Content:
Introduction: 0:00
Abducens nerve scheme: 00:41
Abducens nerve nucleus: 01:53
Abducens nerve course: 04:05
Lateral rectus muscle function: 05:04
Clinical Relevance: 06:25
Recap: 07:06


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Abducens nerve is purely a motor nerve supplying the lateral rectus muscle involved in abduction of the eye

Abducens/abducent nerve Nucleus:
Nucleus of abducens nerve (nucleus nervi abducentis)
○ Facial nerve goes around this nucleus forming the facial colliculus (colliculus facialis)
○ A somatomotor nucleus that is located in the pons innervates the lateral rectus

Course:
Emerges from the medullopontine sulcus between the pons and medulla oblongata
Leaves the brainstem on the ventral side
Runs on the base of the skull, penetrates the dura mater then enter the cavernous sinus
Enters the orbit via the superior orbital fissure and common tendinous ring
Then innervates the lateral rectus

Function of lateral rectus muscle:
Abduction of the eye

Hering's Law of equal innervation:
Coordinates both eyes together, so that the medial and the lateral rectus muscle contracts equally, while deactivating the contralateral muscle through the medial longitudinal fasciculus.

Clinical Relevance:
Abducens nerve can get compressed by a lesion or rise in intracranial pressure.
Compression causes paralysis of lateral rectus muscle, resulting in medial deviation of affected eye, giving a fully adducted eye at rest and an inability to abduct the eye.


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.

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