Anatomy All except one are true regarding cavernous sinus A Cavernous sinus roof is formed by meningeal layer of duramater, and floor is formed by endosteal layer of duramater. B It is an unpaired venous sinus. C 3rd and 4th cranial nerve and internal carotid artery pierce roof of cavernous sinus D Abducens nerve passes through the cavernous sinus. 💡 Explanation All except one are true regarding cavernous sinus ✓ Correct Answer: B. It is an unpaired venous sinus.