DOI: 10.1148/rg.281075040
RadioGraphics 2008;28:185-204
© RSNA, 2008
Vascular Lesions of the Orbit: More than Meets the Eye1
Wendy R. K. Smoker, MD,
Lindell R. Gentry, MD,
Norbert K. Yee, MBBS,
Deborah L. Reede, MD, and
Jeffrey A. Nerad, MD
1 From the Departments of Radiology (W.R.K.S., N.K.Y.) and Ophthalmology (J.A.N.), University of Iowa Hospitals and Clinics, 200 Hawkins Dr, 0453-G JCP, Iowa City, IA 52242; Department of Radiology, University of Wisconsin Hospitals, Madison, Wis (L.R.G.); and Department of Radiology, Long Island College Hospital, Brooklyn, NY (D.L.R.). Recipient of a Certificate of Merit award for an education exhibit at the 2004 RSNA Annual Meeting. Received March 6, 2007; revision requested April 11 and received June 27; accepted July 2. All authors have no financial relationships to disclose.
Address correspondence to W.R.K.S. (e-mail: wendy-smoker{at}uiowa.edu).
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Abstract
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Vascular lesions of the orbit may be classified on the basis of their natural history, growth pattern, and histologic composition as capillary hemangiomas, venous vascular malformations, venous lymphatic malformations, arterial and arteriovenous lesions, or neoplasms. Most follow a characteristic pattern of clinical development and have one or more specific imaging features that allow diagnosis. Hemangiomas typically manifest at or soon after birth and subsequently involute. They are nonencapsulated, poorly circumscribed, often lobulated, and largely extraconal in location. Cavernous malformations are septate and well circumscribed, may exhibit progressive enhancement on delayed images, and do not involute. Orbital varices appear distended on images obtained with the patient prone or during the Valsalva maneuver. Venous lymphatic malformations show multiple fluid-fluid levels, enlarge during viral infections, and may manifest as chocolate-colored cysts after an acute hemorrhage. Arteriovenous malformations, fistulas, and aneurysms have typical angiographic features. Hemangiopericytomas arise from the paranasal sinuses and show early tumor blush and persistent staining on angiographic images. Hemangioblastomas appear as enhancing mural nodules with associated cysts and serpentine flow voids on magnetic resonance (MR) images. Choroidal hemangiomas and melanomas can be differentiated on the basis of their appearances on T2-weighted MR images. Patients with vascular orbital and ocular metastases commonly have a history of breast or lung primary tumors.
© RSNA, 2008
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LEARNING OBJECTIVES FOR TEST 4
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After reading this article and taking the test, the reader will be able to:
- Describe the classification of vascular lesions of the orbit.
- Recognize the clinical features of each lesion.
- Identify the imaging features that permit differentiation among lesions.
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Introduction
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Vascular lesions of the orbit are uncommon, and some are extremely rare. Because of the confusion and controversy surrounding their nature, nomenclature, and classification, such lesions often present a diagnostic dilemma. Several possible classification schemes exist: In one, proposed by Mulliken and Glowacki, lesions are classified on the basis of their natural history, including their growth pattern and histologic composition (1). Another system of classification, proposed by the Orbital Society, is based on hemodynamic flow (2). In this article, we have chosen to use the system proposed by Mulliken and Glowacki. We therefore have described the clinical and imaging features of these lesions according to their classification in the following groups: (a) capillary hemangiomas, (b) venous vascular malformations (cavernous malformations and orbital varices), (c) venous lymphatic malformations (capillary, cavernous, and cystic lymphatic malformations), (d) arterial and arteriovenous lesions (arteriovenous malformations, arteriovenous fistulas, and ophthalmic artery aneurysms), (e) neoplasms (hemangioblastomas, hemangiopericytomas, choroidal hemangiomas, choroidal melanomas, and vascular metastases), and (f) miscellaneous (Coats disease). The term mixed lesions has been used to describe those that have characteristics of two or more different lesions. The imaging features of each lesion, especially features that help differentiate it from others, are described in detail.
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Capillary Hemangiomas
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Capillary hemangioma, also known as benign hemangioendothelioma, is the most common orbital vascular tumor in infants, with an overall incidence of 5.6% (3).
Lesions usually appear at or shortly after birth, rapidly increase in size for 6–12 months, and then gradually involute over the next 5–7 years (3–5). They generally are reported to be more common in females (female-to-male ratio, 3:2) (3).
Most capillary hemangiomas are entirely extraconal in location or have a substantial extraconal component. They may be superficial or deep, commonly extend across tissue planes, and may extend intracranially through the optic canal or superior orbital fissure (3). The extraocular muscles and lacrimal glands occasionally are involved (5). At physical examination, superficial lesions appear red, whereas subcutaneous lesions appear blue. Capillary hemangiomas may cause proptosis, globe displacement, and, occasionally, amblyopia. They may expand slightly during crying or straining (5). Complications are rare but may include profuse hemorrhage, thrombosis, optic nerve compression, bone remodeling, and calcification (4,5). Capillary hemangiomas may occur as isolated findings or may be found in association with other manifestations in various syndromes (eg, the rare neurocutaneous syndrome known as PHACE, which is characterized by posterior fossa brain malformations, large facial hemangiomas, arterial anomalies, cardiac anomalies and aortic coarctation, and eye abnormalities such as colobomas, optic nerve hypoplasia, increased retinal vascularity, and glaucoma) (6–8).
Capillary hemangiomas are nonencapsulated and consist of multiple lobules separated by vascular fibrous septa. Histologic analysis demonstrates capillary-sized vascular spaces surrounded by proliferating benign endothelial cells (Fig 1) (3). Treatment options include observation and topical, oral, or intralesional corticosteroid therapy (Fig 2). Interferon therapy, laser therapy, and surgery typically are reserved for patients with potentially life-threatening complications (5).
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Figure 1. Hemangioma. Histologic photomicrograph (original magnification, x100; hematoxylineosin stain) shows capillary-sized vascular spaces surrounded by proliferating benign endothelial cells (arrows).
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Figure 2a. Hemangioma. (a) Photograph of a 4-month-old boy shows a large orbital and facial hemangioma. (b) Photograph of the same patient at 8 years of age, after treatment with oral prednisone, shows marked lesion involution.
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Figure 2b. Hemangioma. (a) Photograph of a 4-month-old boy shows a large orbital and facial hemangioma. (b) Photograph of the same patient at 8 years of age, after treatment with oral prednisone, shows marked lesion involution.
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Computed tomography (CT) is the preferred modality for the initial imaging evaluation because it can be performed without sedation. Because hemangiomas are nonencapsulated, they are usually lobulated, irregularly marginated, and heterogeneous and demonstrate intense homogeneous enhancement at CT after the administration of contrast material (Fig 3) (3). At ultrasonography (US), hemangiomas typically are compressible and appear hyperechoic (5). At MR imaging, the lesions are usually hypointense on T1-weighted images, and iso- to hyperintense on T2-weighted images. They enhance intensely after the administration of contrast material (Fig 4). Lobules with thin septa, combined with intralesional and perilesional flow voids, are characteristic features (3).
