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 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

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.

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.

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.

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

.

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.

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.

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.

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.

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

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)

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.

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.

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.

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

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.

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.

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

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.

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.

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

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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