Anatomic Considerations: Orbital Spaces
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Outside of the globe,
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we usually think about orbital anatomy
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in three different spaces.
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The intraconal space, with the cone representing the muscles,
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the conal space of the muscles.
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And then, we have the extraconal space.
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And there is different pathology that occurs in each of these spaces.
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So, let's start with the intraconal spaces, the space
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inside the muscle cone. This includes orbital fat,
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arteries and veins, and various nerves, which include the
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optic nerve as the dominant nerve of the orbit.
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The oculomotor cranial nerves, three, four, and six.
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And then, there are also branches of the fifth cranial nerve.
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In this diagram, we can analyze the orbit
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in terms of the various spaces.
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That space, which is within the muscle cone,
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is the intraconal space.
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We consider the muscles themselves
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part of the conal space.
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And this is seen both on the axial diagram to the
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right and the coronal diagram to the left.
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And we have our inferior rectus muscle,
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our medial rectus muscle, lateral rectus muscle,
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superior rectus muscle, superior oblique muscle.
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And this muscle above the superior rectus
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muscle is the levator palpebrae muscle.
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Outside the muscle cone is the extraconal space.
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And as you can see, this includes orbital fat and bone,
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as well as, more medially,
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the paranasal sinuses.
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And the paranasal sinus,
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which leads to the most orbital pathology,
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is the ethmoid sinuses, seen here.
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Superficially, we also have an extraconal space.
David M Yousem, MD, MBA
Professor of Radiology, Vice Chairman and Associate Dean
Johns Hopkins University
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