Dural sinuses
Superior sagittal sinus (SSS)
Runs posteriorly in the midline at the junction between falx cerebri and calvarium. Terminates in the venous confluence but may also terminate in either (often the right) or both transverse sinuses.
Receives:
- Superficial cortical veins
- Vein of Trolard
In young children the SSS is composed by multiple irregular channels rather than a single sinus. It takes its final form later in childhood.
Inferior sagittal sinus (ISS)
Smaller caliber than the superior sagittal sinus, runs in the inferior free margin of falx cerebri, above corpus callosum. Joins the vein of Galen to form straight sinus at the apex between falx and tentorium.
Receives:
- Veins from the deep and medial aspects of the cerebral hemispheres
- Tributaries from corpus callosum
Straight sinus (SS)
Forms by the confluence of the vein of Galen and the inferior sagittal sinus. Runs posteriorly and inferiorly from the apex of falx and tentorium to the confluence of sinuses. May be duplicated or triplicated.
Receives:
- Inferior sagittal sinus
- Tributaries from falx and tentorium
- Veins from cerebral hemispheres
- Superior cerebellar veins
Occipital sinus (or marginal sinus)
Smallest of the cranial sinuses but occasionaly can become very large. Usually single but occasionally duplicated. It is formed around the margin of foramen magnum, runs in the attached margin of falx cerebelli. Joins the terminal part of the transverse sinus or the confluence of sinuses. Communicates with the posterior internal vertebral venous plexus.
Receives:
- Tributaries from the margins of foramen magnum
Confulence of sinuses (torcular herophili or torcula)
The connecting point between the superior sagittal sinus, straight sinus, transverse sinuses and occipital sinus.
Transverse sinus (TS)
Runs inside the attachment of the tentorial leaves to the calvarium. Extends from the confluence of sinuses to the posterior border of the petrous part of the temporal bone where it leaves the tentorium and becomes the sigmoid sinus. The right TS is usually dominant. The left TS may be hypoplastic or aplastic.
Receives:
- The larger TS receives most venous drainage from the superior sagittal sinus
- The smaller/hypoplastic TS usually receives blood from the straight sinus
- Inferior cerebral and cerebellar veins
- Vein of Labbé
- Superior petrosal sinus
- Mastoid and condyloid emissary veins
- Diploic veins
Sigmoid sinus
The continuation of the transverse sinus, forms an S-shaped inferior curve behind the inferior part of the temporal bone (petrous part), reaches the jugular foramen where it drains into the internal jugular vein.
Receives:
- Venous drainage from transverse sinus
- Inferior cerebral and cerebellar veins
- Diploic and emissary veins
Superior petrosal sinus
Runs within the attachment of the tentorium and the superior border of the petrous part of the temporal bone. Extends from the transverse sinus to the posterior part of the cavernous sinus.
Receives:
- Petrosal vein
- Inferior cerebral veins
- Inferior cerebellar veins
- Labyrinthine vein
Inferior petrosal sinus
Runs in the petrosal sulcus (junction between the petrous part of temporal and basilar part of occipital bones). Extends from the posteroinferior part of the cavernous sinus to the jugular bulb (superior part of internal jugular vein).
Receives:
- Internal auditory veins
- Tributaries from pons, medulla oblongata and inferior cerebellum
Sphenoparietal sinus (sinus of Breschet)
Runs medially along the under surface of the lesser wing of the sphenoid bone. Drains usually into the cavernous sinus but may also drain posteriorly into the transverse sinus.
Receives:
- Tributaries from superficial middle cerebral vein
- Frontal ramus of middle meningeal vein
- Anterior temporal and diploic veins
Lateral tentorial sinus
Intratentorial venous channel that drains into the TS.
Drains:
- Posteroinferior group of superficial cerebral veins from lateral inferior and basal surface of temporal and occipital lobes
Cavernous sinus
Lies adjacent to either side of the body of the sphenoid bone. Extends from the superior orbital fissure anteriorly to the apex of the petrous part of the temporal bone posteriorly.
It is not a typical “sinus” but an irregularly shaped, trabeculated space containing vascular and nervous elements.
The cavernous part of ICA and the abducens nerve course inside the cavernous sinus. The oculomotor, trochlear, ophthalmic and maxillary nerves course through the lateral dural wall of the sinus.
The venous element is a plexus of many small veins whose anterior and posterior communicating channels run in the diaphragma sellae and form the coronary sinus that surrounds the pituitary. It drains via the superior and inferior petrosal sinus into the transverse sinus and via veins that course through foramen Vesalii, foramen ovale and foramen lacerum, into the pterygoid plexus.
Receives:
- Superior and inferior ophthalmic veins
- Small cerebral veins
- Sphenoparietal sinus
Communicates with:
- Contralateral cavernous sinus
- Pterygoid venous plexus
- Superior petrosal sinus
- Inferior petrosal sinus
- Clival venous plexus
Normal anatomic variants
- Absent or hypoplastic superior sagittal sinus - occasionally mistaken for thrombosis of SSS on radiologic studies. A telltale sign of a hypoplastic SSS are prominent frontal cortical veins that drain into the (normal) SSS, which begins posteriorly near the coronal suture.
- Off-midline SSS terminating directly into TS
- Hypoplastic or absent transverse sinus
- Variations in the size of the jugular bulbs
- Jugular bulb diverticulum
- High riding jugular bulb - Large jugular bulb reaching above the internal acoustic meatus
- Dehiscence of the jugular bulb - A high riding jugular bulb bulges into the middle ear cavity
- Giant arachnoid granulations (seen as round filling defects in SSS)
Anatomic anomalies
- Persistence of the embryonic falcine sinus, usually accompanies vein of Galen malformation
- Torcular-lambdoid inversion - abnormally high tentorium with torcular lying above the level of the lambdoid, usually seen in Dandy-Walker spectrum disorders