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Cranial Nerves

Pupillary Defects

February 15th, 2021

Horner's Syndrome

Horner's syndrome is a classic triad that occurs due to compression of the sympathetic chain.
  • Look For

  • Partial ptosis: drooping of the eyelid
  • Miosis: pupillary constriction
  • Anhidrosis: lack of sweating
  • Causes of Horner's Syndrome

  • Brain lesion - hypothalamus, thalamus, pons, medullaTumour, bleed
  • Spinal cord lesionTrauma, inflammation, AVM, demyelination, tumour, infarct
  • Apical lung lesion (Pancoast syndrome)
  • Brachial plexus lesion

Oculomotor Nerve (III) Palsy

  • Look For

  • Eye deviated down and out
  • Diplopia
  • Ptosis
  • Mydriasis: pupillary dilatation
  • Loss of pupillary reflexes
  • Causes of Occulomotor Nerve Palsy

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

Adie's Tonic Pupil

  • Look For

  • Dilatation of one or both pupils
  • Unresponsiveness to light
  • Intact accomodation reflex (near light dissociation)
  • Significance

  • Indicates loss of postganglionic parasympathetic innervation of the sphincter pupillae and ciliary muscles.
This finding is commonly associated with knee / ankle areflexia (Holmes-Adie syndrome)
  • Causes of Adie's Tonic Pupil

  • Viral infection
  • Trauma
  • Orbital tumour
  • Vasospasm (migraine)
  • Idiopathic

Argyll Robertson Pupil

  • Look For

  • Pupillary constriction
  • Unresponsiveness to light
  • Intact accomodation reflex (near light dissociation)
  • Significance

  • Previously pathognomonic for neurosyphillis, though more recently associated with conditions affecting the Edinger Westphal nucleus (accessory occulomotor nucleus) within the midbrain.
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