Amaurosis Fugax

I love that word, Amaurosis Fugax. It comes from the Greek word "amaurosis" which means dark and the Latin word "fugax" which means fleeting (an appropriate name for someone experiencing transient vision loss. It is not on my Neurology wish list of topics to cover but I had a patient with this today and thought it would be a good little topic. Neurology has been going well so far but has very long hours and assigned readings. I am exhausted by the end of the day and am afraid that this one new topic a day may be every other day instead. I will do my best!

A brief case description of my patient today. She is a 68 yo female with a Pmhx of HLD and hypothyroidism who presented to the ED with a cc of right intermittent monocular visual loss. It started 4 days ago when was paying bills that the patient had a sudden painless loss of vision or "graying" as she described it. Pt had no HA, stroke-like symptoms, nausea, vomiting, tremors or loss of conciousness. The episode lasted about one minute and vision fully resolved. Pt again experienced a similar episode later that day that lasted longer but her vision returned to normal. She went to work the next day and while sitting at the computer she had a similar episode which only caused visual loss in her right lower and temporal visual field and didn't fully resolve. She went to an opthomologist who did a fundoscopic exam and they found a few Hollenhorst plaques in the right retinal artery. She came to the ED and was admitted to our service for treatment and r/o of stroke as well as temporal arteritis. CT of the head and neck was negative, CTA showed mild atherosclerosis of the right internal carotid, MRI was normal, EKG showed NRS, TTE bubble study was pending and SED rate and CRP were negative. 

 Questions to ask the patient

• Was the vision loss monocular or binocular? It is important to establish whether the visual loss was monocular or binocular. Transient monocular visual loss points to pathology anterior to the optic chiasm (eye, optic nerve, optic artery) which could be a disease of the eye itself or ischemia secondary to atherosclerosis of the ipsilateral internal carotid. Transient binocular visual loss suggests a more posterior process, involving the optic chiasm, tracts, or radiations, or the visual cortex. Patients with homonymous visual field defects often report monocular visual loss and attribute it to the eye with the temporal field cut. 
• How long did the episode last? Episodes lasting seconds can be caused by papilledema. Episodes lasting 1-15 minutes is more consistent with thromboembolic disease (this is what the patient was experiencing). Episodes lasting 30 minutes or longer with headache points more towards a migraine with aura. 
• Description of the visual symptoms - Transient visual loss secondary to any cause can be described as blurring or fogging (I think of how my patient described it as a "graying") to complete blackness and it can involve the entire visual field or just parts of it. The description of the loss of vision as field of vision as a curtain being pulled down over eye is highly suggestive of retinal ischemia. Positive visual phenomena, such as photopsias or scintillations that march across the visual field, suggest migraine as the most likely diagnosis. Seizures affecting visual cortex often involve positive visual symptoms, but are typically maximal at onset and lack the evolution or build-up characteristic of migraine. Patients who experience viual loss due to hemorrhage of the anterior chamber may describe that the visual field appears red (erythropsia) during the episodes. 

Causes of Amaurosis Fugax

Monocular

• Ischemia - The end result of all the following disorders is ischemia to the retina, the optic nerve, or both. The disease include Large artery occlusive disease (atherothrombosis, embolus, dissection), small artery occlusive disease (anterior ischemic optic neuropathy, vasculitis), venous disease, cardiac disease, hypercoagulable disorders, and systemic hypoperfusion. 
• Retinal Vein occlusion - Occlusion or thrombosis of the central retinal vein is associated with chronic glaucoma, atherosclerotic risk factors, hyperviscosity, and coagulopathy. The cause of retinal vein occlusion is often unknown.
• Optic Neuropathy - Patients with a chronic optic neuropathy may experience episodes of transient loss or blurring of vision, usually in association with elevation of body temperature such as exersise or a hot shower (interesting!). Episodes typically last several minutes or until the body temperature returns to normal. It is classically associated with multiple sclerosis. 
• Papilledema
• Optic nerve compression

Binocular

• Migraine
• Seizure
• Vertibrobasilar Ischemia

Tests to Order

• Opthamologic evaluation
• ESR
• Carotid Dopplers
• Cardiac evaluation - TTE and bubble study, 12 lead EKG possible Holter moniter 
• MRI of brain
• Hypercoagulability
• EEG - if pt's hx suggests seizures

Our team still has a few tests to run on the patient. We ordered a Neuro-Opthamology consult and the TTE was still pending. Eventhough her right internal carotid had mild atherosclerosis, my attending said it wasn't really enough to be the cause. I may update this blog when we get a better understanding of what the etiology is.