Correlation between the regional brain volume and glymphatic system activity in progressive supranuclear palsy.

Introduction: Tau protein accumulation in the brain is thought to be one of the causes of progressive supranuclear palsy (PSP). The glymphatic system was discovered a decade ago as a waste drainage system in the brain that promotes the elimination of amyloid-beta and tau protein. We here evaluated the relationships between glymphatic system activity and regional brain volumes in PSP patients.

Method: Subjects were 24 patients with PSP and 42 healthy participants who underwent diffusion tensor imaging (DTI). We computed the diffusion tensor image analysis along the perivascular space (DTI‑ALPS) index as a proxy of glymphatic system activity, and estimated the relationships between the DTI‑ALPS index and regional brain volume in PSP patients by whole-brain and region-of-interest analyses, including analyses of the midbrain and third and lateral ventricles.

Results: The DTI‑ALPS index was significantly lower in patients with PSP, compared with healthy subjects. Further, there were significant correlations between the DTI‑ALPS index and the regional brain volumes in the midbrain tegmentum, pons, right frontal lobe, and lateral ventricles in patients with PSP.

Conclusions: Our data suggest that the DTI‑ALPS index is a good biomarker for PSP and might be effective to distinguish PSP from other neurocognitive disorders.