138 Chapter 6 S.6.8.1 Supplementary results Our model resulted in 15 distinct subgroups with unique combinations of brain MRI markers. Below is a more detailed description of the brain MRI markers and the most important characteristics per subgroup. Subjective and relative cut-off points where used for the below used description of the subgroups. For continuous variables the subgroups were split into three thirds, with the highest, moderate and lowest values. WMH shape was considered as regular/moderate/irregular looking at all shape markers together and assessing the main shape. A low solidity, low convexity, high concavity index, and high fractal dimension indicate a more irregular shape. A high eccentricity indicates a rounder shape, while a low eccentricity indicates a more elongated shape. Total WMH volumes were used to describe relatively low/ moderate/high WMH volumes. WMH below ~20 ml were considered relatively low volumes, between ~20 ml and ~30 ml relatively moderate volumes and above ~30 ml as relatively high volumes. Total brain volumes above ~74% of intracranial volume were considered as relatively low atrophy, between ~72 and ~74% of intracranial volume as relatively moderate atrophy and below ~72% of intracranial volume as relatively severe atrophy. Subgroup 1 has relatively low WMH volumes, no infarcts, microbleeds or enlarged PVS, a moderately irregular WMH shape and relatively low atrophy. Subgroup 2 has relatively high WMH volumes, a high prevalence of subcortical infarcts (100%), some cortical, and cerebellar infarcts, an irregular WMH shape, some enlarged PVS (in and around the basal ganglia) and microbleeds, and relatively severe cerebral atrophy. Subgroup 3 has relatively high WMH volumes, some enlarged PVS (in and around the basal ganglia), an irregular WMH shape, and relatively severe cerebral atrophy. Subgroup 4 has relatively low WMH volumes, no infarcts, almost no enlarged PVS, a relatively regular WMH shape, some microbleeds, and relatively low cerebral atrophy. Subgroup 5 has relatively low WMH volumes, cerebellar infarcts (98%), some enlarged PVS (in and around the basal ganglia, and white matter) and microbleeds, a moderately irregular WMH shape, and moderate cerebral atrophy. Subgroup 6 has relatively low WMH volumes, a moderately irregular WMH shape, no infarcts, no enlarged PVS or microbleeds, and moderate cerebral atrophy.
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