The trochlear nerve (CN IV) is unique among cranial nerves in that it:

• A Exits the brainstem from its ventral surface
• B Is the only cranial nerve to exit dorsally and fully decussate before exiting
• C Has the longest intracranial course of any cranial nerve
• D Both B and C ✓

Explanation

CN IV (trochlear nerve) has two unique features: it is the only cranial nerve to (1) exit from the dorsal surface of the brainstem (inferior colliculus level) and (2) completely decussate within the brainstem before exiting — so each trochlear nucleus innervates the contralateral superior oblique. Additionally, CN IV has the longest intracranial course (~75 mm) of any cranial nerve, making it vulnerable to injury in head trauma, especially with tentorial herniation. These features are classic NEET PG exam points.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.