The cavernous sinus contains several cranial nerves within its lateral wall and the internal carotid artery within its cavity. Which nerve is most susceptible to damage by a cavernous sinus thrombosis, because it runs freely within the sinus lumen rather than in the lateral wall?

• A CN III (oculomotor nerve)
• B CN V1 (ophthalmic division of trigeminal)
• C CN VI (abducent nerve) ✓
• D CN IV (trochlear nerve)

Explanation

Within the cavernous sinus, CN VI (abducent nerve) runs freely within the venous blood in the lateral part of the sinus cavity, directly beside the internal carotid artery. CN III, IV, V1, and V2 are embedded in the lateral dural wall of the sinus and are relatively protected. Therefore, CN VI is most vulnerable to damage in cavernous sinus thrombosis, carotid-cavernous fistula, or pituitary apoplexy — producing lateral rectus palsy (convergent squint with failure of abduction) as an early sign.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.