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This is an MRI of the brain,

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an eleven-year-old child with headache.

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At first glance,

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we're not seeing any big mass,

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we're not seeing any mass effect.

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We're not seeing any midline shift.

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We're not seeing any signs of hydrocephalus.

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So at first approximation,

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we're not seeing anything majorly abnormal.

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If we look closely at the thalamus,

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we're seeing some subtle hyperintense signal

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in the thalami, bilaterally patchy.

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Now, the thalamus is gray matter,

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but it actually is so heavily myelinated,

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because there are so many connections coming to

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and from the thalamus that it actually,

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typically, in a myelinated individual,

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has signal that looks very

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similar to white matter.

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See this white matter here

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of the optic radiations,

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this dark signal on T2-weighted imaging,

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that's typically what the thalamus looks like.

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Here we're seeing these heterogeneous

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bright areas.

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That brings about a classic differential of

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things with bilateral thalamic abnormalities.

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Now,

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there's acute disseminated encephalomyelitis,

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for instance,

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and other acute demyelinating disorders,

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such as anti-MOG antibodies.

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Those won't usually present with

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headaches as an outpatient.

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Those are going to be more acute presentations

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with neurologic deficits.

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There is bithalamic gliomas.

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Now, a bilateral thalamic glioma is usually not

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going to be this patchy area of infiltration.

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It will typically be expansile,

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and when it goes across,

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it will be crossed through the mass intermedia

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or the interthalamic adhesion.

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So, I don't think that this

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is a bithalamic glioma.

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There's something called an artery

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of percheron infarction,

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which is related to a stroke from basilar perforators.

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And in some individuals,

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a single trunk of the basilar perforator

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supplies the medial aspect of both thalami.

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Well,

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an artery percheron infarction will first of all

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be the medial aspect of both thalami,

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not this patchy involvement of the

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whole thalamus bilaterally.

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And it will also show diffusion restriction.

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So that's not what this is.

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Now, you can also get a venous infarction

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and venous congestion from thrombosis

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of the vein of Galen and internal cerebral veins.

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Well, on this T2-weighted image,

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we're seeing normal T2 flow voids in the

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posterior aspect of the internal cerebral veins

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in the vein of Galen.

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We're also not seeing any signal abnormality

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on diffusion-weighted imaging.

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And additionally,

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that's also an abnormality that would

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typically be the medial thalamus,

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and it would also be an abnormality that would

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occur as more of an acute presentation,

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not an outpatient for headaches.

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Now, there's also Wernicke's encephalopathy.

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Wernicke's encephalopathy is a bilateral

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thalamic abnormality,

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medial thalami that you don't want to miss.

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You want to be aware it,

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you want it to come to your mind.

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Well, that also is going to present more in the

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acute setting. Now, in an acute setting,

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if you see bilateral thalamic abnormalities,

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even if you may think it's ADEM,

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there's very few entities where

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giving Thiamine replacement,

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which is the treatment for Wernicke's encephalopathy,

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there's very few entities

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where that would hurt.

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So, if I see a patient with an acute abnormality,

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where there's bilateral thalamic abnormalities,

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I'll often sort of suggest,

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is there a contraindication to Thiamine?

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That's my way of saying, well,

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it may not be Wernicke's,

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but in the off chance that it is,

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it wouldn't hurt.

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There's another bilateral thalamic abnormality

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that comes up in differentials,

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that's often discussed on board exams.

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That's Creutzfeldt-Jakob disease.

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Now, that's very rare

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and that's even more rare in children.

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So, that's not something I'm worried

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about in an adolescent,

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but that is at least something to be aware of

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or thinking about with bilateral

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thalamic abnormalities.

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The other entity with bilateral thalamic

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abnormalities is neurofibromatosis type 1.

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Now, we're not seeing a lot of other abnormalities

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of NF 1 here, except if we look closely,

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we see signal abnormality in

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the right globus pallidus.

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So, we're not seeing other definite abnormalities.

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But it turns out that this child with

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headaches actually had neurofibromatosis type 1.

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Just a very subtle clinical case of it.

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So, in general,

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most of the patients with neurofibromatosis type 1

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that get MRI,

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we know in the beginning that that's

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what their diagnosis is.

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But every now and then, there's going to be

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a patient where they get an MRI,

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and we don't know that that's

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what the diagnosis is.

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And this is one of those examples.