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Figure 3. Capillary hemangioma in a 4-month-old boy with proptosis of the left eye, inferior displacement of the globe, and a bluish discoloration under the skin. Axial contrast-enhanced CT image depicts an intensely enhancing, irregularly marginated lesion with intraconal (dots) and extraconal (arrows) components.
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Figure 4a. Typical capillary hemangioma in a 41/2-month-old girl with proptosis of the right eye and cutaneous hemangioma. (a) Axial T1-weighted MR image demonstrates an extraconal, lobulated, irregularly marginated lesion with hypointense signal and small serpentine flow voids (arrow). (b) Axial T2-weighted fat-suppressed image shows the same lesion with slight signal hyperintensity, characteristic fine internal septa, and flow voids (arrow). (c) Axial contrast-enhanced T1-weighted fat-suppressed image demonstrates homogeneous intense enhancement of the lesion and provides improved delineation of the flow voids (arrow).
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Figure 4b. Typical capillary hemangioma in a 41/2-month-old girl with proptosis of the right eye and cutaneous hemangioma. (a) Axial T1-weighted MR image demonstrates an extraconal, lobulated, irregularly marginated lesion with hypointense signal and small serpentine flow voids (arrow). (b) Axial T2-weighted fat-suppressed image shows the same lesion with slight signal hyperintensity, characteristic fine internal septa, and flow voids (arrow). (c) Axial contrast-enhanced T1-weighted fat-suppressed image demonstrates homogeneous intense enhancement of the lesion and provides improved delineation of the flow voids (arrow).
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Figure 4c. Typical capillary hemangioma in a 41/2-month-old girl with proptosis of the right eye and cutaneous hemangioma. (a) Axial T1-weighted MR image demonstrates an extraconal, lobulated, irregularly marginated lesion with hypointense signal and small serpentine flow voids (arrow). (b) Axial T2-weighted fat-suppressed image shows the same lesion with slight signal hyperintensity, characteristic fine internal septa, and flow voids (arrow). (c) Axial contrast-enhanced T1-weighted fat-suppressed image demonstrates homogeneous intense enhancement of the lesion and provides improved delineation of the flow voids (arrow).
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Venous Vascular Malformations
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Cavernous Malformations
Cavernous malformations, also known as cavernous hemangiomas, are the most common vascular lesions in adults. However, their incidence is low overall, with two or fewer cases diagnosed per year at major referral institutions (9). There is substantial disagreement in the literature about the exact nature of cavernous malformations. Some writers contend that the lesions are of venous origin, whereas others have proposed that they represent low-flow arteriovenous malformations (10). Cavernous malformations occur most often in women (60%–70%) between the ages of 18 and 72 years (mean age, 43–48 years), slowly and progressively enlarge, and do not involute (9). An observed association between cavernous malformations and abrupt proptosis during puberty or pregnancy is suggestive of a contribution by hormone- or cytokine-mediated angiogenic factors to lesion growth (11). Since cavernous malformations are ordinarily slow growing, they more often manifest with progressive, painless proptosis (9). The lesions often are discovered incidentally at imaging evaluations for symptoms such as headache. Less common symptoms include pain, lid swelling, diplopia, a palpable lump, and recurrent episodes of obscured vision (3).
Cavernous malformations usually are solitary and most often occur in the lateral aspect of the retrobulbar intraconal space. They are rarely intramuscular. They uncommonly involve the orbital apex, but when they do, they may cause monocular vision loss due to the compression of blood vessels that supply the optic nerve. They occasionally (5%–10%) extend intracranially through the superior orbital fissure (4,5). Bone remodeling is not uncommon, and intralesional calcification occurs occasionally (9). Associations with Maffucci syndrome and blue rubber bleb nevus syndrome have been reported (12,13).
Cavernous malformations have a distinct fibrous pseudocapsule and, hence, are well circumscribed. At histologic analysis, large dilated vascular channels lined by flattened or attenuated endothelial cells with an intervening fibrous interstitium are visible (Fig 5) (9).
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Figure 5. Cavernous malformation. Histologic photomicrograph (original magnification, x100; hematoxylineosin stain) shows dilated cavernous spaces that are lined by endothelial cells, separated by fibrous septa (arrows), and surrounded by a fibrous pseudocapsule (stars). Some of the spaces contain red blood cells (arrowheads).
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The lesions are usually managed conservatively, and surgical excision is reserved for those that cause severe proptosis or optic nerve compression (9). Because of the inaccessibility of the small feeding arteries and the multiple collateral pathways available for recanalization, embolization therapy is not often performed.
Lesion-specific features seen on A-mode US images include well-defined borders due to the pseudocapsule, moderate to high internal reflectivity from the surfaces of large vascular spaces, moderate acoustic attenuation from intravascular blood, and a honeycomb-like structure (14). B-mode US can help differentiate the typically encapsulated cavernous malformations from other, infiltrating lesions. Color Doppler US is useful for detecting and quantifying blood flow and for mapping the vasculature for surgical planning (9).
On CT images, cavernous malformations typically are well circumscribed, round or ovoid, homogeneously hyperattenuating, intraconal lesions. They occasionally contain microcalcifications (phleboliths) and may produce expansion of the orbital walls (Fig 6) (9). The lesions may displace adjacent structures but do not invade them. At multiphase dynamic contrast material–enhanced CT, poor enhancement is noted in the early arterial phase because of the low-flow arterial supply; contrast material does not fill the central part of the lesion until the late venous phase (9).
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Figure 6. Cavernous malformation in a 39-year-old woman with painless progressive proptosis. Axial contrast-enhanced CT image shows an enhancing intraconal mass (dot) immediately adjacent to the lateral rectus muscle (black arrows). The mass is causing medial deviation of the optic nerve (white arrow).
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At MR imaging, the signal in cavernous malformations usually appears isointense to that of muscle on T1-weighted images (Fig 7a) and hyperintense to that of muscle on T2-weighted images. Internal septa are visible within larger lesions. Cavernous malformations demonstrate progressive accumulation of contrast material on late phase dynamic images and delayed images (Fig 7b, 7c) (15).
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Figure 7a. Large cavernous malformation in a 43-year-old woman with painless proptosis of the right eye. (a) Axial T1-weighted MR image shows a well-circumscribed, hypointense intraconal lesion causing orbital expansion (arrows). (b) Axial contrast-enhanced T1-weighted fat-suppressed MR image, obtained immediately after the intravenous administration of a gadolinium-based contrast material, shows inhomogeneous enhancement predominantly in the center of the lesion (dot). (c) Axial contrast-enhanced T1-weighted fat-suppressed MR image, obtained 1 hour later, shows the characteristic complete enhancement of the lesion.
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Figure 7b. Large cavernous malformation in a 43-year-old woman with painless proptosis of the right eye. (a) Axial T1-weighted MR image shows a well-circumscribed, hypointense intraconal lesion causing orbital expansion (arrows). (b) Axial contrast-enhanced T1-weighted fat-suppressed MR image, obtained immediately after the intravenous administration of a gadolinium-based contrast material, shows inhomogeneous enhancement predominantly in the center of the lesion (dot). (c) Axial contrast-enhanced T1-weighted fat-suppressed MR image, obtained 1 hour later, shows the characteristic complete enhancement of the lesion.
