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Alright, let's look at another of the

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intracranial complications of sinusitis.

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We look on the CT scan.

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We notice the patient has pretty forward sinusitis.

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There's a fluid level in the right frontal sinus.

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We have opacification of the left frontal sinus.

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We have involvement of the ethmoid

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sinuses, left greater than right.

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We have sphenoid sinuses, a little bit more of an

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acute air-fluid level on top of chronic inflammation.

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Same thing in the maxillary antra.

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We notice that the patient has had a medial antrostomy

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already and partial ethmoidectomy most likely.

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And as we move from the bone windows to the

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soft tissue windows, we notice that there is

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a small collection that is adjacent to the

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ethmoid and displacing the medial rectus muscle.

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So a small subperiosteal

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abscess, and in the same case,

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we notice more superiorly that we have a low

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density collection here, which is in the left

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frontal region, and we see that this collection

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is actually lifting the superior sagittal sinus

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from its bony dural attachment, and

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this collection crosses the midline.

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So the sagittal sinus is located here.

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This can only be in the epidural space.

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Remember that the epidural space can cross

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the midline, whereas the subdural collection

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cannot cross the midline because of the falx.

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So this collection is an epidural abscess,

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associated with the frontal sinusitis

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on the left side, as well as a subperiosteal abscess

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affecting the orbit, so two for one on this case.

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What we wanna make sure that we see,

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though, is a good-appearing superior

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sagittal sinus — that it is not thrombosed.

1:56

For that, I recommend you look on the sagittal scan.

1:59

This is actually a MIP image, maximum intensity

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projection image, where we see the normal sagittal sinus

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here, I window it a little bit better, and the

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collection of the epidural abscess is superficial to the

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sagittal sinus, but the sagittal sinus is not thrombosed.

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So a very good example of potential

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complications of both frontal,

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as well as ethmoid sinusitis. You'd expect

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this patient to also have meningitis.

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And on an MRI scan, remember that these

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collections of purulent material are going to

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be positive on a diffusion-weighted imaging,

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so it'll be bright on DWI and low on an ADC map.