2. INTRODUCTION
The Internal carotid artery is a terminal branch of the common
carotid artery.
Origin It arises most frequently between C3 and C5 vertebral
level and upper border of thyroid cartilage where the common
carotid bifurcates to form the internal carotid and the external
carotid artery (ECA).
It has no branches outside the skull and passes straight up in
the carotid sheath, beside the pharynx to the carotid canal in
the base of the skull.
7. SURFACE ANATOMY OF ICA
ICA IS MARKED BY JOINING FOLLOWING 2 POINTS:
A POINT IN THE ANT. BRORDER OF SCM AT THE LEVEL OF
UPPER BORDER OF THYROID CARTILAGE
2ND POINT –POSTERIOR BORDER OF CONDYLE OF
MANDIBLE
8. SEGMENTS OF ICA:
The course of ica is divided into segments .There are seven segments in the Bouthillier
classification:
1.cervical segment (C1)
2. petrous (horizontal) segment (C2)
3. lacerum segment (C3)
4. cavernous segment (C4)
5. clinoid segment (C5)
6. ophthalmic (supraclinoid) segment (C6)
7. communicating (terminal) segment (C7)
11. Cervical part
1.It ascends vertically in the neck from its origin to the
base of the skull to reach the lower end of the carotid
canal. This part is enclosed in the carotid sheath (with the
internal jugular vein and the vagus nerve).
2.No branches arise from the internal carotid artery in the
neck.
3.Its initial part usually shows a dilatation, the carotid
sinus which acts as a baroreceptor ,carotid body which is
a chemoreceptor.
4. The lower part of the artery (in the carotid triangle) is
comparatively superficial. The upper part, above the
posterior belly of digastric, is deep to the parotid gland,
the styloid apparatus, and many other structures.
12. Relations of cervical ica
Anterior or superficial 1 In the carotid triangle: a. Anterior border of
sternocleidomastoid
b. The external carotid artery is anteromedial to it
2 Above the carotid triangle : a. Posterior belly of digastric b. Stylohyoid c.
Stylopharyngeus d. Styloid process e. Parotid gland with structures within it.
Posterior 1.longus capitis 2.Superior cervical ganglion 3. Carotid sheath 4.The
glossopharyngeal, vagus, accessory and hypoglossal nerves at the base of the
skull.
Medial 1 Pharynx 2 The external carotid is anteromedial to it below the parotid.
Lateral 1 Internal jugular vein 2 Temporomandibular joint (at the base of the skull)
14. Relations of cervical ica
Anterior or superficial 1 In the carotid triangle: a. Anterior border of
sternocleidomastoid
b. The external carotid artery is anteromedial to it
2 Above the carotid triangle : a. Posterior belly of digastric b. Stylohyoid c.
Stylopharyngeus d. Styloid process e. Parotid gland with structures within it.
15. Medial 1 Pharynx 2 The external carotid is anteromedial to
it below the parotid.
Lateral 1 Internal jugular vein 2 Temporomandibular joint
(at the base of the skull)
16. Posterior 1.longus capitis
2.Superior cervical ganglion 3.
Carotid sheath 4.The
glossopharyngeal, vagus,
accessory and hypoglossal
nerves at the base of the skull.
17.
18. Sometimes show a prominent
loop as it lies lateral to
oropharynx , k/a the
TONSILLAR LOOP.
19. Petrous segment c2
In the carotid canal, the artery first runs
upwards, and then turns forwards and
medially at right angles. It emerges at
the apex of the petrous temporal bone,
in the posterior wall of the foramen
lacerum where it turns upwards and
medially
an ascending, or vertical portion; the
genu, or bend; and the horizontal
portion.
20. The artery is surrounded by venous and sympathetic
plexuses. It is related to the middle ear and the
cochlea (posterosuperiorly); the auditorytube and
tensor tympani (anterolaterally); and the trigeminal
ganglion (superiorly)
Branches: a. Caroticotympanic branches enter the
middle ear, and anastomose with the anterior and
posterior tympanic arteries .
b. The pterygoid branch (small and inconstant) enters
the pterygoid canal with the nerve of that canal and
anastomoses with the greater palatine artery.
21.
22. VARIANTS AND ANOMALIES OF PETROUS SEGMENT
Aberrant ICA- Traverses posterolaterally and
present as a pulsatile retrotympanic mass.
Persistent stapedial artery( PSA) is rare.
Caused by intrapetrous embryonic vascular
channels.
