In vivo imaging markers of glymphatic dysfunction in amyotrophic lateral sclerosis: Analysis of ALPS index and choroid plexus volume.

Background: The glymphatic system, essential for brain waste clearance, has been implicated in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Emerging imaging markers, such as the analysis along the perivascular space (ALPS) index and choroid plexus volume (CPV), may provide insights into glymphatic function, but their relevance to ALS remains unclear.

Objective: To assess glymphatic dysfunction in ALS patients using the ALPS index and CPV.

Methods: In this prospective single-center study, we analyzed 51 ALS patients and 51 age- and sex-matched healthy controls (HC). The ALPS index was calculated using diffusion tensor imaging, and 3D T1-weighted MRI was used for automated estimation of CPV and its fraction (CPV/total intracranial volume). Diagnostic performance was assessed using area under the receiver operating curve (AUC). Correlations between imaging markers and clinical parameters were also examined.

Results: ALS patients had a significantly lower ALPS index (ALS: 1.45 ± 0.15; HC: 1.55 ± 0.16; p = 0.002) and higher CPV fraction (ALS: 0.12 ± 0.04 %; HC: 0.10 ± 0.02 %; p < 0.001). The ALPS index and CPV fraction had AUCs of 0.70 and 0.72, respectively. A significant inverse correlation was observed between the ALPS index and CPV fraction (r = -0.31, p = 0.002). Both markers correlated with aging but not with clinical disability or progression rate.

Conclusion: This study identifies glymphatic dysfunction in ALS, as evidenced by changes in the ALPS index and CPV. Larger studies are warranted to validate these findings and assess their potential as biomarkers for ALS.