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The superior sagittal sinus is in the superior border of the
falx cerebri (Fig. 8 .44) . It begins anteriorly at the foramen
cecum, where it may receive a small emissary vein from the
nasal cavity, and ends posteriorly in the confluence of
sinuses, usually bending to the right to empty into the right
transverse sinus . The superior sagittal sinus communicates
with lateral extensions (lateral lacunae) of the sinus containing
numerous arachnoid granulations.
The superior sagittal sinus usually receives cerebral
veins from the superior surface of the cerebral hemispheres,
diploic and emissary veins, and veins from the falx cerebri.
Inferior sagittal and straight sinuses
The inferior sagittal sinus is in the inferior margin of the
falx cerebri (Fig. 8 .44) . It receives a few cerebral veins and
veins from the falx cerebri, and ends posteriorly at the anterior
edge of the tentorium cerebelli, where it is j oined by
the great cerebral vein and together with the great cerebral
vein forms the straight sinus (Fig. 8 .44) .
The straight sinus continues posteriorly along the junction
of the falx cerebri and the tentorium cerebelli and ends
in the confluence of sinuses, usually bending to the left to
empty into the left transverse sinus.
The straight sinus usually receives blood from the inferior
sagittal sinus , cerebral veins (from the posterior part
of the cerebral hemispheres) , the great cerebral vein (draining
deep areas of the cerebral hemispheres) , superior cerebellar
veins, and veins from the falx cerebri.
Confluence of sinuses, transverse and
sigmoid sinuses
The superior sagittal and straight sinuses, and the occipital
sinus (in the falx cerebelli) empty into the confluence of
sinuses, which is a dilated space at the internal occipital
protuberance (Fig. 8 . 44) and is drained by the right and
left transverse sinuses.
The paired transverse sinuses extend in horizontal
directions from the confluence of sinuses where the tentorium
cerebelli j oins the lateral and posterior walls of the
cranial cavity.
The right transverse sinus usually receives blood from
the superior sagittal sinus and the left transverse sinus
usually receives blood from the straight sinus .
The transverse sinuses also receive blood from the superior
petrosal sinus, veins from the inferior parts of the cerebral
hemispheres and the cerebellum, and diploic and
emissary veins.
As the transverse sinuses leave the surface of the occipital
bone, they become the sigmoid sinuses (Fig. 8 .44) ,
888 which turn inferiorly, grooving the parietal, temporal, and
occipital bones , before ending at the beginning of the internal
jugular veins. The sigmoid sinuses also receive blood
from cerebral, cerebellar, diploic, and emissary veins.
Cavernous sinuses
The paired cavernous sinuses are against the lateral aspect
of the body of the sphenoid bone on either side of the sella
turcica (Fig. 8 . 4 5 ) . They are of great clinical importance
because of their connections and the structures that pass
through them.
The cavernous sinuses receive blood not only from cerebral
veins but also from the ophthalmic veins (from the
orbit) and emissary veins (from the pterygoid plexus
of veins in the infratemporal fossa) . These connections
provide pathways for infections to pass from extracranial
sites into intracranial locations. In addition, because structures
pass through the cavernous sinuses and are located
in the walls of these sinuses they are vulnerable to injury
due to inflammation.
Structures passing through each cavernous sinus are :
• the internal carotid artery, and
• the abducent nerve [VI] .
Trochlear nerve [IV] Abducent nerve [VI]
I nternal carotid artery
Oculomotor nerve [ I l l ]
Pituitary gland
Diaphragma sellae
Cavernous (venous) sinuses
Ophthalmic division of trigeminal nerve [V1 ]
Maxillary division of trigeminal nerve [V2]
Fig. 8.45