Association of glymphatic system disturbance with neural dysfunction in amyotrophic lateral sclerosis.

BACKGROUND

Formation and aggregation of pathological proteins in the brain constitutes a critical hallmark of amyotrophic lateral sclerosis (ALS). However, the role of the glymphatic system in the clearance of pathological proteins in ALS remains unclear. The purpose of this cross-sectional study was to evaluate glymphatic system disturbance in ALS and its relation to neural function.

METHODS

This study included 38 healthy controls (HCs) and 30 patients with ALS who underwent diffusion tensor imaging (DTI) and resting-state functional magnetic resonance imaging (rs-fMRI). The disease severity, duration, and progression rate of ALS were recorded. Glymphatic system function was indirectly evaluated by DTI analysis along the perivascular space (ALPS) surrounding the deep medullary vein. Neural activity was examined in sensorimotor-related brain areas by measuring amplitude of low-frequency fluctuation (ALFF) based on rs-fMRI. A two-sample -test or Mann-Whitney test was used to examine between-group differences in ALPS, diffusivities measured along the x-, y-, and z-axis in the association (Dxx_association, Dyy_association, Dzz_association) and projection (Dxx_projection, Dyy_projection, Dzz_projection) fiber areas, and ALFF indices. The associations between ALPS, diffusivities, ALFF, and clinical assessments were determined via Spearman correlation analysis, and diagnostic performance was evaluated with receiver operating characteristic curve analysis.

RESULTS

Patients with ALS exhibited significantly decreased ALPS and increased diffusivities (Dyy_association and Dyy_projection) as compared to HCs (all P values <0.05). Patients with ALS showed decreased ALFF in sensorimotor-related regions, including the bilateral primary motor and somatosensory areas (all P values <0.001) and left supplementary motor area (P=0.031). ALPS and diffusivities were correlated with ALFF in the sensorimotor-motor regions (all P values <0.05), and ALPS and ALFF correlated with disease severity and duration (all P values <0.05). ALPS, diffusivities, and ALFF showed moderate ability to diagnose ALS.

CONCLUSIONS

The glymphatic system function was impaired in ALS. This may contribute to spontaneous neural activity disturbance and could represent a mechanism for the development of sensorimotor deficits frequently observed in patients with ALS.