<p>The split-hand phenomenon is an early and specific feature of amyotrophic lateral sclerosis (ALS). This study aimed to investigate whether the split-hand phenomenon in ALS is associated with the white matter degeneration of the brain. Patients diagnosed with clinically definite or probable ALS were prospectively recruited and underwent both nerve conduction studies to assess the split-hand index (SHI) and brain diffusion tensor imaging (DTI). Demographic, clinical, and electrophysiological data were all collected. A total of 35 patients with ALS (18 male; median age, 66.0 years) were enrolled in this study. The axial diffusivity (AD) and mode of anisotropy (MO) values of DTI in the corticospinal tract (CST) positively correlated with the SHI. However, there were no significant correlations between the SHI and the fraction anisotropy (FA), mean diffusivity (MD), and radial diffusivity (RD) scalars. In addition, patients having ALS with bilateral split-hand phenomenon showed reduced AD values in the left CST and reduced MO values in the bilateral CST compared with those without the split-hand phenomenon. However, there were no significant differences in FA, MD, and RD scalars. Our findings suggest that the split-hand phenomenon is associated with degenerative brain changes, particularly in the CST.</p>