CEREBRAL VENOUS SINUSES

•Venous spaces, walls are formed by duramater.

•Have an inner lining of endothelium, no muscles in

their wall and have no valves

•Receives venous blood from brain, meanings and bones

of skull.

VENOUS SINUSES OF DURAMATER

•Cranial venous sinuses communicates with veins

outside the skull by emissary veins – helps to

keep the pressure of blood in the sinuses

constant

•23 venous sinuses

8paired

7unpaired

Paired venous sinuses (one sinus each on right and left side)

Unpaired venous sinuses (median in position)

1)Cavernous sinus2)Superior petrosal sinus3)Inferior petrosal sinus4)Transverse sinus5)Sigmoid sinus6)Sphenoparietal sinus7)Petrosquamous sinus8)Middle meningeal sinus/veins

1)Superior sagittal sinus2)Inferior sagittal sinus3)Straight sinus4)Occipital sinus5)Anterior intercavernous sinus6)Posterior intercavernous sinus7)Basilar plexus of veins

CAVERNOUS SINUS•Large venous sinus situated in the middle cranial fossa on

either side of body of sphenoid bone.

•Interior divided into spaces by trabeculae

•Floor is formed by endosteal duramater

•Lateral wall medial wall and roof is formed by the

meningeal duramater

•Anteriorly- extends up to the medial end of superior orbital

fissure

Posteriorly- up to the petrous temporal bone

•2cm long and 1cm wide

RELATIONS

Structures outside the sinus

•Superiorly- optic tract, optic chiasma, olfactory tract, internal

carotid artery and anterior perforated substance.

•Inferiorly- foramen lacerum and the junction of the body and

greater wing of the sphenoid bone

•Medially- hypophysis cerebri and sphenoidal air sinus

•Laterally- temporal lobe with uncus

•Anteriorly- superior orbital fissure and the apex of the orbit

•Posteriorly- apex of the petrous temporal and the crus

cerebri of the midbrain

Structures in the lateral wall of the sinus, from above

downwards

•Occulomotor nerve

•Trochlear nerve

•Ophthalmic nerve

•Maxillary nerve

•Trigeminal ganglion

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

The structures in the lateral wall and in the center of the

sinus are separated from blood by the endothelial lining

TRIBUTARIES OR INCOMING CHANNELS•From the orbit

1)Superior ophthalmic vein

2)A branch of inferior ophthalmic vein or sometimes the

vein itself

3)the central vein of the retina may drain either into the

superior ophthalmic vein or into the cavernous sinus.

•From the brain

1)superior middle cerebral vein

2)inferior cerebral veins from the temporal vein

•From the meninges

1)sphenoparietal sinus

2)the frontal trunk of middle meningeal vein may

drain either into the pterygoid plexus through the

foramen ovale or into the cavernous sinus.

Draining channels and communicationsThe cavernous sinus drains

•Into the transverse sinus through the superior petrosal sinus

•Into the internal jugular vein through the inferior petrosal sinus and

through the plexus around the internal carotid artery

•Into the pterygoid plexus of veins through the emissary veins passing

through the foramen ovale, the foramen lacerum and the emissary

sphenoidal foramen.

•Into the facial vein through the superior ophthalmic vein

•The right and left cavernous sinuses communicate with each other

through the anterior and posterior inter cavernous sinuses and

through the basilar plexus of veins.

•All these communications are valve less and blood can flow through

them in either direction

Superior sagittal sinus•Occupies the upper convex attached margin of the falx cerebri

•Begins anteriorly at the crista gali by the union of tiny meningeal

veins

•Here it communicates with veins of frontal sinus and occasionally

with the veins of nose through foramen caecum.

•As it runs upwards and backwards it becomes progressively larger in

size

•It is triangular in cross section.

•It ends near the side

usually the right

transverse sinus and

becomes continues

with it.

•The junction of all

these sinuses is

called the confluence of sinuses.

The interior of sinus shows

•Openings of the superior cerebral veins

•Openings of venous lacunae, usually three on each side

•Arachnoid villi and granulations projecting into the lacunae as well

as into the sinus

•Numerous fibrous bands crossing the inferior angle of the sinus

Tributaries•Superior cerebral sinus which never open into the

venous lacunae

•Parietal emissary veins

•Venous lacunae, usually three on each side which first

receive the diploic and meningeal veins and then open

into the sinus

•Occasionally a vein from the nose opens into the sinus

when the foramen caecum is patent.

INFERIOR SAGITTAL SINUS

•The inferior saggital sinus a small channel lies

in the posterior two thirds of the lower, concave

free margin of the falx cerebri.

•It ends by joining the great cerebral vein to

form the straight sinus

STRAIGHT SINUS•Lies in the median plane within the junction of falx

cerebri and the tentorium cerebelli

•It is formed anteriorly by the union of the inferior

sagittal sinus with the great cerebral vein and ends at

the internal occipital protuberance by continuing as the

transverse sinus(usually left).

•Receives a few of the superior cerebellar veins

TRANSVERSE SINUS•Large sinuses –right sinus is larger than left

•Right sinus is situated in the posterior part of the

attached margin of the tentoriun cerebelli

•It is usually a continuation of superior saggital sinus

•Left sinus is a continuation of straight sinus

•Each sinus extends from the internal occipital

protuberance to the posteroinferior angle of the parietal

bone at the base of mastoid process where it bends

downwards and becomes the sigmoid sinus

Its tributaries are

•Superior petrosal sinus

•Inferior cerebral veins

•Inferior cerebellar veins

•Diploic (posterior temporal) vein

•Inferior anastomotic vein

Sigmoid sinus•Each sinus right and left is the direct continuation of

the transverse sinus

•S-shaped

•Extends from the posterioinferior angle of the parietal

bone to the posterior part of jugular foramen where it

becomes the superior bulb of the internal jugular vein

•It grooves the mastoid part of the temporal bone

where it is separated anteriorly from the mastoid

antrum and mastoid air cells by only a thin plate of

bone

Tributaries are

•The mastoid and condylar emissary veins

•Cerebellar veins

•The internal auditory vein

Other sinusesOccipital sinus

is small and lies in attached margin of the falx cerebri

It begins near the foramen magnum and ends in the confluence of

sinuses

Sphenoparietal sinus

Right and left lies along the free margin of the lesser wing of

sphenoid bone and drain into the anterior part of the cavernous sinus

Each sinus may receive the frontal trunk of the middle meningeal vein

Superior petrosal sinus

Lie in the anterior part of the attached margin of the tentorium

cerebelli along the upper border of the petrous temporal bone. It

drains the cavernous sinus into the transverse sinus

Inferior petrosal sinus

Right and left lie in the corresponding petro occipital fissure, and

drain the cavernous sinus into the superior bulb of the internal

jugular vein

Basilar plexus of veins

Lies over the clivus of the skull. It connects two inferior petrosal

sinuses and communicates with the internal vertebral venous plexus

Middle meningeal veins

Form two main trunks one frontal or anterior and one parietal or

posterior which accompany the two branches of the middle meningeal

artery.

Frontal trunk end either in the pterygoid plexus through th foramen

ovale or in sphenoparietal or cavernous sinus

Parietal trunk ends in the pterygoid plexus through the foramen

spinosum

The meningeal veins are nearer to the bone than artries and are

therfore more pliable to injury in fractures of skull

anterior and posterior intercavernous sinuses

They connect the cavernous sinuses