Orbital Vascular Anomalies

Etiology

Several classification systems have been proposed and evolved over a period of years.

Classification based on endothelial proliferative activity by Mulliken and Glowacki (1982)[1]

Vascular anomalies have been subclassified into hemangiomas and vascular malformations.

Hemangiomas

Hemangiomas are lesions showing increased mitotic activity. This has been further subdivided into two phases - The proliferative phase and Involuting phase.[2]

Characteristics Of Proliferative Phase Hemangiomas

1. Endothelial hyperplasia with [3H] thymidine incorporation
2. Presence of multi-laminated basement membrane beneath the endothelium
3. Rapidly growing lesion during early infancy

Characteristics Of Involuting Phase

1. Fibrosis and fat deposition on histology
2. Low to absent thymidine labeling
3. Rapid growth followed by regression

Vascular Malformations

These constitute the structural abnormalities with normal endothelial activity, consisting of abnormal vascular elements, namely capillary, venous, lymphatic, and arterial, in mostly combined or rarely isolated forms.

Classification based on hemodynamic properties by the Orbital Society (1999)[3]

1. No flow lesions
2. Venous flow lesions
3. Arterial flow lesions

Rootman's Hemodynamic Model of Orbital Vascular Malformations

1. Type 1 – No flow lesions, with no connection to the venous system. It included combined venous-lymphatic malformations (VLMs), erratically called "lymphangiomas."
2. Type 2 – Low flow lesions (venous), with direct communication with the venous system. It was further subclassified as – distensible (rich venous communication), non-distensible (scarce communication), and combined (features of both).
3. Type 3 – High flow lesions (arterial), which were further subdivided into arteriovenous (AV) malformations, with direct antegrade flow through the malformation to the venous side, and cavernous hemangioma (low-flow AV malformation), with direct arterial in-flow and venous out-flow mechanisms.[4]

This hemodynamic conceptualization of vascular lesions helps determine the threshold of intervention and facilitates specific adjunct procedures such as pre-operative embolization, intra-operative application of glue, etc., to achieve safer and predictable outcomes.[5]

The International Society for the Study of Vascular Anomalies (ISSVA) classification – With the advent of modern technology and advancements in interventional radiology, an updated nomenclature system was laid down by the 20th ISSVA workshop in 2014, which incorporated the clinical features and natural course, hemodynamic properties, radiological characteristics, as well as histopathological findings of vascular lesions. This was subsequently expanded and revised in 2018 with biological and genetic updates.[6]

OVAs can be classified as vasoproliferative tumors and malformations.

Subclassification Of Vasoproliferative Tumors

Benign

1. Infantile hemangioma – It can be of superficial, deep, mixed (superficial + deep), reticular/abortive (minimal growth) type or other forms. It can exhibit focal, multifocal, segmental, or indeterminate (features of both focal and segmental) patterns. It can also be found in association with PHACE (Posterior fossa malformations, Hemangioma, Arterial anomalies, Cardiovascular anomalies, Eye anomalies, sternal clefting and/or supraumbilical raphe) and LUMBAR syndrome (Lower body hemangioma, Urogenital anomalies, Ulceration, Myelopathy, Bony deformities, Anorectal malformations, Arterial anomalies, and Renal anomalies). 
2. Congenital hemangioma – Rapid involuting (RICH), non-involuting (NICH), or partially involuting (PICH)
3. Tufted angioma
4. Epithelioid hemangioma
5. Spindle cell hemangioma
6. Pyogenic granuloma
7. Others

Locally Aggressive

This group comprises hemangioendothelioma and Kaposi sarcoma 

Malignant

These include angiosarcoma, an epithelioid variant of hemangioendothelioma, or others.

Subclassification of Vascular Malformations 

Simple  

1. Capillary malformations (CM)
2. Venous malformations (VM)
3. Lymphatic malformations (LM) – They may be macrocystic, microcystic, or mixed
4. Arteriovenous malformations (AVM) – High flow lesions
5. Arteriovenous fistula (AVF) – High flow lesions

