1	Orbital Masses: How to Differentiate True Vascular Lesions from Non-Vascular Mimickers Colin S. Poon, M.D., Ph.D. Gordon Sze, M.D. Michele H. Johnson, M.D. Division of Neuroradiology, Department of Diagnostic Radiology, Yale University School of Medicine and Yale-New Haven Hospital New Haven, CT, U.S.A.
2	Introduction
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4	In this presentation, our objectives include: Review the anatomy of the orbits, with emphasis on the major arterial and venous structures. Describe the normal and variant blood flow patterns within the orbits and flow alterations related to orbital pathology. Illustrate the distinguishing features between true vascular lesions and soft tissue processes that mimic vascular lesions.
5	Outline A brief review of orbital vascular anatomy Interactive cases to illustrate the learning points Summary of key concepts
6	Normal arterial anatomy
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8	Normal venous anatomy
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10	CTA of orbit (Set 1 of 4)
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14	Case 1
15	28 year old male with right proptosis. MRI was performed. What is your diagnosis?
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23	Case 2
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31	Case 3
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37	Case 4
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42	Case 5
43	53 year old female with history of lupus, presenting with right sided diplopia. MRI and CT were obtained.
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45	CT brain without contrast. The bilateral superior ophthalmic veins (yellow arrows) are shown. There is asymmetric dilatation of the right superior ophthalmic vein. The cavernous sinuses (white arrows) are symmetric and within normal limits.
46	Angiography was performed. You will be shown three images from a right internal carotid artery injection in lateral projection, representative of arterial to venous phase.
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49	Can you find the clue to explain the patient’s CT finding?
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51	Arterial phase. This is a normal right ICA arteriogram. The right ophthalmic artery arises from the internal carotid artery as it exits the cavernous sinus.
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55	"Diagnosis" Diagnosis: Normal variant in venous drainage of the brain. Discussion: The drainage of supratentorial venous blood into the anterior cavernous sinus causes transient venous overflow in the anterior cavernous sinus, and reflux of venous blood into the proximal superior and inferior ophthalmic veins.
56	Case 6
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67	Summary of key concepts Orbital symptoms and signs are nonspecific. They may be seen in diseases within or outside of the orbits, and may be of vascular or nonvascular etiologies. New imaging techniques, such as high resolution MRI and multi-detector CT, MRA and CTA, allow us to evaluate confidently the fine vascular and soft tissue structures of the orbit. Orbital soft tissue masses, such as metastasis and orbital neurofibroma, may mimic vascular pathology. Careful analysis of its enhancement pattern and anatomical relationship with normal orbital vascular structures can help one to avoid diagnostic pitfalls.
68	"A lesion with prominent vessels..." A lesion with prominent vessels and intense enhancement pattern is more likely to be a vascular lesion. Orbital vessels communicate directly with the extra-orbital vascular systems. Their normal blood flow pattern is easily affected by diseases within or outside of the orbit. Understanding of normal versus abnormal blood flow patterns of the orbit is key to accurate diagnosis.
69	References Ettl A, Krammer J, Daxer A et al. High resolution magnetic resonance imaging of neurovascular orbital anatomy. Ophthalmology 1997; 104:869-877. Aviv RI, Casselman J. Orbital imaging: Part 1. Normal anatomy. Clinical Radiology 2005; 60:279-287. Bilaniuk LT. Vascular lesions of the orbit in children. Neuroimaging Clinics of North America 2005; 15:107-120. White JH, Fox AJ, Symons SP. Diagnosis and anatomic mapping of an orbital varix by computed tomographic angiography. Am J. Ophthalmology 2005; 140:945-947. Rootman J. Vascular malformations of the orbit: hemodynamic concepts. Orbit 2003; 22(2):103-120. Stiebel-Kalish H, Setton A, Nimii Y, et al. Cavernous sinus dural arteriovenous malformations: patterns of venous drainage are related to clinical signs and symtoms. Opthalmology 2002; 109:1685-1691.
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