Lesion-specific perfusion levels affect myelin loss and repair

Remyelination in MS lesions is heterogeneous and often fails. A key factor to explain this may be the level of perfusion of single MS lesions, which is critical for myelin repair. A new study analysed the relationship between perfusion and subsequent myelin content changes in the white matter lesions in 15 relapsing-remitting MS patients using ¹¹C-PIB PET and 3T MRI. It was found that lesion-specific perfusion at baseline is an independent predictor of successful myelin repair [1].

¹¹C-PIB PET allows to simultaneously map demyelination and remyelination in vivo and to generate quantitative maps of brain perfusion. In 15 relapsing-remitting MS patients, ¹¹C-PIB PET and 3T MRI were performed at baseline and 2-4 months later. At baseline, 904 lesions were identified on T2-weighted scans. Gadolinium-enhancing lesions were excluded. Successful repair of lesions was defined as remyelination of ≥50% of demyelinated voxels, and demyelination over the follow-up in <25% of voxels that were classified as normally myelinated at study entry.

There was lower perfusion in white matter lesions than in normal-appearing white matter (0.43 vs 0.49; P<0.001). However, single-lesion R1 values were very heterogeneous (range 0.08-2.5). In single lesions, higher baseline perfusion was associated with more extensive remyelination (β=0.32; P<0.001) and reduced demyelination (β=-0.28; P<0.001). Lesion-specific perfusion at baseline was an independent predictor of successful myelin repair (OR 8.4; P<0.001).

1. Colombi A, et al. Lesion-specific perfusion levels affect myelin loss and repair in multiple sclerosis: a positron emission tomography study. MSVirtual 2020, Abstract PS11.03.