Oculomotor nerve

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The third of the cranial nerves. Leaves skull via Superior orbital fissure

Supplies

Contents

Lesion

  • loss of motor to most of eye movements and parasympathetic supply to pupil
  • All muscles paralysed except lateral rectus and superior oblique
  • Eye points down and out
  • Pupillary fibres run on outside of 3rd nerve
    • Pupillary-sparing lesion is likely to be ischaemic
    • Pupillary-involving is likely to be compressive → More dangerous

Examination

  • General
    • Ptosis
  • Acuity
    • normal
  • Fields
    • normal (limited by ptosis)
  • Pupil
    • dilated
    • no reaction if complete lesion
  • Movements
  • Fundi
    • normal
    • Papilloedema if space occupying lesion

Causes

Investigations

  • blood glucose
  • CT / MRI
  • carotid arteriography
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