Figure 1 Regional fractional anisotropy (FA) reductions in amyotrophic lateral sclerosis group whole-brain comparison with healthy controls, alongside published postmortem observations

Consistent corpus callosum (CC) and rostral corticospinal tract (CST) tract involvement was seen despite the inclusion of a large number of patients with few clinical upper motor neuron signs. Similar white matter tract degeneration sections alongside those taken from an historical pathologic study⁵ (left-side images of A–D) confirmed prominent involvement of the CC and rostral CST (A and B, thick black lines indicating primary motor cortex), with caudal CST changes seen in uncorrected FA results (A, C, and D). Images shown were corrected (red–yellow scale) and uncorrected (red-only scale) for multiple comparisons (p < 0.05; radiologic convention used for display in all images).