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Intradural Extramedullary Lesion Differential Diagosis

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Well, if you've watched any of the Dave Yousem presentations,

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you know I like mnemonics.

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And my favorite mnemonic

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for describing pathology in the central

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nervous system is VITAMIN C and D.

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This refers to vascular, infectious, traumatic,

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acquired, metabolic, idiopathic, neoplastic,

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congenital and drugs. With respect to

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the intradural extramedullary space,

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neoplasms are going to be the predominant abnormality,

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followed by some of the congenital and

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infectious and vascular lesions.

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But we're going to focus mostly on the neoplastic

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category. Fortunately, as I said,

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this is a happy zone,

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because most of the lesions in the neoplastic

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category are benign lesions, and of these,

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schwannomas and meningiomas tend to predominate.

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So here are the intradural extramedullary neoplastic category lesions,

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and they are the nerve sheath tumors.

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So, in general,

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a generic term would be nerve sheath tumors.

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And within that, we would have schwannomas

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and neurofibromas, and potentially even

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plexiform neurofibromas, or malignant peripheral nerve

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sheath tumors. Of the nerve sheath tumors,

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schwannomas are more common than neurofibromas.

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The other neoplasms in the intradural extramedullary

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space are predominated by benign conditions.

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So we have our nerve sheath tumors.

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Our next most common is going to be a meningioma,

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obviously occurring in the dura of the thecal sac.

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And then the other benign tumors

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would be a paraganglioma.

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And down in the filum terminale region,

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we have ependymomas. They may say ependymomas?

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I thought we discussed those in the intradural

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extramedullary compartment.

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And that is true, that when they occur in the spinal

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cord, they are obviously intramedullary lesions,

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but the filum terminale is not considered

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part of the spinal cord.

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It's considered a fibrous tissue at the end of

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the spinal cord, beyond the spinal cord.

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And so, tThese are usually characterized as intradural

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extramedullary lesions, and they are usually low

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grade neoplasms or relatively benign.

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The one neoplasm that is malignant that we have

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to worry about is subarachnoid seeding,

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and this is usually from a CNS primary tumor,

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generally in the brain that is shedding cells into the

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subarachnoid space and infiltrating the spinal canal.

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Of the nerve sheath tumors,

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the most common are going to be schwannomas.

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And these nerve sheath tumors are most commonly

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intradural extramedullary. However,

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sometimes you will find them in the extradural

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compartment and sometimes you will find them spanning

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intradural and extradural, so-called dumbbell lesions,

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which have a component that is still within the thecal sac

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and a different component that is outside the thecal sac.

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So these are our nerve sheath tumors.

Report

Description

Faculty

David M Yousem, MD, MBA

Professor of Radiology, Vice Chairman and Associate Dean

Johns Hopkins University

Tags

Spine

Neuroradiology

Neoplastic

Musculoskeletal (MSK)

MRI

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