Brain MRI Detection of an Abnormal Peak Width of Skeletonized Mean Diffusivity in REM Sleep Behavior Disorder

Background and purpose: Peak width of skeletonized mean diffusivity (PSMD) is a novel marker of white matter damage, which may be related to small vessel disease. This study aimed to investigate the presence of white matter damage in patients with isolated rapid eye movement sleep behavior disorder (RBD) using PSMD.

Methods: We enrolled patients with newly diagnosed isolated RBD confirmed by polysomnography and age- and sex-matched healthy controls. Diffusion tensor imaging (DTI) was conducted using a 3-Tesla MRI scanner. We measured the PSMD based on DTI in several steps, including preprocessing, skeletonization, application of a custom mask, and histogram analysis, using the Functional Magnetic Resonance Imaging of the Brain Software Library program. We compared the incidence of PSMD between patients with RBD and healthy controls and performed a correlation analysis between PSMD and clinical factors in patients with RBD.

Results: Thirty patients with isolated RBD and 41 healthy controls were enrolled. The PSMD was significantly higher in patients with RBD than that in the healthy controls (3.078 vs. 2.746 × 10^-4 mm²/s, p = 0.001). In addition, PSMD positively correlated with age in patients with RBD (r = 0.477, p = 0.007). However, PSMD was not associated with other clinical or polysomnographic factors.

Conclusion: Patients with isolated RBD had a higher PSMD than healthy controls, indicating the evidence of white matter damage in patients with RBD. This finding highlights the potential of PSMD as a marker for detecting white matter damage, which may be related to small vessel diseases, in patients with sleep disorders.