MRI of paraventricular white matter lesions in amyotrophic lateral sclerosis. Analysis by diffusion-weighted images

Magnetic resonance images in some cases of amyotrophic lateral sclerosis (ALS) revealed abnormal signals in both the paraventriculer white matter and in the posterior limbs of the internal capsule. We examined T2- and diffusion-weighted MR images of these lesions in 18 cases of ALS. There were symmetrical high-signal areas in the posterior limbs of the internal capsule in all of the cases. The high-signal areas in the internal capsule corresponded to the pyramidal tracts in the anatomical atlas by Talairach. In 5 of the cases of ALS, T2-weighted MR images showed discrete paraventricular white matter lesions as well. The mean age of the ALS patients with paraventricular white matter lesions was higher than that of the ALS patients without such lesions. Proton densities calculated from the conventional MR images were higher in both the capsular and paraventricular lesions. The diffusion coefficients perpendicular to the pyramidal tract in the internal capsular lesions were within the normal range, where as the diffusion coefficients in the paraventricular lesions were increased in all directions. Thus, diffusion anisotropy was lost in the paraventricular lesions. These findings are similar to those observed in the white matter lesions of cerebro-vascular origin. As a result, the pathology of the paraventricular lesions in ALS was confirmed to be different from that of the internal capsular lesions. (author)