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Case 2 - Orbital Medial Wall Fracture

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In the last case, we saw a patient who had multiple,

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multiple fractures of various types.

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Let's look at this patient who effectively got punched

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in the eye. Which eye are we got to look for?

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Well,

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if it's a right-handed person who is punching,

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it's going to be the left eye.

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So here we go on the axial scans. Again,

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Focus on the thin section images.

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If your institution is only giving you you the

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reconstructed five millimeter

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or three millimeter sections,

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I would recommend that you request to have the

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raw data thin sections for all the trauma cases.

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This is useful for identifying subdural

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hematomas in the brain,

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but also for relatively subtle fractures.

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So we at Johns Hopkins always get the

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full data set, including the thinnest,

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most raw data of the sections,

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and those are usually at 0.5 to 0.75 mm.

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So looking at this patient, we come to the

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marker for the floor of the orbit, which is the

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infraorbital foramen on the right side,

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and on the affected left side,

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we see that there are some bone fragments

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that are along the wall of the infraorbital foramen.

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We see that there is an air fluid level of

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material that is hyperdense lying in the

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maxillary antrum. Again, suggestive of trauma.

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As we come further anteriorly,

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we see some air in the soft tissues as well as

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air along the floor. And coming further superiorly,

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we can see that there is a comminuted fracture of the

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lamina papyracea with marked displacement here

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more posteriorly and a bone fragment that is

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displaced. And we can measure the distance here.

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This appears to be indenting

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the medial rectus muscle.

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The lateral orbital wall looks fine.

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The superior orbit looks fine, even though

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there is some fluid in the frontal sinus.

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And again, we look at wherever we're seeing

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the little droplets of air,

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we can see that there is usually a fracture nearby,

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right?

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And the absence of any air on the unaffected side.

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Let's look quickly at the soft tissues to make

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sure that there's no soft tissue ocular injury.

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Okay, so there's the hyperdense blood collection layering

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in the maxillary antrum. Here's our globe.

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And the lens looks pristine.

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The interior chamber looks good.

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That bright margin of the cornea and

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sclera overlying the globe looks fine.

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Retrobulbar space looks fine.

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So the soft tissues look good other than the

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presence of orbital emphysema. As I mentioned,

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the coronal reconstructions and the

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sagittal reconstructions are useful for

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identifying fractures of the orbit.

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They're great for identifying the depression

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of the orbital fracture.

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They're great for identifying the medial

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orbital wall fracture fragment.

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And we can see that air.

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Now, I want to point out a few subtle things

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about the coronal image here.

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So the subtle things I want to point out here are

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what's going on with the extraocular muscles?

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So for that,

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we want to look at the soft tissue windows.

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And as we can see here,

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there is mal orientation of

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the medial rectus muscle.

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There is fat herniating at the corner here between

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the orbital floor and the medial orbital wall.

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Both of these could be an indicator for entrapment.

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When the muscle goes through the fracture

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fragment or the fat goes through the fracture

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fragment, with tugging of the muscle, there's a good

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chance that the patient has entrapment.

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Again, this is a clinical evaluation but we do have

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our imaging findings that are suggestive that

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the patient will likely have entrapment.

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You notice that in this case the

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superior-inferior dimension

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of the inferior rectus muscle and its shape is

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different than the normal inferior rectus muscle.

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So this kind of edema of the inferior rectus muscle

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might also be an indicator that that muscle might

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be in part entrapped or just traumatized.

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On the coronal scan,

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I want to point out another finding and that

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is that just previously on the previous case

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I mentioned to you the importance of not

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mistaking the entry of the anterior ethmoidal artery

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from a fracture. Notice on the left side, however,

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that the wall of the entry of the anterior ethmoidal artery

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has been fractured and it's mal oriented.

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This is important because injury to the

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anterior ethmoidal artery can lead to a large

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expanding hematoma in the orbit.

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And a large expanding hematoma in the orbit,

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the risk is that the upper

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nerve could be compressed and lead

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to ischemic optic neuropathy.

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So the importance of mentioning that the

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anterior ethmoidal artery wall is involved is that

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they will be more careful at observing the patient

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to making sure that there isn't increasing proptosis

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or increasing pressure in the eye that might suggest

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that the optic nerve might become at risk.

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And this is, again, seen not as well

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but you want to compare where that fracture is

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with the contralateral side to make sure

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that the superior oblique muscle,

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which is the one that's closest

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to that entry site,

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is not much larger on the affected side

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than the unaffected side. Finally,

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I want to again emphasize that when

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I'm looking at orbital trauma cases,

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I do spend sometime on the sagittal scan because,

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as you can see here,

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the floor fracture is very nicely demonstrated

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on the sagittal scan,

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and you can actually measure the degree of

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the superior-inferior depression, as well as

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sometimes see the muscle entrapped

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in the fracture fragment.

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One of the things that we do mention about when

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we have orbital floor fractures is, is there

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involvement of the infraorbital nerve?

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This doesn't really affect how

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they treat the fracture,

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but it will explain hypoesthesia in the V2

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distribution. So what do I mean by hypoesthesia?

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So you have this absence of sensation and numbness

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that can occur in the second division of the

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fifth cranial nerve, the maxillary nerve,

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as it is affected by the infraorbital

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foramen fracture.

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And this can also be demonstrated

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on the sagittal reconstruction,

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where we see a portion of the infraorbital foramen

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in here. The contralateral side,

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nice, smooth, intact orbital floor.

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This is the normal infraorbital nerve

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coming out at the floor of

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the right orbit as compared to the left orbit.

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So here's our normal nerve looking just fine.

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So important features to consider when one is

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dealing with orbital floor and

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medial orbital wall fractures.

Report

Faculty

David M Yousem, MD, MBA

Professor of Radiology, Vice Chairman and Associate Dean

Johns Hopkins University

Tags

Neuroradiology

Head and Neck

Emergency

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