COL4A2 and perivascular space measurement: Several PVS risk loci (at FOXF2, EFEMP1, KCNK2 and NBEAL1-ICA1L) are known risk loci for other cSVD features (WMH, SVS)5,22,23, and mutations in two MTAG genes cause monogenic SVD (at COL4A1-COL4A2 and STN1)24,25.