Normal asymmetric superior ophthalmic vein dilatation: morphological features and differentiation from carotid...

Asymmetry of the superior ophthalmic vein (SOV) is occasionally encountered on routine imaging and may reflect either pathology or normal variation. This study aimed to characterize normal asymmetric SOV dilatation and differentiate it from pathological dilatation due to carotid cavernous fistula (CCF).

We retrospectively measured SOV diameters at the distal, middle, and proximal levels on three-dimensional time-of-flight magnetic resonance angiography in 200 patients without abnormal intracranial findings and 30 patients with CCF. Significant asymmetry was defined as a side-to-side diameter difference of >0.5 mm at one or more levels. SOV hyperintensity was also assessed. Morphological features were compared between normal asymmetric and CCF-related pathological SOV dilatation.

Significant SOV asymmetry was observed in 31 of 200 patients (15.5%) without abnormal intracranial findings. Pathological dilatation showed significantly larger SOV diameters at all three levels than normal asymmetric dilatation. SOV hyperintensity was more frequent in pathological dilatation than in normal asymmetric dilatation (21/30 [70.0%] vs. 8/31 [25.8%], P < 0.001). Normal asymmetric SOV dilatation was more prominent at the distal and middle levels and showed relative tapering at the proximal level. For identifying normal asymmetric SOV dilatation, the middle-to-proximal ratio showed moderate discriminatory performance (area under the curve, 0.791; 95% confidence interval, 0.675-0.907; cutoff, >1.139; sensitivity, 93.5%; specificity, 63.3%).

Proximal tapering of a dilated SOV may be a morphological feature of normal asymmetric dilatation and may serve as an adjunctive imaging clue for differentiation from CCF-related pathological dilatation.