Suboccipital cavernous sinus

The suboccipital cavernous sinuses are paired venous plexuses that surround the horizontal (distal V3) portion of the vertebral arteries at the craniocervical junction. Its name derives from its resemblance to the cavernous sinus as it is a venous cushion surrounding a large arterial loop at the skull base, supported by a framework of fibrous rings, and associated with adjacent nerves ¹.

Gross anatomy

The suboccipital cavernous sinus anastomoses with the following ^2-4:

• superoanteriorly: lateral condylar vein (connecting to the internal jugular vein besides the occipital condyle)
• superomedially: anterior condylar vein (connecting to the jugular bulb via the hypoglossal canal) and marginal sinus (connecting to the occipital and basilar venous sinuses and to the vertebral venous plexus)
• superoposteriorly: posterior condylar vein (connecting to the jugular bulb or sigmoid sinus via the posterior condylar canal)
• inferolaterally: vertebral artery venous plexus surrounding the vertical (proximal V3) segment of the artery at the C2 level (connecting to the vertebral venous plexus and vertebral veins)
• medially: anterior internal vertebral venous plexus
• posteriorly: anastomotic vein connecting to the variable suboccipital venous plexus between the deep and intermediate back muscle layers

The suboccipital cavernous sinus cushions the horizontal portion of the V3 segment of the vertebral artery, the posterior meningeal artery, C1 nerve, and the periarterial autonomic nerve plexus ².

Radiographic appearance

CT

The suboccipital cavernous sinus is well visualized on contrast-enhanced CT ⁴.

MRI

The suboccipital cavernous sinus is well visualized on contrast-enhanced, fat-suppressed T1-weighted images ^2,3.

Related pathology

Given its location at the skull base surrounding the vertebral artery, it can become involved in an (extradural spinal) arteriovenous fistula ^5-7.