This document discusses the anatomy of the cavernous sinus (CS). It describes the CS as being located on either side of the sella turcica and extending from the sphenoid fissure to the petrous apex. It contains the internal carotid artery as well as cranial nerves III, IV, V1 and V2. The CS drains into the inferior petrosal sinus and receives blood from various veins including the sphenoparietal sinus and ophthalmic veins. The document discusses the osseous structures surrounding the CS and details the arterial, venous and neural compartments within the sinus.

1. ANATOMY OF CAVERNOUS
SINUS
 Earliest description of CS by Ridley in 1695.
 Winslow in 1732 gave name CS due to presence of
fibrous trabeculae.
 Controversy still persists regarding whether CS is a
venous channel or a true venous plexus.
 Taptas in 1982 argued in favour of CS an irregular
network of veins- a part of ED venous network at skull
base.
 However good venous injection techniques not supported
this.

2.  2 CS on either side of Sella tursica irregular form
larger behind than front.
 Extends from sphenoid fissure to petrous apex.
 First surgical excursion to CS credited to Krogius
in 1895.
 In 1965 Parkinson showed this space can be
approached safely followed by-DOLNEC

3. Osseous Relationships
 Related to sphenoid bone and sella tursica.
 Postr border of sella is a square plate of bone
terminates sprly in postr clinoids.
 On each side of fossa is S shaped groove lodges
ICA.
 Distal extremity of lesser wing terminates in antr
clinoids which form the lateral wall of IC end of
optic canal.

5. Osseus Relationships
 Controlled removal of AC is the mile stone in surgical
treatment of CS lesions.
 Complete clinoidectomy exposes clinoid segment of ICA
and Antr extn of lateral venous space of CS.
 Fibrous or osseus bridge exist between AC,MC or PC
makes the removal of AC difficult.
 Connection between AC and MC makes distal end of
carotid sulcus to carotico-clinoid foramen.

7. Osseus Relationships
 Although not involved in the formation of CS
structures within the middle cranial fossa like
carotid canal, FO,FR,FS,arcuate eminence and
cochlea are important land marks.

9. CAROTID CANAL
 Located at anterolateral aspect of petrous bone.
Part of the canal wall is formed by the postr
part of grtr wing of sphenoid

10. .
 Canal contains hori segment of ICA and symp
fibres.
 ICA courses antrly and medially within petrous
bone to emerge near petrous apex.
 At postr and medial wall canal is separated from
cochlea by a thin plate of bone.

11. CAROTID CANAL
 At the most distal end under V3 ICA is covered only by
dura or thin layer of cartilage.
 Removal of spr wall at this region exposes 20 mm of ICA.
 FR situated most antr and intr part of grtr wing of
sphenoid bone.
 FO and FS situated posterolateral to this.
 Eustachian tube and Tensor tympani are located antr and
parallel to hori segment of ICA below floor of MCF.

12. CAROTID CANAL
 Geniculate ganglion of 7th
nerve located in the floor
of MCF is usually covered by a layer of bone.
 Vulnerable to traction damage when dura mater of
MCF is elevated.

13. ARTERIAL COMPARTMENT
 ICA enters the skull thru carotid canal located
medial to styloid anteromedial to jugular foramen.
 ICA ascends a short distance curves antrly and
medially, ascends and leaves the carotid canal to
enter CS between lingula of sphenoid bone and
petrous temporal bone.

14. ARTERIAL COMPARTMENT
 Inside the vertical portion of carotid canal ICA is
adherent to bone by a strong layer of CT making
mobilisation of ICA difficult.
 Vertical segment of ICA
*jugular fossa postrly
*eustachian tube antrly
*tympanic bone anterolaterally
*length is 6-15mm

15. ARTERIAL COMPARTMENT
 Hori segment of ICA is related to otic apparatus
and 7th
N.
 Dense CT is absent in this segment.
 Length is 15-25mm
 Branches are
* Caroticotympanic artery
* Vidian or Pterygoid artery( usually from Int:
Maxillary Artery)

16. ARTERIAL COMPARTMENT
 ICA enters intracranial cavity passing between
lingula of sphenoid and petrous apex crossing FL
 As it enters IC cavity it is surrounded by venous
plexus and symp fibres.

19. INTRACAVERNOUS ICA(5 Parts)
 Postr Vertical Segment
 Ascends under Gasserion Ganglion.
 A fibrous ring holds the beginning o fpostr vertical
segment and holds between lingula and petrous
apex.

20. INTRACAVERNOUS ICA(5 Parts)
Postr bend
ICA in this portion curves antrly to reach the hori
segment.
 Devptly last segment. This seg usually gives
meningo hypophyseal trunk.

21. MENINGO HYPOPHYSEAL
TRUNK
 Largest and most constant branch of Postr bend.
 Present in 88-100% cases.
 Arises from middle of outer wall of postr bend.
 Gives 3 branches.
1) Tentorial Artery- Courses posterolaterally
exiting the CS between 2 layers beneath the 4th
N
to supply tentorium

22. MENINGO HYPOPHYSEAL
TRUNK
 2) Infr Hypophyseal Artery- Traverses medially
and slightly antrly towards the pituitary gland.
 Anastomoses directly with opp artery.
 3) Dorsal Meningeal Artery- Courses in a
postero infero medial direction. Supplies dura
along the upper clivus.

25. IC-ICA Horizontal Segment.
 Longest. Avg 20mm
 Courses forwards and located close to medial wall of CS.
 At the antr end hori seg curves upwards forming the antr
bend.
 Antr vertical seg begins distal to antr bend and passes
upwards medial to antr clinoid process to perforate roof of
CS.
 Vertical seg is obscured by ACP and limited proximally
and distally by dural rings.

26. IC-ICA Horizontal Segment.
 Arteruy of Inf CS arises from central third of hori
seg courses laterally with 6th
N
 Mc Connel`s Capsular Artery -arises from medial
aspect of hori seg
 Courses towards the pituitary gland
 Ophthalmic Artery arises from CS in 8 % cases
 Persistent Trigeminal Artery present in 2% cases

27. VENOUS COMPARTMENT
 Recent surgical explorations of CS show it to be
more consistent with venous channel than plexus.
 Divided into medial, lateral anteroinf and
posterosup compartments.
 As afferents each CS receives spheno parietal
sinus, spr ophthalmic vein, sfl sylvian vein, middle
meningeal vein and spr petrosal sinus.
 On efferent side, CS drains into Inf Petrosal sinus.

30. NEURAL COMPARTMENT
III,IV,V1,V2 lie between 2 dural layers that form
lateral wall of CS.
Sfl layer of lateral wall is a thick layer formed by the
duramater.
This layer continues antrly over the spr surface of
ACP enveloping ICA to form distal dural ring.
The inner layer has a reticular consistency and
incomplete in 40% of cases.

31. NEURAL COMPARTMENT
 Thru the inner layer run III,IV and V1.
 The inner layer extents antrly and infrly to ACP
surrounds antr loop of ICA and forms the proximl
ring and also antr loop of CS.
 III N pierces CS in the middle of occulomotor
trigone in the upper part of lateral wall of CS.
 Courses antrly and leaves the CS on nhe
inferolateral surface of ACP

32. NEURAL COMPARTMENT
 IV th N enters posterolateral to III N courses
anterolateroinferior to enter the SOF.
 V1 enters the lower part of lateral wall of CS runs
antrly and upwards to pass thru SOF
 VI enters CS thru Dorello`s canal and courses
inside the sinus lateral to ICA.
 This canal is limited sprly by petroclinoid ligament
also known as Gruber`s ligament

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