Combined Vascular Malformations

These are defined as two or more vascular components found within a single lesion. For example, when CM, LM, and AVM components are found within one lesion, it is termed "capillary-lymphatic-arteriovenous" malformation (CLAVM). Similarly, a lesion comprising venous and lymphatic components is termed a "venous-lymphatic" malformation (VLM). It is worth noting that the widely used terms such as "cavernous hemangioma" "lymphangioma" are now better avoided since, instead of true neoplasms, they are vascular malformations. Lymphangiomas are now accurately known as VLMs. Cavernous hemangioma is, in fact, a solitary, encapsulated venous malformation (VM). Similarly, clinicians must refrain from using the terms "orbital varix" and "capillary hemangioma" in their daily practice.[5] 

In 1990, Schobinger clinical staging system for AVMs was introduced, which divided them into four stages - Stage 1 (quiescent stage) AVMs which are warm and pink-blue in color; Stage II (expansion) AVMs exhibiting pulsations, thrill, and bruit; Stage III (destruction) characterized by ulceration, bleeding, and dystrophic skin changes; and Stage IV (decompensation) AVMs leading to high-output cardiac failure.[7]

Anomalies of Major Named Vessels

They are also known as "channel type" or "truncal" vascular malformations, affecting lymphatics, arteries, and veins.

Syndromic Malformations

This includes Klippel-Trenaunay syndrome, Parks Weber syndrome, Servelle Martorell syndrome, and Sturge-Weber syndrome.

Epidemiology

Orbital vascular anomalies (OVAs) account for approximately 10% of all orbital pathologies.[8] In a large study conducted in 2011, approximately one-fourth of cases of all orbital masses comprised “vasculogenic lesions,” whereas, in another series, the incidence was found to be 12%.[9] However, the studies did not utilize the latest established ISSVA guidelines for vascular anomalies and thus, may have resulted in gross underestimation. It is, therefore, hypothesized that OVAs might be the most common pathology found within the orbit.[10] 

The rationale behind the existing gender-specific differences amongst the vascular anomalies is unclear. For example, infantile hemangioma (IH) is five times more common in females than males, whereas congenital hemangioma (CH) affects both genders equally. Prematurity, low birth weight, and positive family history are the other predisposing factors of IH.[11] 

Cavernous venous malformations (CVMs), the most common orbital benign lesions of adulthood, are more frequently seen in middle-aged females (20 to 40 years). On the other hand, distensible orbital venous malformations do not have any gender predilection.[12][13]

Pathophysiology

Histopathology

Toxicokinetics

History and Physical

It is imperative to obtain a detailed history and perform a meticulous clinical examination to establish the diagnosis and determine the appropriate management.

Hemangioma

Hemangiomas are the most common vascular tumors of infancy and childhood, frequently affecting the head and neck region. They can be congenital or infantile (previously known as juvenile hemangioma).

Infantile hemangioma, the most common type, clinically arises in the first eight weeks and may be present at birth. The parents usually notice it later when the baby turns a few weeks old. A rapid proliferative phase ensues for 6 to 12 months, followed by an involuting, regressive phase lasting up to 5 to 9 years of age. During the proliferative phase, the tumor presents as a raised, rubbery, and red lesion, previously termed as “strawberry hemangioma.” The involuted phase is characterized by scarring, wrinkling, and telangiectasia.[14] One must look out for mechanical ptosis in cases of IH, which may result in refractive and stimulus-deprivation amblyopia.[15]

Focal IHs are the most common variety presenting as a raised, localized lesion along the area of embryological fusion. On the other hand, segmental IHs appear as flat plaques in a specific geographical distribution.[16] The different types of IH, the patterns exhibited, and the various syndromic associations have been described above.

Congenital hemangioma (CH) presents as full-blown lesions at birth with no proliferative phase. They are less likely to regress spontaneously. RICH, as the name suggests, undergoes a rapid phase of regression and disappears by 1 to 1.5 years of age. RICH may either present flat violaceous lesions or plaques with coarse telangiectasia or as raised greyish lesions, surrounded by a pale halo and multiple telangiectatic vessels. On the contrary, NICH doesn’t show regression and keeps growing in proportion to the child’s growth.[17]

Venous Malformations

Orbital VMs can be distensible or non-distensible. Colletti G et al. in 2018, has re-classified OVMs into three subcategories:[10]

Type 1 – It is a low-flow, non-distensible OVM, wrongly termed a “cavernous hemangioma.”[18] According to the recent updated ISSVA nomenclature, it is better known as “cavernous venous malformation (CVM).”

