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We are discussing extraconal lesions and we deviated to

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describe periorbital cellulitis, which is outside the muscle

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cone, and then talked a little bit about orbital cellulitis,

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where you may have intraconal involvement of the posterior

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aspect of the orbit and the retrobulbar compartment.

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Let's go back to talking about extraconal lesions

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that affect the bones of the wall of the orbit.

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In this case above, one has an area where

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the lateral orbital wall is deficient.

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And we see, in fact,

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some fluid signal density of the cerebrospinal fluid.

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Note that the optic nerve is deviated medially,

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compared to the normal optic nerve.

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This is one of the manifestations of neurofibromatosis type 1,

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where one has sphenoid wing dysplasia, in which the

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sphenoid wing is inappropriately terminated

1:00

compared to the normal left side.

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So, this is an example of sphenoid wing dysplasia as part of

1:07

one of the major criteria for neurofibromatosis type 1,

1:11

where one can get proptosis that may be pulsatile.

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If we look at the image below,

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we see another abnormality of the

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greater wing of the sphenoid.

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Here we have ground glass phenomenon, which is characteristic

1:28

of fibrous dysplasia.

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And fibrous dysplasia is one of the most common

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of the orbital wall abnormalities.

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Previously, we have seen cases of metastases to the orbital

1:43

wall and in children Langerhans cell

1:45

histiocytosis of the orbital wall.

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But of the lesions that affect the bones of the orbit,

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fibrous dysplasia is most common.

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As you can see,

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this encroaches on the orbit and therefore

1:57

may lead to proptosis.

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Another common lesion which can also affect

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the walls of the orbit is a mucocele.

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A mucocele is an obstructed sinonasal osteoma with enlargement

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of the paranasal sinus. When that happens,

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it too may encroach upon the orbit and lead to displacement

2:19

of the extraocular muscles and proptosis.