T2-FLAIR mismatch sign

<aside> 💡

Tumor should not show contrast enhancement.
Cystic/necrotic regions should not be counted as FLAIR-suppressed.
FLAIR suppression may be inhomogeneous within the tumor.
No evident surrounding edema should be present.
In cortical-based tumors, T2 hypointensity corresponding to cortex does not exclude the sign.

Additional application features:

T2–FLAIR mismatch sign (AJNR Am J Neuroradiol, April 2018)

Core criteria for T2–FLAIR mismatch:

T2WI: Complete or near-complete homogeneous hyperintensity.
FLAIR: Central hypointensity with a peripheral hyperintense rim (relative to T2WI). </aside>

![Positive cases for T2-FLAIR mismatch. T2 WI show a complete and homogeneous hyperintense signal (a, c and e) while on FLAIR sequences (b, d and f) the lesions show relatively hypointense signal when compared with T 2WI, except for a peripheral rim of hyperintense signal. Note that the degree of suppression on FLAIR imaging can be uniform (d and f) or inhomogeneous (b). Also, the peripheral high signal rim can be a thin contour circumscribing the whole lesion (b), or it can be an incomplete rim (d and f, arrows). (a, b) and (e, f) were IDH-mutant 1p/19q non-codeleted diffuse astrocytomas (grade II) and C-D was an IDH-mutant 1p/19q non-codeleted anaplastic astrocytoma (grade III). FLAIR, fluid attenuated inversion recovery; IDH, isocitrate dehydrogenase; WI, weighted image.

Catarina Pinto, Carolina Noronha, Ricardo Taipa, Cristina Ramos, T2-FLAIR mismatch sign: a roadmap of pearls and pitfalls, British Journal of Radiology, Volume 95, Issue 1129, 1 January 2022, 20210825, https://doi.org/10.1259/bjr.20210825](attachment:44c55156-322c-4897-892e-fa53f8fd8ece:m_bjr.20210825.g001.jpeg)

Positive cases for T2-FLAIR mismatch. T2 WI show a complete and homogeneous hyperintense signal (a, c and e) while on FLAIR sequences (b, d and f) the lesions show relatively hypointense signal when compared with T 2WI, except for a peripheral rim of hyperintense signal. Note that the degree of suppression on FLAIR imaging can be uniform (d and f) or inhomogeneous (b). Also, the peripheral high signal rim can be a thin contour circumscribing the whole lesion (b), or it can be an incomplete rim (d and f, arrows). (a, b) and (e, f) were IDH-mutant 1p/19q non-codeleted diffuse astrocytomas (grade II) and C-D was an IDH-mutant 1p/19q non-codeleted anaplastic astrocytoma (grade III). FLAIR, fluid attenuated inversion recovery; IDH, isocitrate dehydrogenase; WI, weighted image.

Further reading: