However, ischemic strokes are often

associated with many of the vascular pathologies described below, which also contribute to the total vascular burden. By far, the most prevalent vascular lesions associated with VCI are related SB203580 to alterations in small vessels in the hemispheric white matter (Jellinger, 2013). These microvascular alterations result in different neuropathological lesions, which can occur in isolation but, more typically, coexist in the same brain (Table 1). Confluent white matter lesions, the imaging correlate of which is termed leukoaraiosis (Figure 3), and lacunes, small (<1.5 cm) white matter infarcts typically in the basal ganglia, are common occurrence in VCI and are strongly associated with cardiovascular risk factors, especially hypertension, diabetes, hyperlipidemia, and smoking (Gorelick et al., 2011, Wardlaw et al., 2013a and Wardlaw

et al., 2013b). The vascular pathologies underlying these lesions consist of atherosclerotic plaques affecting small cerebral vessels, deposition of a hyaline substance in the vascular wall (lipohyalinosis), fibrotic changes in the vessel wall resulting in stiffening and microvascular distortion (arteriolosclerosis), and total loss of integrity of the vascular wall (fibrinoid necrosis) Dabrafenib (Figure 5) (Thal et al., 2012). Arterioles become tortuous, have thickened basement membranes, and are surrounded STK38 by enlarged perivascular spaces (Brown and Thore, 2011). Capillaries are reduced in number and “string vessels,” nonfunctional capillaries that have lost endothelial cells and have only a basement membrane, are observed (Brown and Thore, 2011). Collagen deposits are observed in venules (venous collagenosis) (Black et al., 2009 and Brown and Thore, 2011). The white matter damage resulting from these lesions consists of vacuolation, demyelination, axonal loss, and lacunar infarcts.

The white matter lesions generally correspond to hyperintensities observed on MRI, which, however, can also reflect other pathological substrates (Gouw et al., 2011). The white matter lesions evolve over time by expansion of existing lesions, rather than formation of new foci (Maillard et al., 2012), resembling the patterns of progression of amyloid angiopathy (Alonzo et al., 1998 and Robbins et al., 2006). The expansion of the white matter lesions correlates with the evolution of the cognitive impairment (Maillard et al., 2012), new lacunes causing a steeper decline, especially in motor speed and executive functions (Jokinen et al., 2011). White matter lesions and lacunar infarcts are also present in uncommon genetic conditions resulting in VCI and vascular dementia (Federico et al., 2012 and Schmidt et al., 2012). The better studied of these, CADASIL, is associated with extensive leukoaraiosis and lacunar infarcts (Chabriat et al., 2009).