What is the recommended management for an asymptomatic 3.5 mm × 1.5 mm right ophthalmic artery infundibular aneurysm in a patient without prior subarachnoid hemorrhage or significant vascular risk factors?

Management of Right Ophthalmic Artery Infundibulum/Small Aneurysm (3.5mm × 1.5mm)

Conservative management with imaging surveillance is recommended for this asymptomatic ophthalmic artery infundibular dilation, as the literature does not support treatment of infundibula even when they appear in the context of subarachnoid hemorrhage, and treatment should only be directed toward true saccular aneurysms. 1

Distinguishing Infundibulum from True Aneurysm

The critical first step is determining whether this represents a true aneurysm or an infundibular dilation:

• Infundibular characteristics: Funnel-shaped or conical widening at the vessel origin, with the branch artery arising from the apex of the widening, typically <3mm in maximum diameter 2, 3
• Your lesion measures 3.5mm × 1.5mm, which places it at the borderline threshold where infundibula can be considered "enlarged" (>3mm) 2, 3
• True aneurysm characteristics: Saccular or dome-shaped morphology, branch artery arises separately from the aneurysm neck, irregular contour 1

The elongated dimensions (3.5mm × 1.5mm) suggest an infundibular configuration rather than a spherical saccular aneurysm.

Evidence Against Treating Infundibula

The strongest evidence indicates infundibula should not be treated, even in SAH patients:

• A comprehensive literature review found only 7 reported cases where an infundibulum could have been the primary rupture site without an associated aneurysm, and close review revealed "significant limitations" in all 7 reports 1
• The authors concluded that "the literature, and our own experience, do not support the treatment of infundibula, even in SAH patients" 1
• Treatment should be directed toward associated aneurysms, not the infundibulum itself 1

Risk of Transformation to True Aneurysm

While infundibula are generally considered stable, rare case reports document transformation:

• Documented progression from infundibulum to saccular aneurysm occurred over 7-10 years in isolated case reports 4, 5, 3
• One case showed fatal rupture 10 years after an infundibulum was initially documented 4
• Risk factors for transformation include: diameter ≥3mm, presence of other aneurysms, documented de novo aneurysm formation elsewhere, or family history of aneurysms 3

Recommended Management Strategy

For Infundibular Dilations ≥3mm (Your Case):

Imaging surveillance is appropriate rather than intervention:

• Perform follow-up MRA or CTA at yearly intervals for infundibula ≥3mm in diameter 3
• More stringent follow-up (potentially every 6 months) is warranted if the patient has: other documented aneurysms, history of de novo aneurysm formation, or family history of aneurysms 3
• Monitor for morphologic changes suggesting transformation to saccular aneurysm: increasing size, development of dome-shaped contour, or irregular wall 3

If This Represents a True Small Aneurysm:

If high-quality imaging (DSA with 3D rotational angiography) confirms saccular morphology rather than infundibular configuration 6:

• Small unruptured aneurysms <4mm have very low rupture risk in asymptomatic patients without prior SAH
• Ophthalmic segment aneurysms are recognized as "difficult to treat with surgery but may be treated relatively easily with coil embolization" and endovascular techniques 7
• Treatment consideration factors per AHA guidelines: patient age, life expectancy, aneurysm morphology (irregular shape increases rupture risk), and institutional expertise 6, 7
• For a 3.5mm lesion, observation with serial imaging is generally preferred over intervention unless irregular morphology or growth is documented 7

Critical Pitfalls to Avoid

• Do not treat based on size alone: The 3.5mm measurement does not automatically mandate intervention, especially if infundibular morphology is confirmed 1
• Obtain definitive vascular imaging: If initial CTA is equivocal, proceed to DSA with 3D rotational angiography, which has >98% sensitivity and specificity for characterizing small lesions 6, 8
• Do not dismiss the lesion entirely: Even though treatment is not indicated, surveillance is essential for lesions ≥3mm given rare but documented transformation risk 3
• Avoid aggressive intervention for infundibula: The morbidity of treating a benign infundibulum outweighs the extremely low rupture risk documented in the literature 1