CVMs have a propensity to affect the middle third of the orbit and are primarily located in the intraconal space.[19] Almost two-thirds of patients are symptomatic, while the remaining third of cases are diagnosed coincidentally on imaging. Clinical features include gradual-onset axial proptosis, blurred vision, pain, or diplopia. The causes of visual impairment are hyperopic shift (correctable) and compressive optic neuropathy. Hyperopia in these patients is attributed to the flattening of the globe by the lesion. It may also manifest as choroidal folds, disc changes ranging from swelling to optic atrophy, visual field defects, abnormal color vision, and afferent pupillary defects. Limitation of extra-ocular movements and ocular misalignment in primary gaze can be seen in up to 30% of the patients.[20]

Gaze-evoked amaurosis (GEA) is one of the most unusual symptoms of orbital CVM, especially those occupying the extra- as well as the intra-conal spaces of the orbit. Axonal inhibition and optic nerve ischemia are the most probable factors resulting in GEA.[21][22] Optic nerve compromise and permanent axial length modification render the visual impairment irreversible. Recent reports have suggested a positive influence of hormones, such as estrogen or progesterone, on the clinical progression of CVMs.[23]

Type 2 – Previously known as “orbital varices” - these are low-flow, distensible venous malformations that typically present during the second to third decade of life. Although they result due to a congenital weakness in the wall of the veins leading to dilatation of the valveless veins of the orbit, they remain quiescent during childhood, which is then followed by growth around the pubertal period. The presenting clinical features include proptosis, diplopia, visual disturbances, or ecchymosis (due to hemorrhage or thrombosis). Almost 60% of distensible OVMs demonstrate distension on dependent position or Valsalva maneuver. The remaining 40% are usually the more posterior, deeper lesions and hence, show distensibility only on Valsalva-augmented imaging. Distensibility refers to an increase in proptosis due to increased intra-orbital venous pressure and the resultant expansion of the lesion. Hence, clinical evaluation in every suspected case is incomplete without examination at rest, in the dependent position, as well as with the Valsalva maneuver.

Type 3 – OVMs may be infiltrative, affecting the surrounding periorbital and the intracranial venous system. They classically present as enophthalmos a  rest. Significant proptosis results from straining, coughing, or performing Valsalva maneuver, with varying degrees of visual impairment.[6]

Lymphatic Malformations (LM) 

Pure lymphatic malformations of the orbit are rare, as a variable venous component often co-exists in the majority of the cases. They consist of dilated lymphatic channels lined by podoplanin-positive endothelium. LMs are present since birth and can be radiologically classified as microcystic (<2 cm), macrocystic (>2 cm), or mixed, based on the size of the cavity within the lesion. Pure LMs can manifest as isolated, irregular mass occupying the anterior portion of the orbit. They don’t distend on a Valsalva maneuver and cannot be compressed.[24]

Combined Venolymphatic Malformations 

As mentioned above, most lymphatic malformations either have a linked venous component or consist of arterioles and venules that run within the intercystic septa and hence, are often mixed. Studies have shown that the more the superficial location in the orbit, the more predominant will be the lymphatic component, and vice versa.[25]

Microcystic LMs typically infiltrate the tissue and present as diffuse thickening of the eyelid, conjunctiva, or anterior orbit. They can also affect the posterior orbit, sometimes extending till the apex, and manifest as gradual-onset proptosis. Bleeding into the lymphatic channels may lead to the formation of “chocolate cysts,” thereby exerting a mass effect. Sudden worsening of proptosis may result from bleeding within the lesion or the presence of upper respiratory infection of viral etiology that upregulates the lymphatic system and, in turn, causes sudden expansion of the lymphatic plexus. Massive hemorrhage may lead to motility limitation and visual impairment. Macrocystic LMs are typically intraconal and unlike, microcystic LMs, are less prone to intralesional hemorrhage. Ocular complications include corneal exposure, astigmatism, strabismus, optic neuropathy, and secondary glaucoma.

Lymphangioma is incorrect terminology, often misused in everyday practice. Firstly, this term doesn’t represent the true histopathological nature of the lesion, which, besides lymphatic channels, also include venous components, smooth muscle fibers, blood products, and lymphocytic tissue. Secondly, unlike hemangioma, lymphangioma is not a proliferative neoplastic lesion.

