[MR findings of the pyramidal tract in amyotrophic lateral sclerosis]

MR imaging using the conventional spin each technique along with diffusion weighted imaging and water-fat imaging was performed in 16 patients with amyotrophic lateral sclerosis (ALS), 20 normal subjects, and 113 controls with other neurological disorders. Diffusion weighted images in the patients with ALS and the controls disclosed a high signal band from the subcortical area to the medullary pyramids. The high signal band on the diffusion weighted images corresponded to the pyramidal tract in the anatomical atlas described by Talairach. The T1- and T2-relaxation times, proton density, diffusion coefficient and diffusion anisotropy were measured at the points where high signal bands appeared on the diffusion weighted images. The T2-weighted images revealed high signal areas on the posterior limbs of the internal capsules in all the patients with ALS, 60% of the normal subjects, and 73% of the disease controls. The T1-weighted images disclosed high signal areas on the posterior limbs in 62% of the patients with ALS, but not in any of the normal subjects and the disease controls. The proton weighted images disclosed high signal areas on the posterior limbs in all the patients with ALS and 5% of the disease controls, but not in any of the normal subjects. Analysis of diffusion weighted images revealed no significant difference between the patients with ALS and the normal subjects in diffusion coefficient and diffusion anisotropy on the posterior limbs. Measurement of MR parameters (T1- and T2-relaxation times and proton density) showed that the proton density at the posterior limbs increased in ALS. Water-fat images using the method of Dixon revealed abnormal signals in the water images. These signal abnormalities were more prominent in the internal capsule than in the medullary pyramids. Our findings confirm that there is an increase in water molecules that have normal diffusion coefficient and diffusion anisotropy values in patients with ALS.