Orbital Vascular Anomalies - Causes, Symptoms, Diagnosis, and Treatment

What Are Orbital Vascular Anomalies?

These are different lesions that form as a result of variations in the blood supply to the eye. In the traditional sense, the eye (or the orbit in this context) should contain arteries, veins, and associated lymphatics, but in the practical sense, the vascular pattern of the eye is complex with tremendous interindividual variations.

The main source of blood supply to (artery) and from (vein) the orbit are the ophthalmic artery and the main ophthalmic veins (superior and inferior ophthalmic veins), respectively. In a few cases, the ophthalmic artery, which is supposed to arise from the internal carotid artery, arose from the middle meningeal artery (a branch of the maxillary artery), and in a few cases, the ophthalmic artery had two trunks- a small one from the internal carotid artery and a large trunk from the middle meningeal artery.

Structural variations like these, when coupled with the altered nature (vasoproliferative) of the blood vessels, will lead to various orbital vascular anomalies (OVAs).

Understanding these various vascular anomalies is important to establish a diagnosis and plan an appropriate treatment strategy.

What Are the Different Types of OVAs?

Based on their clinical features, hemodynamic properties, radiological features, and histopathological findings, the International Society for the Study of Vascular Anomalies (ISSVA) has classified OVAs into two types; they are-

• Vasoproliferative Tumors- In a few people with genetic predisposition, the endothelium (the thin membrane that lines the inside of the blood vessels) of the ophthalmic blood vessels proliferates at an excess rate resulting in a tumor.

Based on the presence of metastasis (the ability of cancer to spread), they can be further divided into-

1. Benign- These are noncancerous growths that are formed as a result of increased mitotic activity in the endothelium of the blood vessels; the different types of benign eye tumors are-

• Infantile Hemangioma (IH)- It is the most common type seen within the first eight weeks after birth. There are two phases to this tumor- The proliferative phase, which lasts for six months to 12 months, and an involuting regressive phase for five years to nine years. During the proliferative phase, the tumor appears as a red, raised, rubbery lesion known as the “strawberry hemangioma,” and in the involuted phase, it is characterized by scarring, wrinkling, and telangiectasia. Infantile hemangiomas are often associated with LUMBAR and PHACE syndromes. The LUMBAR syndrome is a rare condition comprising lower body hemangioma, urogenital anomalies, ulceration myelopathy, bony deformities, anorectal malformations, and arterial and rectal anomalies.

PHACE is also an uncommon disorder containing posterior fossa malformations, hemangiomas, arterial anomalies, cardiovascular and eye anomalies, sternal clefting, and supraumbilical raphae.

• Congenital Hemangioma- These are full-blown lesions seen at birth, and unlike IH, these do not have a proliferative phase. They can be further divided into RICH (rapidly involuting congenital hemangioma), PICH (partially-involuting congenital hemangioma), and NICH (non-involuting congenital hemangioma), depending on the nature of the regression.

• Tufted Angioma- It is a rare, slowly progressive vascular tumor, often seen in the neck, lower back, or limbs during childhood or infancy. Involvement of the eye is not seen that often but when present, it appears as a mobile, non-tender, cystic, and firm mass in the eyelids. Clinically, it looks similar to a lymphangioma or Kaposi's sarcoma and can be differentiated only with the help of a biopsy.

• Epithelioid Hemangioma- It is a well-formed vascular tumor lined with epithelial cells containing abundant eosinophilic and amphophilic cytoplasm. The most frequent sites are the head and the lower extremities; however, when present in the eye, they cause edema and erythema in the affecting eye. The symptoms are similar to inflammation, but unlike inflammation, they do not subside with Corticosteroids.

• Spindle Cell Hemangioma- It is a benign tumor that usually occurs in the dermis and in the subcutis of the lower extremities. If present in orbit, it will be seen as a well-circumscribed swelling that might extend to the zygoma resulting in facial asymmetry. Other features include displacement of the eyeball and chemosis of the conjunctiva in the affected eye. Depending on the duration of the tumor, there might be a restriction in the ocular motility and a slight reduction in vision.

• Pyogenic Granuloma- These are vascular lesions commonly occurring in the skin and mucosa, including the palpebral conjunctiva. The name itself is a misnomer because the lesions are neither pyogenic nor granulomatous. When present, they are non-tender, fleshy, pedunculated, dome-shaped, and red in color. Most of them form as a result of chalazia, trauma, or surgery. The resultant swelling will contain granulation tissue filled with fibroblasts, endothelial cells of budding capillaries, and other inflammatory cells.

