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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, white matter hyperintensities or WMH) [1] [2] or subcortical gray matter (gray matter hyperintensities or GMH). The volume and frequency is strongly associated with increasing age. [2]
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.
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]
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.
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.
T2 weighted axial scan of a human brain at the level of the caudate heads demonstrates marked loss of posterior white matter, with reduced volume and increased signal intensity. The anterior white matter is spared. Features are consistent with X-linked adrenoleukodystrophy. Specialty: Neurology
Differential diagnosis include adenoma, myelolipoma, cyst, lipoma, pheochromocytoma, adrenal cancer, metastatic cancer, hyperplasia, and tuberculosis. [3] Some of these lesions are easily identified by radiographic appearance; however, it is often adenoma vs. cancer/metastasis that is most difficult to distinguish.
The white matter with hidden but MRI-visible damage is known as "Normal-appearing white matter" (NAWM) [136] and is where lesions appear. [22] The NAWM is considered a non-visible kind of lesion, produces disability and it is responsive to natalizumab [137] The pathology of the NAWM differs from areas near the lesions or near the cortex.