Nigrostriatal free-water imaging and volumetry outperform quantitative T1 in neurodegenerative Parkinson syndromes.

BACKGROUND

The relative value of nigrostriatal volumetry, quantitative T1 relaxation, and multicompartment diffusion MRI in neurodegenerative Parkinson syndromes is unclear.

OBJECTIVES

To compare quantitative T1 relaxation and diffusion microstructure imaging-derived free fluid fraction (V-CSF) in the putamen and substantia nigra, together with putaminal volume, across Parkinson's disease, multiple system atrophy, progressive supranuclear palsy, and healthy controls.

METHODS

We retrospectively studied 178 participants, including 59 individuals with Parkinson's disease, 30 with MSA, 60 with PSP, and 29 healthy controls assessed between 2018 and 2023. Linear models adjusted for age and sex tested group differences and associations with Hoehn and Yahr stage.

RESULTS

Putaminal volume and V-CSF differed across groups (both p < 0.001), whereas putaminal quantitative T1 did not (p = 0.10). Nigral V-CSF showed broader separation than nigral quantitative T1. In multiple system atrophy, lower putaminal quantitative T1 was associated with higher Hoehn and Yahr stage (p = 0.028).

CONCLUSIONS

Diffusion-derived free fluid and volumetry captured neurodegeneration more consistently than quantitative T1.