23. LACERUM SEGMENT C3
SHORTEST segment
Courses above but not through the
foramen lacerum forming lateral loop of the
ICA , and ascends in the vertical canal of
the of the foramen lacerum toward the
posterior carvernous sinus.
Ica doesnot go through fl but walks over it
Pierces the dura
Ends at the superior margin of the
petrolingual ligament to become cavernous
segment
24. Cavernous segment c4
Distal to petrolingual ligament, ICA enters cavernous
sinus
Usually has a vertical portion, a posterior bend, a
horizontal portion, and an anterior bend
Ends at the proximal dural ring, which incompletely
surrounds the ICA
Normal ICA forms s shaped loop as it lies in the lateral
wall of the cavernous sinus, usually referred to as the
carotid siphon
25. Meningohypophyseal artery( posterior trunk)- arises near
C4/C5 junction.
1. Marginal tentorial branch or artery of Bernasconi and
Cassinari 2. Dorsal meningeal artery 3. Inferior hypophyseal
artery
Inferior cavernous artery Supplies wall of cavernous
sinus and its contents . Anastomoses with middle
meningeal artery
Small capsular branches to supply anterior of pituitary
gland
26.
27.
28. Clinoid segment c5
Begins at the proximal dural ring and
ends at the distal dural ring where the
ICA becomes intradural
Part of the anterior loop of the ICA
Enters subarchnoid space near
anterior clinoid process of sphenoid
No branches
29. Ophthalmic segment c6
Begins at distal dural ring and ends just proximal to origin of the PCoA
Branches: ophthalmic and superior hypophyseal artery
A.k.a supraclinoid segment
30. SUPERIOR HYPOPHYSEAL TRUNK
Supply pituitary stalk and gland,optic chiasm and optic nerve.
OPHTHALMIC ARTERY
From ant aspect of ICA medial to ant clinoid process.
In majority origin is intradural
Course: passes into the orbit via the optic canal with optic nerve
Branches:supply the orbital content and globe
DR MCLESSI -Dorsal nasal artery
-Supraorbital artery
-central Retinal Artery
-Supratrochlear artery
-Muscular artery
-Internal palpebral artery
-Ciliary artery
-Lacrimal artery
-Ethmoidal arteries
31. Ethmoidal arteries- supply to ethmoid sinus
And nose
Anterior ethmoidal artery
Posterior ethmoidal artery
The artery of falx arises from the anterior ethmoidal branches and passes through cribriform plate to
supply the anterior part of the falx cerebri.
May be hypertrophied to supply meningiomas and AV malformations
OA branches anastomoses with maxillary artery branches – potential for collateral flow in cases of
proximal carotid occlusion
Anomalies: intracavernous origin
32. Communicating/terminal segment c7
Extends from below PCoA to terminal ICA bifurcation into anterior
cerebral artery (ACA), middle cerebral artery (MCA) •Passes between
optic (CN2), oculomotor (CN3) nerve
BRANCHES
posterior communicating artery • anterior choroidal artery • anterior
cerebral artery • middle cerebral artery
Forms circle of willis except mca
33.
34.
35. Applied
Abnormal variants like Fenestration of the distal internal carotid artery,Hyperplastic anterior
choroidal artery,pcoa infundibulum,persistant carotid basilar ananstomosis,carotico-cavernous
ananstomosis,persistent trigeminal artery,carotid aneurysm,berry aneurysm in cow.
Iatrogenic Injury to the ICA and the resultant bleeding may lead to catastrophic complications that
include permanent disabilities and death
Though its very rare in extended endonasal surgery (EES) – Less than 1%
36. Risk factors
Category Factors
Anatomy-related Dehiscent ICA canal Sphenoid septa with
attachments to the ICA canals Short distance
between ICAs Vessel wall abnormalities ICA
displacement by the lesion
Pathology-related Adherence of the lesion to ICA Previous extended
surgery Previous radiotherapy Previous
bromocriptine therapy
Skills and resource-related Inexperience in skull base surgery Lack of
adequate instruments and equipment
High-risk Radical resection of an adherent lesion
Encasement of ICA Need for wide exposure (≥2
segments of ICA)
rt cca begins in neck behind rt sternoclavicular jt. and left cca begins in thorax in front of trachea little left to centre of manubrium.travels in carotid sheath from ron to bos,bifurcates,ica remains in carotid sheath.
Boundries-superior-pbd,sh inferiorly- sup belly of omohyoid, post- ant border of scm.
It is related to the middle ear and the cochlea (posterosuperiorly); the auditorytube and tensor tympani (anterolaterally); and the trigeminal ganglion (superiorly
Earlier muscular patch was used.now this endo clips used