Arteriovenous Malformations 

These lesions are characterized by rapid arterial flow into the draining venous channels, thereby bypassing the entire vascular system of the orbit. Clinically, they present as pulsating proptosis. Thrombosis may manifest as an acute swelling, and hemorrhage may result in ecchymosis. AVMs may also elicit bruit and cause pain and discomfort either at rest or when distended on Valsalva maneuver or straining. Although rare, AVMs are invasive, depict an aggressive natural course, and tend to grow exponentially when treated inappropriately. Schobinger’s classification (as described above) not only provides insights into the clinical staging but also guides the management of these notorious lesions.

Arteriovenous Fistulas (AVFs)

Orbital AVFs, which are usually congenital arterio-venous connections fed by the branches of the ophthalmic artery with an absent intervening bed of capillaries, interspersed within a cellular stroma, clinically manifest as periocular swelling, dilated veins on the fundus, pulsations, and bruit which typically reduce on compressing the ipsilateral common carotid artery (CCA), glaucoma, and visual deficits. In acquired AVFs, the anomalous connection is either due to trauma or idiopathic. The most common periocular AVF is the carotid-cavernous fistula (CCF). It can be of two types: direct and indirect.

In direct CCF, trauma results in the formation of abnormal direct connections between the internal carotid artery (ICA) and the cavernous sinus. Other causes include Ehler-Danlos syndrome type IV, or iatrogenic procedures such as endarterectomy, trans-sphenoidal resection of the tumor in the pituitary region, percutaneous intervention in trigeminal neuralgia, and maxillofacial surgery. On the other hand, in indirect CCF (also known as a dural fistula), low-flow connections between the dural vein and internal or external carotid artery are formed due to an underlying systemic disease. The connections can involve the meningeal branch of the ICA, branches of the external carotid artery (ECA), or meningeal branches of both ICA and ECA.

Among the branches of ECA, the internal maxillary artery is the most implicated vessel. The natural clinical course is usually indolent in cases of dural fistulas and acute in high flow CCFs. The presenting features depend upon whether the fistula is high-flow or lo -flow. The presence of pulsating proptosis and an objective bruit is a more specific feature of high-flow CCFs. Other clinical features include arterialization of vessels, increased episcleral venous pressure, neurogenic strabismus, most commonly sixth nerve palsy, owing to the central location of the sixth nerve adjacent to ICA within the substance of cavernous sinus, optic neuropathy, conjunctival chemosis, congestion, etc.[26]

Evaluation

Imaging forms a critical component of the diagnostic evaluation of OVAs and plays a crucial role in treatment planning. The advent of interventional radiology has strongly influenced the management and yielded favorable outcomes. The use of modern technology has also obviated the need for carrying out a biopsy (for diagnostic purposes) of every suspected lesion.

Hemangioma

Evaluating whether the hemangioma is congenital or infantile is of paramount importance to determine the course of management. Investigations are needed to exclude the differential diagnosis of vascular rhabdomyosarcoma (RMS) and other childhood malignancies. Vascular arterial flow can be highlighted on Color Doppler Ultrasonography (USG). Magnetic resonance imaging (MRI) reveals a lesion that is slightly hypointense to extraocular muscles on T1-weighted (T1W) sequence, markedly enhances on contrast with multiple flow voids, and appears hyperintense on T2-weighted (T2W) MRI. Involution-related and proliferative changes can be demonstrated on MR imaging.

Diffusion-weighted imaging (DWI) MRI has recently gained popularity due to its ability to differentiate benign from malignant lesions qualitatively and quantitatively by means of apparent diffusion coefficient (ADC) values. In the case of IH, a bright ADC map reveals enhanced diffusion with higher ADC values, as opposed to RMS, which shows restricted diffusion on the ADC map with lower values of the diffusion coefficient.[27] On computed tomography (CT) scan, hemangioma appears as a hyperdense lesion with homogenous contrast enhancement. Expansion of the orbital cavity can be appreciated on imaging in case of large lesions, whereas small lesions produce scalloping of the bone adjacent to it.[28]

Vascular Malformations

Cavernous Venous Malformation (CVM)

