Multiple sclerosis shrinks intralesional, and enlarges extralesional, brain parenchymal veins.

Objectives: Many multiple sclerosis (MS) lesions develop around small veins that are surrounded by perivenular inflammatory cells, but whether veins in the brains of people with MS are smaller or larger than similar veins in healthy volunteers or people with other neurologic diseases remains unknown. This question can be addressed by high-resolution, high-field-strength MRI.

Methods: In a cross-sectional study performed on a standard 3 T clinical scanner, we acquired whole-brain T2*-weighted images with 0.55 mm isotropic voxels and reconstructed the courses of deep and superficial veins within the white matter. We compared the apparent diameters of intralesional and perilesional veins to those of extralesional MS veins, veins in healthy volunteers, and veins in individuals with other neurologic diseases.

Results: We studied veins in 19 MS cases, 9 healthy volunteers, and 8 individuals with other neurologic diseases, analyzing a total of 349 veins. The mean diameter of intralesional veins (0.76 ± 0.14 mm) was smaller than that of perilesional (1.18 ± 0.13 mm; p < 0.001) and extralesional (1.13 ± 0.14 mm; p < 0.001) veins, regardless of lesion size and location. Perilesional and extralesional MS veins were larger than non-MS veins (0.94 ± 0.14 mm; p < 0.001), and intralesional MS veins were smaller (p < 0.001).

Conclusions: The small apparent size of intralesional MS veins may reflect compression by the perivascular inflammatory cuff within active lesions or hardening of the vascular wall in chronic lesions. The finding that extralesional veins are larger than similar veins in non-MS lesions may result from diffuse disease-related processes.