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Figure 7c. Large cavernous malformation in a 43-year-old woman with painless proptosis of the right eye. (a) Axial T1-weighted MR image shows a well-circumscribed, hypointense intraconal lesion causing orbital expansion (arrows). (b) Axial contrast-enhanced T1-weighted fat-suppressed MR image, obtained immediately after the intravenous administration of a gadolinium-based contrast material, shows inhomogeneous enhancement predominantly in the center of the lesion (dot). (c) Axial contrast-enhanced T1-weighted fat-suppressed MR image, obtained 1 hour later, shows the characteristic complete enhancement of the lesion.
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Digital subtraction angiography is rarely used for the evaluation of cavernous malformations because it does not always depict them. Conventional angiography with a prolonged injection may demonstrate delayed contrast material pooling, a feature that permits the differentiation of cavernous malformations from vascular lesions with early arterial phase enhancement (eg, capillary hemangiomas, hemangiopericytomas) as well as high-flow arteriovenous malformations, carotid cavernous fistulas, and aneurysms (9).
Orbital Varices
Varices are the most common cause of spontaneous orbital hemorrhage (16). However, these lesions are uncommon overall. They typically manifest in the 2nd or 3rd decade of life, and they affect males and females equally (17). The lesions result from a presumably congenital weakness in the postcapillary venous wall, a condition that leads to the proliferation of venous elements and massive dilatation of the valveless orbital veins (17). Most varices have a large communication with the venous system and distend during maneuvers that increase venous pressure (Fig 8). However, some have only a small communication with the venous system and do not distend but, instead, manifest with thrombosis and hemorrhage, producing a more sustained proptosis (17).
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Figure 8a. Conjunctival orbital varix in a 56-year-old man whose right eyelid bulges when straining. (a) Photograph obtained with the patient at rest shows a relatively normal appearance of the upper eyelid. (b) Photograph obtained during the Valsalva maneuver shows abnormal fullness of the upper eyelid, which appears bluish. (c) Photograph obtained with the upper eyelid elevated shows the varix.
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Figure 8b. Conjunctival orbital varix in a 56-year-old man whose right eyelid bulges when straining. (a) Photograph obtained with the patient at rest shows a relatively normal appearance of the upper eyelid. (b) Photograph obtained during the Valsalva maneuver shows abnormal fullness of the upper eyelid, which appears bluish. (c) Photograph obtained with the upper eyelid elevated shows the varix.
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Figure 8c. Conjunctival orbital varix in a 56-year-old man whose right eyelid bulges when straining. (a) Photograph obtained with the patient at rest shows a relatively normal appearance of the upper eyelid. (b) Photograph obtained during the Valsalva maneuver shows abnormal fullness of the upper eyelid, which appears bluish. (c) Photograph obtained with the upper eyelid elevated shows the varix.
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Patients with orbital varices usually manifest stress proptosis, which is characterized by a dramatic protrusion of the eye. Stress proptosis is associated with various conditions that increase venous hypertension (including coughing, forward bending, or breath holding); it may be markedly worsened by the Valsalva maneuver and may disappear when the venous congestion is relieved. Proptosis that occurs in association with thrombosis or hemorrhage is rapid and painful. Orbital varices often occur in association with contiguous or noncontiguous intracranial venous anomalies (3) and may be treated with surgical excision, if necessary.
The distensibility of varices during the Valsalva maneuver usually is easily demonstrated at US (18). The finding of an intermittently anechoic retrobulbar lesion that exhibits intrinsic flow during the Valsalva maneuver is indicative of a varix, and color Doppler imaging may demonstrate a reversal of flow toward the transducer during the Valsalva maneuver (18).
Axial CT images obtained with the patient in the supine position usually show a normal appearance or only mild enlargement of the involved veins (Fig 9a). A maneuver that increases venous pressure (scanning in the prone position, jugular vein compression with a tourniquet, or the Valsalva maneuver) is required to demonstrate lesion distensibility (Fig 9b) (19). Varices may be smooth contoured, clublike, triangular, or segmentally dilated, or they may appear as a tangled mass of vessels. At MR imaging, varices have hypo- to hyperintense signal on T1-weighted images, have hyperintense signal on T2-weighted MR images, and usually enhance intensely after the administration of contrast material (Fig 10).
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Figure 9a. Bilateral orbital varices in a 27-year-old woman with a sensation of eye pressure when stooping to pick up her child. (a) Axial contrast-enhanced CT image obtained with the patient at rest shows enhanced and slightly elongated soft-tissue lesions (arrows). (b) Axial contrast-enhanced CT image obtained during the Valsalva maneuver shows the marked distention typical of orbital varices (arrows).
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Figure 9b. Bilateral orbital varices in a 27-year-old woman with a sensation of eye pressure when stooping to pick up her child. (a) Axial contrast-enhanced CT image obtained with the patient at rest shows enhanced and slightly elongated soft-tissue lesions (arrows). (b) Axial contrast-enhanced CT image obtained during the Valsalva maneuver shows the marked distention typical of orbital varices (arrows).
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Figure 10a. Orbital varix in a 33-year-old woman with proptosis when straining. (a) Axial T1-weighted MR image obtained with the patient supine shows a well-circumscribed, triangular, homogeneous, hypointense, retrobulbar lesion (dot). (b, c) Contrast-enhanced coronal T1-weighted fat-suppressed images obtained with the patient supine (b) and prone (c) show homogeneous intense enhancement of the lesion in b and enlargement and distention of the lesion in c, features that help confirm the diagnosis of an inferior ophthalmic venous varix.
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Figure 10b. Orbital varix in a 33-year-old woman with proptosis when straining. (a) Axial T1-weighted MR image obtained with the patient supine shows a well-circumscribed, triangular, homogeneous, hypointense, retrobulbar lesion (dot). (b, c) Contrast-enhanced coronal T1-weighted fat-suppressed images obtained with the patient supine (b) and prone (c) show homogeneous intense enhancement of the lesion in b and enlargement and distention of the lesion in c, features that help confirm the diagnosis of an inferior ophthalmic venous varix.
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Figure 10c. Orbital varix in a 33-year-old woman with proptosis when straining. (a) Axial T1-weighted MR image obtained with the patient supine shows a well-circumscribed, triangular, homogeneous, hypointense, retrobulbar lesion (dot). (b, c) Contrast-enhanced coronal T1-weighted fat-suppressed images obtained with the patient supine (b) and prone (c) show homogeneous intense enhancement of the lesion in b and enlargement and distention of the lesion in c, features that help confirm the diagnosis of an inferior ophthalmic venous varix.
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Venous Lymphatic Malformations
Although the term lymphangioma is commonly applied to this lesion, the suffix -oma is typically reserved to describe a neoplasm of proliferating cells, which lymphangioma is not. These lesions should be considered to arise from the pluripotent venous anlage, which may develop into both venous and lymphatic structures (20). Hence, the term venous lymphatic malformation is more accurate than lymphangioma and is preferred over the latter term. The lesions are sometimes referred to as no-flow or low-flow vascular malformations. Orbital venous lymphatic malformations are uncommon, but the frequency of their occurrence is difficult to ascertain because in most studies they are grouped with lesions affecting the eyelid and conjunctiva. They may be evident at birth, but they generally manifest in infancy or childhood (43% are diagnosed before the age of 6 years; 60%, before the age of 16 years) (21). Overall, males and females are affected with approximately equal frequency (22).