USG (A and B – scan) is a useful, non-invasive imaging tool, especially for initial evaluation. A regular, round-shaped lesion with high internal reflectivity and moderate attenuation of echoes is characteristic of CVM. On CT scan, CVM appears as a well-circumscribed, hyperdense, homogenous, intraconal lesion, seen as a discrete mass that does not directly adhere to the extra-ocular muscles and optic nerve and may occasionally erode the bone. Rarely CVM can encroach the orbital apex, resembling the typical pear shape. Phleboliths, which are pathognomonic of VMs, caused due to chronic inflammation in long-standing cases, may be seen as hyperdense, calcified areas within the mass. On Contrast-Enhancement, only minimal to mild contrast enhancement is seen in the early arterial phase followed by diffuse enhancement during the late venous phase. This is because the blood flow within the lesion is independent of the orbital vasculature and is predominantly stagnant. CT – Angiography depicts a nodular pattern of contrast enhancement in the initial phase, owing to small vessels within the lesion. However, radiation-associated ocular complications, mainly lens-related, limit its use as a routine procedure. CVM shows hypointense or isointense signals on T1-weighted (T1W) MRI sequences and heterogeneous hyperintensity on T2-weighted (T2W) MRI due to intervening areas of thrombosis devoid of hyperintense signals.[12]

Dynamic investigations, such as Valsalva-augmented MRI, reveal no significant changes in the features. MR Angiography (MRA) is a non-invasive technique that assists in direct static visualization of the orbital vasculature and provides little knowledge about the blood flow characteristics indirectly. Dynamic assessment can be achieved using 3-Dimensional time-of-flight and phase contrast MRA. It is usually utilized to assess venous flow as a high-flow arterial component causes phase-related artifacts. Although 3D phase-contrast MRA demonstrates the flow characteristics better, it is far more susceptible to motion artifacts than 2-dimensional MRA owing to a longer acquisition time.

Thus, to overcome the above challenge, time-resolved imaging of contrast kinetics (TRICKS) was introduced in 2003-04, where rapid acquisition of dynamic images of contrast flow could be accomplished with excellent temporal and spatial resolution. TRICKS MRA is a non-invasive, sensitive procedure for the dynamic assessment of venous and arterial flow. Besides diagnosis, it also aids in surgical planning and subsequent monitoring. CVM shows negligible and markedly delayed blushing, representing capsular enhancement, on TRICKS.[29]

CVMs appear relatively hyperintense on DWI with ADC values between 1.23 x 10 mm/s and 1.39 x 10 mm/s. This should be differentiated from lymphoma, which shows restriction of diffusion and hence, the low signal intensity with ADC values ranging from 0.44 x 10mm/s to 0.92 x 10 mm/s.[30] Nuclear imaging technique such as Technetium Tc 99m – labeled red blood cell scintigraphy has been proven to be a safe, inexpensive, and highly efficacious diagnostic tool in identifying these tumors and differentiating them from non-vascular tumors. Orbital phlebography and arteriography have also been studied but are no longer used in current practice.

Venous and Lymphatic Malformations

MRI is the investigation of choice for evaluating and guiding the treatment of vascular malformations. Imaging characteristics mainly depend upon the internal composition of the lesion of interest.

Distensible venous malformations (OVM Type – 2, previously known as “varix”) appear isointense on T1W MRI and hyperintense on T2W MRI. They show vivid enhancement on gadolinium contrast injection. It has been seen that high ADC values of greater than 2.8 mm/s on DWI MRI are 100% sensitive and specific for Type – 2 OVM.[31] Phleboliths are appreciated as hypointense spots when present. TRICKS sequences facilitate understanding the dynamic flow of venous malformations.

Lymphatic malformations comprise micro or macro cysts, often depicting fluid-fluid levels on imaging. Only the solid component, represented by the intercystic septae, will enhance on contrast, thus showing an irregular patchy appearance on imaging. MRI is more effective than CT in demonstrating recent and old bleed and the nature of fluid within the cyst. As opposed to venous malformations, direct contrast injection into these lesions doesn’t demonstrate any outflow. Combined malformations may exhibit an anterior lymphatic component and a deep-seated, distensible venous component. 

If, in a child, the lesion extends beyond the eyelids, it is important to evaluate the cheek and the roof of the mouth to rule out co-existing anomalies in these areas. CTA or CE-MRI may be performed to exemplify the extra-orbital components with a special focus on the cheek region and pterygopalatine fossa. If the superior orbital fissure is enlarged, it is vital to look for co-existing vascular anomalies of the brain and skull.

