Evaluation of glymphatic system activity and lateralization by diffusion tensor imaging in Parkinson's disease with excessive daytime sleepiness.

Introduction: This research explored the relationship between glymphatic system function, hemispheric dominance, and excessive daytime sleepiness (EDS) in Parkinson's disease (PD) patients through diffusion tensor image analysis along the perivascular space (DTI-ALPS).

Methods: We analyzed 3.0 T MR scans of PD patients and healthy controls (HCs). We used the ALPS index to assess the glymphatic system, and asymmetry patterns were evaluated via the asymmetry index (AI). PD patients were classified based on Epworth Sleepiness Scale (ESS) scores, and correlations between glymphatic dysfunction and EDS symptoms were examined.

Results: A total of 36 PD patients with EDS (PD-EDS), 56 PD patients without EDS (PD-NEDS) and 50 healthy controls were enrolled in this study. Compared to HCs, both left and right ALPS index were lower in PD-EDS patients (p = 0.001, p = 0.007, respectively), while only the right ALPS index was reduced in PD-NEDS patients (p = 0.001). The left ALPS index was significantly lower than the right across three groups (p < 0.001). PD-EDS patients exhibited reduced leftward asymmetry compared to PD-NEDS (p < 0.001). Notably, ESS scores were correlated negatively with the left ALPS index (r = -0.388, p = 0.028), and correlated positively with AI in PD-EDS patients (r = 0.657, p < 0.001).

Conclusion: The glymphatic system exhibited dysfunction and altered lateralization in PD-EDS patients. The severity of EDS correlated with impairment of the left glymphatic system and its reduced leftward lateralization.