On a coronal MRI through the cavernous sinuses, a mass in the right cavernous sinus spares all cranial nerves embedded in its lateral wall. Which nerve, because of its medial position within the sinus, is MOST likely affected?

• A Oculomotor nerve (CN III)
• B Abducent nerve (CN VI) ✓
• C Maxillary nerve (CN V2)
• D Trochlear nerve (CN IV)

Explanation

Cranial nerves III, IV, V1, and V2 are embedded in the lateral wall of the cavernous sinus from superior to inferior. The abducent nerve (CN VI) runs through the sinus itself, medial to the internal carotid artery, making it vulnerable to intracavernous lesions while the lateral wall nerves remain spared. This is a classic clinical-radiological correlation tested frequently.

Reference: Gray's Anatomy, 42nd ed.

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Written and medically reviewed by the StethoPrep medical team.