Correlation between pyramidal tract degeneration and widespread white matter involvement in amyotrophic lateral sclerosis: a study with tractography and diffusion-tensor imaging.

Our aim was to evaluate the location and extent of white matter involvement in patients with amyotrophic lateral sclerosis (ALS) using diffusion-tensor magnetic resonance imaging (DTI). We obtained fractional anisotropy (FA) values from the internal capsule and various white matter regions of 46 patients with sporadic ALS and 19 control subjects. In ALS patients, FA values in the internal capsule, frontal white matter, genu and splenium of the corpus callosum (p<0.001), parietal and temporal lobe white matter, and posterior cingulum (p<0.05) were significantly lower than in controls. FA values in frontal white matter were lower than in parietal white matter (p<0.001). Decreased FA values in frontal, parietal, and temporal white matter, and the genu of the corpus callosum, correlated significantly with those in the internal capsule (r=0.66 and p<0.001, r=0.47 and p=0.001, r=0.33 and p=0.021, r=0.41 and p=0.005, respectively). No such correlations were found for FA values in other white matter areas or in controls. Patient FA values generally were not correlated with disease duration. DTI demonstrated more widespread involvement of the cerebral white matter in ALS patients than previously believed. The severity of involvement in the frontal, temporal and parietal white matter correlated with severity in the pyramidal tract.