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Case 35 - Diskitis: Summary

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0:01

Let's summarize the findings of the two cases of diskitis and osteomyelitis

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that we just saw. In diskitis and osteomyelitis, we see disk and endplates

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brighter on T2 weighted scan, dark on T1 weighted scan, and they may

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show contrast enhancement. Erosion of the endplates will help you in distinguishing

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degenerative Modic Type 1 changes from infectious inflammatory changes.

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If you have a paravertebral mass, that's not going to occur in the

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degenerative changes. And if it's in the soleus musculature, you may suggest

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that it represents a TB abscess in the soleus. Beware dialysis arthropathy.

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This also can be dark on T1, bright on T2 with endplate erosion,

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sort of like the amyloid deposition disease in the endplates that can simulate

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diskitis and osteomyelitis. Here's an example in the thoracic spine. We

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saw a couple lumbar spine cases, here you have bright signal intensity extending

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from the vertebral body into the disk. There's an epidural component that's

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compressing the spinal cord with abnormal signal in the spinal cord on the

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T1 weighted scan, darkened signal intensity on the post gad scan.

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We see the enhancement in the disk, which should not be there,

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as well as the enhancing inflammatory disease in the epidural space.

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Remember that the adjacent spaces of the retropharyngeal space and prevertebral

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space may show bright signal intensity on T2 weighted scan. If we're in

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front of the longus musculature, we're in the retropharyngeal space. If

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we're behind the longus musculature, we're in the prevertebral space.

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Here we have a post gadolinium and a T2 weighted scan. We notice that

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there is extensive inflammation that is present in the anterior epidural

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space behind the vertebral bodies, but we're also seeing bright signal intensity,

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which is posterior to the longus musculature, in this case, in the prevertebral

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space. That's not as important, clearly, as what's happening more posteriorly,

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and with the compression of the spinal cord by this inflammatory mass.

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Here's another example. This patient had a posterior epidural space abscess.

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This is the non enhancing component of the purulent material, suppurative

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material abscess in the posterior epidural space. Notice that the disks

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and the vertebral body are not showing enhancement and they're not bright

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in signal intensity on the STIR image. In this case, the posterior epidural

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abscess was from a genitourinary tract primary infection, with haematogenous

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spread to the posterior epidural space. Having an epidural abscess in association

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with a genitourinary tract infection, be it of the kidneys or in the

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bladder, is not that unusual and should be sought after if you don't

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see infection primarily from the vertebral column. Let me just go back and

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note that these areas here which are bright on T1 post contrast and

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bright on the T2 weighted scan, represent Hemangioma of bone and are not

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related to the infection. How do we distinguish between a phlegmon versus

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an abscess? This is the question that we've been asking when we talked

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about tonsillitis and peritonsillar abscess. When we talked about retropharyngeal

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space with phlegmon versus abscess, you wanna try to see a rim of

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gadolinium enhancement and fluid signal intensity and an abscess, as opposed

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to, sort of, a more diffused gadolinium enhancement

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with a phlegmon without a central absence of enhancement.

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Both of these will be seen in association with the diskitis osteomyelitis

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with bright signal in the endplates on T2 weighted scan, and enhancement

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of the endplates that occurs in about 97% of patients with diskitis and

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osteomyelitis. One thing that is unique about tuberculosis is, sometimes

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you will see that the inflammatory tissue is actually not all that bright

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on T2 weighted scan. It can be intermediate in signal intensity and that's

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thought to be part of that granulomatous collection that occurs in this

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type of infection. Here is another example of a patient who has a

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rim enhancing collection in the posterior epidural space, and this is located

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at the C7 T1 T2 level. Here you have it on the T2 weighted scan

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with an associated normal signal intensity to the spinal cord.

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The spinal cord may be bright in signal intensity on these type of

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examinations, not just because of compression by the collection, but it

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may be bright in signal intensity because of associated thrombophlebitis

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and venous ischemia that can injure the spinal cord. Here on the

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gradient echo scan and the post gadolinium enhanced scan, we find an interesting

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observation. This collection is in the subdural space.

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Notice that the edge of the dura here

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is actually continuous posteriorly rather than anteriorly. This is because

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this is a collection in the subdural space rather than in the epidural

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space, where that low signal intensity would be displaced anteriorly. So

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this is an a subdural empyema in a patient who had

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fever and neck pain.

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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