Varizen der Orbita
Orbital venous varix (OVV) is an uncommon vascular malformation that is composed of enlarged single or multiple tubular venous channels with direct communication to the systemic venous system.
Orbital venous varices are divided into primary and secondary. Primary orbital varices are idiopathic and most likely congenital. They are confined to the orbit.
Secondary orbital venous varices are those that are acquired due to increased blood flow as a result of intracranial arteriovenous malformations, caroticocavernous fistula, dural arteriovenous fistula, etc., which drain via the orbit . Secondary varix occurs in association with VGAMs and occasionally with venous angiomas. There may be isolated segmental saccular or fusiform dilatation of cortical veins.
The remainder of this article concerns itself with primary orbital venous varices.
Orbital varix is a rare entity, accounting for less than 1.3% of all orbital tumors . Although it is believed to be congenital, and thus present at birth, patients typically do not become symptomatic until later childhood or early adulthood (10-30 years of age). Cases have however been reported at essentially any age .
Typically these lesions present due to intermittent diplopia or proptosis during episodes of straining or prone/stooping positioning . The protracted distension can actually create more room for the globe to fall back into when not distended leading to paradoxical enophthalmos when at rest .
Presentation may also be due to a complication. Orbital venous varices are the most common causes of intraorbital hemorrhage. They may also become acutely symptomatic if they thrombose. In such cases, patients report the acute onset of retro-orbital pain, proptosis and decreased visual acuity.
Rarely, larger lesions involving the superior ophthalmic vein may present as a lacrimal region mass .
There is a reported association with venous anomalies intracranially which may or may not directly communicate with varix .
Without provocative examination (Valsalva maneuver) they can be very difficult or impossible to diagnose, as varix may completely collapse. Contrast-enhanced studies will demonstrate venous phase opacification with enlargement and possibly proptosis on straining.
As with the rest of head and neck imaging, plain films have little if any role in modern radiology. If performed, however, the presence of calcified phleboliths are characteristic .
Ultrasound is an excellent non-invasive modality for assessment of the orbit and can be performed easily with various dynamic maneuvers (e.g. Valsalva maneuver) and in various positions (e.g. sitting vs. lying). Additionally, color Doppler can also give an insight into the flow dynamics of a vascular lesion.
In upright posture and at rest no abnormality may be seen. On straining, venous channels dilate and are associated with increased blood flow. Proptosis may be visible .
If the diagnosis is suspected contrast CT should be performed both at rest and with a Valsalva maneuver, as in some instances no abnormality is visible on routine imaging, and change in size is helpful in distinguishing this entity from other vascular lesions of the orbit.
Non-contrast orbital scan may demonstrate phleboliths. Contrast should be administered during the Valsalva phase. Varix will appear as an irregular or smooth enhancing lesion which significantly increases in size with straining, typically located at the orbital apex . Enhancement should match that of other venous structures (e.g. cavernous sinus).
In the setting of thrombosis, the enhancement may be absent, and no change on the Valsalva maneuver will be detected.
MRI should also be performed with Valsalva or straining. However, since the acquisition time is longer than CT, some patients may find it difficult.
In the absence of thrombosis:
- T1: hypointense c.f. extraocular muscles
- T2: hypointense c.f. extraocular muscles
If thrombosis is present the imaging is more variable:
- T1: heterogeneous with areas of high signal (see aging of blood on MRI)
- T2: heterogeneous with areas of high signal (see aging of blood on MRI)
Treatment and prognosis
These lesions are usually only treated if symptomatic (either due to mass effect or thrombosis/hemorrhage).
The anterior part of varix can usually be relatively easily excised surgically if thrombosed but may be difficult to identify in a supine patient if no thrombosis is present . Subtotal excision may result in recurrence, and repeat treatment is often more complicated. Ideally, the vein should be resected or clipped as far back towards the orbital apex as possible .
Catheterization of the varix may be performed either via the endovascular route (via jugular vein and cavernous sinus) or directly after surgical exposure. Injection of glue/onyx or introduction of micro coils may be beneficial in allowing the surgeon to identify and excise the lesion and reduce intra-operative bleeding .
An orbital venous varix without thrombosis has a limited differential if dynamic views have been performed. Other orbital vascular lesions to be considered in the differential include:
- cavernous venous malformation
- orbital lymphangioma
- secondary orbital venous varix
It should be noted that there is confusion and controversy in the literature as to the precise definitions of orbital vascular malformation with a venous component (e.g. varix, lymphangioma, venous malformation).
When thrombosis has occurred the differential is broader and is essentially that of an orbital mass: