CN III Oculomotor Nerve

Authors

Affiliations

Nathaniel 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

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 sinus¹.

• Next, these three nerves leave the skull through the superior orbital fissure to synapse and innervate the extraocular muscles¹.

• CN III also carries parasympathetics to the pupillary constrictor and to the ciliary muscle of the lens¹.

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 12.6¹)

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.

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