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I just spoke about optic neuritis

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and multiple sclerosis.

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Let's talk about Neuromyelitis optica

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spectrum disorder or NMOSD.

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NMO was initially thought to represent a

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monophasic disorder in which one had

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optic neuritis and transverse myelitis.

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Since the initial description

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over 20 years ago,

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we've had a greater and greater

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understanding about this entity.

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And now there is considered a separate

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and distinct pattern of illness compared

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to multiple sclerosis and compared to

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isolated optic neuritis and compared to,

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for example,

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clinically isolated syndrome.

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What one has for major criteria of NMOSD

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is optic neuritis in one or more eyes,

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transverse myelitis with spinal cord

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lesions that extend over multiple

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segments. On T2 weighted imaging,

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there can be no evidence for sarcoidosis,

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vasculitis or other collagen vascular

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diseases. These are the major criteria.

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Minor criteria may show

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minor abnormalities,

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not fulfilling McDonald criteria,

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but nonspecific T2 weighted scans

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predominantly in the following

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locations: the dorsal medulla,

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which may be in continuity with an

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upper cervical spine cord lesion,

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the hypothalamus,

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the brain stem, or around

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the corpus callosum.

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NMO has a high rate of aquaporin-4

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antibodies found in serum or CSF.

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Now, we may see aquaporin-4 negative NMO,

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but those examples are rare.

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What is NMOSD? Spectrum disorder.

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Neuromyelitis optica spectrum disorder.

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It's really considered an attack by

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these autoimmune aquaporin-4

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antibodies on the astrocytic foot

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processes of the astrocytes as they link

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to the membranes. In addition,

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you have that attack that may occur

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secondarily on the white matter.

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There is another entity that is often

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described in association with NMOSD,

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and those are anti-MOG antibodies.

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MOG being an acronym for myelin

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oligodendrocyte glycoprotein,

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and in some ways, patients.

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With anti-MOG and anti-aquaporin-4

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antibodies may have overlapping

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symptoms.

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They too, the anti-MOG patients may have

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optic neuritis, transverse myelitis,

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as well as brain stem white matter lesions.

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But this disease in general is

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more fulminant than NMOSD.

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With NMO, one has optic neuritis in one

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or more lesions or eyes.

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The NMO manifestation of optic neuritis

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is different than isolated optic neuritis

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or multiple sclerosis optic neuritis

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in that you may see a very long,

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extensive white matter lesion in the

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optic nerve of patients with NMO.

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In other words,

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just as we have short segment disease

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in the spine with MS, but long,

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extensive segment disease in NMO,

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you may have short segment disease in

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the optic nerve with MS or isolated

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optic neuritis, whereas you have a long,

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longitudinal, extensive disease in the

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optic nerve with NMO.

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What do we mean by longitudinally,

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extensive disease?

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By that, we mean that the NMO lesions

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usually span greater than three

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vertebral body lengths.

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In fact, these lesions may be multiple.

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Here on the Sagittal T2 weighted scan,

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you see something that is spanning

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basically from the mid C2 level

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through C3 and C4 and

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extending down to C5.

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There's an additional lesion here which

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again is spanning three different

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vertebral body segments.

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So longitudinally extensive demyelinating disorder.

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At Johns Hopkins,

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we evaluated patients who had

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neuromyelitis optica spectrum disorder

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and evaluated the correlation

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with the brain MR findings.

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This was done by one of my outstanding

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colleagues, Izlem Izbudak,

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who works with the neuroimmunologist.

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She found that 14 out of 27 patients had

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the typical NMO lesions that are located

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around the hypothalamus thalamus,

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around the fourth ventricle or

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around the cerebral aqueduct,

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as well as or located in the dorsal

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medulla near the area postrema.

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The area postrema is just adjacent to

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the inferior posterior portion

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of the fourth ventricle.

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This is from the literature on NMO

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showing lesions that are typical of

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neuromyelitis optica spectrum disorder.

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Here you can see lesions that are.

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Typically in the hypothalamus,

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in the periaqueductal gray matter region

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in the central aspect of the pons,

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as well as at the dorsal

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aspect of the medulla.

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This region over here and here

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would be our area postrema,

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which theoretically is in charge

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of nausea and vomiting,

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as well as the clava,

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the clava being this little

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notch here in the medulla.

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And this is spelled clava, the clava.

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So along here, area postrema and clava.

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And you're seeing that on

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the axial scan as well.

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Why do we care about the differential

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diagnosis between multiple sclerosis

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versus neuromyelitis optica

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spectrum disorder?

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They're both demyelinating lesions.

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Well, interestingly,

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the current drugs that are used

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for multiple sclerosis,

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including interferon and some of the

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anti-antibody agents,

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may actually exacerbate NMO.

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And therefore,

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we don't want to mistake the lesions of

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NMO for multiple sclerosis because the

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patient's symptoms will get worse.

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With respect to NMO,

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standard treatment is IV steroids

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as opposed to interferon,

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and if the patient is having severe

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transverse myelitis or optic neuritis,

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plasma exchange long term.

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You may also see some of the different

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autoantibody agents and imuran

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long term for NMO.