Case of the Week
Section Editors: Matylda Machnowska,1 Anvita Pauranik,2 Vinil Shah3
1University of Toronto, Toronto, Ontario, Canada
2University of British Columbia, Vancouver, British Columbia, Canada
3University of California, San Francisco
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January 13, 2022
Perioperative Ischemic Optic Neuropathy
- Background:
- Ischemic optic neuropathy (ION) is classified as anterior versus posterior depending on involvement of the optic nerve head. Each group is further divided into arteritic (often due to giant cell arteritis), nonarteritic (not related to vasculitis but systemic vascular disease), and perioperative.
- Perioperative ION, although typically classified as posterior ION, can be either anterior or posterior.
- The incidence of perioperative ION has been reported to be 0.028–1.3%.
- Coronary-artery bypass grafting and prolonged spine surgery in the prone position are the 2 most commonly associated procedures.
- Arterial hypotension, excessive fluid replacement for massive blood loss leading to hemodilution, pressure on the eyeball and orbit, dependent position of the head, and prolonged duration of surgery can also significantly increase the risk of perioperative ION in addition to preexisting cardiovascular comorbidities.
- Blood supply to the optic nerve head (ONH) is via posterior ciliary arteries via peripapillary choroid and short posterior ciliary arteries; blood supply between the ONH and site of entry of the central retinal artery (CRA) into the nerve is by the pial vascular plexus, and blood supply posterior to the entry site of the CRA is via branches from the ophthalmic artery.
- Clinical Presentation:
- Patients may wake up with painless, usually bilateral but not uncommonly unilateral massive visual loss, which is often permanent.
- Funduscopy may be normal or demonstrate optic disc edema depending upon involvement of the ONH.
- CT and MRI are commonly performed for evaluation. Diffusion restriction in the optic nerves is not always readily demonstrable on MRI.
- Key Diagnostic Features:
- A characteristic history of painless bilateral sudden vision loss in the context of recent surgery and perioperative cardiovascular event is helpful to make the diagnosis.
- MRI findings of swollen optic nerves with increased T2/FLAIR signal and diffusion restriction in optic nerves are confirmatory.
- Differential Diagnoses:
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Arteritic ION; nonarteritic ION; optic neuritis; toxic, infective, or compressive etiologies
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Jaw claudication is often seen in arteritic ION, while periorbital pain and pain on eye movement may be seen with optic neuritis.
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High DWI and lower ADC values may be seen in MRI compared with optic neuritis and other toxic/inflammatory etiologies.
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Imaging of the brain and orbits can also help to rule out mass lesions, demyelinating disease, or other potential causes of blindness.
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Treatment:
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None proven to be effective
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