VMAT2 availability in Parkinson's disease with probable REM sleep behaviour disorder

Area of Science:

• Neuroscience
• Neurology
• Radiology

Background:

• REM sleep behaviour disorder (RBD) is an early non-motor symptom of Parkinson's disease (PD).
• The extent of striatal dopamine denervation in PD patients with RBD (PD-RBD+) compared to those without (PD-RBD-) is not fully understood.
• Vesicular monoamine transporter 2 (VMAT2) availability serves as an index of nigrostriatal dopamine innervation.

Purpose of the Study:

• To compare VMAT2 availability in the striatum between PD-RBD+, PD-RBD-, and healthy controls (HC).
• To investigate the relationship between VMAT2 availability, clinical measures, and RBD in PD patients.

Main Methods:

• Positron emission tomography (PET) imaging using [11C]DTBZ to measure VMAT2 availability.
• Analysis of VMAT2 binding in striatal regions of interest (ROIs) in 15 PD-RBD+, 15 PD-RBD-, and 15 HC.
• Statistical analysis using mixed-effects models and multiple regressions, controlling for sex, cognitive function, and depression.

Main Results:

• Both PD-RBD+ and PD-RBD- groups exhibited reduced VMAT2 availability compared to HC across multiple striatal regions.
• PD-RBD+ showed lower VMAT2 availability than HC in the caudate, putamen, ventral striatum, globus pallidus, substantia nigra, and subthalamus (except subthalamus and substantia nigra).
• PD-RBD- showed significantly lower VMAT2 availability than HC in all tested regions. No significant interactions between VMAT2 binding and clinical scores were found in PD-RBD+.

Conclusions:

• Striatal dopamine denervation, as measured by VMAT2 availability, is comparable between PD patients with and without RBD.
• VMAT2 and general striatal dopamine denervation may not be primary contributors to the pathophysiology of RBD in Parkinson's disease.
• Further research is needed to explore alternative neurochemical mechanisms underlying RBD in PD.