What is the workup for Amaurosis fugax (Transient Monocular Blindness)?

Workup for Amaurosis Fugax

Amaurosis fugax must be treated as a medical emergency requiring immediate referral to an emergency department or stroke center within 24 hours of symptom onset, as the risk of stroke is highest within the first 7 days and up to 24% of patients have concurrent silent brain infarction. 1, 2

Immediate Triage and Referral

• Do not perform additional testing in the ophthalmology office—immediately refer the patient to a stroke center for comprehensive evaluation 1
• The risk of ischemic stroke ranges from 3-6% within the first 1-4 weeks after presentation, with concurrent stroke present in 20-24% of cases 1
• Silent brain infarction on imaging occurs in approximately 19-24% of patients despite transient symptoms 1, 2, 3

Essential Diagnostic Workup (Performed at Stroke Center)

Neuroimaging (Urgent - Within 24 Hours)

• Diffusion-weighted MRI (DWI-MRI) of the brain is the primary imaging modality, as it detects silent cerebral infarctions missed by CT scanning 1, 2
• Brain CT is insufficient and should not be relied upon as the sole imaging modality 1

Vascular Imaging (Urgent)

• Carotid duplex ultrasound is the initial imaging modality of choice for all patients 2
• Up to 70% of patients with symptomatic retinal artery occlusions have clinically significant carotid stenosis 1, 2, 3
• If high-grade stenosis is suspected, proceed with CT angiography or MR angiography for definitive characterization 2

Cardiac Evaluation

• Transthoracic echocardiography is reasonable to examine for cardioembolic sources, given the high rate of structural heart disease 2
• Transesophageal echocardiography should be reserved for patients with high suspicion for occult cardiac lesions and negative initial workup 2
• Ambulatory cardiac rhythm monitoring (24-hour Holter or event recorder) is appropriate to detect paroxysmal atrial fibrillation 2

Laboratory Studies (Critical for Patients >50 Years)

• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) must be obtained urgently in all patients over 50 years of age to evaluate for giant cell arteritis (GCA) 1, 2, 3
• GCA typically presents with temporal tenderness, jaw claudication, weight loss, proximal myalgia, fever, optic disc swelling, and absence of emboli 1, 2, 3
• If GCA is suspected, immediately initiate high-dose systemic corticosteroids (40-60 mg/day prednisone equivalent) before temporal artery biopsy 2

Ophthalmologic Examination Components

• Fundoscopic examination to identify cholesterol emboli (Hollenhorst plaques), optic disc swelling, or retinal arterial occlusion 3
• Intraocular pressure measurement to exclude glaucoma as an alternative cause 4
• Assessment for presence of emboli versus absence of emboli (the latter suggests GCA) 1, 3

Risk Stratification

The following factors increase stroke risk and should be documented:

• Hypertension, diabetes, hypercholesterolemia, and cigarette smoking 1, 3
• Age over 50 years (particularly Caucasians for GCA risk) 1, 3
• History of prior ischemic stroke (increases recurrence risk 4-fold) 5
• Presence of atrial fibrillation or structural heart disease 2, 3

Common Pitfalls to Avoid

• Delaying referral to perform outpatient testing—this is the most critical error, as stroke risk is maximal in the first week 1, 2
• Failing to evaluate for GCA in patients over 50—missing this diagnosis can result in permanent bilateral blindness 1, 2, 3
• Relying on brain CT instead of DWI-MRI—CT misses the majority of silent infarctions 1
• Assuming transient symptoms mean no infarction occurred—up to 24% have silent brain infarcts despite complete symptom resolution 1, 2, 3
• Confusing transient visual obscurations (TVOs) with amaurosis fugax—TVOs last only seconds, are associated with papilledema, and require evaluation for raised intracranial pressure rather than stroke workup 4

Immediate Treatment Considerations

• Antiplatelet therapy (aspirin 75-325 mg daily) should be initiated as part of stroke prevention unless contraindicated 2
• Consider dual antiplatelet therapy for 21 days in patients with minor stroke symptoms, followed by single agent 2
• Statin therapy should be initiated as part of vascular secondary prevention 2
• If atrial fibrillation is detected, initiate oral anticoagulation according to stroke prevention guidelines 2
• For confirmed GCA, consider IV methylprednisolone (0.25-1 g/day for up to 3 days) for acute visual loss 2