192

E Transverse sinus: courses laterally from the confluence of the sinuses within
the attachment ofthe tentorium cerebelli to the sulcus for the transverse sinus

F Sigmoid sinus: represents the continuation ofthe transverse sinus after it
leaves the tentorium cerebelli near the asterion to course within the sulcus
for the sigmoid sinus; becomes continuous with the internal jugular vein at
the jugular foramen

G. Occipital sinus: ascends to the confluence ofthe sinuses within the attach-
ment ofthe falx cerebelli to the internal occipital crest

H. Cavernous sinus

1 Located in the middle cranial fossa lateral to the body of the sphenoid;
extends from the superior orbital fissure to the apex ofthe petrous part
ofthe temporal bone

H. Cavernous sinus

2. Anteriorly, it receives the superior ophthalmic vein and sphenopanetal
sinus; posteriorly, it drains into the superior and interior petrosal sinuses
(it also communicates with its fellow ofthe opposite side via the mter-
cavernous sinus within the diaphragma sellae)

H. Cavernous sinus
3. Traversed by the oculomotor, trochlear, abducens, and ophthalmic
nerves, and the internal carotid artery; also, numerous fibrous bands
traverse its lumen, giving it a cavernous or labynnthlike structure

H. Cavernous sinus

3. Traversed by the oculomotor, trochlear, abducens, and ophthalmic
nerves, and the internal carotid artery; also, numerous fibrous bands
traverse its lumen, giving it a cavernous or labynnthlike structure

H. Cavernous sinus

4. Clinical note: a fracture ofthe base ofthe skull may tear the internal ca-
rotid artery within the cavernous sinus; the arteriovenous fi.stula thus cre-
ated may produce a throbbing mass in the orbit as the superior ophthalmic
vein and its tributaries become distended with pulsatile arterial blood

I Superior petrosal sinus: from the cavernous sinus, it courses posteriorly
within the attachment ofthe tentorium cerebelli to the sulcus tor the supe-
rior petrosal sinus (along the petrous ridge); drains into the junction ot the
transverse and sigmoid sinuses

J Inferior petrosal sinus: from the cavernous sinus, it descends within the
sulcus for the inferior petrosal sinus between the petrous part ofthe tem-
poral bone and the basilar part ofthe occipital bone; exits the skull through
the jugular foramen and drains into the internal jugular vein

K. Basilar plexus: network of venous channels within the cranial dura mater
covering the clivus; connects the inferior petrosal sinuses

L Marginal sinus: lies within the cranial dura mater lateral to foramen mag-
num; anastomoses with the basilar plexus, internal vertebral venous plexus,
and occipital sinus