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Cranial Nerves
 
 

CN III: Oculomotor Nerve

 
 
 
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Overview

  • Roles

  • Somatic motor - eye movement, eye opening
  • Visceral motor (parasympathetic) - pupillary & ciliary muscles

Occulomotor Nerve Palsy

  • Abnormalities

  • Eye deviated down and out
  • Diplopia
  • Ptosis
  • Mydriasis (pupillary dilatation)
  • Loss of pupillary reflexes
  • Causes of Oculomotor Nerve Palsy

  • Small-vessel ischaemia
  • Midbrain infarct
  • Head trauma
  • Tumour
  • Aneurysm (commonly PCA)

Motor Pathway

Eye movement and eye opening
Cortical Centre
Primary motor cortex (frontal lobe)
 
 
Oculomotor Nucleus
Superior colliculus (midbrain)
 
Pathway
Tegmentum, red nucleus, medial substantia nigra
Foramen
Superior orbital fissure
Division
Superior and inferior branches
 
 
Muscle
Superior branch - superior rectus, levator palpabrae superioris
Inferior branch - inferior rectus, medial rectus, inferior oblique

Parasympathetic Pathway

Pupillary and ciliary movement
Edinger-Westphal nucleus
Superior colliculus (midbrain)
 
Pathway
Tegmentum, red nucleus, medial substantia nigra
Foramen
Superior orbital fissure
 
 
Ciliary Ganglion
 
 
Muscle
Constrictor pupillae, ciliary muscles
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