Which cranial nerve runs free within the lumen of the cavernous sinus, rather than embedded in the dural wall of its lateral side?

• A Oculomotor nerve (III)
• B Abducens nerve (VI) ✓
• C Trochlear nerve (IV)
• D Maxillary division of the trigeminal nerve (V2)

Explanation

Within the cavernous sinus, the oculomotor, trochlear, ophthalmic (V1) and maxillary (V2) nerves all course within the lateral dural wall, while the abducens nerve and the internal carotid artery lie inside the venous lumen itself. This makes the sixth nerve the earliest to be involved in cavernous sinus thrombosis or pituitary tumour expansion, producing ipsilateral lateral rectus palsy with diplopia before the other ocular motor nerves fail.

Reference: Gray's Anatomy, 42nd ed.

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Written and medically reviewed by the StethoPrep medical team.