›

CN 3, Oculomotor Nuclei

Notes

CN 3, Oculomotor Nuclei

WARWICK MODEL OF THE OCULOMOTOR COMPLEX

  • Superior rectus subnuclei project contralaterally, the single levator palpebrae subnucleus projects bilaterally, and the remaining subnuclei project ipsilaterally.

Note - levator palpebrae subnucleus lesions naturally cause bilateral eye muscle palsies and superior rectus subnucleus lesions also produce bilateral palsies because when the superior rectus fibers exit their subnucleus, they immediately pass through the contralateral subnucleus.

  • Ventral subnucleus - innervates medial rectus (truly, three separate oculomotor regions supply the medial rectus muscle).
  • Intermediate subnucleus - innervates inferior oblique.
  • Dorsal subnucleus - innervates inferior rectus.
  • Medial subnucleus - innervates contralateral superior rectus (this subnucleus is commonly unnamed).
  • Central caudal subnucleus - innervates the bilateral levator palpebrae.
  • Visceral nuclei - include the Edinger-Westphal nucleus, anteromedian nucleus, and the nucleus of Perlia.

PERIOCULOMOTOR CELL GROUP:

  • Places the Edinger-Westphal nucleus, anteromedian nucleus, and nucleus of Perlia into a larger context of neural substrate responsible for the accommodation reflex (or near-response) - a three-part reflex that brings near objects into focus through lens thickening, pupillary constriction, and inward rotation of the eyes (eye convergence).
  • Along the dorsal aspect of the oculomotor nucleus, lies the preganglionic perioculomotor cell group - the Edinger-Westphal nucleus lies within this part of the perioculomotor cell group.
  • The preganglionic cell group is responsible for producing the lens thickening and pupillary constriction responses of the accommodation reflex.
  • Along the rostral-caudal length of the medial aspect of the oculomotor nucleus lies the motoneuron division of the perioculomotor cell group. It innervates the multiply innervated muscle fibers of the accommodation reflex, which produce eye convergence. The motoneuron division of the perioculomotor cell group encompasses the anteromedian nucleus, anteriorly, and the nucleus of Perlia in mid-anteroposterior position.

Do not attempt to draw discrete functional meaning from the positions of the Edinger-Westphal nucleus, anteromedian nucleus, and nucleus of Perlia from this diagram: these nuclei are included, here, only to provide historical/ anatomic context to our perioculomotor cell group model. Broadly we still simply consider them to enact the visceral actions of the oculomotor nerve.

SUPRANUCLEAR CONTROL OF THE PERIOCULOMOTOR CELL GROUP

  • Comes from widely distributed areas - the supraoculomotor area (which lies within the mesencephalic reticular formation just dorsal to the oculomotor complex) and numerous cerebral and cerebellar smooth pursuit centers, described elsewhere.