A-V Malformations (AVMs)

Outpatient evaluation of a CCF should include intra-ocular pressure assessment, exophthalmometry, pneumotonometry, and color doppler ultrasonography. A difference in ocular pulse amplitude (OPA) of more than 1.6mm between the eyes is 100% sensitive and 93% specific for CCFs.[32] 

On standard (CT and MRI) scanning, AVMs are identified by the presence of cavernous sinus enlargement with lateral wall convexity, dilated superior ophthalmic vein, and increase in extraocular muscle thickness. The presence of multiple flow voids signals, which correspond to the high flow vessels, is the characteristic feature on MRI. The TRICKS sequences help in delineating the arterial as well as the venous components as a function of time. AVMs appear irregularly tortuous and show vivid contrast enhancement with or without intracranial involvement. Aneurysms usually found at the origin of the ophthalmic artery and rarely, at the intra-orbital location, can also be detected on imaging.

Digital subtraction angiography, where contrast is directly injected into the feeder vessels followed by digital image acquisition, is the gold standard modality for evaluating AVMs. It effectively maps the entire vasculature by delineating the draining venous component and arterial feeder vessels. DSA is both diagnostic as well as therapeutic. Non-invasive neuroimaging modalities, including CT angiography and MR angiography, are found to be highly sensitive for CCFs. High-flow fistulas demonstrate rapid sinus filling with minimal to the absent filling of intracranial vessels, whereas low-flow dural fistulas show delayed slow filling with the intact filling of the intracranial vasculature. Demonstration of nidus on angiography almost always ascertains the diagnosis of an arterio-venous malformation and is typically absent in cases of AV fistula.[33]

Treatment / Management

A correct approach towards diagnosing vascular lesions of the orbit is pivotal in determining the most appropriate management option.

Hemangioma

As discussed above, recognizing infantile hemangioma and its differentiation from congenital hemangioma is vital as the preferred line of treatment differs. Medical management, primarily beta-blockers, namely oral propranolol and topical timolol maleate, forms the mainstay of treatment of IH. The child must undergo a comprehensive cardiac evaluation before initiation of therapy. As per the IH guidelines, a trial of atenolol therapy can be given in patients where propranolol is contraindicated or not tolerated. Gel-forming solution of timolol is as effective as systemic therapy with negligible life-threatening complications.

Before the advent of beta-blocker use, systemic and intralesional steroid therapy was the first line of management. Intralesional sclerosing agents, such as bleomycin, are reserved for patients unresponsive to propranolol therapy and are seldom used as the initial mode of treatment. The role of intralesional bevacizumab is unclear, and the drug is under experimental phases. Lasers are not recommended for IH except for treating residual skin changes and scars following resolution.[34] 

For congenital hemangioma, there is no proven medical management. Surgical excision, usually performed between 2 to 5 years of age, remains the first line of treatment. For very large NICH, pre-operative embolization by an interventional neuroradiologist prevents the risk of excessive bleed during surgery.[35]

Vascular Malformations

Cavernous Venous Malformation (CVM)

Observation and periodic follow-up are encouraged in asymptomatic CVMs.

Indications for surgical intervention include:[36](B2)

1. Symptomatic CVMs
2. Visual loss due to optic nerve compression
3. Disfiguring proptosis
4. Dystopia

The surgical approach mainly depends upon the anatomic location of the lesion and its relation to the surrounding structures.

Anterior and lateral orbitotomy are performed for malformations not involving the orbital apex.[37][38] Lesions in the posterior third of the orbit can be accessed via additional neurological approaches such as transcranial or combined anterior and trans-nasal endoscopic routes, etc.[39] Techniques that assist in excision include cryoextraction via ophthalmic cryoprobe, stereotactic radiotherapy, or pre-operative embolization in conditions where CVM invades the bone. Percutaneous sclerotherapy has also been described as a minimally invasive treatment reserved for patients unwilling to undergo surgery or in cases where iatrogenic risks outweigh the benefits of intervention. Intralesional injection of pingyangmycin (bleomycin A5) reduces the intralesional volume significantly and provides relief from pain as well as proptosis.[40](B2)

Venous and Lymphatic Malformations

The therapy goals in venous malformations are to reduce the symptoms (persistent pain), improve function (optic neuropathy and corneal exposure leading to visual loss, tense hemorrhage), and achieve acceptable cosmesis. Management options for orbital venous malformations are as follows:[6]

1. Observation – for asymptomatic/minimally symptomatic cases
2. Surgery – for isolated, localized lesions where complete excision is feasible with minimal morbidity. Surgical can be performed to debulk an extensive lesion or as an adjunct to sclerotherapy
3. Sclerotherapy – for extensive facial involvement and lesions not amenable to surgical resection

