Learning objectives
To highlight the importance of fluid-attenuated inversion recovery (FLAIR) sequence in magnetic resonance imaging (MRI) in standard examination of brain parenchyma.
To illustrate the spectrum of pathological findings in brain with hypointense signal appearance on FLAIR images
and to emphasize difference with normal findings in pediatric population with similar signal changes.
Background
FLAIR has high sensitivity in discovering pathological lesions in brain parenchyma,
whereas most of the lesions demonstrate hyperintensity in comparison to the normal brain parenchyma.
In a small number of lesions FLAIR heterogeneous or hypointense signal can be observed.
- FLAIR MR imaging has assumed an important role in routine brain imaging
- Enhance the visibility of several abnormal lesions compared with T2-weighted spin-echo MR imaging sequences
Signal intensity (SI) is result of complex interactions between the relaxation times (T1 and T2) of the lesion...
Imaging findings OR Procedure details
Hypointensity on FLAIR images has been described as part of some infectious diseases,
during several inflammation processes,
or in the lesions with water,
lipid or paramagnetic substances content.
Several brain tumors may demonstrate characteristic hypointense FLAIR signal,
including meduloblastoma,
rarely lymphoma,
but also some types of cortical tubers.
Inherited metabolic disorders,
like adrenoleukodistrophy,
may also present with the central zone low signal intensity within the affected white matter.
However,
it is also observed that in the pediatric patients during the normal myelination process the white...
Conclusion
FLAIR hypointensity could be normal finding in pediatric patients during myelination.
In adult population only a few of pathological conditions appear as FLAIR low signal intensity.
Radiologists should be aware of these findings and the fact that FLAIR hypointensity could correlate with severity of several diseases.
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