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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.
Fractional anisotropy (FA) is a scalar value between zero and one that describes the degree of anisotropy of a diffusion process. A value of zero means that diffusion is isotropic, i.e. it is unrestricted (or equally restricted) in all directions.
Cranial imaging is not used for diagnosis of this condition. However, if an MRI is performed, it may show cortical restricted diffusion with unusual characteristics of reversible T2 hypointensity in the subcortical white matter. [10]
Evidence from subcortical small infarcts suggests that motor fibers are somatotopically arranged in the human corona radiata. Following subtotal brain damage, localization of the corticofugal projection in the corona radiata and internal capsule can assist in evaluating a patient's residual motor capacity and predicting their potential for functional restitution.
SAH in CAA usually occurs in those who age more than 60 years, temporary motor and sensory deficits, and intracranial bleed in white matter adjacent to cerebral cortex. Basal ganglia, posterior fossa, and brainstem are spared. Boston criteria is used to determine the likelihood of a cerebral hemorrhage due to CAA.
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.
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.
Face of the giant panda sign; Axial T2-weighted MRI of the brain at the level of the midbrain showing the characteristic ‘face of the giant panda’ sign, with normal red nuclei and substantia nigra (pars reticulata) against a background of hyperintensity in the tegmentum, as well as hypointensity of the superior colliculi