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A hyperintensity or T2 hyperintensity is an area of high intensity on types of magnetic resonance imaging (MRI) scans of the human brain or of another mammal that reflect Brain injury produced largely by demyelination and axon loss. These small regions of high intensity are observed on T2 weighted MRI images (typically created using 3D FLAIR) within cerebral white matter ( white matter lesions, Leukoaraiosis or WMH) or subcortical gray matter ( gray matter hyperintensities or GMH). The volume and frequency is strongly associated with increasing age. They are also seen in a number of neurological disorders and Mental disorder. For example, deep white matter hyperintensities are 2.5 to 3 times more likely to occur in bipolar disorder and major depressive disorder than control subjects. WMH volume, calculated as a potential diagnostic measure, has been shown to correlate to certain cognitive factors. Hyperintensities appear as "bright signals" (bright areas) on an MRI image and the term " bright signal" is occasionally used as a synonym for a hyperintensity.
Hyperintensities are commonly divided into 3 types depending on the region of the brain where they are found. Deep white matter hyperintensities occur deep within white matter, periventricular white matter hyperintensities occur adjacent to the lateral ventricles and subcortical hyperintensities occur in the basal ganglia.
Hyperintensities are often seen in auto immune diseases that have effects on the brain.
Postmortem studies combined with MRI suggest that hyperintensities are dilated perivascular spaces, or demyelination caused by reduced local blood flow.
It is also thought that WMH have a negative impact on cognition in people with Alzheimer's disease. In people with Alzheimer's, higher WMH are associated with higher amyloid beta deposits, possibly associated with Microangiopathy and reduced amyloid beta clearance.
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