surfaces  Anterior , Posterior & Inferior.
• Angles  superior, anterior & posterior.

• In this surface:
large circular opening 
do tunnel
ascends vertically then
Do bend then
Runs horizontally forward and medially
ICA passes

Lacerum segment C3
• C3 is the shortest segment
• Passes over foramen lacerum forming the lateral loop
ICA does not go through the F lacerum but walks over it
• Ascends in the canalicular portion of the foramen
lacerum to the juxtasellar position
• Piercing the Dura
• Passes the petrolingual ligament to become the
cavernous segment
• Branches:
1. Caroticotympanic artery
2. Pterygoid ( Vidian artery )

Foramen Lacerum
• Triangular hole in the base of the skull.
• Located between the sphenoid, Apex of
petrous bone & basilar part of occipital bone.
• Situated Anteromedial to the carotid canal
C canal
F L
Mid line

Gasserian Ganglion
• It is a sensory ganglion of the trigeminal nerve
• that occupies a cavity (Meckel's cave) in the
dura mater,
• covering the trigeminal impression near the
apex of the petrous part of the temporal
bone.

Meckel’s cave
• Known also as Trigeminal cave
• It is an Arachnoidal pouch containing cerebrospinal
fluid
• formed by two layers of dura mater near the apex of
the petrous part of the temporal bone
• Contains the trigeminal Ganglion
• Bounded by
 Tentorium cerebelli superolaterally
 Cavernous sinus superomedially
 Clivus medially
 Posterior petrous inferiolaterally

Superficial Petrosal nerve
• Nerve in the skull that branches from the
facial nerve.
• forms part of a chain of nerves that innervate the
lacrimal gland
• It proceeds towards the foramen lacerum, where it
joins the deep petrosal nerve to form the nerve of
the pterygoid canal, which passes over the foramen
lacerum

Petrolingual ligament
The petrolingual ligament is the posteroinferior
attachment of the lateral wall of the cavernous
sinus, where the internal carotid artery enters
the cavernous sinus.

The petrous segment of the internal carotid artery
finishes and the cavernous segment begins at the superior
margin of this ligament.
The ligament is surgically important due to its
identification as a landmark for dissection of the internal carotid
artery during the approaches to posterolateral intracavernous
and extracavernous lesions.
It can be well exposed after mobilization of the gasserian
ganglion, or after the trigeminal root and ganglion have been
split along the junction of V2 and V3 (the transtrigeminal
approach).

Cavernous segment C4
• Covered by vascular membrane lining the
sinus
• Still surrounded by the PGSNs
• The Pathway:
Pass anteriorly,  superomedially bends
posteriorly( Medial loop )  travels horizontally
 bends anteriorly ( anterior loop )
• Ends at the proximal dural ring

Branches of C4
1. Meningio hypophyseal trunk
2. Anterior meningeal artery
3. A to inferior portion of the cavernous sinus
4. Capsular aa that supply the capsule of pituitary
Mention Blood supply of Pituitary.
Ant. Lobe of pituitary has no specific Blood supply

N.B.
Rupture aneurysm of ICA ( C4 ) does not
cause SAH
As it is still not intra subdural space
It is just penetrates the outer Dural layer

Clinoid segment C5
• The ICA becomes Intradural
• Begins at the proximal Dural ring
• Ends at the distal Dural ring

Ophthalmic segment C6
• Begins at the distal Dural ring
• Ends just proximal to P- Com- A
• Branches:
1. Ophthalmic A
2. Superior hypophyseal a.

Communicating segment C7
• Begins proximal to P-comm origin
• Ends just below anterior perforated substance
where terminates into ACA & MCA

Carotid siphon
• Not a segment, but region
• Incorporating the
Cavernous, opthalmic & comm segment
“When viewed from laterally, the cavernous(C3) and intracranial (C4)
portions have several curves that forman S-shape, and together these portions
are called the carotid Siphon.” Rhoton,2002.
• Begins at the posterior bend of cavernous ICA
• Ends at the ICA bifurcation

ICA anatomy

More Related Content

What's hot

Similar to ICA anatomy

More from Mohamed E Elsebaey

Recently uploaded

ICA anatomy