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As we review the pathology in the extraconal space,

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we will start with the distinction between periorbital

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cellulitis and orbital cellulitis.

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And I want to review the

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anatomy that is important with regard to periorbital

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cellulitis, also known as preseptal cellulitis,

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and orbital cellulitis, also known as postseptal cellulitis.

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What does the septum refer to?

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That refers to the orbital septum.

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And the orbital septum is identified as this white structure

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along the medial and lateral aspect of the orbit.

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Now, it is in close proximity to the medial check ligament,

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usually, just superficial to it.

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On the diagram on the right,

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we see that the orbital septum is actually oriented more

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superiorly and inferiorly,

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and is identified as attaching to the

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superior tarsal plate and the inferior

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tarsal plate of the eyelid.

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So, it's actually a structure that is vertically oriented,

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but we identify it most commonly for distinction of

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periorbital cellulitis and orbital cellulitis

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on our axial CT imaging.

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Here is a patient who presented with

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inflammation around the left eye,

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and what one can see is involvement of the soft

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tissues of the skin and subcutaneous fat.

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This patient has a small area where there is a ring

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enhancement that is identified as an abscess.

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But this is in the periorbital space, and everything that

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we see is superficial to the orbital septum.

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So this is preseptal cellulitis,

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also known as preseptal cellulitis.

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As we look on the sagittal image,

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you're seeing the superior orbital

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septum and the inferior orbital septum.

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And everything that we are seeing is superficial to it.

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As we described previously,

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the most common source of infection in the orbit,

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after skin surface infections, or scratches, or irritations

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or bites is from the paranasal sinuses.

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Here is a patient who has diffused ethmoid sinusitis on the

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right side, with inflammation that is extending to involve the

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extraconal space in a periosteal periorbital abscess.

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Diffuse opacification of the ethmoid sinus is

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going to the sphenoid sinus,

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and then the collection,

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which is in the extraconal space

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of the periorbital periosteal abscess.

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This is another example of a periosteal abscess in a child.

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In fact,

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children have the highest rate of periosteal abscesses,

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associated with ethmoid sinusitis,

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in part because the periosteum in the child has a greater

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number of perforations than in the adult patient.

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What to do about periosteal abscesses?

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In general, these are evaluated and then treated with

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intravenous antibiotics initially.

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If the patient does not respond with intravenous antibiotics

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in the first 24 to 48 hours, or has increasing symptoms,

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then surgical treatment is required.

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While it used to be that the patients would undergo a medial

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canthotomy to get to this collection and drainage,

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nowadays, the treatment is generally endoscopic.

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So they will go into the sinonasal cavity and drain the

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ethmoid sinusitis,

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and enter the collection from the paranasal sinuses,

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endoscopically, and drain it in that fashion.

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In this way,

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the patient does not have any facial scarring

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from the surgical approach.

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If, on the other hand,

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one sees a collection of air within the periosteal abscess,

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it suggests multi microbial pathogens,

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and therefore, they are more likely to aggressively treat with surgery,

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expecting that the antibiotics may not be as helpful.

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Remember that preseptal cellulitis or periorbital cellulitis,

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by contrast,

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is treated as an outpatient with PO, oral antibiotics.

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And this remains superficial to the orbital septum,

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as you can see with this inflammatory condition here.