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)

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.
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 (Innovative Sport Medicine Calgary). His interests are in paediatrics, 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…..