10 Nov 21. Featured Paper
MRI-derived g-ratio & lesion severity in newly diagnosed multiple sclerosis
Elizabeth N York, Sarah-Jane Martin, Rozanna Meijboom, Michael J Thrippleton, Mark E Bastin, Edwin Carter, James Overell, Peter Connick, Siddharthan Chandran, Adam D Waldman, David P J Hunt, the Future-MS consortium
Myelin loss is associated with axonal damage in established multiple sclerosis.
This relationship is challenging to study in vivo in early disease.
Here, we ask whether myelin loss is associated with axonal damage at diagnosis, by combining non-invasive neuroimaging & blood biomarkers.
Myelin integrity was evaluated using aggregate g-ratios, derived from magnetization transfer saturation (MTsat) & neurite orientation dispersion & density imaging (NODDI) diffusion data.
We found significantly higher g-ratios within cerebral white matter lesions (suggesting myelin loss) compared with normal-appearing white matter (0.61 vs 0.57, difference 0.036, 95% CI 0.029 to 0.043, p < 0.001).
Lesion volume (Spearman’s rho rs= 0.38, p < 0.001) & g-ratio (rs= 0.24 p < 0.05) correlated independently with plasma neurofilament.
In patients with substantial lesion load (n = 38), those with higher g-ratio (defined as greater than median) were more likely to have abnormally elevated plasma neurofilament than those with normal g-ratio (defined as less than median) (11/23 [48%] versus 2/15 [13%] p < 0.05).
These data suggest that, even at multiple sclerosis diagnosis, reduced myelin integrity is associated with axonal damage.
MRI-derived g-ratio may provide useful additional information regarding lesion severity, & help to identify individuals with a high degree of axonal damage at disease onset.
They demonstrate that g-ratio of cerebral white matter lesions varies at diagnosis, & show that high g-ratio of lesions is associated with elevated plasma neurofilament.
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Featured paper: MRI-derived g-ratio & lesion severity in newly diagnosed multiple sclerosis
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