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Transdural Herniation of the Spinal Cord

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Here is another patient who had a thoracic

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myelopathy. On the sagittal T1-weighted,

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sagittal T2-weighted and post-gad

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T1-weighted scans that are depicted here,

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we see deviation of the spinal cord anteriorly

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at the T6 and T7 level.

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This is best seen on the T2-weighted scan.

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Now, we're not seeing any of the border

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of an arachnoid cyst,

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but we do see that widening of the

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CSF space at the same level.

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So our differential diagnosis here includes an

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acquired arachnoid cyst, leading

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to the spinal cord deviation.

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And we want to look on the axial scans to see

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whether there is cord signal abnormality

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that might account for that myelopathy.

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Let's look at the axial scans through

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the region of interest.

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So what we see is that there is indeed

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deviation of the spinal cord anteriorly,

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and we also see a small amount

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of central high signal intensity within the spinal cord.

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So this may account for the patient's

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myelopathy. This, however,

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is not an example of an arachnoid cyst.

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This is what is known as transdural herniation

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of the spinal cord and this is best

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depicted on a CT myelogram.

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So let's go to the CT myelogram that was

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performed, as well. Here is the CT myelogram,

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which I will magnify for you and show the same

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element of deviation of the spinal cord

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anteriorly with widening of

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the subarachnoid space.

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On the axial scans, you'll see that the spinal

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cord is unusually deviated anteriorly and you

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may get the sense that there is a portion of

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the spinal cord which may even

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be outside the thecal sac.

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That is the term that is used with transdural

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herniation of the spinal cord.

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It is a cause of a thoracic myelopathy,

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or is the cause of a myelopathy, is secondary

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to a rent in the thecal sac with a spinal

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cord herniating through it.

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And that rent in the thecal sac most commonly

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is secondary to either trauma or degenerative disease.

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In this case, there is just mild degenerative changes.

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But that must have, as you can see here,

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a small osteophyte,

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which may have led to the tearing of the dura

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and allowing the spinal cord to herniate

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through the dura into the extradural space and

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leading to an appearance that

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simulated an arachnoid cyst.

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So this is what's known as TDH, transdural

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herniation of the spinal cord.

Report

Description

Faculty

David M Yousem, MD, MBA

Professor of Radiology, Vice Chairman and Associate Dean

Johns Hopkins University

Tags

Spine

Neuroradiology

Musculoskeletal (MSK)

MRI

Acquired/Developmental

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