Progressive supranuclear palsy and idiopathic Parkinson's disease are associated with local reduction of in vivo brain viscoelasticity

Abstract

Objectives: To apply three-dimensional multifrequency MR-elastography (3DMRE) for the measurement of local cerebral viscoelasticity changes in patients with Parkinson's disease (PD) and progressive supranuclear palsy (PSP).

Methods: T1-weighted anatomical imaging and 3DMRE were performed in 17 PD and 20 PSP patients as well as 12 controls. Two independent viscoelasticity parameters, |G*| and φ, were reconstructed combining seven harmonic vibration frequencies (30-60 Hz). Spatially averaged values were compared by one-way ANOVA, groups were compared using unpaired t test and Mann-Whitney test, respectively. Correlation between clinical data and parameters of brain elasticity and volume were calculated by Pearson's correlation coefficient.

Results: In patients, |G*| was significantly reduced in the frontal and mesencephalic regions (p < 0.05). Beyond that, reduced mesencephalic |G*| discriminated PSP from PD (p < 0.05). Neurodegeneration causes significant brain atrophy (p < 0.01) and is pronounced in PSP patients (p < 0.05 vs. PD). Reduced brain viscoelasticity is correlated with brain atrophy in PSP (r=0.64, p=0.002) and PD (r=0.65, p=0.005) patients but not in controls.

Conclusions: MRE-measured viscoelasticity reflects local structural changes of brain tissue in PSP and in PD and provides a useful parameter to differentiate neurodegenerative movement disorders based on imaging examinations.

Key points: • 3D multifrequency MR-elastography reveals diffuse regional changes in brain viscoelasticity in neurodegenerative disorders. • Reduced mesencephalic viscoelasticity separates PD and PSP. • Reduced brain viscoelasticity and brain atrophy as independent hallmarks of neurodegeneration hypothesized.

Keywords: Magnetic resonance elastography, MRE; Mesencephalon; Parkinson’s disease; Progressive supranuclear palsy; Tau protein.