Although venous lymphatic malformations may enlarge slowly, producing progressive proptosis, restriction of eye movements, or vertical globe displacement, many manifest abruptly because of hemorrhage. Hemorrhages within these malformations often occur after minor trauma or infection and occasionally develop spontaneously. A spontaneous intralesional hemorrhage may produce variable-sized chocolate-colored cysts that may cause acute proptosis and, occasionally, optic nerve compression (Fig 11) (22). Intralesional lymphocytes may proliferate during viral infections and may cause lesion enlargement, with resultant worsening proptosis (Fig 12) (23). Evidence suggests that the more superficial the location of the malformation, the larger its lymphatic component (20).
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Figure 11. Venous lymphatic malformation in a 47-year-old woman with acute proptosis and restricted movement of the left eye. Photograph shows multiple chocolate-colored cysts produced by hemorrhage within the lymphatic malformation, with resultant superior displacement of the globe.
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Figure 12a. Venous lymphatic malformation in a 5-year-old girl. (a) Photograph shows mild proptosis of the left eye during an upper respiratory tract viral infection. (b) Photograph obtained after the patient recovered from the viral infection shows the resolution of proptosis.
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Figure 12b. Venous lymphatic malformation in a 5-year-old girl. (a) Photograph shows mild proptosis of the left eye during an upper respiratory tract viral infection. (b) Photograph obtained after the patient recovered from the viral infection shows the resolution of proptosis.
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Lymphatic malformations are unencapsulated, diffuse, and multicompartmental, often including both intraconal and extraconal components that are insinuated between normal orbital structures. The lesions may extend across tissue planes to infiltrate the eyelid and orbit, and they may cause bone remodeling. Orbital venous lymphatic malformations are isolated from the normal orbital vasculature and, unlike varices, are not affected by postural changes (22). However, they may be associated with intracranial vascular malformations, especially developmental venous anomalies (20).
Histologic analysis demonstrates delicate, bloodless, lymph-filled, endothelium-lined vascular channels of various luminal diameters (from capillary to cavernous to cystic sizes) (Fig 13). Intervening connective-tissue septa contain lymphocytes and fragile blood vessels (neovascular tufts) that are thought to be the sources of hemorrhage (5).
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Figure 13. Venous lymphatic malformation. Histologic photomicrograph (original magnification, x200; hematoxylineosin stain) shows a large, bloodless, endothelium-lined channel (stars), small lymph-filled channels (white arrows), and a large lymphoid follicle (black arrows).
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Because the natural history of these lesions is variable and unpredictable, their treatment is controversial and problematic; the best method of treatment depends on the growth, size, location, and morphology of the particular lesion. Observation and conservative management, when possible, are recommended. Surgery has been suggested for lesions that cause marked stretching or compression of the optic nerve; however, complete surgical excision of diffuse lesions is usually impossible, and recurrence is common. Surgery is therefore reserved for dire situations such as optic nerve dysfunction, corneal compromise, severe discomfort, or impending amblyopia (23). Various alternative therapies have proved successful or promising, including the intralesional injection of sclerosing agents (24), fractionated beta irradiation (25), carbon dioxide laser ablation (26), and intralesional injection of steroids.
MR imaging is the modality of choice for the evaluation of lymphatic malformations because it best depicts the various components (23). The signal intensity of the lesions depends on the type of fluid within the cystic components, whether hemorrhage has occurred, and the age of the hemorrhage. T1-weighted images best depict lymphatic or proteinaceous fluid, and T1-weighted fat-suppressed images are best for detecting blood or blood products (23). T2-weighted fat-suppressed images provide improved visibility of components that contain nonhemorrhagic fluid. The use of contrast material does not typically provide significant additional information, but an absence of enhancement is indicative of a lymphatic component (23). Fluid-fluid levels produced by hemorrhages of various ages within multiple cysts are almost pathognomonic (Fig 14) (22).
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Figure 14a. Venous lymphatic malformation in an 11-year-old boy with progressive proptosis of the right eye and lateral displacement of the globe. (a) Axial unenhanced CT image demonstrates multiple fluid-fluid levels (arrows) within a lobulated, predominantly extraconal lesion, features typical of a lymphatic malformation with an intralesional hemorrhage. (b) Axial T2-weighted fat-suppressed MR image demonstrates multiple fluid-fluid levels within the lesion, which has both intra- and extraconal components.
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Figure 14b. Venous lymphatic malformation in an 11-year-old boy with progressive proptosis of the right eye and lateral displacement of the globe. (a) Axial unenhanced CT image demonstrates multiple fluid-fluid levels (arrows) within a lobulated, predominantly extraconal lesion, features typical of a lymphatic malformation with an intralesional hemorrhage. (b) Axial T2-weighted fat-suppressed MR image demonstrates multiple fluid-fluid levels within the lesion, which has both intra- and extraconal components.
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At US, cystic components usually demonstrate low-level internal echoes, but an intracystic clot may be hyperechoic (5). At CT, venous lymphatic malformations typically are poorly circumscribed, multicompartmental, and heterogeneously hyperattenuating, and they enhance minimally after contrast material administration. Phleboliths may be present (27).
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Arterial and Arteriovenous Lesions
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Arteriovenous Fistulas
Arteriovenous fistulas that involve the orbit are rare (4). Fed by ophthalmic artery branches, they consist of multiple congenital microvascular connections between arteries and veins without an intervening capillary bed but with a cellular stroma interspersed between vessels.
These lesions typically manifest with periorbital swelling, dilated retinal veins and epibulbar vessels, visible or palpable pulsations, an audible bruit, glaucoma, and, occasionally, visual field defects due to ophthalmic artery steal syndrome. The pulsation and bruit can usually be diminished by compression of the ipsilateral common carotid artery (5).
US, CT with standard and angiographic protocols, and MR imaging with standard and angiographic protocols can help diagnose arteriovenous fistulas; however, conventional catheter-based angiography typically is required for precise definition and treatment planning (Fig 15). Treatment involves embolization and in some cases surgery.
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Figure 15a. Orbital arteriovenous malformation in a 33-year-old man with proptosis and visible pulsations of the globe. (a) Lateral projection from catheter-based angiography demonstrates early filling of a dural arteriovenous fistula (black arrow) fed by a dilated right ophthalmic artery (arrowheads). Intracranial venous drainage is faintly visible (white arrow). (b) Lateral projection from a later phase of the same angiographic examination shows rapid filling of the large intracranial venous component of the malformation (arrows).
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Figure 15b. Orbital arteriovenous malformation in a 33-year-old man with proptosis and visible pulsations of the globe. (a) Lateral projection from catheter-based angiography demonstrates early filling of a dural arteriovenous fistula (black arrow) fed by a dilated right ophthalmic artery (arrowheads). Intracranial venous drainage is faintly visible (white arrow). (b) Lateral projection from a later phase of the same angiographic examination shows rapid filling of the large intracranial venous component of the malformation (arrows).
