Imaging description

The superior ophthalmic vein (SOV) is formed by the confluence of the angular, supraorbital, and supratrochlear veins. Anteriorly, it is located medially near the trochlea. As it passes posteriorly, it courses beneath the superior rectus muscle and curves laterally. It passes outside the muscular annulus and enters the cavernous sinus [1, 2]. The vein is valveless throughout its course.

The diameter of the normal SOV ranges from 1 to 2.9 mm as measured on coronal MR images, with a mean diameter of approximately 2 mm [3]. When evaluating an SOV that appears enlarged it is important to assess for symmetry and enhancement characteristics. However, note that mild asymmetry can be normal.

Enlargement of the SOV has been described in several conditions. In the acute setting, enlargement may be caused by a cavernous-carotid fistula (CCF) or increased intracranial pressure (ICP).

A CCF may develop from trauma, surgery, or spontaneously. Fistulas can be described according to the Barrow classification, forming via a direct connection from the internal carotid artery or indirectly via the internal and/or external carotid arteries [4]. Radiologic findings include enlargement of the ipsilateral SOV, often with arterialized enhancement and signal characteristics on CT angiography (CTA) and MR angiography (MRA). The globe is often proptotic (Figure 17.1). Evaluation with conventional angiography is usually required to delineate the sites of fistula formation and for treatment [5].