White matter changes in patients with narcolepsy type 2: Peak width of skeletonized mean diffusivity study.

Objectives: This study aimed to investigate white matter (WM) microstructural alterations in patients with narcolepsy type 2 (NT2) using Peak Width of Skeletonized Mean Diffusivity (PSMD), a novel imaging marker associated with small vessel disease (SVD). The study compared PSMD metrics between patients with NT2 and healthy controls to investigate structural disruptions and their implications for NT2 pathophysiology.

Methods: A total of 42 participants were enrolled, including 20 patients with newly diagnosed NT2 and 22 healthy controls. Diffusion tensor imaging (DTI) was performed using a 3 T MRI scanner. PSMD was calculated using a multi-step process involving preprocessing, skeletonization, application of a custom mask, and histogram analysis with the FSL program. PSMD values were compared between patients with NT2 and healthy controls, and correlation analyses were conducted to examine associations between PSMD and clinical variables.

Results: Patients with NT2 exhibited significantly higher PSMD compared to healthy controls (2.172 × 10 mm/s vs. 2.031 × 10 mm/s, p = 0.011). PSMD also positively correlated with age in both patients with NT2 (r = 0.608, p = 0.004) and healthy controls (r = 0.696, p < 0.001).

Conclusion: Patients with NT2 demonstrate increased PSMD, indicating WM microstructural changes potentially linked to SVD. These findings highlight the utility of PSMD as a sensitive neuroimaging marker for detecting WM alterations in sleep disorders. Further studies are needed to validate these results and investigate the underlying mechanisms of WM changes in NT2.