The prevalence of white matter lesions in the general population is reported to be between 39 to 96% 11. EpidemiologyĬhronic small vessel disease is more common with increasing age. However, hemorrhagic manifestations of small vessel disease ( cerebral microbleeds, intracerebral hemorrhage, and cortical superficial siderosis) are also important to consider for differential diagnosis and therapeutic reasons 15,16. The nature of infarcts and white matter changes are primarily ischemic, so other terms used include small vessel chronic ischemia, microvascular ischemia, ischemic microangiopathy, and variants of the above terms such as ischemic white matter disease. Many variant terms for this entity presume an age-related etiology, such as age-related white matter hyperintensities/changes/disease/damage 16, although noting that not all age-related white matter changes are attributed to small vessel disease 14. The most common is arteriolosclerosis, or age and vascular risk factor related small vessel disease, which based on a progressive clinical syndrome of cognitive impairment and compatible imaging features is diagnosed as Binswanger disease 14, although this term has fallen in popularity. Many etiopathogenic types of small vessel disease are described (see below). Less commonly, the lesions are called unidentified bright objects on MRI, but this term has also confusingly been used to refer to the focal areas of signal intensity in brains of children with neurofibromatosis type 1, which is an unrelated process. Similar terms focussed on the white matter include white matter disease, white matter damage, and leukoencephalopathy (the latter usually used in the context of CADASIL) 16. These lesions are also called white matter lesions, white matter hyperintensities (for MRI), or white matter changes 16. The term leukoaraiosis is a radiological descriptor applied to white matter hypodensities on CT and high signal changes on T2-weighted MRI of presumed vascular origin 14,16. Analogous signal changes in the subcortical gray matter and brainstem are typically excluded from discussion unless explicitly stated, leading to terms that focus on small vessel disease of white matter 16. The latter has received much attention in particular and is the focus of this article. With respect to morphologic changes visible on imaging, small vessel disease includes small subcortical (lacunar) infarcts (of deep gray nuclei and deep white matter), hemorrhages, perivascular spaces, and diffuse white matter changes 14,16. The arterial bed has been a primary focus of the literature, with arterial small vessel disease being a proposed term for this entity, but venous collagenosis is also responsible for some of the changes 15. The small vessels involved are too small to visualize by imaging, so imaging focuses on their sequelae. With respect to anatomy, small vessels include arterioles, capillaries, and small veins/venules. There is wide variability in the literature regarding terminology for small vessel disease.
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