CRACKCast E021 – Diplopia

In CRACKCast, Podcast by Adam Thomas2 Comments

This episode of CRACKCast covers Rosen’s Emergency Medicine, Chapter 021 – Diplopia. Here the podcast reviews how to risk stratify diplopia and when to be most concerned for this uncommon chief complaint.

Shownotes – PDF Here 

Rosen’s in Perspective

Diplopia is uncommon presentation to the ED, representing 1.4% of eye emergencies; however, it can be extremely debilitating for patients when it does occur. Diplopia can be:

  • Monocular (15%) – persists in one eye even if the other eye is closed
  • Binocular (85%) – resolves when either eye is closed

Monocular = distortion with the light path through the eye (typically an eye issue)

Binocular = pathology can exist in multiple locations, including:

  • Ocular
  • Ocular muscle
  • Cranial nerves (CN VI palsy a very common cause of diplopia)
  • Upper versus lower neuron disease
  • Ocular centre dysfunction in CNS
  • Brainstem

 1) List the differential diagnosis (critical emergent, urgent) for Diplopia (including at least 7 causes of binocular diplopia)


  • Basilar Artery Thrombosis
  • Botulism
  • Basilar Meningitis
  • Aneurysm


  • Vertebral Dissection
  • Myasthenia Gravis
  • Wernicke’s Encephalopathy
  • Orbital Apex Syndrome / Cavernous Sinus Process


  • Brainstem Tumour
  • Miller-Fisher Syndrome
  • Multiple Sclerosis
  • Graves Disease
  • Ophthalmoplegic Migraine
  • Ischemic Neuropathy
  • Orbital myositis / pseudotumor
  • Orbital apex mass

2) Describe the mechanisms of normal extraocular movements

  • Remember: SO4 – LR6 (and the rest are 3)”

3) Describe specific cranial nerve palsies causing diplopia


1) What are the 5 most important questions to ask yourself about diplopia?

  1. Is the diplopia monocular?
  2. Is the binocular diplopia a result of a restrictive, mechanical orbitopathy?
  3. Is the binocular diplopia a result of a palsy of the oculomotor CNs (III, IV, or VI) in a single eye?
  4. Is the binocular diplopia a result of a neuroaxial process involving the brainstem and related CNs?
  5. Is the binocular diplopia a result of a neuromuscular disorder?

2) Describe your approach to diplopia in the sick patient

This post was uploaded and copyedited by Riley Golby (@RileyJGolby)

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Adam Thomas

Adam Thomas

CRACKCast Co-founder and newly minted FRCPC emergency physician from the University of British Columbia. Currently spending his days between a fellowship in critical care and making sure his toddler survives past age 5.
Adam Thomas
- 12 hours ago
Chris Lipp
Chris Lipp is one of the founding Fathers for CrackCast. He currently divides his time as an EM Physician in Calgary (SHC/FMC) and in Sports Medicine. His interests are in endurance sports, exercise as medicine, and wilderness medical education. When he isn’t outdoors with his family, he's brewing a coffee or dreaming up an adventure…..