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Wyburn-Mason Syndrome
The Wyburn-Mason (Bonnet-Dechaume-Blanc) syndrome is an exceedingly rare oculocerebrocutaneous syndrome that consists of unilateral arteriovenous malformations of the visual pathways and midbrain (28). These malformations result from persistence of embryonic vascular tissue that normally should have differentiated into arteries, veins, and capillaries during the 2nd month of gestation. The syndrome is congenital, nonhereditary, and without race or sex predilection. It may occur with associated facial vascular nevi or telangiectasias (Fig 16a). Symptoms are highly variable and depend on the size of the malformations. Patients may present with cosmetic facial deformity, headache, seizure, intracranial hemorrhage, optic atrophy, and, occasionally, pulsatile exophthalmos (29). The arteriovenous malformations may be large and may occur in deep brain locations that make treatment difficult; hence, the overall prognosis is poor (Fig 16b, 16c) (30).
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Figure 16a. Wyburn-Mason syndrome in a 16-year-old boy. (a) Photograph shows telangiectasias. (b, c) Axial contrast-enhanced CT images (b at a lower level than c) show an arteriovenous malformation that extends from the orbit and optic chiasm along the optic pathway to the midbrain (white arrows). An associated venous varix (black arrow in c) drains the midbrain portion of the malformation. (Case courtesy of Anton N. Hasso, Loma Linda, Calif.)
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Figure 16b. Wyburn-Mason syndrome in a 16-year-old boy. (a) Photograph shows telangiectasias. (b, c) Axial contrast-enhanced CT images (b at a lower level than c) show an arteriovenous malformation that extends from the orbit and optic chiasm along the optic pathway to the midbrain (white arrows). An associated venous varix (black arrow in c) drains the midbrain portion of the malformation. (Case courtesy of Anton N. Hasso, Loma Linda, Calif.)
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Figure 16c. Wyburn-Mason syndrome in a 16-year-old boy. (a) Photograph shows telangiectasias. (b, c) Axial contrast-enhanced CT images (b at a lower level than c) show an arteriovenous malformation that extends from the orbit and optic chiasm along the optic pathway to the midbrain (white arrows). An associated venous varix (black arrow in c) drains the midbrain portion of the malformation. (Case courtesy of Anton N. Hasso, Loma Linda, Calif.)
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Carotid Cavernous Fistulas
Carotid cavernous fistulas result from abnormal communication between the cavernous sinus and one or more branches of the internal or external carotid artery. The fistulas occur in middle to late adulthood and are more common in women. They may result from direct trauma, surgery, dural sinus thrombosis, or atherosclerosis or may occur spontaneously. Spontaneous carotid cavernous fistulas have been reported in patients with Ehlers-Danlos syndrome, osteogenesis imperfecta, and pseudoxanthoma elasticum (16). The fistulas often manifest with the classic triad of pulsatile exophthalmos, conjunctival chemosis, and an auscultatory bruit (Fig 17) (31). However, a gradual decrease in visual acuity, with or without palsy of cranial nerves III, IV, V, and VI, may be the only sign (31). Ischemic ocular necrosis has been reported but is extremely rare. Secondary findings such as proptosis, congestive extraocular muscle enlargement, superior ophthalmic vein distention, and cavernous sinus dilatation are usually identified at CT or MR imaging performed with standard or angiographic protocols (Fig 18); however, conventional catheter angiography is usually required for lesion classification and treatment planning before embolization. Carotid cavernous fistulas may be classified on the basis of the source of their arterial supply into the following four subtypes: (a) main internal carotid artery, (b) dural branch of the internal carotid artery, (c) dural branch of the external carotid artery, or (d) dural branches of both the internal and the external carotid arteries (32).
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Figure 17. Right carotid cavernous fistula in a 67-year-old woman. Photograph shows conjunctival injection and mild proptosis. The patient also had papilledema and a bruit over the eye.
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Figure 18a. Carotid cavernous fistula in a 52-year-old woman with proptosis, chemosis, and conjunctival injection. (a, b) Axial T2-weighted MR images (b at a higher level than a) depict a markedly enlarged right cavernous sinus with large, prominent flow voids (arrows in a) and marked enlargement of the right superior ophthalmic vein (arrows in b). (c) Axial maximum intensity projection image from MR angiography optimally demonstrates the fistula and the arterialized superior ophthalmic vein (arrows).
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Figure 18b. Carotid cavernous fistula in a 52-year-old woman with proptosis, chemosis, and conjunctival injection. (a, b) Axial T2-weighted MR images (b at a higher level than a) depict a markedly enlarged right cavernous sinus with large, prominent flow voids (arrows in a) and marked enlargement of the right superior ophthalmic vein (arrows in b). (c) Axial maximum intensity projection image from MR angiography optimally demonstrates the fistula and the arterialized superior ophthalmic vein (arrows).
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Figure 18c. Carotid cavernous fistula in a 52-year-old woman with proptosis, chemosis, and conjunctival injection. (a, b) Axial T2-weighted MR images (b at a higher level than a) depict a markedly enlarged right cavernous sinus with large, prominent flow voids (arrows in a) and marked enlargement of the right superior ophthalmic vein (arrows in b). (c) Axial maximum intensity projection image from MR angiography optimally demonstrates the fistula and the arterialized superior ophthalmic vein (arrows).
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Ophthalmic Artery Aneurysms
Intracanalicular ophthalmic artery aneurysms are extremely rare. The more common carotid-ophthalmic artery aneurysms account for a small percentage of cerebral aneurysms. They arise at the origin of the ophthalmic artery from the supraclinoid internal carotid artery (Fig 19). Although they most often extend intracranially above the sella, they may sometimes extend into or through the optic canal. Lesions with a maximal diameter of 2–3 mm are usually asymptomatic, whereas those with a diameter of more than 3 mm may compress the artery or optic nerve or, if they rupture, cause intracranial subarachnoid hemorrhage (4).
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Figure 19a. Ophthalmic artery aneurysm in a 44-year-old woman with a subarachnoid hemorrhage. (a) Axial contrast-enhanced source image from CT angiography shows an enhancing lesion (white arrow) at the origin of the left ophthalmic artery, a finding suggestive of an aneurysm. The proximal segment of the ophthalmic artery (black arrows) is clearly depicted. (b) Three-dimensional surface-shaded reconstruction image shows the dome of the aneurysm (white arrow) projecting superiorly and medially. The left ophthalmic artery (black arrows) arises from the side of the aneurysm and courses anteriorly.
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Figure 19b. Ophthalmic artery aneurysm in a 44-year-old woman with a subarachnoid hemorrhage. (a) Axial contrast-enhanced source image from CT angiography shows an enhancing lesion (white arrow) at the origin of the left ophthalmic artery, a finding suggestive of an aneurysm. The proximal segment of the ophthalmic artery (black arrows) is clearly depicted. (b) Three-dimensional surface-shaded reconstruction image shows the dome of the aneurysm (white arrow) projecting superiorly and medially. The left ophthalmic artery (black arrows) arises from the side of the aneurysm and courses anteriorly.
