High Resolution Diffusion Tensor Imaging of Brainstem Nuclei Across the Healthy Lifespan

Motivation: Brainstem nuclei are understudied in brain development/aging due to typically low spatial resolution of diffusion MRI. Goal(s): To investigate micro-structural changes with age/sex in red nucleus and substantia nigra across the lifespan. Approach: Diffusion tensor imaging was acquired with 1 mm³ voxels to assess age trajectories in 193 healthy controls (5-83 years; 105 females). Results: Diffusion metrics had non-linear age trajectories that differed from volume and susceptibility. For both nuclei, mean diffusivity showed a quadratic age trajectory (minima ~50 years) with similar values between males and females in children, but became divergent at older ages (females higher). Impact: High-resolution diffusion MRI of brainstem nuclei indicated marked non-linear changes with age across the typical lifespan that differed with sex. This establishes a baseline for investigation of micro-structural alterations of the red nucleus and substantia nigra in neurological disorders.