Cortical macro- and microstructural changes in isolated rapid eye movement sleep behavior disorder

Area of Science:

• Neuroimaging
• Neurodegenerative Disorders
• Sleep Medicine

Background:

• Isolated REM sleep behavior disorder (iRBD) is a prodromal stage for Lewy body diseases.
• Cortical microstructural changes are implicated in neurodegeneration.
• Cortical mean diffusivity (cMD) and cortical thickness (CTh) are potential imaging biomarkers, but their role in iRBD is unstudied.

Purpose of the Study:

• To investigate cMD and CTh in patients with iRBD.
• To explore the relationship between cMD, CTh, and clinical/neuropsychological features in iRBD.
• To determine if cMD is a sensitive biomarker for early cortical changes in prodromal Lewy body diseases.

Main Methods:

• Diffusion tensor imaging (DTI) was used to measure cMD.
• Structural MRI was used to measure CTh.
• Thirty-six iRBD patients and 29 healthy controls (HC) were assessed for associations with clinical and cognitive measures.

Main Results:

• Patients with iRBD exhibited significantly increased cMD in rostral and caudal cortical regions compared to HC (Cohen's d > 0.5).
• Cortical thinning was observed only in caudal regions of iRBD patients.
• Elevated cMD correlated with longer iRBD duration, later disease onset, higher MDS-UPDRS III scores, apathy, and poorer performance on the Grooved Pegboard and Symbol-Digit Modality Tests.

Conclusions:

• cMD is elevated in the cortex of individuals with iRBD, suggesting early microstructural alterations.
• cMD appears to be a more sensitive biomarker than CTh for detecting early cortical changes in prodromal Lewy body diseases.
• cMD holds promise as a valuable imaging biomarker for identifying individuals at high risk for neurodegeneration.