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Tumors
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Hemangioblastomas
Hemangioblastoma is a benign vascular tumor that is commonly associated with von Hippel-Lindau disease. Most hemangioblastomas that occur within the orbit are located in the retina, although locations within the optic nerve have been reported (33). Von Hippel-Lindau disease is an autosomal dominant genetic disorder with variable expressivity that is localized to chromosome 3. It is characterized by both benign and malignant tumors. The finding of a single cerebellar hemangioblastoma in a patient with a family history of von Hippel-Lindau disease is considered sufficient for diagnosis. Without a family history, at least two cerebellar hemangioblastomas or one hemangioblastoma plus one associated visceral tumor (renal cell carcinoma, pheochromocytoma) are necessary for a diagnosis of von Hippel-Lindau disease. Histologically, the retinal tumors first described by von Hippel are hemangioblastomas, and the term retinal angioma is therefore a misnomer (34). Hemangioblastomas represent 1%–2% of all primary tumors of the central nervous system. Seventy percent of patients who present with a hemangioblastoma do not have a family history of von Hippel-Lindau disease. However, patients with a sporadic nonhereditary hemangioblastoma should undergo further evaluation for evidence of von Hippel-Lindau disease (35).
Ocular abnormalities due to a retinal hemangioblastoma are the earliest manifestations of von Hippel-Lindau disease in about 50% of cases (34). The hemangioblastoma typically appears as a dilated artery leading from the optic disc to a peripheral (most often temporal) tumor with an engorged draining vein that leads back to the optic disc (34). Less commonly, the lesion is near or on the optic disc. Patients with a retinal hemangioblastoma are usually asymptomatic until the 3rd decade of life, although the enlargement of a centrally located lesion may produce an earlier vision loss (34). A retinal hemangioblastoma may be a predisposing factor for retinal detachment, macular edema, and glaucoma. Early detection, followed by laser coagulation or cryotherapy, may prevent vision loss.
Hemangiopericytomas
Hemangiopericytomas, which were first described in 1942 by Stout and Murray (36), are rare, slow-growing, highly vascular tumors that are relatively common in the musculoskeletal system (lower extremities), pelvis, and retroperitoneum. Approximately 15% of these tumors arise in the extracranial part of the head and neck, usually in the nasal cavity or paranasal sinuses. Origin within the orbit is rare (37). The tumors may occur at any time, from infancy through late adult life, although the mean ages at diagnosis in two large patient series were 45 years and 42 years (38). Overall, hemangiopericytomas demonstrate no predilection for either sex; however, occurrence in the orbit is more common in males (38). Hemangiopericytomas most often manifest with slowly progressive, sometimes painful proptosis and decreased visual acuity. Other symptoms include extraocular motility abnormalities, visual field deficits, and congestion of the retinal and choroidal vessels (39). Histologic findings range from benign to malignant characteristics, with many tumors demonstrating both. Although metastases are uncommon, they were reported in 15% of patients in one series, with the lung being the most common site (38).
These mesenchymal tumors arise from the pericytes of Zimmerman, contractile cells that surround the outer aspect of small vessels and that are thought to regulate lumen size and produce collagen. Tumors are classified as sinusoidal, solid, or mixed (38). Histologic analysis demonstrates staghorn-like capillary spaces lined by plump, proliferating pericytes, with intervening fibrous septa (Fig 20) (3,5). The classic staghorn-like vascular pattern is not unique to hemangiopericytomas; it is encountered in a variety of other neoplasms, including synovial sarcomas, fibrous histiocytomas, and malignant peripheral nerve sheath tumors (40).
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Figure 20. Hemangiopericytoma. Histologic photomicrograph (original magnification, x50; hematoxylineosin stain) shows staghorn-shaped capillary spaces lined by plump pericytes (arrows).
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Hemangiopericytomas are usually lobulated, encapsulated, and well circumscribed, but they may have infiltrative margins. Although the superior half of the orbit was reported by some to be the most common primary orbital location (41), others have not found such a predilection (39). The typical location is extraconal; lesions commonly arise in the adjacent paranasal sinuses (Fig 21). The standard treatment is wide surgical excision. Postoperative irradiation is recommended for incompletely excised lesions. Local recurrence in approximately 30% of cases has been reported, and lesions may recur up to 30 years after initial treatment (38).
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Figure 21. Hemangiopericytoma in a 47-year-old man with proptosis of the left eye. Axial contrast-enhanced CT image shows a lobulated, slightly and homogeneously enhancing left ethmoid sinus mass that has eroded the medial orbital wall. Note the extraconal extension of the lesion into the orbit and the resultant displacement of the globe.
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At US, hemangiopericytomas are moderately hyperechoic, with high vascularity on color Doppler images, a feature that permits their differentiation from cavernous hemangiomas (5). At CT, they are typically homogeneous and lobulated (Fig 21). The lesions may be well circumscribed and confined to the orbit, or they may have indistinct, irregular margins. When large, they may cause osseous erosion and remodeling and may involve the central nervous system. Rarely, intralesional calcification is present (39). Hemangiopericytomas enhance intensely (3,6), and some may be confused with cavernous hemangiomas. Dynamic contrast-enhanced CT may help distinguish between the two lesions, as hemangiopericytomas exhibit marked early arterial phase and early venous phase enhancement followed by rapid washout (42). At MR imaging, the signal intensity of hemangiopericytomas is similar to that of gray matter on T1- and T2-weighted images, a feature that helps differentiate these lesions from cavernous malformations (3). Digital subtraction angiography demonstrates a prominent arterial supply with an early florid blush and persistent tumor staining, features that help differentiate hemangiopericytomas from meningiomas (which typically contain multiple vessels and show a late tumor blush) and schwannomas (which typically show no tumor blush).
Choroidal Hemangiomas
These congenital vascular hamartomas typically manifest in middle-aged or elderly people (mean age, 31 years; age range, 7–58 years) (43). Although some reports indicate a strong male predominance (44), others indicate an almost equal distribution in both sexes (45). The solitary or circumscribed choroidal hemangioma is a benign vascular neoplasm that is confined to the choroid, has distinct margins, and is typically located posterior to the equator of the globe (43). In contrast, the diffuse hemangiomas that occur in Sturge-Weber syndrome not only involve the choroid but also may involve the ciliary body, iris, and, occasionally, nonuveal tissues including the episclera, conjunctiva, and limbus. Both types of choroidal hemangiomas are stable lesions with little or no tendency to enlarge.
The clinical appearance of the circumscribed choroidal hemangioma is that of a smoothly elevated, slightly dome-shaped, reddish-orange choroidal mass that blends with the surrounding choroid. At times, these lesions can barely be distinguished from the choroidal background (43).
Choroidal hemangiomas are classified histologically as capillary, cavernous, or mixed. Asymptomatic circumscribed choroidal hemangiomas do not require treatment unless retinal detachment occurs. In cases of retinal detachment, the most widely accepted form of treatment is laser photocoagulation.
CT is useful for diagnosis, but MR imaging is considered to provide depiction superior to that of CT (Fig 22). At CT, circumscribed choroidal hemangiomas in the absence of retinal detachment appear as ill-defined masses that exhibit intense enhancement after the administration of contrast material. At MR imaging, the lesions are more clearly depicted: Most have a lenticular shape with a maximal diameter of 3–11 mm (average, 7.5 mm) and signal that is hyperintense to that of vitreous on T1-weighted images, although some lesions may appear isointense to vitreous. On T2-weighted fast spin-echo images, the signal is typically hyperintense, usually appearing isointense to that of vitreous. The lesions enhance intensely after the administration of contrast material (45). Clinically, a circumscribed choroidal hemangioma may be confused with a uveal melanoma; however, the isointensity of the signal in a choroidal hemangioma to that of vitreous fluid on T2-weighted fast spin-echo MR images is an important imaging feature that permits differentiation between the two lesions. Diagnostic specificity of 93% and sensitivity of 96% with unenhanced MR imaging have been reported (45). The additional use of contrast-enhanced dynamic MR imaging resulted in reported sensitivity of 100% and specificity of 88% for differentiation between the two lesions (45).
