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Normal Brain MRI in Patients with NF1

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This is an MRI of the brain

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in a one-and-a-half-year-old child

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that has clinical features

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of neurofibromatosis type 1.

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So the MRI of the brain is being performed

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as a baseline evaluation and to see if

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there's any intracranial manifestations.

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So, we look at the classic places that

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we look for myelin vacuolization.

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We look at the globus pallidus,

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and we're not definitely seeing it.

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We look at the thalami,

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and we're not seeing anything convincing.

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We look at the brainstem,

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we're not seeing any abnormalities.

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And the cerebellum, we're not.

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So, patients with neurofibromatosis type 1,

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especially when they're young,

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can actually have MRIs of the brain

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that look normal.

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But how do you report that?

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What do you do when the geneticist or the

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pediatrician sends you an MRI in a patient

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where they clinically know the patient

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has neurofibromatosis type 1?

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And you're saying the MRI

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of the brain is normal?

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Well, those are not incompatible entities,

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especially in young children,

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there are definitely times where there is

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either low lesion burden or normal.

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So how do I report that,

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and how do I tell them?

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Well, if it's a known diagnosis

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of neurofibromatosis type 1, I will say,

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at the impression,

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MRI of the brain is within normal limits.

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But then I will follow it with

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a statement such as,

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there are no intracranial stigmata of

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neurofibromatosis type 1 at the present time.

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That's a way of sort of saying, well,

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I know the patient has NF 1

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because you told me that.

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I know what NF 1 looks like

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because this is one of the things that I do,

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and I'm not seeing those things,

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and you're not seeing them at the present

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time is also sort of conveying

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to them that, you know

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that two or three years from now,

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there may be lesions.

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We know myelin vacuolization occurs over time.

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We know that.

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Now, this patient also,

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their optic nerves,

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this is something I would consider to be a

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normal degree of tortuosity at this age,

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but probably upper normal.

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So, I don't know if I would necessarily

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describe it in the report,

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given that, if the patient has NF one,

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that they're going to get follow-up exams.

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But what if this was instead of a patient

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that had a known diagnosis of NF 1,

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what if this was a patient with some

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Café-au-lait spots, some birthmarks that they said,

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well, maybe they have NF 1?

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Well, that's a little bit different.

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And in that case,

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saying there's subtle tortuosity of the

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optic nerves without discrete lesion

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at least can let them know,

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well,

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they may not have confirmed a diagnosis of NF 1,

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but they should at least keep looking,

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because it is very possible that the rest

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of the brain doesn't show signs

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of NF 1 at the present time.

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This very subtle tortuosity of the optic

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nerve could be the early manifestation

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of NF 1 changes.

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And if the patient didn't get continued

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follow-up, they would never know.

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So, just because an MRI of the brain

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looks normal in NF 1,

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that does not mean that the patient

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doesn't have NF 1.

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It just means that there's no macroscopic

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manifestations at this time.

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Now, while we're not seeing any discrete

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lesions in the brainstem,

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I'm going to zoom in, and we see these

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paired hyperintense abnormalities right here.

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What is this?

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Is this myelin vacuolization?

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It's not.

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So if we look at the brainstem anatomy,

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here's the midbrain, the pons,

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the medulla,

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and where the pons and the medulla join

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is the pontomedullary sulcus.

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And this right here is volume averaging of

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CSF within the lateral aspect

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of the pontomedullary sulcus.

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So, this does not represent areas

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of myelin vacuolization.

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So this patient, again,

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does not have any discrete convincing

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lesions of myelin vacuolization

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at the present time.

Report

Description

Faculty

Asim F Choudhri, MD

Chief, Pediatric Neuroradiology

Le Bonheur Children's Hospital

Tags

Syndromes

Pediatrics

Neuroradiology

Neuro

MRI

Brain

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