170 Chapter 9 9.1 ENGLISH SUMMARY 9.1.1 Background Cerebral small vessel disease (SVD) is a major contributor to cognitive impairment and dementia. White matter hyperintensities (WMHs) are a key imaging marker of SVD and are visible on brain MRI. In neuroimaging research WMHs were traditionally quantified using their volume. However, this is a rather crude marker that fails to fully capture the heterogeneity of cerebral SVD. When inspecting MRI scans visually, WMHs can appear very different from each other in shape and location, even if their calculated volumes may be roughly the same. However, measures to objectively quantify such differences that may easily be caught by the eye of a neuroradiologist, were lacking. In this thesis, WMH shape is investigated as a novel marker of SVD to improve our understanding of WMHs. 9.1.2 Aim The overarching aim of this thesis was to exploit the shape of WMHs for better characterization of WMH to improve the clinical interpretation of WMHs and to investigate related disease outcomes. This thesis was mostly based on non-demented and community-dwelling older individuals. Moreover, a study set up focusing on a memory-clinic population was discussed to get more pathology-focused insights into the formation of WMH. 9.1.3 Summary of results In Chapter 2 the association of different cardiovascular risk factors with WMH shape was investigated in older adults of the ‘biomarker development for postoperative cognitive impairment in the elderly’ (BIOCOG) study. The study included nondemented older adults scheduled for major elective surgery. The association between cardiovascular risk factors and quantitative MRI-based WMH shape and volume markers were examined using linear regression analysis. Presence of hypertension was associated with a more irregular shape of periventricular/confluent WMH, but not with total WMH volume. Presence of diabetes was associated with deep WMH volume. Body mass index or hyperlipidemia showed no association with WMH markers. This study showed that different cardiovascular risk factors seem to be related to a distinct pattern of WMH shape markers in non-demented older adults. These findings may suggest that different underlying cardiovascular pathological mechanisms lead to different WMH MRI phenotypes, which may be valuable for early detection of individuals at risk for stroke and dementia.
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