Longitudinal intracortical diffusivity changes in de-novo Parkinson's disease: A promising imaging biomarker

Cognitive impairment and dementia in Parkinson's disease (PD) are highly disabling non-motor symptoms with no effective treatment currently available. As cortical degeneration is thought to be involved in the development of these comorbidities, novel imaging biomarkers capable of detecting early cortical deterioration are needed. Recently, an increase in mean diffusivity (MD) within the cerebral cortex has been proposed as a highly sensitive imaging indicator of early microstructural cortical damage in neurodegenerative diseases. Using the Parkinson's Progression Markers Initiative (PPMI), we studied longitudinal changes in intracortical MD in recently-diagnosed and drug-naïve PD patients (n = 64). Compared to healthy controls (n = 20), de novo PD patients showed a higher one-year MD increase in frontal and occipital cortices (p < 0.05, corrected). These PD-specific MD changes correlated with changes in cognitive measures. Importantly, cortical MD increases were widespread in the PD group and loss of cortical thickness was only increased in a small parietal cluster. These results suggest that intracortical MD changes could be promising imaging biomarker in clinical trials targeting the prevention and treatment of early cortical degeneration in PD, but further research confirmation is needed.