Accessory nucleus of oculomotor nerve - Brain - Brainstem - e-Anatomy
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Accessory nucleus of oculomotor nerve

Nucleus accessorius nervi oculomotorii

  • Synonym: Accessory oculomotor nucleus
  • Acronym: Edinger-Westphal nucleus
  • Related terms: Accessory nuclei of oculomotor nerve; Nucleus of oculomotor nerve: Accessory nuclei of oculomotor nerve

Definition

Muhammad A. Javaid

The accessory nucleus of oculomotor nucleus, also known as the Edinger-Westphal nucleus or the accessory nucleus of oculomotor nerve, is situated posterior to the main oculomotor nucleus in the midbrain. This parasympathetic nucleus innervates the ciliary muscle and the pupillary constrictor muscle in the iris, playing a crucial role in controlling lens shape (accommodates for near vision) and pupil size (constricts the pupil).

The axons from the accessory nucleus of oculomotor nucleus, which are preganglionic, accompany the other oculomotor nerve fibers to the orbit, where they synapse in the ciliary ganglion. Postganglionic fibers then pass through the short ciliary nerves to reach their target muscles, i.e. the ciliary muscle and constrictor pupillae muscle in the iris.

Afferents of the accessory nucleus or Edinger-Westphal nucleus:

This nucleus also receives corticonuclear fibers for the accommodation reflex and fibers from the pretectal nucleus for the direct and consensual light reflexes.

References

  • Snell, R.S. (2010). ‘Chapter 11: The Cranial nerve nuclei and their central connections and distribution ’, in Clinical Neuroanatomy. (7th ed.) Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, pp.331-357.

  • Joyce C, Le PH, Peterson DC. Neuroanatomy, Cranial Nerve 3 (Oculomotor) [Updated 2023 Mar 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537126/

  • Heiland Hogan MB, Subramanian S, Das JM. Neuroanatomy, Edinger–Westphal Nucleus (Accessory Oculomotor Nucleus) [Updated 2022 Dec 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554555/

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