OBJECTIVES The purpose of this study is to identity the recovery process of the corticospinal tract with diffuse axonal injury (DAI) using diffusion tensor imaging (DTI). DESIGN A 47-year-old female patient and six age-matched control subjects were evaluated. The patient presented with quadriparesis (more severe in the right extremities than the left ones) due to DAI at the onset of traumatic brain injury. Over the 24-month period following the onset of the injury, motor function of the four extremities slowly recovered to range which was close to normal. Two longitudinal DTIs were acquired from the patient (at 10 weeks and 24 months from onset) and from the control subjects. Fractional anisotropy (FA) and an apparent diffusion coefficient were measured using the region of interest (ROI) method. RESULTS On the 10-week DTI, FAs of ROIs of the brainstem in both hemispheres of the patient were significantly lower than those of the control subjects. Compared to normal controls, the patient showed significantly increased FA in both sides of the brainstem at 24 months after the onset, which occurred in parallel with the improvement in motor function. CONCLUSIONS Recovery in this patient could be attributed to the recovery of the corticospinal tract with diffuse axonal injury.