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So here is a 31-year-old female

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presenting with headaches.

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And the MRI shows a rather well-defined

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mass in the right medial temporal lobe.

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And you can see that the tumor is

0:15

kind of homogeneously bright,

0:17

very well-defined on T2 two weighted images.

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But more importantly is majority of the tumor is

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dark in the central part on the FLAIR images,

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except this thin peripheral bright

0:29

rim on the FLAIR images.

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And this is what we call a T2 FLAIR mismatch sign.

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And typically, these tumors also do not

0:39

show any enhancement.

0:39

As you can see,

0:40

there is no enhancement

0:42

on the post-contrast images.

0:43

And majority of these tumors also show very

0:47

facilitated diffusion in this

0:49

central portion of the tumor,

0:51

which is almost gelatinous

0:54

and very soft on surgery.

0:57

Neurosurgeons will classically

0:59

tell you that these are

1:00

gelatinous soft tumors,

1:01

which are very easy to resect.

1:03

And this is what we have described

1:07

as the T2 FLAIR mismatch sign.

1:09

A classic example in a younger patient.

1:12

And once we see this sign,

1:13

we know that this tumor is going to be IDH-mutated

1:17

non-codeleted astrocytoma.

1:20

And this is one example over here.