Cavernous sinus
ANATOMY:
- There are 2 Cavernous Sinuses on either side of Sella tursica irregular form larger behind than front.
- Extends from sphenoid fissure to petrous apex.
- Each cavernous sinus is a large venous space situated in the middle cranial fossa on either side of the body of sphenoid bone. Its interior is divided into a number of trabeculae or caverns.
- The floor of the sinus is formed by the endosteal dura mater. The lateral wall, roof and medial wall are formed by the meningeal duramater.
OSSEOUS RELATIONSHIP:
- Related to sphenoid bone and sella tursica.
- On each side of fossa is S shaped groove lodges Internal carotid artery.
- Fibrous or osseous bridge exist between Anterior, Middle or Posterior Compartment.
- Connection between AC and MC makes distal end of carotid sulcus to carotico-clinoid foramen.
Structures in the lateral wall of the sinus from above downwards:
- Oculomotor nerve
- Trochlear nerve
- Ophthalmic nerve- in the anterior part of the sinus, it divides into the lacrimal, frontal and nasociliary nerves.
- Maxillary nerve- it leaves the sinus by passing through the foramen rotundum on its way to the pterygopalatine fossa.
- Trigeminal ganglion- the ganglion and its dural cave project into the posterior part of the lateral wall of the sinus.
Structures passing through the center of the sinus:
- Internal carotid artery with the venous and sympathetic plexus around it.
- Abducent nerve, inferolateral to the internal carotid artery.
Tributaries (incoming channels) of cavernous sinus
- Superior ophthalmic vein.
- A branch of inferior ophthalmic vein or sometimes vein itself.
- Central vein of retina (it may also drain into superior pophthalmic vein).
- Superficial middle cerebral vein.
- Inferior cerebral vein.
- Sphenoparietal sinus.
- Frontal trunk of middle meningeal vein (it may also drain into pterygoid plexus or into sphenoparietal sinus).
Draining channels (communications) of cavernous sinus
- Into transverse sinus through superior petrosal sinus.
- Into internal jugular vein through inferior petrosal sinus and through a plexus around the ICA.
- Into pterygoid plexus of veins through emissary vein.
- Into facial vein through superior ophthalmic vein.
- Right and left cavernous sinus communicates with each other by anterior and posterior intercavernous sinuses and through basilar plexus of veins.
VENOUS COMPARTMENT:
- Divided into medial, lateral anteroinferior and posterosuperior compartments.
- As afferents each CS receives spheno parietal sinus, frontal trunk of middle meningeal, superior & inferior ophthalmic vein, superficial middle cerebral vein, inferior cerebral vein
- Superior opthalmic vein connects facial vein to cavernous sinus.
- Veins communicating the cavernous sinus to pterygoid plexus pass through fossa of vesalius.
- On efferent side, CS drains into Inferior Petrosal sinus.
NEURAL COMPARTMENT:
- III,IV,V1,V2 lie between 2 dural layers that form lateral wall of CS.
- Superficial layer of lateral wall is a thick layer formed by the duramater.
- This layer continues anteriorly over the superior surface of Anterior clinoid process(ACP) enveloping ICA to form distal dural ring.
- The inner layer has a reticular consistency and incomplete in 40% of cases.
- Through the inner layer run III,IV and V1.
- The inner layer extents anteriorly and inferiorly to ACP surrounds anterior loop of ICA and forms the proximl ring and also anterior loop of CS.
- III N pierces CS in the middle of occulomotor trigone in the upper part of lateral wall of CS.
- Courses anteriorly and leaves the CS on nhe inferolateral surface of ACP
- IV th N enters posterolateral to III N courses anterolateroinferior to enter the Superior Orbital Fissure.
- V1 enters the lower part of lateral wall of CS runs anteriorly and upwards to pass through SOF
- VI enters CS through Dorello`s canal and courses inside the sinus lateral to ICA.
- This canal is limited superiorly by petroclinoid ligament also known as Gruber`s ligament.
APPLIED ANATOMY
- Cavernous sinus thrombosis may be caused by infection in dangerous area of face, nasal,cavities and paranasal sinuses. It presents as:-
- Nervous symptoms:– Severe pain in the distribution of ophthalmic nerve. Involvement of 3rd, 4th, and 6th cranial nerves causes paralysis of extraocular muscles with diplopia.
- Venous symptoms:- Edema of eyelids, cornea and root of nose with exopthalmos.
- Commmunication b/w cavernous sinus and ICA, after trauma, may cause pulsatile exopthalmos.
Exam Question
- Structures passing through cavernous sinus are internal carotid artery & abducent nerve.
- As afferents each CS receives spheno parietal sinus, frontal trunk of middle meningeal, superior & inferior ophthalmic vein, superficial middle cerebral vein, inferior cerebral vein.
- III , IV, V1, V2, VI are the cranial nerves that travels through the cavernous sinus.
- Superior ophthalmic vein directly communicates with cavernous sinus.
- Abducent nerve & internal carotid artery Are the direct content of cavernous sinus
- Facial vein is connected to cavernous sinus via superior opthalmic vein.
- Veins communicating the cavernous sinus to pterygoid plexus pass through fossa of vesalius.
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