What is the initial approach to a patient presenting with diplopia in the emergency department?

Diplopia Workup in the Emergency Department

Immediate Life-Threatening Assessment

Any patient with pupil-involving third nerve palsy (anisocoria with ptosis and ophthalmoplegia) requires immediate neuroimaging with MRA or CTA to exclude posterior communicating artery aneurysm, which is a neurosurgical emergency. 1 If initial vascular imaging is negative but clinical suspicion remains high, proceed to catheter angiography after brain MRI with contrast 1.

Critical Red Flags Requiring Urgent Action

• Pupil-involving third nerve palsy: Immediate MRA or CTA mandatory 1
• Acute isolated third nerve palsy (any type): CT head and CTA brain to rule out compressive aneurysm 2
• Signs of increased intracranial pressure: Immediate ophthalmology/neurosurgery consultation 1
• Recent head trauma with diplopia: Urgent CT scan of orbits to identify fractures, muscle entrapment, and foreign bodies 3
• Age >60 years with diplopia within past month: Obtain inflammatory markers (ESR/CRP) to exclude giant cell arteritis 2

---

Systematic History Taking

Document these specific elements to narrow the differential:

• Onset pattern: Sudden onset suggests vascular (stroke, aneurysm) or traumatic causes; gradual onset suggests compressive lesions, thyroid eye disease, or myasthenia gravis 1, 4
• Trauma history: Even without recalled trauma, occult orbital fractures can present with strabismus 1, 3
• Associated neurological symptoms:
  • Ptosis suggests third nerve involvement 1
  • Facial numbness indicates cavernous sinus pathology 1
  • Vision loss suggests concurrent optic neuropathy 1
  • Headache with diplopia post-trauma warrants concern for orbital or CNS injury 3

---

Focused Physical Examination

Essential Components

• Visual acuity and refraction: Establish baseline vision; high hyperopia or anisometropia may contribute to decompensated strabismus 1
• Pupillary examination: Assess for anisocoria (third nerve), relative afferent pupillary defect (optic nerve), and accommodation deficit 1
• Extraocular motility testing: Evaluate versions (both eyes together), ductions (each eye separately), saccades, smooth pursuit, and vergence 1
• Intraocular pressure: Measure to exclude acute angle-closure glaucoma as a cause of pain and diplopia 1
• Confrontational visual fields: Screen for concurrent visual pathway lesions 3
• Slit-lamp and dilated fundus examination: Rule out globe injury and optic nerve pathology 3

Trauma-Specific Examination

• Exophthalmometry: Measure proptosis if orbital trauma suspected 3
• Facial sensation testing: Assess infraorbital nerve function in orbital floor fractures 3
• Resistance to retropulsion: Test for orbital mass or hemorrhage 3

---

Neuroimaging Strategy

First-Line Imaging Based on Clinical Scenario

For cranial nerve palsies (especially third nerve):

• MRI brain with and without gadolinium + MRA or CTA is preferred 1
• This applies to pupil-involved third nerve palsy, pupil-spared third nerve palsy with incomplete ptosis/partial muscle involvement, and isolated fourth or sixth nerve palsies requiring anatomic localization 1

For acute orbital trauma:

• CT scan of orbits is the initial imaging modality of choice 3
• Rapidly identifies orbital fractures, bone fragments, muscle entrapment, and ferrous-metallic foreign bodies 3
• MRI should be considered if soft tissue detail is needed or central nervous system pathology is suspected 3

For suspected cavernous sinus thrombosis:

• CT head and CT venogram 2

For suspected orbital apex syndrome or retro-orbital mass:

• Contrast-enhanced CT of brain and orbits 2

Imaging NOT Recommended

• Unenhanced plain CT of the head or orbits is largely not useful in the workup of diplopia 2
• Orbital or skull radiographs are insufficient to detect pathology 5

---

Disposition and Referral Strategy

Immediate Consultation Required

• Pupil-involving third nerve palsy: Neurosurgery/ophthalmology 1
• Signs of increased intracranial pressure: Neurosurgery 1
• Suspected cavernous sinus thrombosis: Neurology/ophthalmology 2
• Giant cell arteritis with elevated inflammatory markers: Rheumatology/ophthalmology 2

Outpatient Referral Appropriate

Isolated fourth or sixth nerve palsies without other neurological signs can be referred to neurology or ophthalmology for outpatient workup rather than requiring immediate imaging in the ED, due to limited resources and lower risk of life-threatening pathology 2. However, patients over 60 years should have inflammatory markers checked before discharge 2.

---

Initial Symptomatic Management

While awaiting definitive diagnosis or specialist evaluation:

• Occlusion therapy: Eye patch, occlusive contact lens, or Bangerter foil for immediate symptomatic relief 1
• Prism correction: Press-on (Fresnel) prisms can provide temporary relief, though effectiveness is limited in incomitant deviations 1

---

Common Pitfalls to Avoid

• Do not assume pupil-sparing third nerve palsy is always microvascular: If ptosis is incomplete or muscle involvement is partial, vascular imaging is still required 1
• Do not discharge isolated sixth nerve palsy without considering increased intracranial pressure: Isolated sixth nerve palsy may occur with elevated ICP without direct nerve compression 5
• Do not miss bilateral involvement: Multiple ipsilateral cranial nerve palsies (III, IV, VI) suggest cavernous sinus or orbital apex pathology 5
• Do not overlook myasthenia gravis: Fatigable ptosis and upgaze weakness suggest neuromuscular junction pathology requiring different workup 6