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Head CT showing periventricular white matter lesions. Leukoaraiosis is a particular abnormal change in appearance of white matter near the lateral ventricles. It is often seen in aged individuals, but sometimes in young adults. [1] [2] On MRI, leukoaraiosis changes appear as white matter hyperintensities (WMHs) in T2 FLAIR images.
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. [citation needed] Hyperintensities are often seen in auto immune diseases that have effects on the brain. [6]
Mild Moderate Severe ARIA-E Edema: FLAIR hyperintensity confined to sulcus and/or cortex/subcortical white matter in one location < 5 cm FLAIR hyperintensity 5 to 10 cm, or more than 1 site of involvement, each measuring < 10 cm FLAIR hyperintensity measuring > 10 cm, often with significant subcortical white matter and/or sulcal involvement.
Others classify them as hippocampal, cortical, and WM lesions, [23] and finally, others give seven areas: intracortical, mixed white matter-gray matter, juxtacortical, deep gray matter, periventricular white matter, deep white matter, and infratentorial lesions. [24] The distribution of the lesions could be linked to the clinical evolution [25]
The idea of DAI first came about as a result of studies by Sabina Strich on lesions of the white matter of individuals who had sustained head trauma years before. [37] Strich first proposed the idea in 1956, calling it diffuse degeneration of white matter; however, the more concise term "diffuse axonal injury" came to be preferred. [38]
White matter is the tissue through which messages pass between different areas of grey matter within the central nervous system. The white matter is white because of the fatty substance (myelin) that surrounds the nerve fibers (axons). This myelin is found in almost all long nerve fibers, and acts as an electrical insulation.
Fluid-attenuated inversion recovery (FLAIR) [2] is an inversion-recovery pulse sequence used to nullify the signal from fluids. For example, it can be used in brain imaging to suppress cerebrospinal fluid so as to bring out periventricular hyperintense lesions, such as multiple sclerosis plaques.
The gray matter remains normal in all characteristics while the white matter changes texture, becoming soft and gelatinous. Rarefaction of the white matter is seen through light microscopy and the small number of axons and U-fibers that were affected can also be seen. Numerous small cavities in the white matter are also apparent.