By Prem Subramanian, M.D., Ph.D. (University of Colorado)
Vascular malformations of the orbit represent a set of uncommon diseases that usually create controversy among physicians leading to delay in diagnosis, treatment and referrals.
Classification of the vascular anomalies in the orbit follows the International Society for the Study of Vascular Anomalies guidelines that classifies them into two categories: Vascular tumors and vascular malformations. Vascular Malformations are further classified into three categories depending on hemodynamic flow: Those with high blood flow that usually involve the arteries, those with low blood flow affecting the veins or lymphatics and those with mixed flow including arteriovenous fistulas.
Capillary Hemangioma
Also known as benign hemangioendothelioma, it is the most common orbital vascular tumor in infants. Lesions usually appear shortly after birth, grow rapidly in 6-12 months, then start regressing. They can be superficial, appearing red in color or deep, appearing blue. Most are extraconal, but they can extend intracranially. They are nonencapsulated, and usually isolated, but can be part of a neurocutaneous syndrome, PHACES (Posterior fossa Malformation-Hemangioma-Arterial anomalies -Cardiac defects- Eye Abnormalities-Sternal Cleft). They can cause proptosis, strabismus and amblyopia. Treatment is controversial and undertaken to treat or prevent vision loss. Oral beta blocker use is a promising treatment modality but must be used with caution in infants. Other treatment modalities include steroid (injected or systemic) or laser.
Arteriovenous malformation
High flow, rare, congenital lesions. They consist of multiple microvascular connections between arteries and veins with no capillary beds. Symptoms include eyelid swelling, proptosis, pulsation of the eye and occasional visual field defect due to ophthalmic artery steal syndrome. Audible bruit may be heard. Angiography is required for precise definition. Treatment is through embolization and sometimes surgery.
Wyburn Mason Syndrome (Bonnet- Duchaume –Blanc)
Unilateral arteriovenous malformation in the visual pathway and midbrain due to persistent undifferentiated embryonic vessels. It is congenital and nonhereditary and can be associated with facial vascular nevi or telangectasia. Clinical presentation varies and include headaches, seizures, acute stroke, decreased visual acuity, proptosis and visual field defect. Dilated, tortuous vessels can appear on retinal exam. Treatment is controversial and prognosis is poor.
Carotid cavernous fistula
It is an abnormal communication between the cavernous sinus and one branch of the internal or external carotid artery. It is an acquired disease most commonly occurring in middle aged women. It can appear after trauma, surgery, rupture of intracavernous ICA aneurysm or in association with connective tissue diseases or vascular diseases. Symptoms are due to engorgement of veins that drain through the cavernous sinus and include pulsatile proptosis, progressive visual loss, sudden redness with engorgement of conjunctival vessels, and diplopia. Eye exam can show a bruit as well as cranial nerve III, IV, V and/or VI palsy. CT or MRI can show muscle enlargement, superior ophthalmic vein engorgement, or cavernous sinus distention. Angiography should be done for precise definition and treatment options. Embolization is the treatment of choice.
Cavernous malformations
Also known as cavernous hemangiomas. Solitary, slow growing lesions that are usually intraconal. They are often found in middle aged women and are actually the most common vascular malformations in adults. Clinically, they can remain asymptomatic or can manifest as progressive, painless swelling and proptosis.
Cavernous malformations have distinct histological features showing large vascular channels lined by endothelial cells. CT shows well circumscribed, homogeneous lesion with occasional microcalcification. Surgery with complete resection is not necessary unless there is severe proptosis or optic nerve compression.
Orbital varices
They are a type of venous malformations of the orbit where venous walls are thinned and distended. They commonly present in the second or third decade of life and are usually unilateral. Clinical presentation includes stress proptosis –proptosis that increases with maneuvers that rise venous pressure like coughing, straining, forward bending or Valsalva… Complications like hemorrhage and thrombosis are rare but may lead to rapid proptosis, pain, diplopia and optic nerve compression.
Most patients do not need treatment; indications for treatment are recurrent thrombosis, severe proptosis or optic nerve compression. Treatment options include scleroterapy, electrothrombosis, emboliztion and surgical resection.
Venolymphatic Malformations –Lymphangiomas
These no-flow lesions of venous/ lymphatic proliferation occur mainly in the first or second decade of life. They tend to start in the supero-nasal quadrant of the orbit and more than 50% affect the conjunctiva causing lymphangiectasias. Lymphangiomas can cause slow, progressive painless proptosis, and they commonly bleed internally with chocolate cyst formation after a minor trauma or infection. Acute painful proptosis, diplopia and optic nerve compression may result. Lesion tend to enlarge during infection due to increased lymphocyte populations.
The malformations are unencapsulated, multicompartmental and can be intra or extraconal. MRI is the modality of choice to image these lesions. Treatment is controversial but the most acceptable method is to observe and treat conservatively if possible. Complete surgical resection is impossible and recurrence almost always occurs; thus, surgery is performed to alleviate symptoms of severe proptosis, optic nerve compression, glaucoma or amblyopia. New promising techniques include sclerosing agents, radiation and intralesional steroids, and their use in combination with surgery also can be very successful.