Could changes in arterioles impede the perivascular drainage of interstitial fluid from the cerebral white matter in leukoaraiosis?

Aims: Leukoaraiosis (LA) is the increase in fluid in cerebral white matter with hyperintensity on T2-weighted MR imaging that occurs in 25% of individuals over 65 years of age and in Alzheimer's disease. Age, hypertension, diabetes mellitus and cardiac disease are the major risk factors for LA. Ischaemia is considered to be the cause of LA, but the aim of the present study is to assess whether changes in arterioles in LA could impede perivascular lymphatic drainage of interstitial fluid from the cerebral white matter. Methods: We quantified arteriolosclerosis and immunohistochemical changes in the extracellular matrix in arterioles of cerebral white matter in 20 hypertension autopsy cases with LA and in 10 controls. Results: The ratio of the area immunoreactive for collagen types I, III, V and VI to the cross-sectional area of arterioles was significantly higher in LA patients compared with controls (P < 0.001). Changes were observed in collagen IV and laminin. The walls of white matter arterioles in LA were significantly thicker (P < 0.01), and lumina were significantly smaller (P < 0.01). Arterioles had a significantly higher sclerotic index [1 - (internal/external diameter)] in LA than in adjacent cortex or control white matter (P < 0.01). Conclusions: Our results show that thickening and sclerosis of the walls of arterioles in cerebral white matter in LA are associated with the accumulation of extracellular matrix components. Although these changes may result in decreased perfusion, they could also impede perivascular lymphatic drainage of interstitial fluid from white matter in LA.