Intra-operative mapping and glue (n-butyl cyanoacrylate) embolization aid in surgical excision, thereby reducing the risk of rupture and troublesome bleed. Macrocystic lymphatic malformations demonstrate an excellent response to sclerotherapy, whereas microcystic lymphatic malformations, in addition to sclerotherapy, may require surgical intervention. The most commonly used sclerosant is the aqueous bleomycin solution after reconstituting with lignocaine and adrenaline.[41]

Microcystic LMs also respond well to drugs like sirolimus. If microcystic LMs extend into the orbital apex, the lesion can be truncated to avoid the risk of functional damage following complete excision. Surgical decapping of the cysts may occasionally be performed in cases of hemorrhagic macrocystic lesions.

A-V Malformations (AVMs)

A crisp understanding of the hemodynamics of AVMs facilitates decision-making regarding the appropriate management strategy. A combined approach involving pre-operative embolization with subsequent resection of the nidus is the preferred line of management. Caution should be maintained to completely resect the nidus to prevent recurrence, as a recurrent AVM grows exponentially and is more cumbersome to treat. Not all AVMs are amenable to resection. Some of these can be managed conservatively as they may carry significant surgical morbidity and iatrogenic risk of damaging surrounding structures. Specific indications of surgical excision include recurrent hemorrhage, pain, and associated visual disturbances.

Successful closure of high-flow direct CCFs can be achieved with minimal morbidity using recently emerged endovascular techniques. Endovascular embolization via transarterial route into the cavernous sinus, using materials such as detachable balloon, n-butyl cyanoacrylate, or ethyl vinyl alcohol polymer, is the preferred management strategy. Recently, due to the non-availability of detachable balloons, coiling has emerged as the treatment modality of choice.[42][43][44] In cases with associated ICA wall tear, flow-diverting stent-assisted embolization is a viable option as it avoids misdirection of the material into the arterial circulation, thereby preventing life-threatening complications.[45] Endovascular intervention in high-flow CCFs has shown 90-100% success rates with low (<1%) mortality.[46][47][48](B2)

Dural fistulas are frequently managed via a conservative approach as approximately 70% of these close spontaneously due to localized thrombosis of the superior ophthalmic vein. In the absence of high-risk features, a conservative approach is the first line of treatment, including observation, intermittent carotid compression, or IOP-lowering agents.[49][50][51] (B2)

While performing carotid massage, it is advisable to use the contralateral hand to compress the ipsilateral ICA. This is because if cerebral ischemia occurs due to resultant low arterial pressure, contralateral hemiparesis will itself release the pressure on the artery, simulating a feedback circuit. Carotid compression in the presence of atherosclerotic disease further aggravates the risk of stroke due to pre-existing carotid insufficiency. The additional technique involves superomedial SOV compression in these cases.[26]

Indications of Intervention in Dural AVFs

1. Persistent diplopia
2. Uncontrollable IOP
3. Severe proptosis with exposure keratopathy
4. Optic neuropathy
5. Ischemic retinopathy
6. Cortical venous drainage from fistula
7. Severe bruit (rare)

The endovascular approach for dural AVFs is similar to high flow CCFs.

Differential Diagnosis

The differential diagnosis of orbital vascular anomalies depends upon whether the mass is intraconal or extraconal, the nature of the lesion, and its relative localization within the orbit. The differential diagnoses for a well-circumscribed solid tumor encompass cavernous venous malformation, schwannoma, solitary fibrous tumor, lymphoid lesions of the orbit – lymphoma, or benign reactive hyperplasia orbital metastasis, fibrous histiocytoma, or neurofibroma.

Surgical Oncology

Radiation Oncology

Pertinent Studies and Ongoing Trials

Treatment Planning

Toxicity and Adverse Effect Management

Medical Oncology

Staging

Prognosis

Every orbital vascular anomaly behaves distinctly. The prognosis mainly depends upon the nature, extent, and localization of the lesion and the visual acuity, and the status of the optic nerve.

Complications

Lesions extending up to the orbital apex, large-sized anomalies, and those associated with optic neuropathy have a higher risk of vision-related complications following surgery. Other possible complications include ptosis and motility limitations, which usually resolve within a span of a few months. Recurrence is not uncommon. The risk of amblyopia should be an important consideration while managing vascular anomalies of childhood.[52]