2. Malignant- These are orbital tumors that have formed as a result of metastasis. The most commonly seen malignant orbital tumors are hemangioendothelioma and Kaposi's sarcoma.

Vascular Malformations- Based on the structure that is deformed, the vascular malformations are further divided into-

• Simple Malformations- They are further divided into-

1. Capillary Malformations (CM)- Capillaries are the smallest blood vessels in the vascular system; they supply oxygen and nutrients to the organs and other body systems.There are two different kinds of capillary malformations- Nevus simplex and port-wine stain; the latter differs from the former in having a well-defined border. Both appear as flat patches of red skin and do not fade over time. Naevus simplex is more common and is seen between the eyebrows (angel’s kiss) or on the eyelids.
2. Orbital Venous Malformations (OVM)- Defects in the structure of the veins or their corresponding valves will cause reverse flow of the blood into the orbit, thereby altering the hemodynamics. Based on the distensibility, the venous malformations are further subdivided into-

• Type 1- Also known as cavernous venous malformation, it is a low-flow, non-distensible OVM primarily located in the intraconal space. Symptoms include gaze-evoked amaurosis (GEA), axial proptosis, blurred vision, pain, and diplopia.

• Type 2- Also known as orbital varices, these are low-flow and distensible OVMs that are mostly formed as a result of congenital weakness in the walls of the vein. Symptoms are proptosis, diplopia, visual disturbances, and ecchymosis.

• Type 3- These are the high-flow distensible venous malformations that lead to enophthalmos (at rest), significant proptosis (from coughing, straining, or performing Valsalva maneuver), and visual impairment

3. Lymphatic Malformations (LM)- These are abnormalities in the lymphatic vessels that supply the eye, causing cysts. Based on the size, the cysts can be microcystic (less than 2 mm) or macrocytic (more than 2 mm).

4. Arteriovenous Malformations (AVM)- These are a result of abnormalities in the arteries and the veins that supply the eye. The lesions caused due to AVMs are painful and aggressive in nature; they are often associated with swelling and hemorrhage.

5. Arteriovenous Fistula (AVF)- These are acquired malformations caused by trauma, surgery, or underlying systemic conditions, leading to an abnormal connection between the internal carotid artery and the cavernous sinus. Symptoms include swelling, bruit, glaucoma, and visual defects.

A few rare OVAs include combined malformations, truncal vascular malformations, and syndromic malformations. The symptoms of these variations are similar to that of cavernous hemangioma or lymphangioma, which are true neoplasms, whereas the OVAs are vascular malformations.

How Are OVAs Diagnosed?

Imaging plays an important role in the diagnosis of OVAs; the different types of imaging are-

• Color Doppler Ultrasonography (USG)- Vascular arterial flow can be highlighted using this technique. It is a non-invasive imaging tool, useful in the primary diagnosis of hemangiomas and cavernous venous malformations.

• Magnetic Resonance Imaging (MRI)- Helps to identify AVMs due to their characteristic presence of flow voids signals in the image. A new popular version of this technique is the diffuse-weighted imaging (DWI) MRI, which uses apparent diffusion coefficient (ADC) values to differentiate benign from malignant lesions.

• Computed Tomographic (CT) Scan- Can be used to diagnose AVMs and cavernous venous malformations (CVM). On a CT scan, a typical AVM can be identified by the presence of cavernous sinus enlargement with lateral wall convexity, and a CVM will appear as a well-circumscribed discrete mass that does not adhere to the surrounding muscles.

• Magnetic Resonance Angiography (MRA)- Can diagnose venous and lymphatic malformations along with CVMs and AVMs.

How Are OVAs Treated?

• Treatment depends on the type of OVA; for hemangiomas, the first line of treatment is medical therapy with primary beta-blockers like Propranolol or Timolol maleate. If the patient is unresponsive, intralesional sclerosing agents like Bleomycin can be prescribed. For congenital hemangiomas, there is no standard therapy, and surgical excision is the only option that is performed between the ages of two to five years.

• For vascular malformations, observation is indicated for asymptomatic lesions, and surgery is suggested for symptomatic lesions that can be completely excised. Sclerotherapy is only preferred when there is extensive facial involvement and complete surgical resection is not possible.

Conclusion:

Diagnosis plays an important role in treating OVAs. Having a multidisciplinary team of ophthalmologists, interventional neuroradiologists, and a pediatrician will help to prevent misdiagnosis and mismanagement. Effective communication with the patient or patient’s parents will maximize favorable outcomes.