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

Adam Thomas is a MedEd re-purpose-r. He cofounded the CrackCast project to fill the obvious gap in current FOAMed. He is a true podcasting supporter, and finds it to be the best way he learns. Currently a resident in the FRCP program at the University of British Columbia.
Adam Thomas
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Chris Lipp
Chris Lipp is one of the founding Fathers for CrackCast and an EM Resident in Victoria, BC. His interests are in sports, exercise, and wilderness medicine. When he isn’t out on one of his accidental 20km trail runs, you can find him jamming with friends, or outdoors, and reading Rosen’s…..
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