Which cranial nerve is the only one that exits the brainstem from its dorsal aspect?

• A Oculomotor nerve
• B Abducens nerve
• C Trochlear nerve ✓
• D Hypoglossal nerve

Explanation

The trochlear nerve is unique among cranial nerves in emerging from the dorsal surface of the brainstem, just below the inferior colliculus, after completely decussating within the midbrain. It then wraps around the cerebral peduncle to reach the cavernous sinus. The oculomotor and abducens nerves emerge ventrally from the interpeduncular fossa and pontomedullary junction respectively, and the hypoglossal emerges as rootlets from the preolivary sulcus.

Reference: Gray's Anatomy, 42nd ed.

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Written and medically reviewed by the StethoPrep medical team.