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As I mentioned in the introduction to the orbital inflammatory portion of

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the clinical scenario, the differential diagnosis for the infections involving

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the orbit that we see in the emergency room include orbital pseudotumor

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and cavernous carotid fistula, both of which can lead to an edematous, irritated,

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painful orbit. Orbital Pseudotumor, I mentioned as various synonyms including

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idiopathic orbital inflammation or idiopathic orbital inflammatory syndrome,

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and includes... Some of the entities that include IGG,

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inflammatory processes. And these can affect any part of the orbit.

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It can affect the eyelids, it can affect the ciliary apparatus,

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it can affect the retina, it can affect the muscles, it can affect

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the fat tissue, it can affect the optic nerve and the optic nerve

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sheath complex. The most common thing that we see with orbital pseudotumor

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is a mass, an inflammatory mass, which may affect either the lacrimal apparatus

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or the muscles, so that's the myositis that you see there.

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Or it can just be a general inflammatory process.

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These inflammatory processes will respond incredibly quickly to the administration

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of steroids and that's why it's very important that we distinguish between

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an infectious orbital inflammation versus the non infectious pseudotumor.

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Because one takes antibiotics, the other takes steroids, and if you give

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steroids to the one who's requires antibiotics, the infection can explode.

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And if you give antibiotics to the one that's idiopathic and

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more of a autoimmune disorder, it doesn't really help. So distinguishing

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these two is important, and usually, the presence of sinusitis or the presence

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of a fever will help make that distinction.

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Here is a patient who demonstrates abnormal enhancement along the posterior

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aspect of the globe representing scleral pseudotumor. This is manifested

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as the brighter signal intensity along the posterior ocular membranes on

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the left side compared to the right side, where you see the normal

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amount of enhancement around the periphery of the globe.

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And there is a little bit of stranding and enhancement in the retrobulbar

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space at the junction of the optic nerve with the posterior aspect of

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the globe. So there is some inflammation in the retrobulbar space as well.

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Here is a patient who has marked enlargement of the left superior ophthalmic

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vein compared with the right. On this example, we can see the normal

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curvature that occurs with the superior ophthalmic vein as it enters through

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the superior orbital fissure. And the contralateral side, the left side,

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which is the pathologic side, we see that there is marked enlargement of

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the caliber of the left superior ophthalmic vein compared to the right superior

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ophthalmic vein. For those of you who have more conspicuity, you would notice

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that the patient also has proptosis of the left globe compared with the

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right globe. On the coronal reconstruction of the axial scan, remember that

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the superior ophthalmic vein runs actually just in association with the

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superior rectus muscle, it usually runs just above it. In this case,

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it's markedly enlarged and you see that on the medial aspect compared to

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the contralateral superior rectus, superior ophthalmic vein complex.

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So we wear a new look and make sure that this vein enhances

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normally, that it's not a thrombose vein, because that thrombophlebitis

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of the superior ophthalmic vein may also lead to an inflamed,

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irritated, painful, proptotic globe. Here is an MRI scan. The MRI scan shows

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enhancement of the left cavernous sinus compared with the right cavernous

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sinus, in the early arterial phase. Here we see the

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cavernous carotid artery, and absence of enhancement of the

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right cavernous sinus. Contrast that with the abnormal

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left cavernous sinus where we see enhancement at a time point where we

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should not be seeing the venous side of things, this is just an

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arterial phase of the cavernous CC fistula, the cavernous carotid fistula.

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In this case on the post contrast scan, you also see

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a filling defect within that superior ophthalmic vein. And again, this is

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what I cautioned you about. You can have thrombophlebitis of the superior

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ophthalmic vein as an isolated problem, or in association

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with the cavernous carotid artery fistula. Notice that there is different

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flow voids here in the left cavernous sinus because there is a artery

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to venous communication between the carotid artery and the cavernous sinus.

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This is also demonstrated here on the angiogram. We have the AP view

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of the angiogram and the lateral view of the angiogram, and

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we've injected the ICA. And what you see is that on the injection

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of the internal carotid artery, you see this filling of the cavernous sinus

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and filling of the inferior and superior ophthalmic veins leading to

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early opacification of the scleral blush here. And this is also demonstrated

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on the AP view. So three different examples. One showing a CC fistula with

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the arteriogram. Another showing a CC fistula with superior ophthalmic vein

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thrombosis. And the first case showing the CC fistula on a CT scan.