Is an MRI (Magnetic Resonance Imaging) indicated for a patient with a change in vision?

MRI for Patients with Change in Vision

MRI is strongly indicated for patients with change in vision, as it is the preferred imaging modality for evaluating most causes of visual loss. 1

Imaging Selection Based on Clinical Presentation

Monocular Visual Loss

• MRI of orbits without and with contrast is the preferred modality for:
  • Intraocular masses
  • Optic nerve pathology
  • Globe and orbital disease 1
  • Suspected optic neuritis (95% sensitivity for detecting abnormal enhancement) 1

Binocular Visual Field Defects

• MRI of brain without and with contrast is indicated for:
  • Junctional scotoma or bitemporal visual defects (requires thin-slice imaging for pituitary/suprasellar evaluation) 1
  • Homonymous hemianopia or quadrantanopia (post-chiasm lesions) 1
  • Suspected demyelinating disorders (multiple sclerosis, neuromyelitis optica) 1

Clinical Scenarios Requiring Urgent MRI

1. Suspected optic neuritis:

   • MRI of orbits AND brain with contrast to:
     • Evaluate optic nerve enhancement
     • Assess for intracranial demyelinating lesions (predictor of multiple sclerosis) 1, 2

2. Optic nerve or pre-chiasmal symptoms:

   • MRI to evaluate for optic nerve sheath meningiomas, optic nerve gliomas, or other compressive lesions 1, 3
   • Diagnostic delays with these conditions are common and can lead to permanent vision loss 3

3. Acute visual loss with post-chiasm symptoms:

   • MRI to evaluate for stroke, hemorrhage, or venous sinus thrombosis 1

When CT May Be Preferred Over MRI

• Suspected orbital trauma or fracture 1
• Suspected metallic foreign body (MRI contraindicated) 1
• Need to evaluate bone involvement or calcification 1
• Acute setting when rapid imaging is needed (non-contrast head CT) 1

Common Pitfalls to Avoid

1. Misdiagnosis of optic nerve sheath meningiomas:

   • 71% of cases have delayed diagnosis (average 62.6 months)
   • Most common misdiagnosis is optic neuritis (48%)
   • Errors often due to incorrect MRI protocols (no orbital sequence or contrast) or misinterpretation 3

2. Inadequate imaging protocols:

   • For orbital pathology: Must include fat-suppressed, contrast-enhanced sequences 1
   • For suspected demyelination: Brain and orbit imaging should be performed together 1

3. Relying on non-contrast imaging alone:

   • Contrast is essential for detecting enhancement of the optic nerve in optic neuritis 1
   • Contrast helps distinguish active demyelinating lesions 1

Important Considerations

• Plain radiographs are insufficient for evaluating vision loss 1
• In pediatric patients with non-traumatic vision loss, MRI of head and orbits with and without contrast is the most useful imaging modality 1
• For conditions like glaucoma, cataracts, or macular degeneration identified on ophthalmologic examination, cross-sectional imaging is usually not necessary 1
• Rare conditions like Susac's syndrome (encephalopathy, branch retinal artery occlusions, hearing loss) require MRI for diagnosis 4

MRI provides superior soft-tissue resolution for evaluating the visual pathway from the globe to the visual cortex, making it the imaging modality of choice for most patients with visual changes where structural causes are suspected.