Conor Owens-Walton, et al. – University of Southern California.
Background: Studies have drawn opposing conclusions as to what changes, if any, occur to white matter (WM) in patients with PD. Meta-analyses have suggested that this may be due to WM metrics, such as fractional anisotropy (FA) and mean diffusivity (MD), revealing greater integrity early in PD and lesser integrity late in the disorder.
This Study: Owens-Walton and colleagues assessed diffusion tensor imaging data collected from 1,651 patients and 885 controls at 17 centers from across the world.
- Data from patients in early PD (Hoehn and Yahr [HY] stage 1) found higher WM integrity compared to controls, particularly in the anterior and retrolenticular limbs of the internal capsule.
- Global FA became lower in patients than controls at HY3, with this difference becoming more pronounced at HY4/5.
- When data were collapsed across stages, significant differences were only observed in the fornix (lower FA, higher MD) and the hippocampal portion of the cingulum (lower MD).
Bottom Line: WM integrity metrics increase early in PD, potentially due to compensatory mechanisms, and decrease as the disorder progresses.
Open Questions: What compensatory mechanisms occur early in PD? Could these potentially be exploited for treatments?
