Characterizing white matter changes in chronic schizophrenia: A free-water imaging multi-site study

Area of Science:

• Neuroimaging
• Psychiatry
• White Matter Imaging

Background:

• Diffusion tensor imaging (DTI) studies in chronic schizophrenia often show inconsistent white matter abnormalities.
• Conventional fractional anisotropy (FA) measures can be confounded by extracellular free-water (FW).
• Previous studies suggest reduced FW-corrected FA (FA_T) but minimal extracellular volume changes in schizophrenia.

Purpose of the Study:

• To validate findings of reduced FA_T in chronic schizophrenia using a larger, multi-site sample.
• To investigate white matter integrity using FW-corrected DTI metrics.
• To differentiate between tissue degeneration and extracellular changes in schizophrenia.

Main Methods:

• Tract-based spatial statistics (TBSS) applied to 188 healthy controls and 281 chronic schizophrenia patients.
• Free-water corrected diffusion tensor maps analyzed for FA_T and FW.
• Analysis of 42 regions of interest (ROIs) and average whole-brain metrics.

Main Results:

• Reduced FA_T observed in chronic schizophrenia patients in specific regions: bilateral anterior internal capsule, bilateral posterior thalamic radiation, genu and body of corpus callosum.
• A significant group effect for FW was found, but no specific contrasts survived multiple comparisons correction.
• FA_T reductions occurred without significant changes in extracellular FW.

Conclusions:

• Findings validate previous reports of localized FA_T reductions in chronic schizophrenia.
• White matter tissue degeneration in chronic schizophrenia may be more localized than previously thought.
• FW-corrected DTI metrics provide a more precise assessment of white matter integrity in schizophrenia.