VASCULAR LESIONS

An important vascular lesion to consider in the orbit is orbital varix. They appear as fusiform or globular densities on the CT scan and enhance brightly with contrast. A mixture of flow void and flow enhancement may be seen on MR. By increasing venous pressure with a Valsalva maneuver, the varix may increase in size, confirming the diagnosis.

Arteriovenous malformations of the orbit are rare as isolated lesions and are usually associated with intracranial AV malformations. Also, a carotid-cavernous fistula often produces profound dilatation of the intraorbital venous structures. The Wyburn-Mason syndrome consists of an AV malformation extending from the midbrain along the anterior visual pathways to the orbit and retina. Retinal angiomatosis is a feature of von Hippel-Lindau disease. The extraocular vascular lesions usually present with orbital congestion and proptosis. Those involving the globe may present with visual deficits or hemorrhage. Serpiginous areas of flow-void often provide the clue for diagnosis on MR scans 

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