Uploaded April 2023 | Updated September 2026, 2 weeks ago

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Content:
0:00 Introduction
00:52 Trochlear Nerve Scheme
02:08 Course of the Trochlear Nerve
06:07 Functions of the Superior Oblique
07:55 Trochlear Nerve Palsy
09:32 Recap


Trochlear Nerve Scheme / Overview:
- Trochlea is Latin for ''Pulley'', due to the function of the superior oblique muscle
- Nucleus of the trochlear nerve located in the midbrain, at the level of inferior colliculi
- Emerges from the posterior surface of the midbrain, and turns anteriorly
- Enter and run on the lateral wall of the cavernous sinus
- Enters the orbit via the superior orbital fissure, to innervate the superior oblique
- Exclusively a somatomotor nerve.

Course of the Trochlear Nerve:
- Nucleus of the Trochlear nerve (nuclei nervi trochlearis) is located in the midbrain, at the level of the inferior colliculus (coliculi inferiores)
- Nucleus is located at the same area as the oculomotor nerve nuclei, just a level lower.
- The trochlear nerve crosses to the contralateral side, leaves from the posterior surface of the midbrain, and turns anteriorly.
- Pierces the dura mater, and then runs through the lateral wall of the cavernous sinus.
- Goes through the superior orbital fissure, to innervate the superior oblique.

Functions of the Superior Oblique Muscle:
- Origin: Body of the sphenoid bone medial to the common tendinous ring.
- Runs anteriorly, muscle tendon hooks around the trochlea of the superior oblique
- Then takes a sharp posterior lateral turn
- Insertion; Posterior Superolateral aspect of eyeball (deep to rectus superior, via trochlea orbitae)
- Causes: Abduction, depression, internally rotation of the eyeball

Clinical Relevance:
- Damage to the trochlear nerve can be caused by either congenital or acquired causes.
- When the nerve is damaged, it causes the eye to naturally shift upwards and externally rotate leading to diplopia (double vision)
- To compensate and reduce the diplopia, patients usually get a head tilt and chin tuck.
- Congenital: Malformations of nucleus or nerve
- Acquired: Trauma, or stroke in the midbrain.


Sources:
- Singh, I. (2017). Human neuroanatomy (10th ed.). Helwany M, Bordoni B. Neuroanatomy, Cranial Nerve 1 (Olfactory) [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-
- Kozlowski, T. (2017). Memorix Anatomy: The Complete Study Guide. 2nd ed. Thieme Medical Publishers.

Pictures and visuals:
- Complete Anatomy
- Biorender
- Powerpoint
- Camtasia 2021