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Optic Neuritis, Multiple Sclerosis

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This was a 34-year-old with right-sided visual loss.

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For the evaluation of patients with visual loss,

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we much prefer MRI over CT scan,

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both for the evaluation of the optic nerve,

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as well as for intracranial causes of visual loss.

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In this case, we have the T1-weighted scan,

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the T2-weighted scan, and the postgadolinium

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fat-suppressed T1-weighted scan.

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As we scroll through the images,

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we identify abnormal signal intensity

0:35

in the right optic nerve.

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This is well demonstrated on the T2-weighted scan

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where fat suppression has been applied, and we see that

0:44

the right optic nerve is bright in signal intensity,

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and we've lost the distinction between the

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optic nerve and the optic nerve sheath.

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Contrast that with the normal left side

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where the optic nerve is seen,

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as well as the CSF of the optic nerve sheath.

1:02

On the postgadolinium-enhanced scan.

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We also note that the optic nerve

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is showing contrast enhancement.

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Contrast that with the contralateral optic nerve,

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which is non-enhancing.

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As I mentioned previously,

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you may see a little faint enhancement

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of the optic nerve sheath meninges in the normal case.

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Continuing to scroll.

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We want to see where this lesion

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extends intracranially.

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At this level,

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we are at the beginning of the orbital apex.

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At the orbital apex,

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we continue to see the orbital fat,

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but we haven't extended intracranially.

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We see now that we have the optic nerves that are of

1:43

similar signal intensity, and therefore,

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have returned to normal signal.

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And again, we are not seeing the same discrepancy in the

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contrast enhancement of the optic nerves.

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So, this is a lesion that is confined to the

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intraorbital portion of the optic nerve.

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We continue to scroll more posteriorly

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and we come to the optic chiasm.

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The optic chiasm on the T2-weighted scan,

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because it is a white matter tract,

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has signal intensity similar to the white matter

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elsewhere in the brain, and we don't see any areas of

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high signal intensity to suggest it is involved.

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Let's go back and re-scroll and look at the

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size of the optic nerve sheath complex.

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For that, I prefer to look at the T1-weighted scans.

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On this T1-weighted scan,

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we see that the optic nerve sheath complex, outlined by fat,

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is similar in size between the right and the left side.

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And therefore, making it less likely that this represents a tumor.

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So again,

2:50

we are looking at the optic nerve sheath complex from

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right to left on the T1-weighted scan,

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outlined in the fat of the orbit of the intraconal space.

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Given a young woman who has visual loss and abnormal

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signal intensity, without optic nerve enlargement,

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the most likely diagnosis is going to be optic neuritis.

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When one considers the diagnosis of optic neuritis,

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there are multiple possible etiologies,

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including infectious, inflammatory, and demyelinating disorders.

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Once we start proposing that this could

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be a demyelinating disorder,

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we better look carefully at the brain.

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As we were scrolling through the orbits,

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we might have noted

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that there were abnormal areas of signal intensity

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within the brain, associated with the lateral ventricles.

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However, this is much better seen on the FLAIR imaging.

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This is the FLAIR image through the brain.

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What we see on the FLAIR imaging is

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a little bit of motion artifact.

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But even without a great-quality scan,

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we note that there are periventricular areas of high

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signal intensity around the frontal horns of the

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lateral ventricles, and also at the top

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of the left lateral ventricle.

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If one has optic neuritis in association

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with intracranial lesions,

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it raises the possibility of multiple sclerosis.

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80% of patients who have multiple sclerosis,

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at some point during their disease, will have an

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episode of optic neuritis.

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However, the same is not true with regard to

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patients who have optic neuritis.

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We say that 50% of patients who have optic neuritis

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will have it as an isolated lesion without

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any other systemic manifestations.

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The other 50%, over the course of their lifetime,

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will ultimately carry the diagnosis of multiple sclerosis.

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However, if one has lesions on the brain MRI,

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at the same time as the optic neuritis presents itself,

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the likelihood of having multiple sclerosis ultimately,

5:10

as a final diagnosis increases by threefold.

Report

Description

Faculty

David M Yousem, MD, MBA

Professor of Radiology, Vice Chairman and Associate Dean

Johns Hopkins University

Tags

Orbit

Non-infectious Inflammatory

Neuroradiology

Neuro

MRI

Head and Neck

Brain

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