Management of Unilateral Proptosis with Inferior Dystopia and Normal EOM/No Diplopia
Observe the patient if there is no diplopia in primary gaze or reading position, but immediately pursue vascular imaging and expanded diagnostic workup to identify the underlying cause of proptosis. 1
Immediate Diagnostic Priorities
Order MRA or CTA urgently to rule out carotid-cavernous fistula (CCF), which can present with isolated proptosis and inferior globe displacement even when standard MRI appears normal. 2 CCFs may show secondary findings including vascular congestion, extraocular muscle enlargement, and enlarged superior ophthalmic veins that may not be apparent on routine MRI sequences. 2 If MRA/CTA is negative but clinical suspicion remains high based on the proptosis, proceed to digital subtraction angiography (DSA), which is the gold standard for CCF diagnosis. 2
Expanded Workup
Obtain CT orbits with contrast as complementary imaging to provide information about orbital volumes, osseous anatomy, and may reveal calcifications or subtle masses missed on MRI. 2
Check inflammatory markers including ESR, CRP, and serum IgG4 levels to evaluate for idiopathic orbital inflammatory syndrome (IOIS) or IgG4-related orbital disease, which are primary considerations when standard imaging appears normal but significant proptosis exists. 2
Consider infectious workup including syphilis and Lyme serology if clinical context suggests inflammatory or infectious etiology. 2
Observation Strategy
Patients can be observed without immediate intervention when there is no diplopia in primary gaze or reading position and normal extraocular movements. 1 However, this observation period requires:
Serial monitoring for development of compressive optic neuropathy with visual acuity, color vision, pupillary examination, and visual field testing at each visit. 2
Repeat imaging in 2-4 weeks if initial additional workup is negative to assess for progression or evolution of findings. 2
Immediate escalation if diplopia develops or strabismus becomes measurable, as this would indicate disease progression requiring more aggressive management. 1
Critical Pitfalls to Avoid
Significant proptosis with inferior dystopia is never normal and demands explanation, even with preserved extraocular movements and no diplopia. 2 The absence of diplopia does not exclude serious pathology.
Standard brain MRI protocols may miss orbital pathology; ensure dedicated orbital imaging with appropriate sequences was performed. 2
Do not delay vascular imaging, as CCFs can present with isolated proptosis and may have devastating consequences if missed. 2
Do not start steroids without adequate workup, as this can mask diagnoses and worsen outcomes in infectious or neoplastic conditions. 2
Differential Diagnosis Framework
The differential for unilateral proptosis with inferior dystopia includes:
Vascular lesions: CCF (most urgent), orbital varices, or vascular malformations 2
Inflammatory conditions: IOIS, IgG4-related orbital disease, thyroid eye disease (though typically bilateral) 2
Neoplastic processes: Orbital tumors including atypical lipomatous tumors, metastases (including from thyroid carcinoma), or lacrimal gland masses 3, 4
Hemorrhagic conditions: Spontaneous orbital hemorrhage related to inferior rectus muscle, though this typically presents with acute pain 5
When to Escalate Management
If orbital decompression becomes indicated for severe proptosis or compressive optic neuropathy develops, consult an orbital disease specialist immediately. 1 High-dose pulse steroid infusion or orbital radiation treatment may be indicated depending on the underlying etiology. 1
Consider teprotumumab if thyroid eye disease is confirmed, though this requires active disease and has multiple contraindications including inflammatory bowel disease and pregnancy. 1