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Demyelinating lesions begin with the appearance of some areas named NAWM (normal appearing white matter) which despite its name, is abnormal in several parameters. These areas show axonal transections and stressed oligodendrocytes (the cells responsible for maintaining the myelin), and randomly, they show clusters of activated microglia named ...
Fluid-attenuated inversion recovery (FLAIR) is a magnetic resonance imaging sequence with an inversion recovery set to null fluids. For example, it can be used in brain imaging to suppress cerebrospinal fluid (CSF) effects on the image, so as to bring out the periventricular hyperintense lesions, such as multiple sclerosis (MS) plaques. [ 1 ]
Normally two different kind of lesions appear on a normal MRI: T2-hypertense lesions and T1-hypointense. The first one are demyelinating lesions and appear brighter than the surroundings in T2-MRI. The T1-hypointense are areas less dense than the surrounding NAW, and appear black on T1-MRI. They are mainly axonal degeneration areas.
MRI scans showing hyperintensities. A hyperintensity or T2 hyperintensity is an area of high intensity on types of magnetic resonance imaging (MRI) scans of the brain of a human or of another mammal that reflect lesions produced largely by demyelination and axonal loss.
Axial T2 FLAIR sequence MR image of a middle-aged man with leukoaraiosis. MRI image: Leukoaraiosis in a 90-year-old patient with cerebral atrophy. 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 ...
MRI-abnormal areas with hidden damage appear in the brain and spine (NAWM, NAGM, DAWM). Some clusters of activated microglia, axonal transection and myelin degeneration are present. [7] [8] [9] Leaks in the blood–brain barrier appear and immune cells infiltrate, causing demyelination. [10] and axon destruction. [11]
A more specific MRI, Fluid attenuation inversion recovery (FLAIR) MRI show the signal intensity of the brain. Subjects with tumefactive multiple sclerosis may see a reduction of diffusion of the white matter in the affected area of the brain. [11]
Brain lesions associated with a clinically isolated syndrome may be indicative of several neurological diseases, like multiple sclerosis (MS) or neuromyelitis optica. In order for such a diagnosis, multiple sites in the central nervous system must present lesions, typically over multiple episodes, and for which no other diagnosis is likely.