Figure 2 Regional fractional anisotropy (FA) reductions and radial diffusivity (RD) increases in amyotrophic lateral sclerosis (ALS) group whole-brain comparison with healthy controls

The close overlap between FA reductions (top panel, red–yellow) and RD (lower panel, blue) findings suggests that involvement of the corpus callosum and rostral corticospinal tract in ALS reflects a secondary demyelinating process due to an anterograde Wallerian degeneration. Both measures were corrected for multiple comparisons (p < 0.05; radiologic convention used for display in all cases with sagittal sections specifically marked for side).