Microglial Activation and Progression of Nigrostriatal Dysfunction in Isolated REM Sleep Behavior Disorder

Area of Science:

• Neuroscience
• Neurology
• Molecular Imaging

Background:

• Increased microglia activation, detected via 11C-(R)-PK11195-PET, is observed in isolated REM sleep behavior disorder (iRBD) patients.
• The precise role of this microglial activation in iRBD pathogenesis remains unclear.

Purpose of the Study:

• To investigate the relationship between activated microglia and the progression of nigrostriatal dysfunction in iRBD patients.
• To determine if baseline microglial activation predicts future neurodegeneration in the nigrostriatal pathway.

Main Methods:

• Longitudinal study involving 15 iRBD patients previously assessed with 11C-(R)-PK11195 and 18F-DOPA-PET.
• Repeat 18F-DOPA-PET scans after 3 years to assess changes in dopamine transporter availability (Ki).
• Analysis of 18F-DOPA Ki changes using both region-of-interest and voxel-based approaches.

Main Results:

• Significant reductions in 18F-DOPA Ki were observed in the putamen and caudate over 3 years.
• These reductions were more pronounced and widespread in patients exhibiting higher baseline nigral microglia activation.
• Baseline 11C-(R)-PK11195 binding in the left substantia nigra predicted the extent of 18F-DOPA Ki reduction in the left caudate.

Conclusions:

• Elevated baseline microglia activation in iRBD is associated with accelerated nigrostriatal pathway degeneration.
• This suggests a potentially detrimental, rather than protective, role for microglia in iRBD.
• Further research is needed to clarify the clinical and therapeutic implications of these findings.