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Case 17 - Malignant Otitis Externa

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0:01

Although it's not as common as pharyngitis, tonsillitis,

0:05

and dental infections,

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I did want to mention one additional inflammatory

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process that you should be aware of in the emergency

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evaluation of a patient. In this case, with ear pain.

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Now,

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this is a 73-year-old elderly gentleman

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who had diabetes.

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And what we see on these two images is the characteristic

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features of Malignant Otitis Externa

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or Necrotizing External Otitis.

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There will be different terms

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used for the same entity.

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What you see is the inflammatory process in the

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external auditory canal with some erosion

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of the walls of the external auditory canal.

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And then you also see some undercutting of

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the clivus on the right side on the CT scan.

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This patient had previously had irrigation of this

0:59

right ear by the local MD and developed cranial

1:06

neuropathies and additional sort of deep-seated

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skull pain. If we look on the MRI scan,

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it's really quite striking what's going on.

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Now note that this is an MRI scan in which we've applied

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fat suppression and giving gadolinium.

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What you see is the markedly narrowed external auditory

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canal with inflammatory changes on either

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side of the anterior and posterior border.

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We see the mastoid air cells are opacified and enhancing.

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Unfortunately,

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we also see the flow void of the internal carotid artery

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surrounded by enhancing inflammatory tissue.

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As this inflammatory process is extending to the

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skull base. These are the longest colli muscles.

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The right side shows enhancement.

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The left side is normal, not enhancing.

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So we have inflammation even in the pre

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vertebral musculature on the right side.

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We also notice the clivus.

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The clivus has fat within it and should show

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fat suppression as you see on the left side.

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On the right side, we have enhancement of this bone,

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the clivus.

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So enhancement of this clivus section right here,

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because the patient has skull base osteomyelitis.

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This inflammatory process extends into the

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parapharyngeal space of the nasopharynx. Here's

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the normal parapharyngeal space showing

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absence of enhancement.

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So this entity of Malignant Otitis Externa,

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which starts as an external otitis,

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basically a swimmer's ear, if you will,

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can go even so far as the skull base,

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with skull base osteomyelitis,

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vasculitis and cellulitis extending

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to the parapharyngeal space.

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The theory is that with the irrigation

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of the external ear, the pathogen,

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which in most cases is pseudomonas, gets driven into

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the fissures of santorini between the bony portion of

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the external auditory canal and the cartilaginous

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portion of the external auditory canal,

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are these things called the fissures of santorini,

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which extend inferiorly and medially

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into the parapharyngeal space.

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And so, the irrigation under pressure actually drives the

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pseudomonas into the skull base, leading to spread of

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the infection to the longest musculature, the clivus,

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the carotid artery and the parapharyngeal space.

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This is a deadly disease.

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It's not quite as deadly as what was in the pre

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antibiotic era where we said

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it had a 70% mortality rate.

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At this juncture, we're probably at about

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20% mortality rate, which is still very high.

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And the reason is because the patient, who's typically

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diabetic, has a hard time fighting

4:09

off this pseudomonas infection.

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We are talking here about mastoiditis

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and middle ear cavity disease.

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I want to just mention one other factor, and that is

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that from the middle ear cavity and the mastoid air

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cells, you have the potential to spread to the jugular

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foramen the sigmoid sinus and the transverse sinus

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as one of the complications of otomastoiditis.

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In this case we see a thrombus in

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the transverse sinus of the brain.

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It's outlined by a little bit of contrast enhancement,

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and that may lead into the sigmoid sinus, and from there,

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into the jugular vein and potentially be another

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source of septic thromboemboli into

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the lung. From the middle ear cavity,

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you can also lead to meningitis by erosion of the

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tegmen tympani, extending to the meninges of the

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middle cranial fossa floor. And from there, we

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can also involve the cavernous sinus.

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So otomastoiditis has lots and lots of potential

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destructive complications.

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They include bony destruction with

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osteomyelitis at the skull base, you can have a

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subperiosteal abscess, which we've shown

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an example for in the oral orbits.

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You could have spread to the extraaxial space and

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meningitis and epidural abscess. You could have

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cranial nerve involvement as you have spread to the

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petrous apex, taking out the meckel's cave and the 6th

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cranial nerve in gradenigo syndrome. That's G-R-

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A-D-E-N-I-G-O. And then thrombosis of the venous sinuses.

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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