What is the next step in evaluating a 75-year-old female with diplopia (double vision) without pupil involvement, normal Complete Blood Count (CBC), Comprehensive Metabolic Panel (CMP), Hemoglobin A1C (A1C), Erythrocyte Sedimentation Rate (ESR), and C-reactive protein, and no history of trauma?

Neuroimaging for Diplopia in a 75-Year-Old Female

MRI with gadolinium and magnetic resonance angiography (MRA) is the recommended next step for evaluating diplopia without pupil involvement in a 75-year-old female with normal laboratory values and no history of trauma. 1

Diagnostic Approach to Diplopia Without Pupil Involvement

Initial Assessment

• In older patients with diplopia without pupil involvement, the etiology is often microvascular disease associated with diabetes, hypertension, or hyperlipidemia 1
• However, even with normal laboratory values and without pupil involvement, a compressive lesion cannot be ruled out, especially with partial extraocular muscle involvement 1

Recommended Imaging

• Primary recommendation: MRI with gadolinium and MRA 1

  • Provides excellent visualization of cranial nerves, brain stem, and orbital structures 2
  • Superior for detecting small lesions that may be causing compression 3
  • Allows assessment of both vascular and parenchymal causes 1

• Alternative option: CT angiography (CTA) if MRI is contraindicated 1

  • Less sensitive for soft tissue abnormalities but can detect vascular causes 1

Differential Diagnosis to Consider

• Compressive lesions (tumors including meningioma, schwannoma, metastatic lesions) 1
• Microvascular ischemia (despite normal labs) 1
• Demyelinating disease 1
• Leptomeningeal disorders 1
• Viral illnesses 1

Management Algorithm

1. Neuroimaging first: MRI with gadolinium and MRA 1

   • Focus on cranial nerves, cavernous sinus, and brain stem 1
   • Include high-resolution T2-weighted images of cranial nerves 1

2. If neuroimaging is normal:

   • Proceed with serologic testing for infectious diseases (syphilis, Lyme) 1
   • Consider lumbar puncture (including glucose, protein, cell count, cytology, and culture) 1

3. Symptomatic management while awaiting diagnosis:

   • Temporary measures for diplopia may include occlusion, prism correction, or botulinum toxin injection 1

Important Considerations and Pitfalls

• Age-related risk: At 75 years old, this patient is at higher risk for both microvascular and neoplastic causes 4, 5
• Normal laboratory values do not rule out pathology: Despite normal CBC, CMP, A1C, ESR, and CRP, serious underlying conditions can still be present 1
• Pitfall to avoid: Unenhanced plain CT of the head or orbits is largely not useful in the work-up of diplopia 4
• Caution: Delaying imaging in older patients with diplopia, even without pupil involvement, may miss important pathology that requires urgent intervention 5, 6
• Follow-up: If initial imaging is negative but symptoms persist, repeat imaging may be warranted in 2-3 months 5

Special Considerations for Specific Cranial Nerve Palsies

• If clinical examination suggests specific cranial nerve involvement:
  • Third nerve palsy: Urgent neuroimaging to rule out aneurysm, even if pupil-sparing 1, 4
  • Fourth nerve palsy: MRI with contrast if hyperdeviation worsens in downgaze 5
  • Sixth nerve palsy: MRI with contrast to evaluate for lesions in prepontine cistern, skull base, cavernous sinus, or sella 1
  • Multiple cranial nerve palsies: Focus imaging on cavernous sinus and superior orbital fissure 5