What is the differential diagnosis for a 50-year-old woman with a history of migraines (migraine headaches) presenting with acute onset of visual loss and blurriness, except for the central portion of her vision, without improvement in visual symptoms after treatment with a migraine cocktail of IV Compazine (prochlorperazine), Benadryl (diphenhydramine), and Toradol (ketorolac), and normal diagnostic imaging and exams?

Differential Diagnosis for Acute Peripheral Visual Field Loss with Preserved Central Vision

The most critical diagnosis to exclude in this patient is retinal pathology—specifically retinal detachment, retinal artery or vein occlusion, or acute posterior vitreous detachment—which requires urgent ophthalmologic consultation despite the reportedly normal funduscopic exam in the emergency department. 1

Primary Differential Diagnoses

Retinal/Ocular Pathology (Most Urgent)

• Retinal detachment can present with peripheral visual field loss described as a "curtain" or tunnel vision, and early detachment may not be obvious on non-dilated funduscopic examination by non-ophthalmologists 1
• Branch or central retinal artery occlusion can cause acute monocular visual loss with peripheral field defects, though central vision may be initially preserved depending on the location 1
• Retinal vein occlusion presents with sudden, painless monocular vision loss and may show subtle funduscopic changes that require expert ophthalmologic examination 1
• Acute posterior vitreous detachment with or without retinal tear can cause visual disturbances and requires dilated funduscopic examination by ophthalmology 1

Optic Nerve Pathology

• Optic neuritis typically presents with painful monocular vision loss, though pain may be mild or absent in some cases, and MRI with contrast showing optic nerve enhancement would be diagnostic 1, 2
• Anterior ischemic optic neuropathy (arteritic or non-arteritic) causes acute monocular vision loss and may show optic disc edema on funduscopy, though this can be subtle initially 1
• Optic nerve compression from mass lesions would typically show abnormalities on the MRI that was already performed 1

Migraine-Related Phenomena

• Persistent migraine aura or prolonged aura can last beyond the typical 5-60 minutes, sometimes for days, though this is a diagnosis of exclusion after ruling out structural causes 3, 4, 5
• Retinal migraine (migraine with retinal aura) causes transient monocular visual disturbances including scotomas, but symptoms typically resolve within 60 minutes 1, 3
• Migraine aura without headache can occur, particularly in patients over 40 years old with a history of migraine, but the persistence of symptoms beyond hours makes this less likely 3, 4, 5

Posterior Circulation Pathology

• Occipital lobe infarction would typically be visible on MRI brain, though very early ischemia (<6 hours) might not show on standard sequences 1
• Posterior reversible encephalopathy syndrome (PRES) can cause visual disturbances but typically has additional neurological symptoms and characteristic MRI findings 3

Critical Next Steps

Immediate Ophthalmologic Evaluation

• Formal ophthalmologic examination with dilated funduscopy is mandatory to definitively exclude retinal pathology, as emergency department funduscopic exams have limited sensitivity for early retinal detachment and vascular occlusions 1
• Optical coherence tomography (OCT) and fluorescein angiography may be needed to identify subtle retinal or choroidal pathology not visible on standard funduscopy 1
• Visual field testing (perimetry) can help localize the lesion along the visual pathway and quantify the deficit 1

Additional Diagnostic Considerations

• MRI orbits with and without contrast with fat suppression sequences should be obtained if optic neuritis is suspected, as this would show abnormal optic nerve enhancement in 95% of cases 1, 2
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) should be checked urgently if giant cell arteritis is a consideration (age >50, new headache, jaw claudication, scalp tenderness), as this requires immediate high-dose corticosteroids 1, 6
• Repeat MRI brain with diffusion-weighted imaging (DWI) may be considered if initial MRI was performed very early and posterior circulation stroke remains a concern 1

Key Clinical Pitfalls to Avoid

• Do not assume a normal funduscopic exam in the ED excludes serious retinal pathology—early retinal detachment, small retinal tears, and subtle vascular occlusions require dilated examination by an ophthalmologist 1
• Do not diagnose persistent migraine aura without excluding structural and vascular causes first—this is a diagnosis of exclusion that should only be made after comprehensive ophthalmologic and neurologic evaluation 3, 4, 5
• Do not rely solely on the patient's description of "pinhole" or tunnel vision—formal visual field testing is needed to accurately characterize the deficit and localize the lesion 1
• Do not miss giant cell arteritis in patients over 50—this is a medical emergency requiring immediate treatment to prevent permanent bilateral blindness 1, 6

Diagnostic Algorithm

1. Urgent ophthalmology consultation (within 24 hours) for dilated funduscopic examination, OCT, and formal visual field testing 1

2. If ophthalmologic exam is normal:

   • Check ESR/CRP if age >50 or any features suggesting giant cell arteritis 1, 6
   • Consider MRI orbits with contrast if optic neuritis suspected (though pain is typically present) 1, 2
   • Consider repeat brain MRI with DWI if stroke concern persists 1

3. If all structural causes excluded:

   • Consider persistent migraine aura as diagnosis of exclusion 3, 4
   • Initiate migraine prophylaxis and close follow-up 1
   • Document visual symptoms with headache diary 1

4. If symptoms worsen or new symptoms develop:

   • Immediate re-evaluation for evolving stroke, progressive retinal detachment, or other time-sensitive pathology 1, 6