Cavernous sinus
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SPHENOID vs CAVERNOUS
- Sphenoid sinuses - air-filled.
- Cavernous sinuses - venous blood.
- Lateral wall, from superior to inferior, lie CN 3, CN 4, CN 5 (1st division), CN 5 (2nd division). Medial to CN 5 (1st division) is CN 6. More medial is the internal carotid artery. The internal carotid artery doubles back above the cavernous sinus and runs in between its roof and the ipsilateral optic nerve.
Clinical correlation - cavernous sinus aneurysm
FORAMEN
- CN 2 passes through the optic canal.
- CNs 3, 4, and 6 pass through the superior orbital fissure.
- CN 5 (1st division) passes through the superior orbital fissure and CN 5 (2nd division) passes through foramen rotundum.
- CN 5(3rd division) does not enter the cavernous sinus; it exits the cranium through foramen ovale.
- Roof lies at the level of the anterior clinoid process.
- Anteriorly, the cavernous sinus extends to the superior orbital fissure.
- Posteriorly, it reaches the clivus.
- Medially, it neighbors the sella turcica.
- Laterally, it neighbors the medial temporal lobe.
- Envelops the trigeminal ganglion.
- Medial upper-third is formed by the posterolateral cavernous sinus.