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Figure 22a. Circumscribed choroidal hemangioma in an 8-year-old girl. (a, b) Axial unenhanced (a) and contrast-enhanced (b) CT images show a slightly hyperattenuating, homogeneously enhancing lentiform lesion based on the lateral retinochoroidal layer of the left eye. (c–e) Axial unenhanced T1-weighted (c), unenhanced T2-weighted (d), and contrast-enhanced T1-weighted fat-suppressed (e) MR images show the same lesion (arrows in c). In c, the signal of the lesion is slightly hyperintense to that of the vitreous; in d, it is nearly isointense to that of the vitreous; and in e, it is homogeneously and intensely enhanced.
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Figure 22b. Circumscribed choroidal hemangioma in an 8-year-old girl. (a, b) Axial unenhanced (a) and contrast-enhanced (b) CT images show a slightly hyperattenuating, homogeneously enhancing lentiform lesion based on the lateral retinochoroidal layer of the left eye. (c–e) Axial unenhanced T1-weighted (c), unenhanced T2-weighted (d), and contrast-enhanced T1-weighted fat-suppressed (e) MR images show the same lesion (arrows in c). In c, the signal of the lesion is slightly hyperintense to that of the vitreous; in d, it is nearly isointense to that of the vitreous; and in e, it is homogeneously and intensely enhanced.
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Figure 22c. Circumscribed choroidal hemangioma in an 8-year-old girl. (a, b) Axial unenhanced (a) and contrast-enhanced (b) CT images show a slightly hyperattenuating, homogeneously enhancing lentiform lesion based on the lateral retinochoroidal layer of the left eye. (c–e) Axial unenhanced T1-weighted (c), unenhanced T2-weighted (d), and contrast-enhanced T1-weighted fat-suppressed (e) MR images show the same lesion (arrows in c). In c, the signal of the lesion is slightly hyperintense to that of the vitreous; in d, it is nearly isointense to that of the vitreous; and in e, it is homogeneously and intensely enhanced.
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Figure 22d. Circumscribed choroidal hemangioma in an 8-year-old girl. (a, b) Axial unenhanced (a) and contrast-enhanced (b) CT images show a slightly hyperattenuating, homogeneously enhancing lentiform lesion based on the lateral retinochoroidal layer of the left eye. (c–e) Axial unenhanced T1-weighted (c), unenhanced T2-weighted (d), and contrast-enhanced T1-weighted fat-suppressed (e) MR images show the same lesion (arrows in c). In c, the signal of the lesion is slightly hyperintense to that of the vitreous; in d, it is nearly isointense to that of the vitreous; and in e, it is homogeneously and intensely enhanced.
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Figure 22e. Circumscribed choroidal hemangioma in an 8-year-old girl. (a, b) Axial unenhanced (a) and contrast-enhanced (b) CT images show a slightly hyperattenuating, homogeneously enhancing lentiform lesion based on the lateral retinochoroidal layer of the left eye. (c–e) Axial unenhanced T1-weighted (c), unenhanced T2-weighted (d), and contrast-enhanced T1-weighted fat-suppressed (e) MR images show the same lesion (arrows in c). In c, the signal of the lesion is slightly hyperintense to that of the vitreous; in d, it is nearly isointense to that of the vitreous; and in e, it is homogeneously and intensely enhanced.
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Choroidal Melanomas
These lesions are the most common primary intraocular tumors in adults and the most commonly occurring uveal melanoma, with an estimated prevalence of five to seven cases per 1 million adults in the general population. Melanomas may occur in any of the three subdivisions of the uvea: the iris, the ciliary body, and the choroid. Melanomas involving the ciliary body and choroid are thought to arise from preexisting melanocytic nevi (46). These tumors are most common among people of northern European descent and are uncommon among African Americans (white-to-black ratio, 15:1) (47). Sixty-five percent of melanomas occur in those older than 50 years (48). Patients may be asymptomatic and the lesion discovered during a routine ophthalmologic examination. Symptomatic patients may experience a vision loss, photopsia, and visual field deficits. Tumors initially have a flat growth profile within the choroid but later become elevated, erupting through the Bruch membrane and assuming a characteristic mushroom shape that extends toward the vitreous chamber (49).
Factors that are indicative of an unfavorable prognosis include increasing tumor size, extraocular growth, infiltration of the ciliary body, and intense pigmentation (50–52). Melanomas primarily metastasize to the liver, and some metastases manifest before primary tumor detection. Other sites of metastasis, in order of decreasing frequency, are lung, bone, kidney, and brain (49).
There is disagreement about the optimal method for managing choroidal melanomas, and clinical trials are ongoing. Treatment selection depends on the site of origin (choroid, ciliary body, or iris), size, and location of the primary lesion as well as whether extraocular extension, recurrence, or metastases are present. Large melanomas (>10 mm thick) traditionally have been managed with enucleation (53). For medium-sized lesions (3–10 mm thick), plaque brachytherapy and external-beam radiation therapy have been accepted as alternatives to enucleation. Small tumors (<3 mm thick) should be monitored every 3–6 months with US. Transpupillary thermotherapy was shown to be effective for small lesions, with fewer complications than radiation therapy and without the need for incisional surgery (54).
Choroidal melanomas are typically assessed with an ophthalmologic examination, fluorescein angiography, or US. However, these methods have limitations in the presence of opacities, and CT provides a valuable method by which to demonstrate these lesions (55). At unenhanced CT, the lesions appear elevated, hyperattenuating, and sharply marginated. In addition, contrast-enhanced dynamic CT may help distinguish uveal melanomas from other lesions, such as choroidal hemangiomas, by providing information about vascularity and perfusion (55). Most choroidal melanomas appear as well-defined solid masses at MR imaging. Those that are hemorrhagic or necrotic have varied MR imaging appearances. Because of the paramagnetic effects of melanin, intensely melanotic melanomas have shorter T1 and T2 relaxation times, producing increased signal intensity on T1-weighted images and markedly decreased signal intensity on T2-weighted images (Fig 23) (56). Among ocular tumors, only melanomas manifest these signal intensity characteristics. Unfortunately, amelanotic and slightly melanotic melanomas do not show the same signal intensity characteristics. Instead, the signal in these lesions may appear isointense on T1-weighted images and only slightly hypointense on T2-weighted images, similar to that in choroidal metastases and other tumors of the globe. Following the administration of contrast material, choroidal melanomas demonstrate moderate to strong enhancement. Contrast-enhanced fat-suppressed MR imaging also may demonstrate scleral invasion, tumor extension to the optic disc, and extraocular invasion. In one study, retinal detachment, which is regarded as a sign of progressive tumor development occurring in the late stages of tumor growth, was correctly distinguished from melanoma in all patients at MR imaging with the use of a surface coil (57).
