The abducens nerve (CN VI) is especially vulnerable to raised intracranial pressure producing a 'false localizing sign.' This is because the nerve:

• A Exits via the cavernous sinus where it is compressed by the internal carotid artery
• B Has the longest intracranial course, making it stretch as the brainstem herniates caudally ✓
• C Runs through the foramen ovale, which narrows with raised pressure
• D Shares its nucleus with fibers from CN V

Explanation

CN VI has the longest intracranial course of any cranial nerve; it runs a particularly long and vulnerable course from the pontomedullary junction over the petrous apex to enter the cavernous sinus. With raised ICP, the brainstem is displaced caudally, stretching the abducens nerve over the petrous ridge, causing ipsilateral lateral rectus palsy (failure to abduct the eye) that is a 'false localizing sign' because CN VI palsy does not necessarily indicate a lesion at or near the abducens nucleus. CN VI does not exit via the foramen ovale (that is CN V3).

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

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Written and medically reviewed by the StethoPrep medical team.