The relationship of (A) myelin-associated glycoprotein (MAG), (B) myelin-basic protein (MBP), (C) proteolipid protein (PLP), and the (D) MAG/PLP ratio to small vessel disease (SVD) in the deep parietal white matter in the SWDBB cohort. Both MAG and the MAG/PLP ratio correlated negatively with SVD severity (r=−0.384, P=0.0001 and r=−0.368, P=0.0002, respectively), whereas PLP correlated positively with SVD (r=0.305, P=0.0009). Myelin-associated glycoprotein was significantly reduced in cases with SVD severity of 1, 2 (**P<0.01), and 3 (***P<0.001) compared with those with no SVD. The MAG/PLP ratio was significantly reduced in cases with SVD severity of 3 compared with those with a score of 0 (*P<0.05). Myelin-basic protein did not vary significantly between the different SVD groups.