[MR imaging of the brain of amyotrophic lateral sclerosis]

To investigate imaging characteristics of amyotrophic lateral sclerosis (ALS), the author reviewed magnetic resonance (MR) images of the brain of 50 ALS patients. MR images demonstrated abnormal foci in the internal capsule in nine patients, representing degeneration of the corticospinal tract (CST). These foci were hyperintense relative to cortical gray matter on T2-weighted images and still hyperintense relative to white matter on proton-density-weighted images. In contrast, normal hyperintense foci in the internal capsule representing fibers of the CST were isointense to gray matter on T2-weighted images and iso- or hypointense to white matter on proton-density-weighted images. T2-weighted images showed low signal within the motor cortex in three patients, indicating degeneration of the cortex. The images also demonstrated hyperintense lesions in the white matter of the precentral gyri in all of them, indicating degeneration of the CST. Other studies, however, reported that low signal within the motor cortex in aged normal controls was frequently observed. Therefore, the low signal was a useful finding only for young ALS patients. T2-weighted images of a patient showed hyperintense lesions in the body of the corpus callosum, representing degeneration of the commissural fibers interconnecting the motor cortices bilaterally.