Superficial white matter microstructure affects processing speed in cerebral small vessel disease.

Area of Science:

• Neuroimaging
• Neurology
• Cognitive Science

Background:

• White matter hyperintensities (WMH) are common in cerebral small vessel disease (CSVD), a major cause of dementia.
• Deep white matter (DWM) changes are well-studied, but superficial white matter (SWM) alterations in CSVD are less understood.
• Processing speed is a primary cognitive deficit in CSVD.

Purpose of the Study:

• To investigate the role of SWM abnormalities in processing speed deficits in CSVD patients.
• To identify specific imaging markers in SWM associated with cognitive function.
• To explore the relationship between SWM microstructure and WMH burden.

Main Methods:

• 141 CSVD patients underwent processing speed assessment (Trail Making Test Part A).
• White matter abnormalities were quantified using WMH volume (T2-FLAIR) and diffusion MRI measures (including free water and mean diffusivity).
• Statistical analyses, including mediation analysis, were performed to assess associations.

Main Results:

• SWM imaging measures strongly correlated with processing speed, even with low SWM WMH burden.
• SWM free water (FW) showed the strongest association with processing speed, followed by SWM mean diffusivity (MD).
• SWM FW fully mediated the relationship between WMH volume and processing speed, highlighting its significance.

Conclusions:

• The superficial white matter plays a crucial role in processing speed in CSVD.
• SWM free water (FW) is a sensitive imaging biomarker for cognitive function in CSVD.
• SWM warrants further investigation as a potential therapeutic and monitoring target in CSVD.