Altered Brain Glymphatic Flow at Diffusion-Tensor MRI in Rapid Eye Movement Sleep Behavior Disorder

Area of Science:

• Neuroimaging
• Neurodegenerative Diseases
• Sleep Medicine

Background:

• Glymphatic system dysfunction is implicated in α-synucleinopathies.
• Noninvasive methods for assessing brain glymphatic function are needed.
• Rapid eye movement sleep behavior disorder (RBD) may precede α-synucleinopathy development.

Purpose of the Study:

• To evaluate brain glymphatic function in isolated RBD using diffusion-tensor imaging analysis along the perivascular space (ALPS).
• To investigate the relationship between glymphatic function and phenoconversion risk to α-synucleinopathies in RBD patients.

Main Methods:

• Prospective study comparing RBD patients, controls, and Parkinson disease (PD) patients.
• Brain MRI with diffusion-tensor imaging (DTI) was performed.
• The ALPS index was calculated to quantify glymphatic activity.

Main Results:

• The ALPS index was significantly lower in RBD patients compared to controls (P = .001).
• No significant difference in ALPS index was observed between RBD and PD groups (P = .68).
• A higher ALPS index was associated with a decreased risk of phenoconversion to α-synucleinopathies in RBD patients (HR, 0.57; P = .03).

Conclusions:

• Diffusion-tensor imaging analysis along the perivascular space (DTI-ALPS) reveals reduced glymphatic activity in RBD.
• Impaired glymphatic function in RBD is linked to an increased risk of developing α-synucleinopathies.