CN III Oculomotor Nerve

Authors

Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Path of the Oculomotor nerve¹

Nerves of the orbit and ciliar ganglion (lateral view)¹

Mode of innervation of the recti medialis and lateralis¹

Oblique section through the right cavernous sinus¹

flowchart TD
  A[Interpeduncular fossa of Midbrain] --> B[Oculomotor Nucleus]
  
  
  B -- Somatic motor --> C[Superior ORbital fissure]
  C --> D[Extraocular muscles]
  D --> E{Somatic Motor}
  
  A --> F[Edinger-Westphal Nucleus]
  F -- Parasympathetic Efferent --> C
  C --> G[Ciliary ganglion]
  G -- Postganglionic parasympathetic fibers --> H{GVE: Sphincter pupillae & Ciliary muscles}

Overview

• CN III refers to nerve fibers containing somatic motor fibers running to extraocular muscles of the eye as well as parasympathetic efferent fibers running to the muscles in the lens.
• CN III is myelinated by Schwann cells and is therefore considered part of the PNS.

Pathway

• CN III travels with CN IV and VI through the cavernous sinus².

• Next, these three nerves leave the skull through the superior orbital fissure to synapse and innervate the extraocular muscles².

• CN III also carries parasympathetics to the pupillary constrictor and to the ciliary muscle of the lens².

Function

Somatic motor control of Extraocular muscles

• Superior Recti
• Medial Recti
• Inferior Recti
• Inferior Oblique

Parasympathetic efferent to lens

Cranial Nerve Sympathetic Pathways (from Blumenfield Figure 12.6²)

Dysfunction

Clinical Presentation

Diploplia

Ptosis

• levator palpebral ptosis damage to lev palp results in no AP

Mydriasis

• Loss of parasympathetic innervation of Constrictor Pupillae

Down & Out Gaze

References

1.

Gray H. Anatomy of the Human Body. 20th ed. (Lewis WH, ed.). Lea & Febiger; 1918. https://www.bartleby.com/107/

2.

Blumenfeld H. Neuroanatomy Through Clinical Cases. 3rd ed. Oxford university press; 2022.