What is the best imaging modality for a patient presenting with diplopia (double vision)?

Imaging for Double Vision (Diplopia)

MRI of the orbits with and without contrast is the preferred first-line imaging modality for patients presenting with diplopia, especially when orbital or skull base pathology is suspected. 1

Diagnostic Approach Based on Clinical Presentation

The optimal imaging choice depends on the suspected anatomical location of the problem:

1. Orbital/Extraocular Muscle Pathology

• First choice: MRI orbits with and without contrast 2, 1
  • Superior for soft tissue characterization of extraocular muscles, optic nerve, and orbital structures
  • Can detect muscular slip or pulley abnormalities when imaged during different gaze positions 2
  • Particularly useful for evaluating primary disease processes affecting extraocular muscles 2

2. Brainstem/Cranial Nerve Pathology

• First choice: MRI brain with contrast plus high-resolution T2-weighted images of cranial nerves 2, 1
  • Focuses on nuclear, cisternal, and skull-base cranial nerve segments
  • Essential for evaluating cranial nerves III, IV, and VI, including the cavernous sinuses 2
  • Preferred for suspected internuclear ophthalmoplegia or brainstem lesions 2

3. Vascular Causes (especially pupil-involving third nerve palsy)

• First choice: CT angiography (CTA) or MR angiography (MRA) 2, 1
  • Critical when vascular compression (especially aneurysm) is suspected 2
  • Should complement anatomic cross-sectional imaging 2

4. Trauma or Suspected Metallic Foreign Body

• First choice: Non-contrast CT orbits 2, 1
  • Superior for detecting foreign bodies, calcifications, and osseous evaluation 2
  • Essential for orbital wall fractures that may cause entrapment 1

Clinical Scenarios Requiring Specific Imaging

• Isolated pupil-involving third nerve palsy: Requires urgent vascular imaging (CTA or MRA) to rule out aneurysm 2, 1

• Multiple ipsilateral cranial nerve palsies (III, IV, VI): Suggests cavernous sinus or orbital apex lesion - MRI with contrast is essential 2

• Internuclear ophthalmoplegia: Requires brain MRI to evaluate for demyelinating disease (especially in younger patients) or stroke (in older patients) 2

• Acute onset diplopia with headache: Requires same-day urgent imaging to rule out life-threatening causes 3

Common Pitfalls to Avoid

1. Using orbital or skull radiographs: These are insufficient to detect pathology in patients with diplopia and have been replaced by CT and MRI 2

2. Delaying imaging for pupil-involving third nerve palsy: This requires urgent vascular imaging to rule out aneurysm 1

3. Failing to consider anatomic localization: The imaging choice should be guided by the suspected location of the lesion based on clinical examination 4, 5

4. Missing cavernous sinus pathology: Multiple cranial nerve involvement suggests cavernous sinus pathology requiring dedicated imaging 2

5. Overlooking vascular causes: When diplopia is of sudden onset, vascular causes must be considered, particularly in older patients 1, 3

Algorithm for Imaging Selection

1. First determine if trauma is involved:

   • If yes → Non-contrast CT orbits
   • If no → Continue to step 2

2. Assess for pupil involvement:

   • If pupil-involving third nerve palsy → Urgent CTA or MRA
   • If no pupil involvement → Continue to step 3

3. Determine suspected anatomical location:

   • Orbital/extraocular muscle pathology → MRI orbits with and without contrast
   • Brainstem/cranial nerve pathology → MRI brain with contrast + high-resolution cranial nerve imaging
   • Cavernous sinus/multiple cranial nerve involvement → MRI brain and orbits with contrast

4. Consider additional imaging based on findings:

   • If vascular malformation or aneurysm is detected → Consider DSA (digital subtraction angiography)
   • If mass near sagittal sinus → Add MR venography or CT venography

By following this evidence-based approach to imaging selection for diplopia, clinicians can efficiently diagnose the underlying cause and initiate appropriate treatment to prevent vision- and life-threatening outcomes.