Background:Bioenergetic disturbance, mainly caused by mitochondrial dysfunction, is an established pathophysiological phenomenon in neurodegenerative movement disorders. The in vivo assessment of brain energy metabolism by 31phosphorus magnetic resonance spectroscopy imaging could provide pathophysiological insights and serve in the differential diagnosis of parkinsonian disorders. In this study, we investigated such aspects of the underlying pathophysiology in patients with idiopathic Parkinson’s disease (PwPD) and progressive supranuclear palsy (PwPSP).Methods:In total, 30 PwPD, 16 PwPSP, and 25 healthy control subjects (HCs) underwent a clinical examination, structural magnetic resonance imaging, and 31phosphorus magnetic resonance spectroscopy imaging of the forebrain and basal ganglia in a cross-sectional study.Results:High-energy phosphate metabolites were remarkably decreased in PwPD, particularly in the basal ganglia (−42% compared with healthy controls and −43% compared with PwPSP, p<.0001). This result was not confounded by morphometric brain differences. In contrast, PwPSP had normal levels of high-energy energy metabolites. Thus, the combination of morphometric and metabolic neuroimaging was able to discriminate PwPD from PwPSP with an accuracy of up to 0.93 [95%-CI: 0.91, 0.94].Discussion:Our study shows that mitochondrial dysfunction and bioenergetic depletion contribute to idiopathic Parkinson’s disease pathophysiology but not to progressive supranuclear palsy. Combined morphometric and metabolic imaging could serve as an accompanying diagnostic biomarker in the neuroimaging-guided differential diagnosis of these parkinsonian disorders.

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Progressive supranuclear palsy (PSP) is a debilitating neurodegenerative disease characterized by an aggressive disease course. Total and intracellular-weighted sodium imaging (23Na-MRI) is a promising method for investigating neurodegeneration in vivo. We enrolled 10 patients with PSP and 20 age- and gender-matched healthy control subjects; all study subjects underwent a neurological examination, whole-brain structural, and (total and intracellular-weighted) 23Na-MRI. Voxel-wise analyses revealed increased brainstem total sodium content in PSP that correlated with disease severity. The ROI-wise analysis highlighted additional sodium level changes in other regions implicated in the pathophysiology of PSP. 23Na-MRI yields substantial benefits for the diagnostic workup of patients with PSP and adds complementary information on the underlying neurodegenerative tissue changes in PSP.