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Inferior petrosal sinus

Recommended video: Petrosal sinuses [03:21]
Anatomy and functions of the inferior and superior petrosal sinuses.
Inferior petrosal sinus (Sinus petrosus inferior)

The inferior petrosal sinus is a paired cranial venous channel that drains the cavernous sinus, midbrain, cerebellum and inner ear. This dural venous sinus emerges from the cavernous sinus within the middle cranial fossa and drains into the internal jugular vein. Occasionally, it may also drain into the suboccipital external vertebral venous plexus.

Throughout its course, the inferior petrosal sinus receives three sets of tributaries; labyrinthine veins, intercavernous sinuses and basilar venous plexus.

Key facts about the inferior petrosal sinus
Drains from Cavernous sinus
Tributaries Labyrinthine veins, intercavernous sinuses, basilar venous plexus
Drains to Internal jugular vein (occasionally to suboccipital external vertebral venous plexus)
Drainage area Middle cranial fossa, medulla oblongata, pons, inferior cerebellar surface, labyrinth of inner ear

This article will discuss the anatomy and function of the inferior petrosal sinus.

  1. Anatomy and course
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Anatomy and course

The inferior petrosal sinus consists of two segments; a long intracranial part and a very short extracranial part. The intracranial part arises from the posterosuperior aspect of the cavernous sinus. It travels posteriorly within the petroocipital fissure of cranial base towards the jugular foramen. Along the way it is joined by several veins; labyrinthine veins from the inner ear vestibule and tributaries from the pons, medulla oblongata and inferior surface of the cerebellum. The basilar venous plexus and intercavernous sinuses also flow into the inferior petrosal sinus. This gives the origin of the inferior petrosal sinus a highly branched and irregular (plexiform) structure, similar to a spider web. The intercavernous sinuses represent an interconnected network of veins that connect the cavernous, superior and inferior petrosal sinuses.

The intracranial part of the inferior petrosal sinus exits the skull through the anteromedial part of the jugular foramen, becoming extracranial. While passing through the foramen, it is accompanied by the glossopharyngeal nerve, vagus nerve, accessory nerve and posterior meningeal artery. After exiting the skull, the vessel travels posteroinferiorly towards the jugular fossa to drain into the medial aspect of the superior bulb of internal jugular vein. In certain individuals, the inferior petrosal sinus is drained into the suboccipital external vertebral venous plexus by a vein passing through the hypoglossal canal of occipital bone.

Explore the anatomy of the dural venous sinuses using the videos, articles, labeled illustrations and quizzes in the following study unit:

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