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Figure 23a. Choroidal melanotic melanoma in a 51-year-old man with decreasing vision in the left eye. (a) Axial T1-weighted MR image demonstrates a round, diffusely hyperintense mass in the posterior-inferior aspect of the left globe. (b) Coronal T2-weighted MR image shows marked signal hypointensity within the lesion (compare this feature with the choroidal hemangioma in Fig 22d). (c) Axial contrast-enhanced T1-weighted fat-suppressed image depicts some homogeneous enhancement of the lesion in comparison with that in a. (Case courtesy of Ho Kyu Lee, University of Iowa Hospitals and Clinics, Iowa City.)
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Figure 23b. Choroidal melanotic melanoma in a 51-year-old man with decreasing vision in the left eye. (a) Axial T1-weighted MR image demonstrates a round, diffusely hyperintense mass in the posterior-inferior aspect of the left globe. (b) Coronal T2-weighted MR image shows marked signal hypointensity within the lesion (compare this feature with the choroidal hemangioma in Fig 22d). (c) Axial contrast-enhanced T1-weighted fat-suppressed image depicts some homogeneous enhancement of the lesion in comparison with that in a. (Case courtesy of Ho Kyu Lee, University of Iowa Hospitals and Clinics, Iowa City.)
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Figure 23c. Choroidal melanotic melanoma in a 51-year-old man with decreasing vision in the left eye. (a) Axial T1-weighted MR image demonstrates a round, diffusely hyperintense mass in the posterior-inferior aspect of the left globe. (b) Coronal T2-weighted MR image shows marked signal hypointensity within the lesion (compare this feature with the choroidal hemangioma in Fig 22d). (c) Axial contrast-enhanced T1-weighted fat-suppressed image depicts some homogeneous enhancement of the lesion in comparison with that in a. (Case courtesy of Ho Kyu Lee, University of Iowa Hospitals and Clinics, Iowa City.)
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Metastases
Uveal metastases typically reach the globe via the posterior ciliary arteries and, therefore, commonly involve the posterior half of the globe (Fig 24) (48). The primary lesions that are the most common sources of uveal metastases are breast and lung carcinomas. Both eyes are affected in about one-third of cases. Metastases, especially those from breast and lung carcinomas, also may involve extraocular muscles.
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Figure 24a. Choroidal metastasis from stomach carcinoma in a 55-year-old man. (a) Axial T1-weighted MR image reveals a posterior choroidal mass with slightly hyperintense signal. (b) Axial T2-weighted MR image demonstrates slightly hypointense signal in the lesion, which appears isointense to muscle (much less hypointense than the choroidal melanotic melanoma in Fig 23b). (c) Axial contrast-enhanced T1-weighted fat-suppressed MR image demonstrates only minimal enhancement of the lesion in comparison with that in a. This lesion may be difficult to differentiate from an amelanotic melanoma on the basis of the MR imaging findings. (Case courtesy of Ho Kyu Lee, University of Iowa Hospitals and Clinics, Iowa City.)
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Figure 24b. Choroidal metastasis from stomach carcinoma in a 55-year-old man. (a) Axial T1-weighted MR image reveals a posterior choroidal mass with slightly hyperintense signal. (b) Axial T2-weighted MR image demonstrates slightly hypointense signal in the lesion, which appears isointense to muscle (much less hypointense than the choroidal melanotic melanoma in Fig 23b). (c) Axial contrast-enhanced T1-weighted fat-suppressed MR image demonstrates only minimal enhancement of the lesion in comparison with that in a. This lesion may be difficult to differentiate from an amelanotic melanoma on the basis of the MR imaging findings. (Case courtesy of Ho Kyu Lee, University of Iowa Hospitals and Clinics, Iowa City.)
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Figure 24c. Choroidal metastasis from stomach carcinoma in a 55-year-old man. (a) Axial T1-weighted MR image reveals a posterior choroidal mass with slightly hyperintense signal. (b) Axial T2-weighted MR image demonstrates slightly hypointense signal in the lesion, which appears isointense to muscle (much less hypointense than the choroidal melanotic melanoma in Fig 23b). (c) Axial contrast-enhanced T1-weighted fat-suppressed MR image demonstrates only minimal enhancement of the lesion in comparison with that in a. This lesion may be difficult to differentiate from an amelanotic melanoma on the basis of the MR imaging findings. (Case courtesy of Ho Kyu Lee, University of Iowa Hospitals and Clinics, Iowa City.)
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Unlike uveal metastases, bilateral uveal melanomas are rare. MR imaging is superior to CT for distinguishing uveal metastases from uveal melanomas (48).
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Coats Disease
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Coats disease is an idiopathic primary vascular anomaly of the retina. It is characterized by retinal telangiectasias and exudative retinal detachment caused by an accumulation of lipoproteinaceous exudate in the retina and subretinal space (58,59). Because of retinal detachment, children often present with leukokoria, and the disease may be difficult to clinically differentiate from retinoblastoma (58). Although the disease is present at birth, signs and symptoms are delayed until retinal detachment produces loss of vision, typically between the ages of 6 and 8 years. Boys are affected approximately twice as often as girls (59).
The primary pathologic processes in Coats disease are the congenital formation of abnormal telangiectatic retinal vessels and the lack of a blood-retina barrier. These result in retinal and subretinal exudates, hemorrhage, and a fibroglillipid reactive process with subsequent organization of the retina (59). The exudate has a very high protein concentration, is unusually rich in lipids, and contains large amounts of free cholesterol crystals. The pathogenesis of this disease remains unknown.
US may demonstrate retinal detachment and particulate echoes from subretinal material, presumably cholesterol crystals. CT findings include a normal-sized globe with increased overall attenuation due to the density of the subretinal exudate (59). CT also may demonstrate the retinal detachment. Important for the distinction of Coats disease from retinoblastoma is the fact that true calcifications are common in retinoblastomas but occur rarely, if ever, in association with Coats disease. At MR imaging, the signal intensity of the globe in Coats disease is somewhat variable, depending on the proportions of proteins and lipids. Most often, there is diffuse signal hyperintensity on both T1- and T2-weighted images (60). After the administration of contrast material, enhancement is visible along the leaves of the detached retina and at the sites where the retina inserts (61). The absence of an enhancing mass helps distinguish Coats disease from retinoblastoma, persistent hyperplastic primary vitreous, and toxocaral endophthalmitis (59). According to one report, proton MR spectroscopy demonstrated a characteristic large lipid peak in subretinal exudates (61).
If the disease is detected in its early stages, photocoagulation or cryotherapy may be used to obliterate the telangiectases. In later stages of the disease, neovascularity of the iris often causes neovascular glaucoma with resultant blindness or severe eye pain, necessitating enucleation (59).
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Summary
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Vascular lesions of the orbit are confusing entities with imaging features that may overlap. However, differentiation of this group of lesions is usually possible on the basis of clinical and imaging data. Diagnosis requires an understanding of the classification of vascular lesions, integration of the individual patient’s history with epidemiologic data, and familiarity with the imaging features that are typical of specific lesions. The use of appropriate imaging techniques (eg, delayed contrast-enhanced imaging for cavernous malformations, prone imaging for orbital varices) and recognition of pathognomonic features (eg, multiple fluid-fluid levels in lymphatic malformations, progressive delayed enhancement in cavernous malformations) are often essential for precise diagnosis.
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Abstract
LEARNING OBJECTIVES FOR TEST...
