A patient with idiopathic intracranial hypertension develops unilateral abducens nerve palsy despite having no mass lesion along the sixth nerve course. This occurs because the abducens nerve is considered a 'false localizing' sign owing to its:
- A Long intracranial course over the clivus before entering the cavernous sinus ✓
- B Short course within the cavernous sinus
- C Passage through the superior orbital fissure
- D Anastomosis with the sympathetic plexus
Correct answer: A. Long intracranial course over the clivus before entering the cavernous sinus
Explanation
The sixth nerve has the longest intracranial course of any cranial nerve, running upwards over the clivus and piercing dura before entering the cavernous sinus. Raised intracranial pressure stretches and compresses it against the petrous apex or clivus, producing a lateral rectus palsy that does not indicate a lesion at the nerve itself. Its cavernous sinus course is short, so option B is incorrect.
Reference: Snell's Clinical Neuroanatomy, 8th ed.
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